SR3 OPTIONS

SR3 Configuration File Format

manual section:

7

Date:

May 01, 2024

Version:

UNKNOWN

Manual group:

MetPX-Sarracenia

SYNOPSIS

name value
name value for use
name value_${substitution}
.
.
.

DESCRIPTION

Options are placed in configuration files, one per line, in the form:

option <value>

For example:

debug true
debug

sets the debug option to enable more verbose logging. If no value is specified, the value true is implicit, so the above are equivalent. A second example:

broker amqps://anonymous@dd.weather.gc.ca

In the above example, broker is the option keyword, and the rest of the line is the value assigned to the setting. Configuration files are a sequence of settings, one per line. Note:

  • the files are read from top to bottom, most importantly for directory, strip, mirror, and flatten options apply to accept clauses that occur after them in the file.

  • The forward slash (/) as the path separator in Sarracenia configuration files on all operating systems. Use of the backslash character as a path separator (as used in the cmd shell on Windows) may not work properly. When files are read on Windows, the path separator is immediately converted to the forward slash, so all pattern matching, in accept, reject, strip etc… directives should use forward slashes when a path separator is needed.

  • # is the prefix for lines of non-functional descriptions of configurations, or comments. Same as shell and/or python scripts.

  • All options are case sensitive. Debug is not the same as debug nor DEBUG. Those are three different options (two of which do not exist and will have no effect, but will generate an ´unknown option’ warning).

The file has an inherent order, in that it is read from top to bottom, so options set on one line often affect later lines:

mirror off
directory /data/just_flat_files_here_please
accept .*flatones.*

mirror on
directory /data/fully_mirrored
accept .*

In the above snippet the mirror setting is off, then the directoy value is set, so files whose name includes flatones will all be place in the /data/just_flat_files_here_please directory. For files which don’t have that name, they will not be picked up by the first accept, and so the mirror on, and the new directory setting will tak over, and those other files will land in /data/fully_mirrored. A second example:

sequence #1:

reject .*\.gif
accept .*

sequence #2:

accept .*
reject .*\.gif

Note

FIXME: does this match only files ending in ‘gif’ or should we add a $ to it? will it match something like .gif2 ? is there an assumed .* at the end?

In sequence #1, all files ending in ‘gif’ are rejected. In sequence #2, the accept .* (which accepts everything) is encountered before the reject statement, so the reject has no effect. Some options have global scope, rather than being interpreted in order. For thoses cases, the last declaration overrides the ones higher in the file..

Variables

One can include substitutions in option values. They are represented by ${name}. The name can be an ordinary environment variable, or a chosen from a number of built-in ones. For example:

varTimeOffset -5m
directory /mylocaldirectory/${%Y%m%d}/mydailies
accept    .*observations.*

rename hoho.${%o-1h%Y%m%d_%H%M%S.%f}.csv

In the last example above, the varTimeOffset will modify the evaluation of YYYYMMDD to be 5m in the past. In the rename option, the time to be substituted is one hour in the past. One can also specify variable substitutions to be performed on arguments to the directory option, with the use of ${..} notation:

  • %… - a datetime.strftime()

    • compatible date/time formatting string augmented by an offset duration suffix (o- for in the past, o+ for in the future)

    • example (complex date): ${%Y/%m/%d_%Hh%M:%S.%f} –> 2022/12/04_17h36:34.014412

    • example (add offset): ${%o-1h%Y/%m/%d_%Hh%M:%S.%f} –> 2022/12/04_16h36:34.014412

  • time offset begin a strtime pattern with %o for an offset +-1(s/m/h/d/w) units.

  • SOURCE - the amqp user that injected data (taken from the notification message.)

  • BD - the base directory

  • BUP - the path component of the baseUrl (or: baseUrlPath)

  • BUPL - the last element of the baseUrl path. (or: baseUrlPathLast)

  • PBD - the post base dir

  • var - any environment variable.

  • BROKER_USER - the user name for authenticating to the broker (e.g. anonymous)

  • POST_BROKER_USER - the user name for authenticating to the post_broker (e.g. anonymous)

  • PROGRAM - the name of the component (subscribe, shovel, etc…)

  • CONFIG - the name of the configuration file being run.

  • HOSTNAME - the hostname running the client.

  • RANDID - a random id that will be consistent within a single invocation.

The %Y%m%d and %h time stamps refer to the time at which the data is processed by the component, it is not decoded or derived from the content of the files delivered. All date/times in Sarracenia are in UTC. use the varTimeOffset setting to adjust from the current time.

Refer to sourceFromExchange for a common example of usage. Note that any sarracenia built-in value takes precedence over a variable of the same name in the environment. Note that flatten settings can be changed between directory options.

Note:

the ${% date substitutions are present, the interpretation of % patterns in filenames
by strftime, may mean it is necessary to escape precent characters them via doubling: %%

Sundew Compatible Substituions

In MetPX Sundew, there is a much more strict file naming standard, specialised for use with World Meteorological Organization (WMO) data. Note that the file naming convention predates, and bears no relation to the WMO file naming convention currently approved, but is strictly an internal format. The files are separated into six fields by colon characters. The first field, DESTFN, gives the WMO (386 style) Abbreviated Header Line (AHL) with underscores replacing blanks:

TTAAii CCCC YYGGGg BBB ...

(see WMO manuals for details) followed by numbers to render the product unique (as in practice, though not in theory, there are a large number of products which have the same identifiers). The meanings of the fifth field is a priority, and the last field is a date/time stamp. The other fields vary in meaning depending on context. A sample file name:

SACN43_CWAO_012000_AAA_41613:ncp1:CWAO:SA:3.A.I.E:3:20050201200339

If a file is sent to sarracenia and it is named according to the Sundew conventions, then the following substitution fields are available:

${T1}    replace by bulletin's T1
${T2}    replace by bulletin's T2
${A1}    replace by bulletin's A1
${A2}    replace by bulletin's A2
${ii}    replace by bulletin's ii
${CCCC}  replace by bulletin's CCCC
${YY}    replace by bulletin's YY   (obs. day)
${GG}    replace by bulletin's GG   (obs. hour)
${Gg}    replace by bulletin's Gg   (obs. minute)
${BBB}   replace by bulletin's bbb
${RYYYY} replace by reception year
${RMM}   replace by reception month
${RDD}   replace by reception day
${RHH}   replace by reception hour
${RMN}   replace by reception minutes
${RSS}   replace by reception second
YYYYMMDD - the current daily timestamp. (v2 compat, prefer strftime %Y%m%d )
HH       - the current hourly timestamp. (v2 compat, prefer strftime %h )
JJJ      - the current hourly timestamp. (v2 compat, prefer strftime %j )

The ‘R’ fields come from the sixth field, and the others come from the first one. When data is injected into sarracenia from Sundew, the sundew_extension notification message header will provide the source for these substitions even if the fields have been removed from the delivered file names.

Note:

The version 2 compatible date strings (e.g. YYYYMMDD) originate with obsolete
WMO practices, and support will be removed at a future date. Please use strftime
style patterns in new configurations.
SR_DEV_APPNAME

The SR_DEV_APPNAME environment variable can be set so that the application configuration and state directories are created under a different name. This is used in development to be able to have many configurations active at once. It enables more testing than always working with the developer´s real configuration.

Example: export SR_DEV_APPNAME=sr-hoho… when you start up a component on a linux system, it will look in ~/.config/sr-hoho/ for configuration files, and write state files in the ~/.cache/sr-hoho directory.

OPTION TYPES

sr3 options come in several types:

count

integer count type.

duration

a floating point number indicating a quantity of seconds (0.001 is 1 milisecond) modified by a unit suffix ( m-minute, h-hour, w-week )

flag

an option that has only True or False values (aka: a boolean value)

float

a floating point number.

list

a list of string values, each succeeding occurrence catenates to the total. all v2 plugin options are declared of type list.

set

a set of string values, each succeeding occurrence is unioned to the total.

size

integer size. Suffixes k, m, and g for kilo, mega, and giga (base 2) multipliers.

str

an string value

OPTIONS

The actual options are listed below. Note that they are case sensitive, and only a subset are available on the command line. Those that are available on the command line have the same effect as when specified in configuration files.

The options available in configuration files:

accelThreshold <size> default: 0 (disabled.)

The accelThreshold indicates the minimum size of file being transferred for which a binary downloader will be launched.

accelXxxCommand

Can specify alternate binaries for downloaders to tune for specific cases.

Option

Defaul value

accelWgetCommand

/usr/bin/wget %s -O %d

accelScpCommand

/usr/bin/scp %s %d

accelCpCommand

/usr/bin/cp %s %d

accelFtpgetCommand

/usr/bin/ncftpget %s %d

accelFtpputCommand

/usr/bin/ncftpput %s %d

use the %s to stand-in for the name of the source file, and %d for the file being written. An example setting to override with:

accelCpCommand dd if=%s of=%d bs=4096k

accept, reject and acceptUnmatched

  • accept <regexp pattern> (optional) [<keywords>]

  • reject <regexp pattern> (optional)

  • acceptUnmatched <boolean> (default: True)

The accept and reject options process regular expressions (regexp). The regexp is applied to the the notification message’s URL for a match.

If the notification message’s URL of a file matches a reject pattern, the notification message is acknowledged as consumed to the broker and skipped.

One that matches an accept pattern is processed by the component.

In many configurations, accept and reject options are mixed with the directory option. They then relate accepted notification messages to the directory value they are specified under.

After all accept / reject options are processed, normally the notification message is accepted for further processing. To override that default, set acceptUnmatched to False. The accept/reject settings are interpreted in order. Each option is processed orderly from top to bottom. For example:

sequence #1:

reject .*\.gif
accept .*

sequence #2:

accept .*
reject .*\.gif

In sequence #1, all files ending in ‘gif’ are rejected. In sequence #2, the accept .* (which accepts everything) is encountered before the reject statement, so the reject has no effect.

It is best practice to use server side filtering to reduce the number of notification messages sent to the component to a small superset of what is relevant, and perform only a fine-tuning with the client side mechanisms, saving bandwidth and processing for all. More details on how to apply the directives follow:

The accept and reject options use regular expressions (regexp) to match URL. These options are processed sequentially. The URL of a file that matches a reject pattern is not published. Files matching an accept pattern are published. Again a rename can be added to the accept option… matching products for that accept option would get renamed as described… unless the accept matches one file, the rename option should describe a directory into which the files will be placed (prepending instead of replacing the file name).

The permDefault option allows users to specify a linux-style numeric octal permission mask:

permDefault 040

means that a file will not be posted unless the group has read permission (on an ls output that looks like: —r—–, like a chmod 040 <file> command). The permDefault options specifies a mask, that is the permissions must be at least what is specified.

The regexp pattern can be used to set directory parts if part of the notification message is put to parenthesis. sender can use these parts to build the directory name. The rst enclosed parenthesis strings will replace keyword ${0} in the directory name… the second ${1} etc.

Example of use:

filename NONE

directory /this/first/target/directory

accept .*file.*type1.*

directory /this/target/directory

accept .*file.*type2.*

accept .*file.*type3.*  DESTFN=file_of_type3

directory /this/${0}/pattern/${1}/directory

accept .*(2016....).*(RAW.*GRIB).*

A selected notification message by the first accept would be delivered unchanged to the first directory.

A selected notification message by the second accept would be delivered unchanged to the second directory.

A selected notification message by the third accept would be renamed “file_of_type3” in the second directory.

A selected notification message by the forth accept would be delivered unchanged to a directory.

It’s named /this/20160123/pattern/RAW_MERGER_GRIB/directory if the notification message would have a notice like:

20150813161959.854 http://this.pump.com/ relative/path/to/20160123_product_RAW_MERGER_GRIB_from_CMC

acceptSizeWrong: <boolean> (default: False)

When a file is downloaded and its size does not match the one advertised, it is normally rejected, as a failure. This option accepts the file even with the wrong size. helpful when file is changing frequently, and there is some queueing, so the file is changed by the time it is retrieved.

attempts <count> (default: 3)

The attempts option indicates how many times to attempt downloading the data before giving up. The default of 3 should be appropriate in most cases. When the retry option is false, the file is then dropped immediately.

When The retry option is set (default), a failure to download after prescribed number of attempts (or send, in a sender) will cause the notification message to be added to a queue file for later retry. When there are no notification messages ready to consume from the AMQP queue, the retry queue will be queried.

baseDir <path> (default: /)

baseDir supplies the directory path that, when combined with the relative one in the selected notification gives the absolute path of the file to be sent. The default is None which means that the path in the notification is the absolute one.

Sometimes senders subscribe to local xpublic, which are http url’s, but sender needs a localfile, so the local path is built by concatenating:

baseDir + relative path in the baseUrl + relPath

When used for reception, it specifies the root of the tree that upstream files are assumed to be from, to be replaced on download by either post_baseDir or the directory setting in effect.

baseUrl_relPath <flag> (default: off)

Normally, the relative path (baseUrl_relPath is False, appended to the base directory) for files which are downloaded will be set according to the relPath header included in the notification message. If baseUrl_relPath is set, however, the notification message’s relPath will be prepended with the sub-directories from the notification message’s baseUrl field.

batch <count> (default: 100)

The batch option is used to indicate how many files should be transferred over a connection, before it is torn down, and re-established. On very low volume transfers, where timeouts can occur between transfers, this should be lowered to 1. For most usual situations the default is fine. For higher volume cases, one could raise it to reduce transfer overhead. It is only used for file transfer protocols, not HTTP ones at the moment.

blocksize <size> default: 0 (auto)

NOTE: EXPERIMENTAL sr3, expected to return in future version** This blocksize option controls the partitioning strategy used to post files. The value should be one of:

0 - autocompute an appropriate partitioning strategy (default)
1 - always send entire files in a single part.
<blocksize> - used a fixed partition size (example size: 1M )

Files can be announced as multiple parts. Each part has a separate checksum. The parts and their checksums are stored in the cache. Partitions can traverse the network separately, and in parallel. When files change, transfers are optimized by only sending parts which have changed.

The outlet option allows the final output to be other than a post. See sr3_cpump(1) for details.

broker

broker [amqp|mqtt]{s}://<user>:<password>@<brokerhost>[:port]/<vhost>

A URI is used to configure a connection to a notification message pump, either an MQTT or an AMQP broker. Some Sarracenia components set a reasonable default for that option. provide the normal user,host,port of connections. In most configuration files, the password is missing. The password is normally only included in the credentials.conf file.

Sarracenia work has not used vhosts, so vhost should almost always be /.

for more info on the AMQP URI format: ( https://www.rabbitmq.com/uri-spec.html )

either in the default.conf or each specific configuration file. The broker option tell each component which broker to contact.

broker [amqp|mqtt]{s}://<user>:<pw>@<brokerhost>[:port]/<vhost>

::

(default: None and it is mandatory to set it )

Once connected to an AMQP broker, the user needs to bind a queue to exchanges and topics to determine the notification messages of interest.

bufsize <size> (default: 1MB)

Files will be copied in bufsize-byte blocks. for use by transfer protocols.

byteRateMax <size> (default: 0)

byteRateMax is greater than 0, the process attempts to respect this delivery speed in kilobytes per second… ftp,ftps,or sftp)

FIXME: byteRateMax… only implemented by sender? or subscriber as well, data only, or notification messages also?

callback <classSpec>

callback appends a flowcallback class to the list of those to be called during processing.

Most customizable processing or “plugin” logic, is implemented using the flow callback class. At different points in notification message processing, flow callback classes define entry_points that match that point in processing. for for every such point in the processing, there is a list of flow callback routines to call.

FlowCallback Reference

the classSpec is similar to an import statement from python. It uses the python search path, and also includes ~/.config/sr3/plugins. There is some shorthand to make usage shorter for common cases. for example:

callback log

Sarracenia will first attempt, to prepend log with sarracenia.flowcb.log and then instantiate the callback instance as an item of class sarracenia.flowcb.Log. If it does not find such a class, then it will attempt to find a class name log, and instantiate an object log.Log.

More detail here FlowCallback load_library

callback_prepend <classSpec>

identical to callback, but meant to specify functions to be executed early, that is prepended to the list of plugins to run.

dangerWillRobinson (default: omitted)

This option is only recognized as a command line option. It is specified when an operation is expected to have irreversibly destructive or perhaps unexpected effects. for example:

sr3 stop

will stop running components, but not those that are being run in the foreground. Stopping those may be surprising to the analysts that will be looking at them, so that is not done by default:

sr3 --dangerWillRobinson stop

stops stops all components, including the foreground ones. Another example would be the cleanup action. This option deletes queues and exchanges related to a configuration, which can be destructive to flows. By default, cleanup only operates on a single configuration at a time. One can specify this option to wreak greater havoc.

declare

env NAME=Value

On can also reference environment variables in configuration files, using the ${ENV} syntax. If Sarracenia routines needs to make use of an environment variable, then they can be set in configuration files:

declare env HTTP_PROXY=localhost
exchange exchange_name

using the admin url, declare the exchange with exchange_name

subscriber

A subscriber is user that can only subscribe to data and return report notification messages. Subscribers are not permitted to inject data. Each subscriber has an xs_<user> named exchange on the pump, where if a user is named Acme, the corresponding exchange will be xs_Acme. This exchange is where an subscribe process will send its report notification messages.

By convention/default, the anonymous user is created on all pumps to permit subscription without a specific account.

source

A user permitted to subscribe or originate data. A source does not necessarily represent one person or type of data, but rather an organization responsible for the data produced. So if an organization gathers and makes available ten kinds of data with a single contact email or phone number for questions about the data and its availability, then all of those collection activities might use a single ‘source’ account.

Each source gets a xs_<user> exchange for injection of data notification messages, and, similar to a subscriber to send report notification messages about processing and receipt of data. Source may also have an xl_<user> exchange where, as per report routing configurations, report notification messages of consumers will be sent.

feeder

A user permitted to write to any exchange. Sort of an administrative flow user, meant to pump notification messages when no ordinary source or subscriber is appropriate to do so. Is to be used in preference to administrator accounts to run flows.

User credentials are placed in the credentials.conf file, and sr3 –users declare will update the broker to accept what is specified in that file, as long as the admin password is already correct.

debug

Setting option debug is identical to use logLevel debug

delete <boolean> (default: off)

When the delete option is set, after a download has completed successfully, the subscriber will delete the file at the upstream source. Default is false.

discard <boolean> (default: off)

The discard option,if set to true, deletes the file once downloaded. This option can be useful when debugging or testing a configuration.

directory <path> (default: .)

The directory option defines where to put the files on your server. Combined with accept / reject options, the user can select the files of interest and their directories of residence (see the mirror option for more directory settings).

The accept and reject options use regular expressions (regexp) to match URL. These options are processed sequentially. The URL of a file that matches a reject pattern is never downloaded. One that matches an accept pattern is downloaded into the directory declared by the closest directory option above the matching accept option. acceptUnmatched is used to decide what to do when no reject or accept clauses matched.

ex.   directory /mylocaldirectory/myradars
      accept    .*RADAR.*

      directory /mylocaldirectory/mygribs
      reject    .*Reg.*
      accept    .*GRIB.*

destfn_script <script> (default:None)

This Sundew compatibility option defines a script to be run when everything is ready for the delivery of the product. The script receives the sender class instance. The script takes the parent as an argument, and for example, any modification to parent.msg.new_file will change the name of the file written locally.

download <flag> (default: True)

used to disable downloading in subscribe and/or sarra component. set False by default in shovel or winnow components.

dry_run <flag> (default: False)

Run in simulation mode with respect to file transfers. Still connects to a broker and downloads and processes messages, but transfers are disabled, for use when testing a sender, or a downloader, say to run in parallel with an existing one, and compare the logs to see if the sender is configured to send the same files as the old one (implemented with some other system.)

durable <flag> (default: True)

The AMQP durable option, on queue declarations. If set to True, the broker will preserve the queue across broker reboots. The queue will be written to and recovered from disk if the broker is restarted.

Note: only persistent messages will remain in a durable queue after a broker restart. Persistent messages can be published by enabling the persistent option (it is enabled by default).

fileEvents <event,event,…>

A comma separated list of file event types to monitor. Available file events: create, delete, link, modify, mkdir, rmdir to only add events to the current list start the event list with a plus sign (+). To remove them, prefix with a minus sign (-).

The create, modify, and delete events reflect what is expected: a file being created, modified, or deleted. If link is set, symbolic links will be posted as links so that consumers can choose how to process them. If it is not set, then no symbolic link events will ever be posted.

Note

move or rename events result in a special double post pattern, with one post as the old name and a field newname set, and a second post with the new name, and a field oldname set. This allows subscribers to perform an actual rename, and avoid triggering a download when possible.

FIXME: rename algorithm improved in v3 to avoid use of double post… just

exchange <name> (default: xpublic) and exchangeSuffix

The convention on data pumps is to use the xpublic exchange. Users can establish private data flow for their own processing. Users can declare their own exchanges that always begin with xs_<username>, so to save having to specify that each time, one can just set exchangeSuffix kk which will result in the exchange being set to xs_<username>_kk (overriding the xpublic default). These settings must appear in the configuration file before the corresponding topicPrefix and subtopic settings.

exchangeDeclare <flag>

On startup, by default, Sarracenia redeclares resources and bindings to ensure they are uptodate. If the exchange already exists, this flag can be set to False, so no attempt to exchange the queue is made, or it´s bindings. These options are useful on brokers that do not permit users to declare their exchanges.

expire <duration> (default: 5m == five minutes. RECOMMEND OVERRIDING)

The expire option is expressed as a duration… it sets how long should live a queue without connections.

A raw integer is expressed in seconds, if the suffix m,h,d,w are used, then the interval is in minutes, hours, days, or weeks. After the queue expires, the contents are dropped, and so gaps in the download data flow can arise. A value of 1d (day) or 1w (week) can be appropriate to avoid data loss. It depends on how long the subscriber is expected to shutdown, and not suffer data loss.

if no units are given, then a decimal number of seconds can be provided, such as to indicate 0.02 to specify a duration of 20 milliseconds.

The expire setting must be overridden for operational use. The default is set low because it defines how long resources on the broker will be assigned, and in early use (when default was 1 week) brokers would often get overloaded with very long queues for left-over experiments.

filename <keyword> (default:None)

From metpx-sundew, the support of this option give all sorts of possibilities for setting the remote filename. Some keywords are based on the fact that metpx-sundew filenames are five (to six) fields strings separated by for colons.

The default value on Sundew is NONESENDER, but in the interest of discouraging use of colon separation in files, the default in Sarracenia is WHATFN

The possible keywords are :

None

  • the filename is not modified at all. (different from NONE!) turn off any Sundew compatibility filename processing.

WHATFN

  • the first part of the Sundew filename (string before first :)

HEADFN

  • HEADER part of the sundew filename

SENDER

  • the Sundew filename may end with a string SENDER=<string> in this case the <string> will be the remote filename

NONE

  • deliver with the complete Sundew filename (without :SENDER=…)

NONESENDER

  • deliver with the complete Sundew filename (with :SENDER=…)

TIME

  • time stamp appended to filename. Example of use: WHATFN:TIME

DESTFN=str

  • direct filename declaration str

SATNET=1,2,3,A

  • cmc internal satnet application parameters

DESTFNSCRIPT=script.py

  • invoke a script (same as destfn_script) to generate the name of the file to write

flatten <string> (default: ‘/’)

The flatten option is use to set a separator character. The default value ( ‘/’ ) nullifies the effect of this option. This character replaces the ‘/’ in the url directory and create a “flatten” filename from its dd.weather.gc.ca path. For example retrieving the following url, with options:

http://dd.weather.gc.ca/model_gem_global/25km/grib2/lat_lon/12/015/CMC_glb_TMP_TGL_2_latlon.24x.24_2013121612_P015.grib2

  flatten   -
  directory /mylocaldirectory
  accept    .*model_gem_global.*

would result in the creation of the filepath:

/mylocaldirectory/model_gem_global-25km-grib2-lat_lon-12-015-CMC_glb_TMP_TGL_2_latlon.24x.24_2013121612_P015.grib2

flowMain (default: None)

By default, a flow will run the sarracenia.flow.Flow class, which implements the Flow algorithm generically. The generic version does no data transfer, only creating and manipulating messages. That is appropriate for shovel, winnow, post & watch components, but components that transfer or transform data need to define additional behaviour by sub-classing Flow. Examples: sarracenia.flow.sender, sarracenia.flow.poll, sarracenia.flow.subscribe.

The flowMain option allows a flow configuration to run a subclass of flow, instead of the default parent class. Example:

flowMain subscribe

In a generic flow configuration file will configure the flow to act as a subscriber component. One can create custom components by subclassing Flow and using the flowMain directive to have it invoked.

force_polling <flag> (default: False)

By default, watch selects an (OS dependent) optimal method to watch a directory.

For large trees, the optimal method can be manyfold (10x or even 100x) faster to recognize when a file has been modified. In some cases, however, platform optimal methods do not work (such as with some network shares, or distributed file systems), so one must use a slower but more reliable and portable polling method. The force_polling keyword causes watch to select the polling method in spite of the availability of a normally better one.

For a detailed discussion, see: Detecting File Changes

NOTE:

When directories are consumed by processes using the subscriber *delete* option, they stay empty, and
every file should be reported on every pass.  When subscribers do not use *delete*, watch needs to
know which files are new.  It does so by noting the time of the beginning of the last polling pass.
File are posted if their modification time is newer than that.  This will result in many multiple notification messages
by watch, which can be minimized with the use of cache.   One could even depend on the cache
entirely and turn on the *delete* option, which will have watch attempt to post the entire tree
every time (ignoring mtime).

**KNOWN LIMITATION**: When *force_polling* is set, the *sleep* setting should be
at least 5 seconds. It is not currently clear why.

header <name>=<value>

Add a <name> header with the given value to a notification message. Used to pass strings as metadata in the notification messages to improve decision making for consumers. Should be used sparingly. There are limits on how many headers can be used, and minimizing the size of messages has important performance impacts.

housekeeping <interval> (default: 300 seconds)

The housekeeping option sets how often to execute periodic processing as determined by the list of on_housekeeping plugins. By default, it prints a log message every houskeeping interval.

include config

include another configuration within this configuration.

inflight <string> (default: .tmp or NONE if post_broker set)

The inflight option sets how to ignore files when they are being transferred or (in mid-flight betweeen two systems). Incorrect setting of this option causes unreliable transfers, and care must be taken. See Delivery Completion for more details.

The value can be a file name suffix, which is appended to create a temporary name during the transfer. If inflight is set to ., then it is a prefix, to conform with the standard for “hidden” files on unix/linux. If inflight ends in / (example: tmp/ ), then it is a prefix, and specifies a sub-directory of the destination into which the file should be written while in flight.

Whether a prefix or suffix is specified, when the transfer is complete, the file is renamed to its permanent name to allow further processing.

When detecting a file with sr3_post, sr3_cpost, or watch, or poll, the inflight option can also be specified as a time interval, for example, 10 for 10 seconds. When set to a time interval, file posting process ensures that it waits until the file has not been modified in that interval. So a file will not be processed until it has stayed the same for at least 10 seconds. This is the same as setting the fileAgeMin setting.

Lastly, inflight can be set to NONE, which case the file is written directly with the final name, where the recipient will wait to receive a post notifying it of the file’s arrival. This is the fastest, lowest overhead option when it is available. It is also the default when a post_broker is given, indicating that some other process is to be notified after delivery.

NOTE:

When writing a file, if you see the error message::

    inflight setting: 300, not for downloads

It is because the time interval setting is only for reading files. The writer
cannot control how long a subsequent reader will wait to look at a file being
downloaded, so specifying a minimum modification time is inappropriate.
in looking at local files before generating a post, it is not used as say, a means
of delaying sending files.

inline <flag> (default: False)

When posting messages, The inline option is used to have the file content included in the post. This can be efficient when sending small files over high latency links, a number of round trips can be saved by avoiding the retrieval of the data using the URL. One should only inline relatively small files, so when inline is active, only files smaller than inlineByteMax bytes (default: 1024) will actually have their content included in the post messages. If inlineOnly is set, and a file is larger than inlineByteMax, the file will not be posted.

inlineByteMax <size>

The maximum size of messages to inline.

when inlining file content, what sort of encoding should be done? Three choices:

  • text: the file content is assumed to be utf-8 text and encoded as such.

  • binary: the file content is unconditionally converted to base64 binary encoding.

  • guess: try making text, if that fails fall back to binary.

inlineOnly

discard messages if the data is not inline.

inplace <flag> (default: On)

Large files may be sent as a series of parts, rather than all at once. When downloading, if inplace is true, these parts will be appended to the file in an orderly fashion. Each part, after it is inserted in the file, is announced to subscribers. This can be set to false for some deployments of sarracenia where one pump will only ever see a few parts, and not the entirety, of multi-part files.

The inplace option defaults to True. Depending of inplace and if the message was a part, the path can change again (adding a part suffix if necessary).

Instances

Sometimes one instance of a component and configuration is not enough to process & send all available notifications.

instances <integer> (default:1)

The instance option allows launching several instances of a component and configuration. When running sender for example, a number of runtime files are created. In the ~/.cache/sarra/sender/configName directory:

A .sender_configname.state         is created, containing the number instances.
A .sender_configname_$instance.pid is created, containing the PID  of $instance process.

In directory ~/.cache/sarra/log:

A .sender_configname_$instance.log  is created as a log of $instance process.

Note

While the brokers keep the queues available for some time, queues take resources on brokers, and are cleaned up from time to time. A queue which is not accessed and has too many (implementation defined) files queued will be destroyed. Processes which die should be restarted within a reasonable period of time to avoid loss of notifications. A queue which is not accessed for a long (implementation dependent) period will be destroyed.

identity <string>

All file notification messages include a checksum. It is placed in the amqp message header will have as an entry sum with default value ‘d,md5_checksum_on_data’. The sum option tell the program how to calculate the checksum. In v3, they are called Identity methods:

cod,x      - Calculate On Download applying x
sha512     - do SHA512 on file content  (default)
md5        - do md5sum on file content
md5name    - do md5sum checksum on filename
random     - invent a random value for each post.
arbitrary  - apply the literal fixed value.

v2 options are a comma separated string. Valid checksum flags are :

  • 0 : no checksum… value in post is a random integer (only for testing/debugging.)

  • d : do md5sum on file content

  • n : do md5sum checksum on filename

  • p : do SHA512 checksum on filename and partstr [1]

  • s : do SHA512 on file content (default)

  • z,a : calculate checksum value using algorithm a and assign after download.

logEvents ( default: after_accept,after_work,on_housekeeping )

The set of points during notification message processing to emit standard log messages. other values: on_start, on_stop, post, gather, … etc… It is comma separated, and if the list starts with a plus sign (+) then the selected events are appended to current value. A minus signe (-) can be used to remove events from the set.

logLevel ( default: info )

The level of logging as expressed by python’s logging. Possible values are : critical, error, info, warning, debug.

logMetrics ( default: False )

Write metrics to a daily metrics file for statistics gathering. can be used to generate statistics. File is in the same directory as the logs, and has a date suffix.

logReject ( default: False )

Normally, messages rejection is done silently. When logReject is True, a log message will be generated for each message rejected, and indicating the basis for the rejection.

logStdout ( default: False )

The logStdout disables log management. Best used on the command line, as there is some risk of creating stub files before the configurations are completely parsed:

sr3 --logStdout start

All launched processes inherit their file descriptors from the parent. so all output is like an interactive session.

This is in contrast to the normal case, where each instance takes care of its logs, rotating and purging periodically. In some cases, one wants to have other software take care of logs, such as in docker, where it is preferable for all logging to be to standard output.

It has not been measured, but there is a reasonable likelihood that use of logStdout with large configurations (dozens of configured instances/processes) will cause either corruption of logs, or limit the speed of execution of all processes writing to stdout.

logRotateCount <max_logs> ( default: 5 )

Maximum number of logs (both messages and metrics) archived.

logRotateInterval <interval>[<time_unit>] ( default: 1d )

The duration of the interval with an optional time unit (ie 5m, 2h, 3d) for rotation of logs and metrics.

messageCountMax <count> (default: 0)

If messageCountMax is greater than zero, the flow will exit after processing the given number of messages. This is normally used only for debugging.

messageRateMax <float> (default: 0)

if messageRateMax is greater than zero, the flow attempts to respect this delivery speed in terms of messages per second. Note that the throttle is on messages obtained or generated per second, prior to accept/reject filtering. the flow will sleep to limit the processing rate.

messageRateMin <float> (default: 0)

if messageRateMin is greater than zero, and the flow detected is lower than this rate, a warning message will be produced:

message_ttl <duration> (default: None)

The message_ttl option set the time a message can live in the queue. Past that time, the message is taken out of the queue by the broker.

mirror <flag> (default: off)

The mirror option can be used to mirror the dd.weather.gc.ca tree of the files. If set to True the directory given by the directory option will be the basename of a tree. Accepted files under that directory will be placed under the subdirectory tree leaf where it resides under dd.weather.gc.ca. For example retrieving the following url, with options:

http://dd.weather.gc.ca/radar/PRECIP/GIF/WGJ/201312141900_WGJ_PRECIP_SNOW.gif

  mirror    True
  directory /mylocaldirectory
  accept    .*RADAR.*

would result in the creation of the directories and the file /mylocaldirectory/radar/PRECIP/GIF/WGJ/201312141900_WGJ_PRECIP_SNOW.gif mirror settings can be changed between directory options.

no <count>

(normally not used by humans)

Present on instances started by the sr3 management interface. The no option is only used on the command line, and not intended for users. It is an option for use by sr3 when spawning instances to inform each process which instance it is. e.g instance 3 will be spawned with –no 3

nodupe_basis <data|name|path> (default: path)

A keyword option to identify which files are compared for duplicate suppression purposes. Normally, the duplicate suppression uses the entire path to identify files which have not changed. This allows for files with identical content to be posted in different directories and not be suppressed. In some cases, suppression of identical files should be done regardless of where in the tree the file resides. Set ‘name’ for files of identical name, but in different directories to be considered duplicates. Set to ‘data’ for any file, regardless of name, to be considered a duplicate if the checksum matches.

This is implemented as an alias for:

callback_prepend nodupe.name

or:

callback_prepend nodupe.data

More information: Duplicate Suppresion

fileAgeMax

If files are older than this setting (default: 7h in poll, 0 in other components), then ignore them, they are too old to post. 0 deactivates the setting.

In a Poll:

fileAgeMin

If files are newer than this setting (default: 0), then ignore them, they are too new to post. 0 deactivates the setting.

nodupe_ttl <off|on|999[smhdw]>

When nodupe_ttl (also suppress_duplicates*, and **cache ) is set to a non-zero time interval, each new message is compared against ones received within that interval, to see if it is a duplicate. Duplicates are not processed further. What is a duplicate? A file with the same name (including parts header) and checksum. Every hearbeat interval, a cleanup process looks for files in the cache that have not been referenced in cache seconds, and deletes them, in order to keep the cache size limited. Different settings are appropriate for different use cases.

A raw integer interval is in seconds, if the suffix m,h,d, or w are used, then the interval is in minutes, hours, days, or weeks. After the interval expires the contents are dropped, so duplicates separated by a large enough interval will get through. A value of 1d (day) or 1w (week) can be appropriate. Setting the option without specifying a time will result in 300 seconds (or 5 minutes) being the expiry interval.

Default value in a Poll is 8 hours, should be longer than nodupe_fileAgeMax to prevent re-ingesting files that have aged out of the duplicate suppression cache.

Use of the cache is incompatible with the default *parts 0* strategy, one must specify an alternate strategy. One must use either a fixed blocksize, or always never partition files. One must avoid the dynamic algorithm that will change the partition size used as a file grows.

Note that the duplicate suppresion store is local to each instance. When N instances share a queue, the first time a posting is received, it could be picked by one instance, and if a duplicate one is received it would likely be picked up by another instance. For effective duplicate suppression with instances, one must deploy two layers of subscribers. Use a first layer of subscribers (shovels) with duplicate suppression turned off and output with post_exchangeSplit, which route notification messages by checksum to a second layer of subscibers (winnow) whose duplicate suppression caches are active.

outlet post|json|url (default: post)

The outlet option is used to allow writing of notification messages to file instead of posting to a broker. The valid argument values are:

post:

post messages to an post_exchange

post_broker amqp{s}://<user>:<pw>@<brokerhost>[:port]/<vhost> post_exchange <name> (MANDATORY) post_topicPrefix <string> (default: “v03”) on_post <script> (default: None)

The post_broker defaults to the input broker if not provided. Just set it to another broker if you want to send the notifications elsewhere.

The post_exchange must be set by the user. This is the exchange under which the notifications will be posted.

json:

write each message (json/v03 encoded) to standard output.

url:

just output the retrieval URL to standard output.

FIXME: The outlet option came from the C implementation ( sr3_cpump ) and it has not been used much in the python implementation.

overwrite <flag> (default: off)

The overwrite option,if set to false, avoid unnecessary downloads under these conditions :

1- the file to be downloaded is already on the user’s file system at the right place and

2- the checksum of the amqp message matched the one of the file.

The default is False.

path <path>

post evaluates the filesystem path from the path option and possibly the post_baseDir if the option is used.

If a path defines a file then this file is watched.

If a path defines a directory then all files in that directory are watched…

This is also used to say which directories to look at for a poll

If this path defines a directory, all files in that directory are watched and should watch find one (or more) directory(ies), it watches it(them) recursively until all the tree is scanned.

The AMQP notification messages are made of the tree fields, the notification message time, the url option value and the resolved paths to which were withdrawn the post_baseDir present and needed.

permDefault, permDirDefault, permLog, permCopy

Permission bits on the destination files written are controlled by the permCopy directives. permCopy will apply the mode permissions posted by the source of the file. If no source mode is available, the permDefault will be applied to files, and the permLog will be applied to directories. If no default is specified, then the operating system defaults (on linux, controlled by umask settings) will determine file permissions. (Note that the chmod option is interpreted as a synonym for permDefault, and chmod_dir is a synonym for permDirDefault).

When set in a posting component, permCopy has the effect of including or excluding the mode header from the messages.

when set in a polling component, permDefault has the of setting minimum permissions for a file to be accepted. (on an ls output that looks like: —r—–, like a chmod 040 <file> command). The permDefault options specifies a mask, that is the permissions must be at least what is specified.

persistent <flag> (default: True)

The persistent option sets the delivery_mode for an AMQP message. When True, persistent messages will be published (delivery_mode=2), when False, transient (non-durable, delivery_mode=1) messages will be published.

Persistent messages are written to disk by the broker, and will survive a broker restart. Any transient messages in a queue will be lost when a broker is restarted. Note: persistent messages will only survive a broker restart when they reside in a durable queue. Non-durable queues, including all messages inside them, will be lost when a broker is restarted.

pollUrl <url>

Specification of a remote server resources to query with a poll See the POLLING in the Command Line Guide.

post_baseDir <path>

The post_baseDir option supplies the directory path that, when combined (or found) in the given path, gives the local absolute path to the data file to be posted. The post_baseDir part of the path will be removed from the posted notification message. For sftp urls it can be appropriate to specify a path relative to a user account. Example of that usage would be: –post_baseDir ~user –url sftp:user@host For file: url’s, baseDir is usually not appropriate. To post an absolute path, omit the –post_baseDir setting, and just specify the complete path as an argument.

post_baseUrl <url>

The post_baseUrl option sets how to get the file… it defines the protocol, host, port, and optionally, the user. It is best practice to not include passwords in urls.

post_broker <url>

the broker url to post messages to see broker for details

post_exchange <name> (default: xpublic)

The post_exchange option set under which exchange the new notification will be posted. when publishing to a pump as an administrator, a common choice for post_exchange is ‘xpublic’.

When publishing a product, a user can trigger a script, using flow callback entry_points such as after_accept, and after_work to modify messages generated about files prior to posting.

post_exchangeSplit <count> (default: 0)

The post_exchangeSplit option appends a two digit suffix resulting from hashing the last character of the checksum to the post_exchange name, in order to divide the output amongst a number of exchanges. This is currently used in high traffic pumps to allow multiple instances of winnow, which cannot be instanced in the normal way. Example:

post_exchangeSplit 5
post_exchange xwinnow

will result in posting messages to five exchanges named: xwinnow00, xwinnow01, xwinnow02, xwinnow03 and xwinnow04, where each exchange will receive only one fifth of the total flow.

post_format <name> (default: v03)

Sets the message format for posted messages. the currently included values are:

  • v02 … used by all existing data pumps for most cases.

  • v03 … default in sr3 JSON format easier to work with.

  • wis … a experimental geoJSON format in flux for the World Meteorological Organization

When provided, this value overrides whatever can be deduced from the post_topicPrefix.

post_on_start

When starting watch, one can either have the program post all the files in the directories watched or not. (not implemented in sr3_cpost)

post_topic <string>

Explicitly set a posting topic string, overriding the usual group of settings. For sarracenia data pumps, this should never be needed, as the use of post_exchange, post_topicPrefix, and relpath normally builds the right value for topics for both posting and binding.

post_topicPrefix (default: topicPrefix)

Prepended to the sub-topic to form a complete topic hierarchy. This option applies to publishing. Denotes the version of messages published in the sub-topics. (v03 refers to sr3_post.7.html) defaults to whatever was received.

prefetch <N> (default: 1)

The prefetch option sets the number of messages to fetch at one time. When multiple instances are running and prefetch is 4, each instance will obtain up to four messages at a time. To minimize the number of messages lost if an instance dies and have optimal load sharing, the prefetch should be set as low as possible. However, over long haul links, it is necessary to raise this number, to hide round-trip latency, so a setting of 10 or more may be needed.

queueName|queue|queue_name|qn

  • queueName <name>

By default, components create a queue name that should be unique. The default queue_name components create follows the following convention:

q_<brokerUser>.<programName>.<configName>.<random>.<random>

Where:

  • brokerUser is the username used to connect to the broker (often: anonymous )

  • programName is the component using the queue (e.g. subscribe ),

  • configName is the configuration file used to tune component behaviour.

  • random is just a series of characters chosen to avoid clashes from multiple people using the same configurations

Users can override the default provided that it starts with q_<brokerUser>.

When multiple instances are used, they will all use the same queue, for trivial multi-tasking. If multiple computers have a shared home file system, then the queue_name is written to:

~/.cache/sarra/<programName>/<configName>/<programName>_<configName>_<brokerUser>.qname

Instances started on any node with access to the same shared file will use the same queue. Some may want use the queue_name option as a more explicit method of sharing work across multiple nodes.

queueBind

On startup, by default, Sarracenia redeclares resources and bindings to ensure they are uptodate. If the queue already exists, These flags can be set to False, so no attempt to declare the queue is made, or it´s bindings. These options are useful on brokers that do not permit users to declare their queues.

queueDeclare

FIXME: same as above.. is this normal?

On startup, by default, Sarracenia redeclares resources and bindings to ensure they are uptodate. If the queue already exists, These flags can be set to False, so no attempt to declare the queue is made, or it´s bindings. These options are useful on brokers that do not permit users to declare their queues.

randomize <flag>

Active if -r|–randomize appears in the command line… or randomize is set to True in the configuration file used. If there are several notification messages because the file is posted by block (the blocksize option was set), the block notification messages are randomized meaning that they will not be posted

realpathAdjust <count> (Experimental) (default: 0)

The realpathAdjust option adjusts how much paths are resolved with the C standard realpath library routine. The count indicates how many path elements should be ignored, counting from the beginning of the path with positive numbers, or the end with negative ones. An adjustment of zero means to apply realpath to the entire path.

Implemented in C, but not python currently.

realpathFilter <flag> (Experimental)

the realpathFilter option resolves paths using the C standard realpath library routine, but only for the purpose of applying accept reject filters. This is used only during posting.

This option is being used to study some use cases, and may disappear in future.

Implemented in C, but not python currently.

realpathPost <flag> (Experimental)

The realpathPost option resolves paths given to their canonical ones, eliminating any indirection via symlinks. The behaviour improves the ability of watch to monitor trees, but the trees may have completely different paths than the arguments given. This option also enforces traversing of symbolic links.

This option is being used to investigate some use cases, and may disappear in future.

sendTo <url>

Specification of a remote resource to deliver to in a sender.

rename <path>

With the rename option, the user can suggest a destination path for its files. If the given path ends with ‘/’ it suggests a directory path… If it doesn’t, the option specifies a file renaming. Often used with variable substitutions, to provide dynamic, patterned names.

report and report_exchange

NOTE: NOT IMPLEMENTEDin sr3, expected to return in future version For each download, by default, an amqp report message is sent back to the broker. This is done with option :

  • report <flag> (default: True)

  • report_exchange <report_exchangename> (default: xreport|xs_*username* )

When a report is generated, it is sent to the configured report_exchange. Administrative components post directly to xreport, whereas user components post to their own exchanges (xs_*username*). The report daemons then copy the messages to xreport after validation.

These reports are used for delivery tuning and for data sources to generate statistical information. Set this option to False, to prevent generation of reports.

reset <flag> (default: False)

When reset is set, and a component is (re)started, its queue is deleted (if it already exists) and recreated according to the component’s queue options. This is when a broker option is modified, as the broker will refuse access to a queue declared with options that differ from what was set at creation. It can also be used to discard a queue quickly when a receiver has been shut down for a long period. If duplicate suppression is active, then the reception cache is also discarded.

The AMQP protocol defines other queue options which are not exposed via sarracenia, because sarracenia itself picks appropriate values.

retryEmptyBeforeExit: <boolean> (default: False)

Used for sr_insects flow tests. Prevents Sarracenia from exiting while there are messages remaining in the retry queue(s). By default, a post will cleanly exit once it has created and attempted to publish messages for all files in the specified directory. If any messages are not successfully published, they will be saved to disk to retry later. If a post is only run once, as in the flow tests, these messages will never be retried unless retryEmptyBeforeExit is set to True.

retry_refilter <boolean> (default: False)

The retry_refilter option alters how messages are reloaded when they are retrieved from a retry queue. The default way (value: False) is to repeat the transfer using exactly the same message as before. If retry_refilter is set (value: True) then all the message’s calculated fields will be discarded, and the processing re-started from the gather phase (accept/reject processing will be repeated, destinations re-calculated.)

The normal retry behaviour is use when the remote has had a failure, and need to re-send later, while the retry_refilter option is used when recovering from configuration file errors, and some messages had incorrect selection or destination criteria.

retry_ttl <duration> (default: same as expire)

The retry_ttl (retry time to live) option indicates how long to keep trying to send a file before it is aged out of a the queue. Default is two days. If a file has not been transferred after two days of attempts, it is discarded.

sanity_log_dead <interval> (default: 1.5*housekeeping)

The sanity_log_dead option sets how long to consider too long before restarting a component.

scheduled_interval,scheduled_hour,scheduled_minute

When working with scheduled flows, such as polls, one can configure a duration (no units defaults to seconds, suffixes: m-minute, h-hour) at which to run a given activity:

scheduled_interval 30

run the flow or poll every 30 seconds. If no duration is set, then the flowcb.scheduled.Scheduled class will look for the other two time specifiers:

scheduled_hour 1,4,5,23
scheduled_minute 14,17,29

which will have the poll run each day at: 01:14, 01:17, 01:29, then the same minutes after each of 4h, 5h and 23h.

shim_defer_posting_to_exit (EXPERIMENTAL)

(option specific to libsrshim) Postpones file posting until the process exits. In cases where the same file is repeatedly opened and appended to, this setting can avoid redundant notification messages. (default: False)

shim_post_minterval interval (EXPERIMENTAL)

(option specific to libsrshim) If a file is opened for writing and closed multiple times within the interval, it will only be posted once. When a file is written to many times, particularly in a shell script, it makes for many notification messages, and shell script affects performance. subscribers will not be able to make copies quickly enough in any event, so there is little benefit, in say, 100 notification messages of the same file in the same second. It is wise set an upper limit on the frequency of posting a given file. (default: 5s) Note: if a file is still open, or has been closed after its previous post, then during process exit processing it will be posted again, even if the interval is not respected, in order to provide the most accurate final post.

shim_skip_parent_open_files (EXPERIMENTAL)

(option specific to libsrshim) The shim_skip_ppid_open_files option means that a process checks whether the parent process has the same file open, and does not post if that is the case. (default: True)

sleep <time>

The time to wait between generating events. When files are written frequently, it is counter productive to produce a post for every change, as it can produce a continuous stream of changes where the transfers cannot be done quickly enough to keep up. In such circumstances, one can group all changes made to a file in sleep time, and produce a single post.

When sleep is set > 0 for use with a poll it has the effect to setting scheduled_interval to that value for compatibility reasons. It is better for poll to use scheduled settings explicitly going forward.

statehost <False|True> ( default: False )

In large data centres, the home directory can be shared among thousands of nodes. Statehost adds the node name after the cache directory to make it unique to each node. So each node has it’s own statefiles and logs. example, on a node named goofy, ~/.cache/sarra/log/ becomes ~/.cache/sarra/goofy/log.

strip <count|regexp> (default: 0)

You can modify the relative mirrored directories with the strip option. If set to N (an integer) the first ‘N’ directories from the relative path are removed. For example:

http://dd.weather.gc.ca/radar/PRECIP/GIF/WGJ/201312141900_WGJ_PRECIP_SNOW.gif

  mirror    True
  strip     3
  directory /mylocaldirectory
  accept    .*RADAR.*

would result in the creation of the directories and the file /mylocaldirectory/WGJ/201312141900_WGJ_PRECIP_SNOW.gif when a regexp is provide in place of a number, it indicates a pattern to be removed from the relative path. For example if:

strip  .*?GIF/

Will also result in the file being placed the same location. Note that strip settings can be changed between directory options.

NOTE::

with strip, use of ? modifier (to prevent regular expression greediness ) is often helpful. It ensures the shortest match is used.

For example, given a file name: radar/PRECIP/GIF/WGJ/201312141900_WGJ_PRECIP_SNOW.GIF The expression: .*?GIF matches: radar/PRECIP/GIF whereas the expression: .*GIF matches the entire name.

sourceFromExchange <flag> (default: off)

The sourceFromExchange option is mainly for use by administrators. If messages received are posted directly from a source, the exchange used is ‘xs_<brokerSourceUsername>’. Such messages could be missing source and from_cluster headings, or a malicious user may set the values incorrectly. To protect against both problems, administrators should set the sourceFromExchange option.

When the option is set, values in the message for the source and from_cluster headers will then be overridden:

self.msg.headers['source']       = <brokerUser>
self.msg.headers['from_cluster'] = cluster

replacing any values present in the message. This setting should always be used when ingesting data from a user exchange. These fields are used to return reports to the origin of injected data. It is commonly combined with:

*mirror true*
*sourceFromExchange true*
*directory ${PBD}/${YYYYMMDD}/${SOURCE}*

To have data arrive in the standard format tree.

sourceFromMessage <flag> (default: off)

The sourceFromMessage option is mainly for use by administrators. Normally the source field from an inbound message is ignored. When this option is set, the field in the message is accepted and used for processing. (overrides source, and sourceFromExchange )

It defaults to off because malicious messages can misrepresent data origin. To be used only with flows of responsibly curated, trustable message flows.

subtopic <amqp pattern> (default: #)

Within an exchange’s postings, the subtopic setting narrows the product selection. To give a correct value to the subtopic, one has the choice of filtering using subtopic with only AMQP’s limited wildcarding and length limited to 255 encoded bytes, or the more powerful regular expression based accept/reject mechanisms described below. The difference being that the AMQP filtering is applied by the broker itself, saving the notices from being delivered to the client at all. The accept/reject patterns apply to messages sent by the broker to the subscriber. In other words, accept/reject are client side filters, whereas subtopic is server side filtering.

It is best practice to use server side filtering to reduce the number of notification messages sent to the client to a small superset of what is relevant, and perform only a fine-tuning with the client side mechanisms, saving bandwidth and processing for all.

topicPrefix is primarily of interest during protocol version transitions, where one wishes to specify a non-default protocol version of messages to subscribe to.

Usually, the user specifies one exchange, and several subtopic options. Subtopic is what is normally used to indicate messages of interest. To use the subtopic to filter the products, match the subtopic string with the relative path of the product.

For example, consuming from DD, to give a correct value to subtopic, one can browse the our website http://dd.weather.gc.ca and write down all directories of interest. For each directory tree of interest, write a subtopic option as follow:

subtopic directory1.*.subdirectory3.*.subdirectory5.#

where:
      *                matches a single directory name
      #                matches any remaining tree of directories.
note:

When directories have these wild-cards, or spaces in their names, they will be URL-encoded ( ‘#’ becomes %23 ) When directories have periods in their name, this will change the topic hierarchy.

FIXME:

hash marks are URL substituted, but did not see code for other values. Review whether asterisks in directory names in topics should be URL-encoded. Review whether periods in directory names in topics should be URL-encoded.

One can use multiple bindings to multiple exchanges as follows:

exchange A
subtopic directory1.*.directory2.#

exchange B
subtopic *.directory4.#

Will declare two separate bindings to two different exchanges, and two different file trees. While default binding is to bind to everything, some brokers might not permit clients to set bindings, or one might want to use existing bindings. One can turn off queue binding as follows:

subtopic None

(False, or off will also work.)

sundew_compat_regex_first_match_is_zero (default: off)

When numbering groups in match patterns, Sundew groups start from 0. Python regular expressions use the zeroth group to represent the entire string, and each match group starts from 1. It is considered less surprising to conform to Python conventions, but doing so unilaterally would break compatbility. So here is a switch to use when bridging between Sundew, sarra v2 and sr3. Eventually, this should always be off. Examples:

in contrast, to get the same result:

  • sundew_compat_regex_first_match_is_zero: False

  • directory setting: /tmp/meteocode/${3}/${1}/${2}

  • to get the same result.

folks who research python re will normally produce the latter version first.

timeCopy (default: on)

On unix-like systems, when the ls commend or a file browser shows modification or access times, it is a display of the posix st_atime, and st_ctime elements of a struct struct returned by stat(2) call. When timeCopy is on, headers reflecting these values in the messages are used to restore the access and modification times respectively on the subscriber system. To document delay in file reception, this option can be turned off, and then file times on source and destination compared.

When set in a posting component, it has the effect of eliding the atime and mtime headers from the messages.

topicCopy (default: off)

Setting topicCopy to true tells sarracenia pass topics through unaltered. Sarracenia has a convention for how topics for products should be organized. There is a topicPrefix, followed by subtopics derived from the relPath field of the message. Some networks may choose to use different topic conventions, external to sarracenia.

timeout <interval> (default: 0)

The timeout option, sets the number of seconds to wait before aborting a connection or download transfer (applied per buffer during transfer).

timezone <string> (default: UTC)

Interpret listings from an FTP server as being in the given timezone as per pytz Examples: Canada/Pacific, Pacific/Nauru, Canada/Eastern, Europe/Paris Has no effect other than in when polling an FTP server.

tlsRigour (default: medium)

tlsRigour can be set to: lax, medium, or strict, and gives a hint to the application of how to configure TLS connections. TLS, or Transport Level Security (used to be called Secure Socket Layer (SSL)) is the wrapping of normal TCP sockets in standard encryption. There are many aspects of TLS negotiations, hostname checking, Certificate checking, validation, choice of ciphers. What is considered secure evolves over time, so settings which, a few years ago, were considered secure, are currently aggressively deprecated. This situation naturally leads to difficulties in communication due to different levels of compliance with whatever is currently defined as rigourous encryption.

If a site being connected to, has, for example, and expired certificate, and it is nevertheless necessary to use it, then set tlsRigour to lax and the connection should succeed regardless.

topic <string>

Explicitly set a subscribing topic string, overriding the value usually derived from a group of settings. For sarracenia data pumps, this should never be needed, as the use of exchange, topicPrefix, and subtopic normally builds the right value.

topicPrefix (default: v03)

prepended to the sub-topic to form a complete topic hierarchy. This option applies to subscription bindings. Denotes the version of messages received in the sub-topics. (v03 refers to sr3_post.7.html)

users <flag> (default: false)

As an adjunct when the declare action is used, to ask sr3 to declare users on the broker, as well as queues and exchanges.

v2compatRenameDoublePost <flag> ( default: false)

version 3 of Sarracenia features improved logic around file renaming, using a single message per rename operation. Version 2 required two posts. When posting, in a mirroring situation, for consumption by v2 clients, this flag should be set.

varTimeOffset (default: 0)

For example:

varTimeOffset -7m

will cause variable substitions that involve the date/time substitutions. so in a pattern like ${YYYY}/${MM}/${DD} will be evaluated to be the date, evaluated seven minutes in the past.

vip - ACTIVE/PASSIVE OPTIONS

The vip option indicates that a configuration must be active on only a single node in a cluster at a time, a singleton. This is typically required for a poll component, but it can be used in senders or other cases.

subscribe can be used on a single server node, or multiple nodes could share responsibility. Some other, separately configured, high availability software presents a vip (virtual ip) on the active server. Should the server go down, the vip is moved on another server, and processing then happens using the new server that now has the vip active. Both servers would run an sr3 instance:

- **vip          <list>          []**

When you run only one sr3 instance on one server, these options are not set, and subscribe will run in ‘standalone mode’.

In the case of clustered brokers, you would set the options for the moving vip.

vip 153.14.126.3

When an sr3 instance does not find the vip, it sleeps for 5 seconds and retries. If it does, it consumes and processes a message and than rechecks for the vip. Multiple vips form a list, where any individual address being active is enough.

SEE ALSO

sr3(1) - Sarracenia main command line interface.

sr3_post(1) - post file notification messages (python implementation.)

sr3_cpost(1) - post file announcemensts (C implementation.)

sr3_cpump(1) - C implementation of the shovel component. (copy messages)

Formats:

sr3_post(7) - the format of notification messages.

Home Page:

https://metpx.github.io/sarracenia - Sarracenia: a real-time pub/sub data sharing management toolkit