This article explains how to manage Fluentd plugins, including adding third-party plugins.
fluent-gemcommand is used to install Fluentd plugins. This is a wrapper around the
fluent-gem install fluent-plugin-grep
Ruby does not guarantee the C extension API compatibility between its major versions. If you update Fluentd's Ruby version, you should reinstall the plugins that depend on C extension.
Any fluentd plugin can unknowingly break fluentd completely (and possibly break other plugins) by requiring some incompatible modules.
There is no way to block this kind of situation. This is because the problem itself is derived from plug-in mechanism, and that's Lightweight Language. One solution is "Do not use unreliable plugins".
Generally speaking, plug-in mechanism can break core functionality not only Fluentd but also in most other software. We shouldn't use unreliable plugins in any software.
We recommend to send feedback to plugin owner if you faced such a fault in plugins.
If you are using
td-agent, make sure that you use
td-agent-gemcommand to install gems for it. Otherwise, you won't be able to find the installed plugins.
Some plugins depend on the native extension library. It means that you need to install development packages to build it e.g.
Install development packages first, if you see logs like this:
Building native extensions. This could take a while...
ERROR: Error installing fluent-plugin-twitter:
ERROR: Failed to build gem native extension.
checking for rb_str_scrub()... yes
make "DESTDIR = " clean
sh: 1: make: not found
make "DESTDIR = "
sh: 1: make: not found
make failed, exit code 127
Gem files will remain installed in /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/string-scrub-0.0.3 for inspection.
Results logged to /opt/td-agent/embedded/lib/ruby/gems/2.1.0/extensions/x86_64-linux/2.1.0/string-scrub-0.0.3/gem_make.out
-poption is used to add an extra plugin directory to the load path. For example, if you put
/path/to/plugin, you can load it by specifying the
-poption like this:
fluentd -p /path/to/plugin
You can specify the
-poption more than once.
By default, Fluentd adds the
/etc/fluent/plugindirectory to its load path. Thus, any additional plugins that are placed in
/etc/fluent/pluginwill be loaded automatically.
td-agent, Fluentd uses the
/etc/td-agent/plugindirectory instead of
/etc/fluent/pluginso put your plugins accordingly.
Fluentd and plugins are evolving so you may hit an unexpected error with the latest version e.g. regression by a new feature, remove a deprecated parameter, change library dependency, etc. To avoid these problems, we recommend fixing fluentd and plugin version on production. If you want to update fluentd or plugins, check the behavior first on your test environment. For example, td-agent fixes fluentd and plugins version in each release.
Fluentd plugins are RubyGems and RubyGems installs the latest version by default. So we don't recommend to execute following commands on production:
gem install fluentd
gem install fluent-plugin-elasticsearch
gem update # This is very dangerous. Update all existing gems
You should specify the target version with
gem install fluentd -v 1.2.1
gem install fluent-plugin-elasticsearch -v 2.10.3
A Ruby application manages gem dependencies using Gemfile and
--gemfileoption takes the same approach, and is useful for managing plugin versions separated from shared gems.
For example, if you have the following Gemfile at
gem 'fluentd', '1.2.1'
gem 'fluent-plugin-elasticsearch', '2.10.3'
You can pass this Gemfile to Fluentd via the
fluentd --gemfile /etc/fluent/Gemfile
When specifying the
--gemfileoption, Fluentd will try to install the listed gems using Bundler. Fluentd will only load the listed gems separated from shared gems, and will also prevent unexpected plugin updates.
If you update Fluentd's Ruby version, Bundler will reinstall the listed gems for the new Ruby version. This allows you to avoid the C extension API compatibility problem.
We can manage Fluentd and its plugins based on Gemfile with
Use the following drop-in file
ExecStart=/opt/td-agent/embedded/bin/fluentd --log /var/log/td-agent/td-agent.log --daemon /var/run/td-agent/td-agent.pid $TD_AGENT_OPTIONS
We can also edit this file using the following command:
$ sudo systemctl edit td-agent.service
And, then add
# You can use fixed version of Fluentd and its plugins
gem "fluentd", "1.2.1"
gem "fluent-plugin-elasticsearch", "2.4.0"
gem "fluent-plugin-kafka", "0.6.5"
gem "fluent-plugin-rewrite-tag-filter", "2.0.1"
gem "fluent-plugin-s3", "1.1.0"
gem "fluent-plugin-td", "1.0.0"
gem "fluent-plugin-td-monitoring", "0.2.3"
gem "fluent-plugin-webhdfs", "1.2.2"
# Add plugins you want to use
gem "fluent-plugin-geoip", "1.2.0"
$ sudo systemctl restart td-agent.service
NOTE: With this approach, you will download all the gems listed in Gemfile even if
td-agentincludes them the first time.
The latest version is used. If command shows the following result:
$ fluent-gem list
fluent-plugin-record-modifier (2.0.1, 0.6.0, 0.5.0)
2.0.1version is used.
If this article is incorrect or outdated, or omits critical information, please let us know. Fluentd is an open-source project under Cloud Native Computing Foundation (CNCF). All components are available under the Apache 2 License.