nrpe #1

Supports: xenial trusty


Nagios is a host/service/network monitoring and management system. The purpose of this addon is to allow you to execute Nagios plugins on a remote host in as transparent a manner as possible. This program runs as a background process on the remote host and processes command execution requests from the check_nrpe plugin on the Nagios host.


This subordinate charm is used to configure nrpe (Nagios Remote Plugin Executor). It can be related to the nagios charm via the monitors relation and will pass a monitors yaml to nagios informing it of what checks to monitor.

Principle Relations

This charm can be attatched to any principle charm (via the juju-info relation) regardless of whether it has implemented the local-monitors or nrpe-external-master relations. For example,

juju deploy ubuntu juju deploy nrpe juju deploy nagios juju add-relation ubuntu nrpe juju add-relation nrpe:monitors nagios:monitors

If joined via the juju-info relation the default checks are configured and additional checks can be added via the monitors config option (see below).

The local-monitors relations allows the principle to request checks to be setup by passing a monitors yaml and listing them in the 'local' section. It can also list checks that is has configured by listing them in the remote nrpe section and finally it can request external monitors are setup by using one of the other remote types. See "Monitors yaml" below.

Other Subordinate Charms

If another subordinate charm deployed to the same principle has a local-monitors or nrpe-external-master relation then it can also be related to the local nrpe charm. For example,

echo -e "glance:\n vip:" > glance.yaml juju deploy -n3 --config glance.yaml glance juju deploy hacluster glance-hacluster juju deploy nrpe glance-nrpe juju deploy nagios juju add-relation glance glance-hacluster juju add-relation glance-nrpe:monitors nagios:monitors juju add-relation glance glance-nrpe juju add-relation glance-hacluster glance-nrpe

The glance-hacluster charm will pass montioring information to glance-nrpe which will amalgamate all montior definitions before passing them to nagios

Check sources

Check definitions can come from three places:

Default Checks

This charm creates a base set of checks in /etc/nagios/nrpe.d, including check_load, check_users, check_disk_root. All of the options for these are configurable but sensible defaults have been set in config.yaml. For example to increase the alert threshold for number of processes:

juju set nrpe load="-w 10,10,10 -c 25,25,25"

Principle Requested Checks

Monitors passed to this charm by the principle charm via the local-monitors or nrpe-external-master relation. The principle charm can write its own check definition into /etc/nagios/nrpe.d and then inform this charm via the monitors setting. It can also request a direct external check of a service without using nrpe. See "Monitors yaml" below for examples.

User Requested Checks

This works in the same way as the Principle requested except the monitors yaml is set by the user via the monitors config option. For example to add a monitor for the rsylog process:

juju set nrpe monitors="
                min: 1
                max: 1
                executable: rsyslogd

External Nagios

If the nagios server is not deployed in the juju environment then the charm can be configured, via the export_nagios_definitions, to write out nagios config fragments to /var/lib/nagios/export. Rsync is then configured to allow a host (specified by nagios_master) to collect the fragments. An rsync stanza is created allowing the Nagios server to pick up configs from /var/lib/nagios/export (as a target called "external-nagios"), which will also be configured to allow connections from the hostname or IP address as specified for the "nagios_master" variable.

It is up to you to configure the Nagios master to pull the configs needed, which will then cause it to connect back to the instances in question to run the nrpe checks you have defined.

Monitors yaml

The list of monitors past down the monitors relation is an amalgamation of the lists provided via the principle, the user and the default checks.

The monitors yaml is of the following form:

# Version of the spec, mostly ignored but 0.3 is the current one
version: '0.3'
# Dict with just 'local' and 'remote' as parts
    # local monitors need an agent to be handled. See nrpe charm for
    # some example implementations
        # procrunning checks for a running process named X (no path)
            # Multiple procrunning can be defined, this is the "name" of it
                min: 1
                max: 1
                executable: nagios3
    # Remote monitors can be polled directly by a remote system
        # do a request on the HTTP protocol
                port: 80
                path: /nagios3/
                # expected status response (otherwise just look for 200)
                status: 'HTTP/1.1 401'
                # Use as the Host: header (the server address will still be used to connect() to)
            # Named basic check
                username: monitors
                password: abcdefg123456
                command: check_apache2

Before a monitor is added it is checked to see if it is in the 'local' section. If it is this charm needs to convert it into an nrpe checks. Only a small number of check types are currently supported (see below) .These checks can then be called by the nagios charm via the nrpe service. So for each check listed in the local section:

  1. The defintion is read and a check defintion it written /etc/nagios/nrpe.d
  2. The check is defined as a remote nrpe check in the yaml passed to nagios

In the example above a check_proc_nagios3_user.cfg file would be written out which contains:

# Check process nagios3 is running (user)
command[check_proc_nagios3_user]=/usr/lib/nagios/plugins/check_procs -w 1 -c 1 -C nagios3

and the monitors yaml passed to nagios would include:

        command: check_proc_nagios3_user

The principle charm, or the user via the monitors config option, can request an external check by adding it to the remote section of the monitors yaml. In the example above direct checks of a webserver and of mysql are being requested. This charm passes those on to nagios unaltered.

Local check types

Supported nrpe checks are: procrunning: min: Minimum number of 'executable' processes max: Maximum number of 'executable' processes executable: Name of executable to look for in process list processcount min: Minimum total number processes max: Maximum total number processes executable: Name of executable to look for in process list disk path: Directory to monitor space usage of

Remote check types

Supported remote types: http, mysql, nrpe, tcp, rpc, pgsql (See Nagios charm for up-to-date list and options)


(string) Root disk check. This can be made to also check non-root disk systems as follows: -u GB -w 20% -c 15% -r '/srv/juju/vol-' -C -u GB -w 25% -c 20% The string '-p /' will be appended to this check, so you must finish the string taking that into account. See the nagios check_disk plugin help for further details.
-u GB -w 25% -c 20% -K 5%
(boolean) If True nagios check definitions are written to '/var/lib/nagios/export' and rync is configured to allow nagios_master to collect them. Useful when Nagios is outside of the juju environment
(string) Hostcheck to inherit
(string) Comma separated list of hostgroups to add for these hosts
(string) Load check (e.g. -w 8,8,8 -c 15,15,15), if 'auto' is set, then NUM_CPUS*0.7 is used for the warning threshold and NUM_CPUS for the critical one
(string) Memory check
-C -u -w 85 -c 90
(string) Additional monitors defined in the monitors yaml format (see README)
(string) Determines whether the nagios host check should use the private or public IP address of an instance. Can be "private" or "public".
(string) a string that will be prepended to instance name to set the host name in nagios. So for instance the hostname would be something like: juju-postgresql-0 If you're running multiple environments with the same services in them this allows you to differentiate between them.
(string) Determines whether a server is identified by its unit name or host name. If you're in a virtual environment, "unit" is probably best. If you're using MaaS, you may prefer "host".
(string) IP address of the nagios master to allow rsyncs from
(string) Number of processes check or 'auto' for the charm to generate thresholds based on processor count
(int) port that nagios-nrpe-server will listen on
(string) A string to be appended onto all the nrpe checks created by this charm to avoid potential clashes with existing checks
(string) Swap check
-w 90% -c 75%
(string) Users check
-w 20 -c 25
(string) Zombie processes check
-w 3 -c 6 -s Z