Logstash gelf output plugin gone after udpate

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Published on November 28th 2018 - Listed in ELK Logstash


Today I was informed that some log data doesn't appear anymore in our ELK stack since yesterday afternoon. What changed yesterday afternoon? This particular log collector machien running Logstash was updated.

# zgrep logstash /var/log/apt/history.log.1.gz -B 3
Start-Date: 2018-11-27  15:52:08
Commandline: /usr/bin/apt-get -y -o Dpkg::Options::=--force-confdef -o Dpkg::Options::=--force-confold dist-upgrade
Install: [...]
Upgrade: [...] logstash:amd64 (5.6.10-1, 5.6.13-1), [...]

By checking the Logstash logs, the reason was pretty well explained:

[2018-11-28T08:13:51,925][ERROR][logstash.plugins.registry] Problems loading a plugin with {:type=>"output", :name=>"gelf", :path=>"logstash/outputs/gelf", :error_message=>"NameError", :error_class=>NameError, :error_backtrace=>["/usr/share/logstash/logstash-core/lib/logstash/plugins/registry.rb:226:in `namespace_lookup'", "/usr/share/logstash/logstash-core/lib/logstash/plugins/registry.rb:162:in `legacy_lookup'", "/usr/share/logstash/logstash-core/lib/logstash/plugins/registry.rb:138:in `lookup'", "/usr/share/logstash/logstash-core/lib/logstash/plugins/registry.rb:180:in `lookup_pipeline_plugin'", "/usr/share/logstash/logstash-core/lib/logstash/plugin.rb:140:in `lookup'", "/usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:103:in `plugin'", "(eval):12:in `initialize'", "org/jruby/RubyKernel.java:1079:in `eval'", "/usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:75:in `initialize'", "/usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:165:in `initialize'", "/usr/share/logstash/logstash-core/lib/logstash/agent.rb:296:in `create_pipeline'", "/usr/share/logstash/logstash-core/lib/logstash/agent.rb:95:in `register_pipeline'", "/usr/share/logstash/logstash-core/lib/logstash/runner.rb:313:in `execute'", "/usr/share/logstash/vendor/bundle/jruby/1.9/gems/clamp-0.6.5/lib/clamp/command.rb:67:in `run'", "/usr/share/logstash/logstash-core/lib/logstash/runner.rb:204:in `run'", "/usr/share/logstash/vendor/bundle/jruby/1.9/gems/clamp-0.6.5/lib/clamp/command.rb:132:in `run'", "/usr/share/logstash/lib/bootstrap/environment.rb:71:in `(root)'"]}
[2018-11-28T08:13:51,955][ERROR][logstash.agent           ] Cannot create pipeline {:reason=>"Couldn't find any output plugin named 'gelf'. Are you sure this is correct? Trying to load the gelf output plugin resulted in this error: Problems loading the requested plugin named gelf of type output. Error: NameError NameError"}

The important part:

:reason=>"Couldn't find any output plugin named 'gelf'.

Let's check the currently installed Logstash plugins:

# /usr/share/logstash/bin/logstash-plugin list --verbose | grep gelf
logstash-input-gelf (3.1.1)

Hmm.. Only the input-gelf plugin is shown, but not the output-gelf plugin. Let's install it manually then:

# /usr/share/logstash/bin/logstash-plugin install logstash-output-gelf
Validating logstash-output-gelf
Installing logstash-output-gelf
Installation successful

A Logstash restart is not needed after this. The logs happily showed up in Kibana again.

Gelf logs reappear in Kibana


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