Nagios Gearman Module
=====================

What is Mod-Gearman
-------------------

http://labs.consol.de/nagios/mod-gearman[Mod_Gearman] is an easy way
of distributing active Nagios checks across your network and
increasing Nagios scalability. Mod-Gearman can even help to reduce the
load on a single Nagios host, because its much smaller and more
efficient in executing checks.

It consists of three parts:

 * There is a NEB module which resides in the Nagios core and adds servicechecks,
   hostchecks and eventhandler to a Gearman queue.
 * The counterpart is one or more worker clients executing the checks.
   Worker can be configured to only run checks for specific host- or
   servicegroups.
 * And you need at least one http://gearman.org[Gearman Job Server]
   running.
 * See the <<_common_scenarios,common scenarios>> for some examples.


Presentations
-------------

 * http://mod-gearman.org/slides/Mod-Gearman-2012-10-18.pdf[Monitoring Conference 2012 in Nürnberg]
 * http://mod-gearman.org/slides/Mod-Gearman-2011-05-24.pdf[Nagios Workshop 2011 in Hannover]


Features
--------
 * Reduce load of your central Nagios machine
 * Make Nagios scalable up to thousands of checks per second
 * Easy distributed setups without configuration overhead
 * Real loadbalancing across all workers
 * Real failover for redundant workers
 * Embedded Perl support for very fast execution of perl scripts
 * Fast transport of passive check results with included tools like
   send_gearman and send_multi


Download
--------
 * Latest stable http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.4.2.tar.gz[version 1.4.2], released January 10 2013
 * Mod Gearman is available for download at: http://mod-gearman.org/download.html
 * Source is available on GitHub: http://github.com/sni/mod_gearman
 * Older versions are available in the <<_archive,download archive>>.
 * Mod-Gearman is also included in http://omdistro.org[OMD].
 * Debian users should use the http://packages.debian.org/source/wheezy/mod-gearman[official packages]
 * SLES/RHEL/Centos users should use the http://mod-gearman.org/download/[prebuild packages]
 * Debian/Ubuntu users might also want to check out the http://mod-gearman.org/download/[unoffical packages]



Support
-------
 * Professional support and consulting is available via http://www.consol.de/open-source-monitoring/support/[www.consol.de]
 * https://groups.google.com/group/mod_gearman[google groups mailinglist]
 * http://www.monitoring-portal.org[german monitoring portal]
 * Mod-Gearman has been succesfully tested with latest Nagios.
   See <<_supported_dependencies,Supported Dependencies>> for details.
 * There are no known bugs at the moment. Let me know if you find one.


Changelog
---------
The changelog is available on
https://github.com/sni/mod_gearman/blob/master/Changes[github].


How does it work
----------------
When the Mod-Gearman broker module is loaded, it intercepts all
servicechecks, hostchecks and the eventhandler events. Eventhandler
are then sent to a generic 'eventhandler' queue. Checks for hosts
which are in one of the specified hostgroups, are sent into a seperate
hostgroup queue. All non matching hosts are sent to a generic 'hosts'
queue.  Checks for services are first checked against the list of
servicegroups, then against the hostgroups and if none matches they
will be sent into a generic 'service' queue. The NEB module starts a
single thread, which monitors the 'check_results' where all results
come in.

++++
<a title="mod gearman architecture" rel="lightbox[mod_gm]" href="http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-e1284455350110.png"><img src="http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-e1284455350110.png" alt="mod_gearman architecture" width="480" height="300" style="float:none" /></a>
++++

A simple example queue would look like:

----
+---------------+------------------+--------------+--------------+
| Queue Name    | Worker Available | Jobs Waiting | Jobs Running |
+---------------+------------------+--------------+--------------+
| check_results | 1                | 0            | 0            |
| eventhandler  | 50               | 0            | 0            |
| host          | 50               | 0            | 1            |
| service       | 50               | 0            | 13           |
+---------------+------------------+--------------+--------------+
----

There is one queue for the results and two for the checks plus the
eventhandler queue.

The workflow is simple:

 1. Nagios wants to execute a service check.
 2. The check is intercepted by the Mod-Gearman neb module.
 3. Mod-Gearman puts the job into the 'service' queue.
 4. A worker grabs the job and puts back the result into the
    'check_results' queue
 5. Mod-Gearman grabs the result job and puts back the result onto the
    check result list
 6. The Nagios reaper reads all checks from the result list and
    updates hosts and services


You can set some host or servicegroups for special worker. This
example uses a seperate hostgroup for Japan and a seperate
servicegroup for resource intensive selenium checks.

It would look like this:

----
+-----------------------+------------------+--------------+--------------+
| Queue Name            | Worker Available | Jobs Waiting | Jobs Running |
+-----------------------+------------------+--------------+--------------+
| check_results         | 1                | 0            | 0            |
| eventhandler          | 50               | 0            | 0            |
| host                  | 50               | 0            | 1            |
| hostgroup_japan       | 3                | 1            | 3            |
| service               | 50               | 0            | 13           |
| servicegroup_selenium | 2                | 0            | 2            |
+-----------------------+------------------+--------------+--------------+
----

You still have the generic queues and in addition there are two queues
for the specific groups.


The worker processes will take jobs from the queues and put the result
back into the check_result queue which will then be taken back by the
neb module and put back into the Nagios core. A worker can work on one
or more queues. So you could start a worker which only handles the
'hostgroup_japan' group.  One worker for the 'selenium' checks and one
worker which covers the other queues. There can be more than one
worker on each queue to share the load.

++++
<a title="mod gearman queues" rel="lightbox[mod_gm]" href="http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman_queues.png"><img src="http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman_queues.png" alt="mod_gearman architecture " width="360" height="270" style="float:none" /></a>
++++


Common Scenarios
----------------

Load Balancing
~~~~~~~~~~~~~~

++++
<a title="Load Balancing" rel="lightbox[mod_gm]"
href="http://labs.consol.de/wp-content/uploads/2010/09/sample_load_balancing.png"><img
src="http://labs.consol.de/wp-content/uploads/2010/09/sample_load_balancing.png"
alt="Load Balancing" width="300" height="125" style="float:none" /></a>
++++

The easiest variant is a simple load balancing. For example if your
single Nagios box just cannot handle the load, you could just add a
worker in the same network (or even on the same host) to reduce your
load on the Nagios box. Therefor we just enable hosts, services and
eventhandler on the server and the worker.

Pro:

 * reduced load on your monitoring box

Contra:

 * no failover



Distributed Monitoring
~~~~~~~~~~~~~~~~~~~~~~

++++
<a title="Distributed Monitoring" rel="lightbox[mod_gm]" href="http://labs.consol.de/wp-content/uploads/2010/09/sample_distributed.png"><img src="http://labs.consol.de/wp-content/uploads/2010/09/sample_distributed.png" alt="Distributed Monitoring" width="350" height="125" style="float:none" /></a>
++++

If your checks have to be run from different network segments, then
you can use the hostgroups (or servicegroups) to define a hostgroup
for specific worker. The general hosts and services queue is disabled
for this worker and just the hosts and services from the given
hostgroup will be processed.

Pro:

 * reduced load on your monitoring box
 * ability to access remote networks

Contra:

 * no failover



Distributed Monitoring with Load Balancing
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

++++
<a title="Distributed Monitoring with Load Balancing" rel="lightbox[mod_gm]" href="http://labs.consol.de/wp-content/uploads/2010/09/sample_distributed_load_balanced.png"><img src="http://labs.consol.de/wp-content/uploads/2010/09/sample_distributed_load_balanced.png" alt="Distributed Monitoring with Load Balancing" width="350" height="225" style="float:none" /></a>
++++

Your distributed setup could easily be extended to a load balanced
setup with just adding more worker of the same config.

Pro:

 * reduced load on your monitoring box
 * ability to access remote networks
 * automatic failover and load balancing for worker

Contra:

 * no failover for the master



NSCA Replacement
~~~~~~~~~~~~~~~~

++++
<a title="NSCA Replacement" rel="lightbox[mod_gm]" href="http://labs.consol.de/wp-content/uploads/2010/09/nsca_replacement.png"><img src="http://labs.consol.de/wp-content/uploads/2010/09/nsca_replacement.png" alt="NSCA Replacement" width="300" height="220" style="float:none" /></a>
++++

If you just want to replace a current NSCA solution, you could load
the Mod-Gearman NEB module and disable all distribution features. You
still can receive passive results by the core send via
send_gearman / send_multi. Make sure you use the same encryption
settings like the neb module or your core won't be able to process the
results or use the 'accept_clear_results' option.

Pro:

 * easy to setup in existing environments



Distributed Setup With Remote Scheduler
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

++++
<a title="Distributed Setup With Remote Scheduler" rel="lightbox[mod_gm]" href="http://labs.consol.de/wp-content/uploads/2010/09/advanced_distributed.png"><img src="http://labs.consol.de/wp-content/uploads/2010/09/advanced_distributed.png" alt="Distributed Setup With Remote Scheduler" width="360" height="270" style="float:none" /></a>
++++

In case your network is unstable or you need a gui view from the
remote location or any other reason which makes a remote core
unavoidable you may want this setup. Thist setup consists of 2
independent Mod-Gearman setups and the slave worker just send their
results to the master via the 'dup_server' option. The master
objects configuration must contain all slave services and hosts.
The configuration sync is not part of Mod-Gearman.

Pro:

 * independent from network outtakes
 * local view

Contra:

 * more complex setup
 * requires configuration sync



Gearman Proxy
~~~~~~~~~~~~~

++++
<a title="Gearman Proxy" rel="lightbox[mod_gm]" href="http://labs.consol.de/wp-content/uploads/2010/09/gearman_proxy.png"><img src="http://labs.consol.de/wp-content/uploads/2010/09/gearman_proxy.png" alt="Gearman Proxy" width="360" height="270" style="float:none" /></a>
++++

Sometimes you may need to reverse the direction of the initial
connection attempt. Usually the worker and the neb module open the
initial connection so they need to access the gearmand port. In cases
where no direct connection is possible use ssh tunnel or the Gearman
proxy. The Gearman proxy just puts jobs from one gearmand into another
gearmand and vice versa.

Just copy the gearman_proxy.pl from the contrib or share directory and
adjust the first few lines to match you needs.

Pro:

 * changes direction of initial connection setup
 * buffers network outages

Contra:

 * two more daemon to monitor and maintain






Installation
------------

OMD
~~~

Using OMD is propably the easiest way of installing and using
Mod-Gearman. You just have to run 'omd config' or set Mod-Gearman
to 'on'.

OMD is available for Debian, Ubuntu, Centos/Redhat and SLES.

--------------------------------------
OMD[test]:~$ omd config set MOD_GEARMAN on
--------------------------------------

NOTE: Mod-Gearman is included in http://omdistro.org[OMD] since version 0.48.


Debian / Ubuntu
~~~~~~~~~~~~~~~
It is strongly recommended to use the
http://packages.debian.org/source/wheezy/mod-gearman[official
packages] or the http://mod-gearman.org/download/[unoffical packages] which
contains Debian Squeeze and various Ubuntu packages.



Centos/Redhat
~~~~~~~~~~~~~
The easy and proper way is to build RPM packages. The following steps
assume a Centos 5.7. Other releases may have different versions but
should behave similar.

NOTE: use the http://mod-gearman.org/download/[prebuild packages] if
available.

Build/install Gearmand rpms
--------------------------------------
#> yum install autoconf automake libtool boost141-devel boost141-program-options
#> cd /tmp
#> wget http://launchpad.net/gearmand/trunk/0.25/+download/gearmand-0.25.tar.gz
#> tar zxf gearmand-0.25.tar.gz
#> ln -s gearmand-0.25/support/gearmand.init /tmp/gearmand.init
#> vi gearmand-0.25/support/gearmand.spec
   change in line 9 and 25:
   Requires: sqlite, libevent >= 1.4, boost-program-options >=  1.39
   in
   Requires: sqlite, libevent >= 1.4, boost141-program-options >=  1.39
#> tar cfz gearmand-0.25.tar.gz gearmand-0.25
#> LIBRARY_PATH=/usr/lib64/boost141:/usr/lib/boost141 \
   LD_LIBRARY_PATH=/usr/lib64/boost141:/usr/lib/boost141 \
   CPATH=/usr/include/boost141 \
   rpmbuild -tb gearmand-0.25.tar.gz
#> yum --nogpgcheck install /usr/src/redhat/RPMS/*/gearmand*-0.25-1*.rpm
--------------------------------------

NOTE: The link to gearmand.init is a workaround, otherwise the build
will fail. It may not be necessary for future gearman versions.

Build/install Mod-Gearman rpms
--------------------------------------
#> wget http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.2.0.tar.gz
#> rpmbuild -tb mod_gearman-1.2.0.tar.gz
#> yum --nogpgcheck install /usr/src/redhat/RPMS/*/mod_gearman-1.2.0-1.*.rpm
--------------------------------------

Finally start and check your installation
--------------------------------------
#> /etc/init.d/gearmand start
#> /etc/init.d/mod_gearman_worker start
#> gearman_top
--------------------------------------


From Source
~~~~~~~~~~~

NOTE: source installation should be avoided if possible. Prebuild packages are way easier to maintain.

Pre Requirements:

 - gcc / g++
 - autoconf / automake / autoheader
 - libtool
 - libgearman (>= 0.14)


Download the tarball and perform the following steps:
--------------------------------------
#> ./configure
#> make
#> make install
--------------------------------------

Then add the mod_gearman.o to your Nagios installation and add a
broker line to your nagios.cfg:

--------------------------------------
broker_module=.../mod_gearman.o server=localhost:4730 eventhandler=yes services=yes hosts=yes
--------------------------------------

see <<_configuration,Configuration>> for details on all parameters


The next step is to start one or more worker. You may use the same
configuration file as for the neb module.

--------------------------------------
./mod_gearman_worker --server=localhost:4730 --services --hosts
--------------------------------------
or use the supplied init script.


NOTE: Make sure you have started your Gearmand job server. Usually
it can be started with

--------------------------------------
/usr/sbin/gearmand -t 10 -j 0
--------------------------------------

or a supplied init script (extras/gearmand-init). Command line
arguments have change in recent gearman versions and you now should
use something like:
--------------------------------------
/usr/sbin/gearmand --threads=10 --job-retries=0
--------------------------------------



Patch Nagios
^^^^^^^^^^^^

NOTE: The needed patch is already applied to Nagios 3.2.2. Use the patch if you
have an older version.

It is not possible to distribute eventhandler with Nagios versions
prior 3.2.2. Just apply the patch from the ./extras/patches directory
to your Nagios sources and build Nagios again if you want to use an
older version. You only need to replace the Nagios binary. Nothing
else has changed. If you plan to distribute only Host/Servicechecks,
no patch is needed.



Configuration
-------------

Nagios Core
~~~~~~~~~~~

A sample broker in your nagios.cfg could look like:

--------------------------------------
broker_module=/usr/local/share/nagios/mod_gearman.o keyfile=/usr/local/share/nagios/secret.txt server=localhost eventhandler=yes hosts=yes services=yes
--------------------------------------

See the following list for a detailed explanation of available
options:


Common Options
~~~~~~~~~~~~~~

Shared options for worker and the NEB module:

config::
    include config from this file. Options are the same as described here.
    'include' is an alias for 'config'.
+
=====
    config=/etc/nagios3/mod_gm_worker.conf
=====


debug::
    use debug to increase the verbosity of the module.
    Possible values are:
+
--
    * `0`   - only errors
    * `1-4` - debug verbosity
    * `5`   - trace and all gearman related logs are going to stdout
--
+
Default is 0.
+
====
    debug=1
====


logmode::
    set way of logging.
    Possible values are:
+
--
    * `automatic` - logfile when a logfile is specified. stdout when
                    no logfile is given.
                    stdout for tools.
    * `stdout`    - just print all messages to stdout
    * `syslog`    - use syslog for all log events
    * `file`      - use logfile
    * `core`      - use Nagios internal loging (not thread safe! Use
                    with care)
--
+
Default is automatic.
+
====
    logmode=automatic
====


logfile::
Path to the logfile.
+
====
    logfile=/path/to/log.file
====


server::
sets the address of your gearman job server. Can be specified
more than once to add more server. Mod-Gearman uses
the first server available.
+
====
    server=localhost:4730,remote_host:4730
====


eventhandler::
defines if the module should distribute execution of
eventhandlers.
+
====
    eventhandler=yes
====


services::
defines if the module should distribute execution of service checks.
+
====
    services=yes
====


hosts::
defines if the module should distribute execution of host checks.
+
====
    hosts=yes
====


hostgroups::
sets a list of hostgroups which will go into seperate queues.
+
====
    hostgroups=name1,name2,name3
====


servicegroups::
sets a list of servicegroups which will go into seperate queues.
+
====
    servicegroups=name1,name2,name3
====


encryption::
enables or disables encryption. It is strongly advised to not disable
encryption. Anybody will be able to inject packages to your worker. Encryption
is enabled by default and you have to explicitly disable it. When using
encryption, you will either have to specify a shared password with `key=...` or
a keyfile with `keyfile=...`.
Default is On.
+
====
    encryption=yes
====

key::
A shared password which will be used for encryption of data pakets. Should be at
least 8 bytes long. Maximum length is 32 characters.
+
====
    key=secret
====

keyfile::
The shared password will be read from this file. Use either key or keyfile.
Only the first 32 characters from the first line will be used.
Whitespace to the right will be trimmed.
+
====
    keyfile=/path/to/secret.file
====

use_uniq_jobs::
Using uniq keys prevents the gearman queues from filling up when there
is no worker. However, gearmand seems to have problems with the uniq
key and sometimes jobs get stuck in the queue. Set this option to 'off'
when you run into problems with stuck jobs but make sure your worker
are running.
Default is On.

+
====
    use_uniq_jobs=on
====



Server Options
~~~~~~~~~~~~~~

Additional options for the NEB module only:

localhostgroups::
sets a list of hostgroups which will not be executed by gearman. They are just
passed through.
+
====
    localhostgroups=name1,name2,name3
====


localservicegroups::
sets a list of servicegroups which will not be executed by gearman. They are
just passed through.
+
====
    localservicegroups=name1,name2,name3
====


queue_custom_variable::
Can be used to define the target queue by a custom variable in
addition to host/servicegroups. When set for ex. to 'WORKER' you then
could define a '_WORKER' custom variable for your hosts and services
to directly set the worker queue. The host queue is inherited unless
overwritten by a service custom variable. Set the value of your custom
variable to 'local' to bypass Mod-Gearman (Same behaviour as in
localhostgroups/localservicegroups).
+
====
    queue_custom_variable=WORKER
====



do_hostchecks::
Set this to 'no' if you want Mod-Gearman to only take care of
servicechecks. No hostchecks will be processed by Mod-Gearman. Use
this option to disable hostchecks and still have the possibility to
use hostgroups for easy configuration of your services.
If set to yes, you still have to define which hostchecks should be
processed by either using 'hosts' or the 'hostgroups' option.
Default: `yes`
+
====
    do_hostchecks=yes
====


result_workers::
Number of result worker threads. Usually one is enough. You may increase the
value if your result queue is not processed fast enough.
+
====
    result_workers=3
====


perfdata::
Defines if the module should distribute perfdata to gearman.
+
====
    perfdata=yes
====
NOTE: processing of perfdata is not part of mod_gearman. You will need
additional worker for handling performance data. For example:
http://www.pnp4nagios.org[PNP4Nagios]. Performance data is just
written to the gearman queue.


perfdata_mode::
    There will be only a single job for each host or servier when putting
    performance data onto the perfdata_queue in overwrite mode. In
    append mode perfdata will be stored as long as there is memory
    left. Setting this to 'overwrite' helps preventing the perf_data
    queue from getting to big. Monitor your perfdata carefully when
    using the 'append' mode.
    Possible values are:
+
--
    * `1` - overwrite
    * `2` - append
--
+
Default is 1.
+
====
    perfdata_mode=1
====


result_queue::
sets the result queue. Necessary when putting jobs from several Nagios instances
onto the same gearman queues. Default: `check_results`
+
====
    result_queue=check_results_nagios1
====


orphan_host_checks::
The Mod-Gearman NEB module will submit a fake result for orphaned host
checks with a message saying there is no worker running for this
queue. Use this option to get better reporting results, otherwise your
hosts will keep their last state as long as there is no worker
running.
Default is yes.
+
====
    orphan_host_checks=yes
====


orphan_service_checks::
Same like 'orphan_host_checks' but for services.
Default is yes.
+
====
    orphan_service_checks=yes
====


accept_clear_results::
When enabled, the NEB module will accept unencrypted results too. This
is quite useful if you have lots of passive checks and make use of
send_gearman/send_multi where you would have to spread the shared key
to all clients using these tools.
Default is no.
+
====
    accept_clear_results=yes
====




Worker Options
~~~~~~~~~~~~~~

Additional options for worker:

identifier::
Identifier for this worker. Will be used for the 'worker_identifier' queue for
status requests. You may want to change it if you are using more than one worker
on a single host.  Defaults to the current hostname.
+
====
    identifier=hostname_test
====


pidfile::
Path to the pidfile.
+
====
    pidfile=/path/to/pid.file
====


job_timeout::
Default job timeout in seconds. Currently this value is only used for
eventhandler. The worker will use the values from the core for host
and service checks.
Default: 60
+
====
    job_timeout=60
====


max-age::
Threshold for discarding too old jobs. When a new job is older than
this amount of seconds it will not be executed and just discarded.
This will result in a message like "(Could Not Start Check In Time)".
Possible reasons for this are time differences between core and
worker (use NTP!) or the smart rescheduler of the core which should be
disabled. Set to zero to disable this check.
Default: 0
+
====
    max-age=600
====


min-worker::
Minimum number of worker processes which should run at any time. Default: 1
+
====
  min-worker=1
====


max-worker::
Maximum number of worker processes which should run at any time. You may set
this equal to min-worker setting to disable dynamic starting of workers. When
setting this to 1, all services from this worker will be executed one after
another. Default: 20
+
====
    max-worker=20
====


spawn-rate::
Defines the rate of spawned worker per second as long as there are jobs
waiting. Default: 1
+
====
    spawn-rate=1
====


load_limit1::
Set a limit based on the 1min load average. When exceding the load limit,
no new worker will be started until the current load is below the limit.
No limit will be used when set to 0.
Default: no limit
+
====
    load_limit1=0
====


load_limit5::
Set a limit based on the 5min load average. See 'load_limit1' for details.
Default: no limit
+
====
    load_limit5=0
====


load_limit15::
Set a limit based on the 15min load average. See 'load_limit1' for details.
Default: no limit
+
====
    load_limit15=0
====


idle-timeout::
Time in seconds after which an idling worker exits. This parameter
controls how fast your waiting workers will exit if there are no jobs
waiting. Set to 0 to disable the idle timeout. Default: 10
+
====
  idle-timeout=30
====


max-jobs::
Controls the amount of jobs a worker will do before he exits. Use this to
control how fast the amount of workers will go down after high load times.
Disabled when set to 0. Default: 1000
+
====
    max-jobs=500
====

fork_on_exec::
Use this option to disable an extra fork for each plugin execution.
Disabling this option will reduce the load on the worker host, but may
cause trouble with unclean plugins. Default: no
+
====
    fork_on_exec=no
====

dupserver::
sets the address of gearman job server where duplicated result will be sent to.
Can be specified more than once to add more server. Useful for duplicating
results for a reporting installation or remote gui.
+
====
    dupserver=logserver:4730,logserver2:4730
====


show_error_output::
Use this option to show stderr output of plugins too. When set to no,
only stdout will be displayed.
Default is yes.
+
====
    show_error_output=yes
====


timeout_return::
Defines the return code for timed out checks. Accepted return codes
are 0 (Ok), 1 (Warning), 2 (Critical) and 3 (Unknown)
Default: 2
+
====
    timeout_return=2
====


dup_results_are_passive::
Use this option to set if the duplicate result send to the 'dupserver'
will be passive or active.
Default is yes (passive).
+
====
    dup_results_are_passive=yes
====


debug-result::
When enabled, the hostname of the executing worker will be put in
front of the plugin output. This may help with debugging your plugin
results.
Default is off.
+
====
    debug-result=yes
====


enable_embedded_perl::
When embedded perl has been compiled in, you can use this
switch to enable or disable the embedded perl interpreter.
See <<_embedded_perl,Embedded Perl>> for details on EPN.
+
====
    enable_embedded_perl=on
====


use_embedded_perl_implicitly::
Default value used when the perl script does not have a
"nagios: +epn" or "nagios: -epn" set.
Perl scripts not written for epn support usually fail with epn,
so its better to set the default to off.
+
====
    use_embedded_perl_implicitly=off
====


use_perl_cache::
Cache compiled perl scripts. This makes the worker process a little
bit bigger but makes execution of perl scripts even faster.
When turned off, Mod-Gearman will still use the embedded perl
interpreter, but will not cache the compiled script.
+
====
    use_perl_cache=on
====


workaround_rc_25::
Duplicate jobs from gearmand result sometimes in exit code 25 of
plugins because they are executed twice and get killed because of
using the same ressource. Sending results (when exit code is 25 )
will be skipped with this enabled.
Only needed if you experience problems with plugins exiting with exit
code 25 randomly. Default is off.
+
====
    workaround_rc_25=off
====




Queue Names
-----------

You may want to watch your gearman server job queue. The shipped
gearman_top does this. It polls the gearman server every second
and displays the current queue statistics.

--------------------------------------
+-----------------------+--------+-------+-------+---------+
| Name                  | Worker | Avail | Queue | Running |
+-----------------------+--------+-------+-------+---------+
| check_results         | 1      | 1     | 0     | 0       |
| host                  | 3      | 3     | 0     | 0       |
| service               | 3      | 3     | 0     | 0       |
| eventhandler          | 3      | 3     | 0     | 0       |
| servicegroup_jmx4perl | 3      | 3     | 0     | 0       |
| hostgroup_japan       | 3      | 3     | 0     | 0       |
+-----------------------+--------+-------+-------+---------+
--------------------------------------


check_results::
this queue is monitored by the neb module to fetch results from the
worker. You don't need an extra worker for this queue. The number of
result workers can be set to a maximum of 256, but usually one is
enough. One worker is capable of processing several thousand results
per second.


host::
This is the queue for generic host checks. If you enable host checks
with the hosts=yes switch. Before a host goes into this queue, it is
checked if any of the local groups matches or a seperate hostgroup
machtes. If nothing matches, then this queue is used.


service::
This is the queue for generic service checks. If you enable service
checks with the `services=yes` switch. Before a service goes into this
queue it is checked against the local host- and service-groups. Then
the normal host- and servicegroups are checked and if none matches,
this queue is used.


hostgroup_<name>::
This queue is created for every hostgroup which has been defined by
the hostgroups=... option. Make sure you have at least one worker for
every hostgroup you specify. Start the worker with `--hostgroups=...`
to work on hostgroup queues. Note that this queue may also contain
service checks if the hostgroup of a service matches.


servicegroup_<name>::
This queue is created for every servicegroup which has been defined by
the `servicegroup=...` option.


eventhandler::
This is the generic queue for all eventhandler. Make sure you have a
worker for this queue if you have eventhandler enabled. Start the
worker with `--events` to work on this queue.


perfdata::
This is the generic queue for all performance data. It is created and
used if you switch on `--perfdata=yes`. Performance data cannot be
processed by the gearman worker itself. You will need
http://www.pnp4nagios.org[PNP4Nagios] therefor.


Performance
-----------

While the main motivation was to ease distributed configuration, this
plugin also helps to spread the load on multiple worker. Throughput is
mainly limited by the amount of jobs a single Nagios instance can put
onto the Gearman job server. Keep the Gearman job server close to the
Nagios box. Best practice is to put both on the same machine. Both
processes will utilize one core. Some testing with my workstation
(Dual Core 2.50GHz) and two worker boxes gave me these results. I used
a sample Nagios installation with 20.000 Services at a 1 minute
interval and a sample plugin which returns just a single line of
output. I got over 300 Servicechecks per second, which means you could
easily setup 100.000 services at a 5 minute interval with a single
Nagios box. The amount of worker boxes depends on your check types.

++++
<a title="mod gearman performance" rel="lightbox[mod_gm]" href="http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman_performance_2.png"><img src="http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman_performance_2.png" alt="mod_gearman performance" width="473" height="122" style="float:none" /></a>
<a title="mod gearman performance" rel="lightbox[mod_gm]" href="http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman_performance_1.png"><img src="http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman_performance_1.png" alt="mod_gearman performance" width="424" height="176" style="float:none" /></a>
++++

See this article about benchmarks with https://labs.consol.de/blog/nagios/monitoring-core-benchmarks/[Nagios3, Nagios4 and Mod-Gearman].


Exports
-------
Exports export data structures from the Nagios core as JSON data. For
each configurable event one job will be created. At the moment, the
only useful event type is the logdata event which allows you to create
a json data job for every logged line. This can be very useful for
external reporting tools.

exports::
Set the queue name to create the jobs in. The return code will be sent
back to the core (Not all callbacks support return codes). Callbacks
are a list of callbacks for which you want to export json data.
+
====
    export=<queue>:<returncode>:<callback>[,<callback>,...]

    export=log_queue:1:NEBCALLBACK_LOG_DATA
====


Embedded Perl
-------------
Since 1.2.0 Mod-Gearman has builtin embedded Perl support which means
generally a big performance boost when you have lots of perl plugins.

To enable embedded Perl you need to run configure with
--enable-embedded-perl

--------------------------------------
  ./configure --enable-embedded-perl otheroptions...
--------------------------------------

The --with-perlcache configure option has been replace by a runtime
configure option 'use_perl_cache'.

NOTE: Not all perl plugins support EPN. You can fix them, add '#
nagios: -epn' in the first 10 lines of the script or set
'use_embedded_perl_implicitly=off' so all scripts without the explicit
tag are run without embedded Perl.

The default configuration of Mod-Gearman enables embedded Perl, but
only uses it for Perl scripts which explicitly set '# nagios: +epn'.
This is a very safe way of using embedded Perl but you probably miss
some plugins which do not set the header and still would run with EPN.
You may want to use the 'mini_epn' from your Nagios installation to
verify if a plugin works with EPN or not.

General EPN documentation is valid for Mod-Gearman as well:

 * http://nagios.sourceforge.net/docs/3_0/embeddedperl.html[Embedded Perl]
 * http://nagios.sourceforge.net/docs/3_0/epnplugins.html[Plugin Guidelines]

NOTE: Mod-Gearman does not fix all of the memory leaks introduced with
Nagios and Embedded Perl, but it moves the leaks away from the core.
And they do not affect Mod-Gearman at all, as they are only in the
preforked worker processes which will be restarted automatically from
time to time (see 'max-jobs').


How To
------

How to Monitor Job Server and Worker
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Use the supplied check_gearman to monitor your worker and job server.
Worker have a own queue for status requests.

--------------------------------------
%> ./check_gearman -H <job server hostname> -q worker_<worker hostname> -t 10 -s check
check_gearman OK - localhost has 10 worker and is working on 1 jobs|worker=10 running=1 total_jobs_done=1508
--------------------------------------

This will send a test job to the given job server and the worker will
respond with some statistical data.


Job server can be monitored with:

--------------------------------------
%> ./check_gearman -H localhost -t 20
check_gearman OK - 6 jobs running and 0 jobs waiting.|check_results=0;0;1;10;100 host=0;0;9;10;100 service=0;6;9;10;100
--------------------------------------



How to Submit Passive Checks
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can use send_gearman to submit active and passive checks to a
gearman job server where they will be processed just like a finished
check would do.

--------------------------------------
%> ./send_gearman --server=<job server> --encryption=no --host="<hostname>" --service="<service>" --message="message"
--------------------------------------


How to build send_gearman.exe
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

After installing strawberry perl, you need to install the
'PAR::Packer' module and run pp:

--------------------------------------
  pp -z 9 -M Class::Load::XS -M Moose -M Nagios::Passive::Base -M Params::Validate::XS -o send_gearman.exe send_gearman.pl
--------------------------------------

Or just use the prebuild one from labs.consol.de:
http://labs.consol.de/wp-content/uploads/2010/09/send_gearman.exe[send_gearman.exe].



How to Submit check_multi Results
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

check_multi is a plugin which executes multiple child checks.
See more details about the feed_passive mode at:
http://www.my-plugin.de/wiki/projects/check_multi/feed_passive[www.my-plugin.de]

You can pass such child checks to Nagios via the mod_gearman
neb module:

--------------------------------------
%> check_multi -f multi.cmd -r 256 | ./send_multi --server=<job server> --encryption=no --host="<hostname>" --service="<service>"
--------------------------------------

If you want to use only check_multi and no other workers, you can
achieve this with the following neb module settings:

 broker_module=/usr/local/share/nagios/mod_gearman.o server=localhost encryption=no eventhandler=no hosts=no services=no hostgroups=does_not_exist

NOTE: encryption is not necessary if you both run the check_multi checks
and the Nagios check_results queue on the same server.


How to Set Queue by Custom Variable
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Set 'queue_custom_variable=worker' in your Mod-Gearman NEB
configuration. Then adjust your nagios host/service configuration and
add the custom variable:

-------
  define host {
    ...
    _WORKER    hostgroup_test
  }
-------

The test hostgroup does not have to exist, it is a virtual queue name
which is used by the worker.

Adjust your Mod-Gearman worker configuration and put 'test' in the
'hostgroups' attribute. From then on, the worker will work on all jobs
in the 'hostgroup_test' queue.


What About Notifications
------------------------
Notifications are currently not possible to distribute via
Mod-Gearman. The Nagios core would have to be patched to support this.
And i think its not very useful at all. So don't expect this feature
to be implemented in the near future.


Supported Dependencies
----------------------

NOTE: Mod-Gearman works best with libgearman/gearmand 0.25 and Nagios 3.2.3. If in
doubt, use these versions.

Lib-Gearman
~~~~~~~~~~~
Mod-Gearman has successfully been tested on the following Gearmand
Versions. It is recommended to always use the latest listed version of
libgearman.

 * https://launchpad.net/gearmand/trunk/0.32[libgearman 0.32]
 * https://launchpad.net/gearmand/trunk/0.25[libgearman 0.25]
 * https://launchpad.net/gearmand/trunk/0.23[libgearman 0.23]
 * https://launchpad.net/gearmand/trunk/0.14[libgearman 0.14]

Nagios
~~~~~~
Mod-Gearman works perfect with the latest stable Nagios 3.2.3. Version
3.3.1 has some serious bugs and is not recommended for use in
production.

 * http://nagios.org[Nagios]

Icinga
~~~~~~
Mod-Gearman has succesfully been tested on Icinga 1.2.0 and is running
perfectly on up to the version 1.8.

 * http://icinga.org[Icinga]





Hints
-----
 - Make sure you have at least one worker for every queue. You should
   monitor that (check_gearman).
 - Add Logfile checks for your gearmand server and mod_gearman
   worker.
 - Make sure all gearman checks are in local groups. Gearman self
   checks should not be monitored through gearman.
 - Checks which write directly to the Nagios command file (ex.:
   check_mk) have to run on a local worker or have to be excluded by
   the localservicegroups.
 - Keep the gearmand server close to Nagios for better performance.
 - If you have some checks which should not run parallel, just setup a
   single worker with --max-worker=1 and they will be executed one
   after another. For example for cpu intesive checks with selenium.
 - Make sure all your worker have the Nagios-Plugins available under
   the same path. Otherwise they could'nt be found by the worker.



Archive
-------

* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.4.2.tar.gz[version 1.4.2 - January 10 2013]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.3.8.tar.gz[version 1.3.8 - August 19 2012]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.3.6.tar.gz[version 1.3.6 - July 19 2012]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.3.4.tar.gz[version 1.3.4 - June 19 2012]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.3.2.tar.gz[version 1.3.2 - May 27 2012]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.3.0.tar.gz[version 1.3.0 - April 27 2012]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.2.8.tar.gz[version 1.2.8 - April 12 2012]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.2.6.tar.gz[version 1.2.6 - March 15 2012]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.2.4.tar.gz[version 1.2.4 - February 27 2012]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.2.2.tar.gz[version 1.2.2 - February 07 2012]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.2.0.tar.gz[version 1.2.0 - January 08 2012]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.1.1.tar.gz[version 1.1.1 - November 10 2011]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.1.0.tar.gz[version 1.1.0 - October 12 2011]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.0.10.tar.gz[version 1.0.10 - August 28 2011]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.0.9.tar.gz[version 1.0.9 - August 16 2011]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.0.8.tar.gz[version 1.0.8 - July 22 2011]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.0.7.tar.gz[version 1.0.7 - July 03 2011]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.0.6.tar.gz[version 1.0.6 - June 04 2011]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.0.5.tar.gz[version 1.0.5 - May 17 2011]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.0.4.tar.gz[version 1.0.4 - April 17 2011]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.0.3.tar.gz[version 1.0.3 - March 23 2011]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.0.2.tar.gz[version 1.0.2 - March 13 2011]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.0.1.tar.gz[version 1.0.1 - March 05 2011]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-1.0.tar.gz[version 1.0 - February 08 2011]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-0.9.tar.gz[version 0.9 - January 17 2011]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-0.8.tar.gz[version 0.8 - November 17 2010]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-0.7.tar.gz[version 0.7 - November 03 2010]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-0.6.tar.gz[version 0.6 - October 13 2010]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-0.5.tar.gz[version 0.5 - October 01 2010]
* http://labs.consol.de/wp-content/uploads/2010/09/mod_gearman-0.4.tar.gz[version 0.4 - September 25 2010]
