NAME

       collectd-exec - Documentation of collectd's "exec plugin"

SYNOPSIS

         # See collectd.conf(5)
         LoadPlugin exec
         # ...
         <Plugin exec>
           Exec "myuser:mygroup" "myprog"
           Exec "otheruser" "/path/to/another/binary" "arg0" "arg1"
           NotificationExec "user" "/usr/lib/collectd/exec/handle_notification"
         </Plugin>

DESCRIPTION

       The "exec plugin" forks of an executable either to receive values or to dispatch
       notifications to the outside world. The syntax of the configuration is explained in
       collectd.conf(5) but summarized in the above synopsis.

       If you want/need better performance or more functionality you should take a long look at
       the "perl plugin", collectd-perl(5).

EXECUTABLE TYPES

       There are currently two types of executables that can be executed by the "exec plugin":

       "Exec"
           These programs are forked and values that it writes to "STDOUT" are read back.  The
           executable is forked in a fashion similar to init: It is forked once and not again
           until it exits. If it exited, it will be forked again after at most Interval seconds.
           It is perfectly legal for the executable to run for a long time and continuously write
           values to "STDOUT".

           See "EXEC DATA FORMAT" below for a description of the output format expected from
           these programs.

           Warning: If the executable only writes one value and then exits I will be executed
           every Interval seconds. If Interval is short (the default is 10 seconds) this may
           result in serious system load.

       "NotificationExec"
           The program is forked once for each notification that is handled by the daemon.  The
           notification is passed to the program on "STDIN" in a fashion similar to HTTP-headers.
           In contrast to programs specified with "Exec" the execution of this program is not
           serialized, so that several instances of this program may run at once if multiple
           notifications are received.

           See "NOTIFICATION DATA FORMAT" below for a description of the data passed to these
           programs.

EXEC DATA FORMAT

       The forked executable is expected to print values to "STDOUT". The expected format is as
       follows:

       Comments
           Each line beginning with a "#" (hash mark) is ignored.

       PUTVAL Identifier [OptionList] Valuelist
           Submits one or more values (identified by Identifier, see below) to the daemon which
           will dispatch it to all it's write-plugins.

           An Identifier is of the form "host/plugin-instance/type-instance" with both
           instance-parts being optional. If they're omitted the hyphen must be omitted, too.
           plugin and each instance-part may be chosen freely as long as the tuple (plugin,
           plugin instance, type instance) uniquely identifies the plugin within collectd. type
           identifies the type and number of values (i. e. data-set) passed to collectd. A large
           list of predefined data-sets is available in the types.db file. See types.db(5) for a
           description of the format of this file.

           The OptionList is an optional list of Options, where each option is a key-value-pair.
           A list of currently understood options can be found below, all other options will be
           ignored. Values that contain spaces must be quoted with double quotes.

           Valuelist is a colon-separated list of the time and the values, each either an integer
           if the data-source is a counter, or a double if the data-source is of type "gauge".
           You can submit an undefined gauge-value by using U. When submitting U to a counter the
           behavior is undefined. The time is given as epoch (i. e. standard UNIX time).

           You can mix options and values, but the order is important: Options only effect
           following values, so specifying an option as last field is allowed, but useless. Also,
           an option applies to all following values, so you don't need to re-set an option over
           and over again.

           The currently defined Options are:

           interval=seconds
               Gives the interval in which the data identified by Identifier is being collected.

           Please note that this is the same format as used in the unixsock plugin, see
           collectd-unixsock(5). There's also a bit more information on identifiers in case
           you're confused.

           Since examples usually let one understand a lot better, here are some:

             PUTVAL leeloo/cpu-0/cpu-idle N:2299366
             PUTVAL alice/interface/if_octets-eth0 interval=10 1180647081:421465:479194

       PUTNOTIF [OptionList] message=Message
           Submits a notification to the daemon which will then dispatch it to all plugins which
           have registered for receiving notifications.

           The PUTNOTIF if followed by a list of options which further describe the notification.
           The message option is special in that it will consume the rest of the line as its
           value. The message, severity, and time options are mandatory.

           Valid options are:

           message=Message (REQUIRED)
               Sets the message of the notification. This is the message that will be made
               accessible to the user, so it should contain some useful information. As with all
               options: If the message includes spaces, it must be quoted with double quotes.
               This option is mandatory.

           severity=failure|warning|okay (REQUIRED)
               Sets the severity of the notification. This option is mandatory.

           time=Time (REQUIRED)
               Sets the time of the notification. The time is given as "epoch", i. e. as seconds
               since January 1st, 1970, 00:00:00. This option is mandatory.

           host=Hostname
           plugin=Plugin
           plugin_instance=Plugin-Instance
           type=Type
           type_instance=Type-Instance
               These "associative" options establish a relation between this notification and
               collected performance data. This connection is purely informal, i. e. the daemon
               itself doesn't do anything with this information. However, websites or GUIs may
               use this information to place notifications near the affected graph or table. All
               the options are optional, but plugin_instance without plugin or type_instance
               without type doesn't make much sense and should be avoided.

       Please note that this is the same format as used in the unixsock plugin, see
       collectd-unixsock(5).

       When collectd exits it sends a SIGTERM to all still running child-processes upon which
       they have to quit.

NOTIFICATION DATA FORMAT

       The notification executables receive values rather than providing them. In fact, after the
       program is started "STDOUT" is connected to "/dev/null".

       The data is passed to the executables over "STDIN" in a format very similar to HTTP: At
       first there is a "header" with one line per field. Every line consists of a field name,
       ended by a colon, and the associated value until end-of-line.  The "header" is ended by
       two newlines immediately following another, i. e. an empty line. The rest, basically the
       "body", is the message of the notification.

       The following is an example notification passed to a program:

         Severity: FAILURE
         Time: 1200928930
         Host: myhost.mydomain.org
         \n
         This is a test notification to demonstrate the format

       The following header files are currently used. Please note, however, that you should
       ignore unknown header files to be as forward-compatible as possible.

       Severity
           Severity of the notification. May either be FAILURE, WARNING, or OKAY.

       Time
           The time in epoch, i. e. as seconds since 1970-01-01 00:00:00 UTC.

       Host
       Plugin
       PluginInstance
       Type
       TypeInstance
           Identification of the performance data this notification is associated with.  All of
           these fields are optional because notifications do not need to be associated with a
           certain value.

ENVIRONMENT

       The following environment variables are set by the plugin before calling exec:

       COLLECTD_INTERVAL
           Value of the global interval setting.

       COLLECTD_HOSTNAME
           Hostname used by collectd to dispatch local values.

USING NAGIOS PLUGINS

       Though the interface is far from perfect, there are tons of plugins for Nagios.  You can
       use these plugins with collectd by using a simple transition layer, "exec-nagios.px",
       which is shipped with the collectd distribution in the "contrib/" directory. It is a
       simple Perl script that comes with embedded documentation. To see it, run the following
       command:

         perldoc exec-nagios.px

       This script expects a configuration file, "exec-nagios.conf". You can find an example in
       the "contrib/" directory, too.

       Even a simple mechanism to submit "performance data" to collectd is implemented. If you
       need a more sophisticated setup, please rewrite the plugin to make use of collectd's more
       powerful interface.

CAVEATS

       •   The user, the binary is executed as, may not have root privileges, i. e.  must have an
           UID that is non-zero. This is for your own good.

       •   Early versions of the plugin did not use a command but treated all lines as if they
           were arguments to the PUTVAL command. When the PUTNOTIF command was implemented, this
           behavior was kept for lines which start with an unknown command for backwards
           compatibility. This compatibility code has been removed in collectd 5.

SEE ALSO

       collectd(1), collectd.conf(5), collectd-perl(5), collectd-unixsock(5), fork(2), exec(3)

AUTHOR

       Florian Forster <octo@verplant.org>