universalCallbacks

Overview

Universal callbacks are operations which are automatically attached to every job that is submitted. These are installed by a site administrator either on the Supervisor's local disk or on a file system which is accessible by the supervisor service.

Setting Up Universal Callbacks

To set up Universal Callbacks, the site administrator needs to make a directory (default $QBDIR/callback) and create a text-based configuration file, called "callbacks.conf" in that directory. Further, in the same directory, files containing the implementation (aka "code") of each Universal Callback must also be installed.

The callbacks.conf file serves as a map that tells the system which callback code should be triggered to run on what events.

The "callbacks.conf" file

The callbacks.conf file is a text file, much like qb.conf, containing one or more lines with a "key = value" pair, associating each implementation file to a trigger event. The syntax is:

The filename points to a file in the same directory that implements the callback code. Note that Universal Callbacks support Python, Perl, and Qube callbacks, and the filename must have the extension .py, .pl, or .qcb, respectively.

The trigger specifies the triggering event that activates the callback, described in details at Triggers

Here's an example:

In this example, there are presumably 4 implementation files in the callback directory, logFailuresToDB.py, mail-status.qcb, submitted.py, and checkWork.pl, that have the implementation code in them.

Use Popen.subprocess in callbacks

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If you ever need to run an external script in a callback, we recommend the use of Popen.subprocess() to run the external script inside the callback. This returns immediately and allows the callback to continue running, rather than blocking and waiting for the external script to complete; otherwise the supervisor process is tied up for the duration of the external script's execution.

Do not use os.system() to run the external script, as this call will block until the external script exits. When a large number of callbacks tie up supervisor processes at the same time, your supervisor performance will suffer.

Never use sys.exit() in a callback

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Do not call sys.exit() at the end of the callback code, this kills the calling supervisor process.

submitted.py