collectd-exec - Documentation of collectd's
# See collectd.conf(5)
Exec "myuser:mygroup" "myprog"
Exec "otheruser" "/path/to/another/binary" "arg0" "arg1"
NotificationExec "user" "/usr/lib/collectd/exec/handle_notification"
exec plugin forks off 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).
There are currently two types of executables that can be executed by the
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
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 it will be
executed every Interval seconds. If Interval is short (the default is 10
seconds) this may result in serious system load.
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
The forked executable is expected to print values to
STDOUT. The expected
format is as follows:
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
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) or N to use the current 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:
Gives the interval in which the data identified by Identifier is being
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
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.
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
Sets user defined meta information. The type key is a single character
defining the type of the meta information.
The current supported types are:
- s A string passed as-is.
Please note that this is the same format as used in the unixsock plugin, see
When collectd exits it sends a SIGTERM to all still running
child-processes upon which they have to quit.
The notification executables receive values rather than providing them. In
fact, after the program is started
STDOUT is connected to
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
The following is an example notification passed to a program:
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 of the notification. May either be FAILURE, WARNING, or OKAY.
The time in epoch, i.e. as seconds since 1970-01-01 00:00:00 UTC. The value
currently has millisecond precision (i.e. three decimal places), but scripts
should accept arbitrary numbers of decimal places, including no decimal places.
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.
The following environment variables are set by the plugin before calling
Value of the global interval setting.
Hostname used by collectd to dispatch local values.
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:
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.
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.
Florian Forster <firstname.lastname@example.org>