Delivery Completion (inflight)
Failing to properly set file completion protocols is a common source of intermittent and difficult-to-diagnose file transfer issues. For reliable file transfers, it is critical that both the sender and receiver agree on how to represent a file that isn’t complete. The inflight option (meaning a file is in flight between the sender and the receiver) supports many protocols appropriate for different situations:
Inflight Table
Delivery Completion Protocols (in Order of Preference) |
||
|---|---|---|
Method |
Description |
Application |
NONE |
File sent with right name. Send sr3_post(7) by AMQP after file is complete.
|
Sending to Sarracenia, and post only when file is complete (Best when available)
|
.tmp (Suffix) |
Files transferred with a .tmp suffix. When complete, renamed without suffix. Actual suffix is settable.
|
sending to most other systems (.tmp support built-in) Use to send to Sundew |
tmp/ (subdir) /dir |
Files transferred to a subdir or dir When complete, renamed to parent dir. Actual subdir is settable. same performance as Suffix method. |
sending to some other systems |
. (Prefix) |
Use Linux convention to hide files. Prefix names with ‘.’ that need that. (compatibility) same performance as Suffix method. |
Sending to systems that do not support suffix. |
number (mtime) fileAgeMin |
Minimum age (modification time) of the file before it is considered complete. Adds delay in every transfer. Vulnerable to network failures. Vulnerable to clock skew. |
Last choice guaranteed delay added Receiving from uncooperative sources. (ok choice with PDS) |
By default ( when no inflight option is given ), if the post_broker is set, then a value of NONE is used because it is assumed that it is delivering to another broker. If no post_broker is set, the value of ‘.tmp’ is assumed as the best option.
NOTES:
On versions of sr_sender prior to 2.18, the default was NONE, but was documented as ‘.tmp’ To ensure compatibility with later versions, it is likely better to explicitly write the inflight setting. The numeric variant is the same as setting fileAgeMin
inflight was renamed from the old lock option in January 2017. For compatibility with older versions, can use lock, but name is deprecated.
The old PDS software (which predates MetPX Sundew) only supports FTP. The completion protocol used by PDS was to send the file with permission 000 initially, and then chmod it to a readable file. This cannot be implemented with SFTP protocol, and is not supported at all by Sarracenia.
Frequent Configuration Errors
Setting NONE when sending to Sundew.
The proper setting here is ‘.tmp’. Without it, almost all files will get through correctly, but incomplete files will occasionally picked up by Sundew.
Using mtime method to receive from Sundew or Sarracenia:
Using mtime is last resort. This approach injects delay and should only be used when one has no influence to have the other end of the transfer use a better method.
mtime is vulnerable to systems whose clocks differ (causing incomplete files to be picked up.)
mtime is vulnerable to slow transfers, where incomplete files can be picked up because of a networking issue interrupting or delaying transfers.
Sources may not to include mtime data in their posts ( timeCopy option on post.)
Setting NONE when delivering to non-Sarracenia destination.
NONE is to be used when there is some other means to figure out if a file is delivered. For example, when sending to another pump, the sender will post the notification message to the destination after the file is complete, so there is no danger of it being picked up early.
When used inappropriately, there will occasionally be incomplete files delivered.