Test your Logstash config and pattern files
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Logstash Tester MIT License


Logstash Tester is a tool to write and run unit tests against your Logstash config files and/or your custom patterns. It uses RSpec and Logstash running in a Docker container

Test it, it works: ./run_example.sh (You must have a running Docker environment).

Type ./logstash-tester.sh -h to see the available options.

Long version

When your logstash config starts getting really long, and you start loosing control of all the cases covered by your custom Grok patterns, you know you're entering Logstash Config Hell.

Logstash Tester helps you (hopefully) to grow your logstash config files, AND keep your sanity, by unit testing everything.

HOWTO use it

You should have a working Docker environment for Logstash Tester to work.

1. The Data Directory

You should have a directory (the data dir) structured in the following way:

  • <data_dir>/config/conf.d Contains the logstash filter configurations
  • <data_dir>/config/patterns Contains your custom patterns
  • <data_dir>/test/filters Your filtering test case files
  • <data_dir>/test/patterns Custom patterns test case files

2. Test case files

Test cases are written in JSON. When logstash-tester runs, it looks for test cases in every file matching <data_dir>/test/patterns/**/*.json and <data_dir>/test/filters/**/*.json.

Test case syntax is pretty straigtforward.

Here's a filter testcase taken from the examples :

  "name": "CUSTOM Syslog message",
  "fields": {
    "type": "syslog"
  "ignore": ["@version", "@timestamp"],
  "cases": [{
    "in": "<22>Feb  2 09:47:12 mail dovecot: pop3-login: Login: user=<somename@somedomain.fr>, method=PLAIN, rip=, lip=",
    "out": {
      "type": "syslog",
      "message": "pop3-login: Login: user=<somename@somedomain.fr>, method=PLAIN, rip=, lip=",
      "syslog_pri": "22",
      "syslog_timestamp": "Feb  2 09:47:12",
      "application": "dovecot",
      "application_host": "mail",
      "protocol": "pop3",
      "action": "login",
      "method": "plain",
      "src": "",
      "dest": "",
      "user": "somename@somedomain.fr"
  • fields: the values are are expected to be appended to the message object by the input plugin.
  • ignore: a list of keys that will be ignored in the logstash output
  • cases: the list of test cases each with an "in" field containing the message to pass through the filtering pipeline and a "out" object field with the exact expected output.

Pattern test cases are described pretty much in the same way :

  "name": "Dovecot Login variations",
  "pattern": "DOVECOT_LOGIN",
  "cases": [
      "in": "pop3-login: Login: user=<somename@somedomain.fr>, method=PLAIN, rip=, lip=",
      "out": {
        "protocol": "pop3",
        "action": "Login",
        "user": "somename@somedomain.fr",
        "method": "PLAIN",
        "remote_ip": "",
        "local_ip": ""

where :

  • pattern: is the custom grok pattern to be tested
  • cases: is the list of test each with an "in" field containing the string to grok parse and a "out" object field with the exact expected output from the grok filter.

Since an example is (sometimes) worth a thousand words, check out the 'example' directory to get the idea of how things are organized.

Other useful info

  • The Logstash filter config files should follow a naming convention ([some-custom-label].filter.conf). They'll be loaded in alphabetical order.

  • Logstash-tester assumes the patternsdir setting in grok filters is set to /etc/logstash/patterns.


Using the "example" data directory:

  • ./logstash-tester.sh -d example

    runs every pattern and filter test case in every json test file.

  • ./logstash-tester.sh -d example filters

    runs filter test cases ignoring pattern tests

  • ./logstash-tester.sh -d example -p syslog filters

    runs only filter test files in 'example/test/filter/syslog'

Type ./logstash-tester.sh -h to know more about the command line options.

Some other stuff

I'm not a rubyist, the ruby code in the test suites was hacked together from bits and pieces found here and there. If you're a rubyist, please clean up my mess and do me a pull request :-). If you're not a rubyistm neither, don't worry, it works.


Logstash Tester drew its inspiration from two interesting projects: