log-module-commands.rst

Log module command

It is sometimes desired to better understand the module usage on the system we manage. Especially to determine what are the modulefiles most used and what are those never used that could be removed. This recipe describes a way to track the module usage by logging each request made.

Implementation

Logging module commands is implemented by the use of a site-specific configuration that traces every call to a modulefile evaluation.

.. literalinclude:: ../../example/log-module-commands/siteconfig.tcl
   :language: tcl
   :caption: siteconfig.tcl
   :lines: 26-54
   :lineno-start: 26

This code defines a logModfileInterp procedure which is set to be evaluated after each evaluation of the execute-modulefile procedure with the trace Tcl command. Thanks to the trace mechanism logModfileInterp receives the arguments passed to execute-modulefile.

The logModfileInterp procedure applies filter to only log load and unload modulefile evaluations. It may be extended to the other evaluation modes (help, display, test, whatis and refresh) by adapting the following line:

.. literalinclude:: ../../example/log-module-commands/siteconfig.tcl
   :language: tcl
   :lines: 36-37
   :lineno-start: 36

In the proposed code, log entries are formatted as a JSON record which is convenient to push these logs in a search and analytics engine like Elasticsearch or Splunk. Such tools help to globally monitor the whole set of log entries produced from thousands of computing nodes.

.. literalinclude:: ../../example/log-module-commands/siteconfig.tcl
   :language: tcl
   :lines: 47-49
   :lineno-start: 47

The :command:`logger` command is run to generate the log message. This is done through a specific execLogger procedure ensuring that the current user environment does not confuse :command:`logger` with unexpected version of the libraries it requires.

.. literalinclude:: ../../example/log-module-commands/siteconfig.tcl
   :language: tcl
   :lines: 13-24
   :lineno-start: 13

Example code also defines a logModuleCmd procedure which is set to be evaluated after each evaluation of the module and the ml procedures with trace Tcl command.

.. literalinclude:: ../../example/log-module-commands/siteconfig.tcl
   :language: tcl
   :caption: siteconfig.tcl
   :lines: 56-76
   :lineno-start: 56

Note

This code example may be extended to log for instance additional information in each message. The upvar Tcl command may be used to retrieve variables from the calling context. However beware that the internal code of Modules may change, so if you rely on internal variables please re-check the code in the :file:`siteconfig.tcl` file deployed after each upgrade of Modules.

Compatible with Modules v4.2+

Installation

Create site-specific configuration directory if it does not exist yet:

$ mkdir |etcdir|

Then copy there the site-specific configuration script of this recipe:

$ cp example/log-module-commands/siteconfig.tcl |etcdir|/

Note

Defined location for the site-specific configuration script may vary from one installation to another. To determine the expected location for this file on your setup, check the value of the siteconfig option on Modules version 4.3 or above:

:ps:`$` module config siteconfig

On older version of Modules, check the modulecmd.tcl script:

:ps:`$` grep '^set g_siteconfig ' $MODULES_CMD

Usage example

Listing available modulefiles, then loading a bare modulefile, then another one with a dependency and purging everything in the end:

:ps:`$` ml av
--------------- :sgrdi:`/path/to/modulefiles` ---------------
bar/1.0  foo/1.0  qux/1.0
:ps:`$` ml foo
:ps:`$` module load bar
Loading :sgrhi:`bar/1.0`
  :sgrin:`Loading requirement`: qux/1.0
:ps:`$` module purge

A log entry can then be retrieved from system log files:

:ps:`$` journalctl -q -t module
Sep 12 20:24:01 hostname module[9925]: { "user": "username", "cmd": "ml", "args": "av" }
Sep 12 20:24:02 hostname module[9925]: { "user": "username", "mode": "load", "module": "foo/1.0", "auto": false }
Sep 12 20:24:02 hostname module[9925]: { "user": "username", "cmd": "ml", "args": "foo" }
Sep 12 20:24:03 hostname module[9925]: { "user": "username", "mode": "load", "module": "qux/1.0", "auto": true }
Sep 12 20:24:03 hostname module[9925]: { "user": "username", "mode": "load", "module": "bar/1.0", "auto": false }
Sep 12 20:24:03 hostname module[9925]: { "user": "username", "cmd": "module", "args": "load bar" }
Sep 12 20:24:04 hostname module[9925]: { "user": "username", "mode": "unload", "module": "bar/1.0" }
Sep 12 20:24:04 hostname module[9925]: { "user": "username", "mode": "unload", "module": "qux/1.0" }
Sep 12 20:24:04 hostname module[9925]: { "user": "username", "mode": "unload", "module": "foo/1.0" }
Sep 12 20:24:04 hostname module[9925]: { "user": "username", "cmd": "module", "args": "purge" }