gomonop - Various monitoring plugins in golang
==============================================

This project is a collection of various monitoring plugins (such as Nagios,
Centreon, or Icinga) written in golang. All plugins are available through a
single executable, `gomonop`. The actual plugin can be selected either
by creating a symlink to the main executable with the appropriate name or by
calling the executable directly with the first argument being the name of the
plugin.

This project is distributed under the terms of the [GPLv3 license](LICENSE).
Its source code is available on the [Nocternity forge](https://git.nocternity.net/projects/gomonop).

Plugins
--------

### SSL certificate expiry

The `check_ssl_certificate` plugin can be used to check that the certificate
from a TLS service has not expired and is not going to expire shortly. It
supports the following command-line flags:

* `-H name`/`--hostname name`: the host name to connect to.
* `-P port`/`--port port`: the TCP port to connect to.
* `-W days`/`--warning days`: a threshold, in days, below which a warning will
  be emitted for this service.
* `-C days`/`--critical days`: a threshold, in days, below which the plugin will
  indicate that the service is in a critical state.
* `--ignore-cn-only`: do not cause errors if a certificate does not have SANs
  and relies on the CN field.
* `-a names`/`--additional-names names`: a comma-separated list of DNS names
  that the certificate should also have.
* `-s protocol`/`--start-tls protocol`: protocol to use before requesting a
  switch to TLS. Supported protocols: `smtp`, `sieve`.

### DNS zone serials

The `check_zone_serial` plugin can be used to check that the version of a
zone served by a DNS is up-to-date compared to the same zone served by
another, "reference" DNS. It supports the following command-line flags:

* `-H name`/`--hostname name`: the host name or address of the server to
  check.
* `-P port`/`--port port`: the port to use on the server to check (defaults
  to 53).
* `-z zone`: the zone to check.
* `-r name`/`--rs-hostname name`: the host name or address of the reference
  server.
* `-p port`/`--rs-port port`: the port to use on the reference server
  (defaults to 53).

### Generic text match counter

The `check_output_matches` plugin can be used to count occurrences of strings
in a program's output or in a text file, and compute its final status based on
that.

It supports the following general command line flags:

* `-f` / `--is-file` indicates that the plugin will be reading from a text file
  instead of running another program;
* `-s` / `--source` is either the name of the file to read, or the command to
  execute. The command may include multiple arguments separated by single
  spaces; it does not support any form of quoting.
* `-T` / `--timeout` can set a timeout for the command. It is disabled by
  default.
* `-S` / `--strict` determines how unmatched lines are handled. By default they
  are ignored, but setting this flag will cause the plugin to enter `CRITICAL`
  mode if unmatched lines are found.

Other flags are available in order to configure the matches. The main flag is
`-m` / `--match`, which adds a new match string to the set of checks to run.
The checks are influenced by the following additional flags, which apply to all
subsequent matches.

* `-r` / `--regexp` indicates that new matches will be based on regular
  expressions instead of substrings.
* `-R` / `--no-regexp` switches back to substring-based matches.
* `-w` / `--warn` can be used to set a warning range. It must be followed by
  a Nagios range specification.
* `-W` / `--no-warn` clears the warning range.
* `-c` / `--critical` can be used to set the critical range. It must be followed
  by a Nagios range specification.
* `-C` / `--no-critical` clears the critical range.

For example, the command below:

    gomonop check_output_matches -s 'find /some/place' \
       -w 4 -r -m '^.*\.warn$' \
       -W -c 0 -R -m fatal

configures a warning if more than 4 files ending in `.warn` are found, and a
critical state if any file with `fatal` in its name is found.

Building from source
--------------------

The plugin can be built for the current host OS and architecture using
`make build`. The actual executable will be created under the `bin` directory,
in a subdirectory named after the host OS and architecture (e.g.
`bin/linux-amd64`). The executable will be named `gomonop`, and a
symlink to the executable for the host OS and architecture will be created
under the `bin` directory.

It is possible to build for other architectures using `make build-cross`.