Post Installation Guide

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This article discusses the post-installation steps for new Fluentd users assuming that Fluentd has been installed using the td-agent package.
System Administration
For td-agent
Configuration File
After successful installation, a td-agent instance will be up and running with a predefined template configuration file.
The default path for this configuration file is:
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/etc/td-agent/td-agent.conf
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You may edit this configuration file according to your own use case.
After editing the configuration file, restart td-agent using systemctl command:
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$ sudo systemctl restart td-agent
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Logging
By default, td-agent writes its operation logs to the following file:
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/var/log/td-agent/td-agent.log
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For more verbose logs, read the article on Troubleshooting.
For calyptia-fluentd
Configuration File
After the successful installation, a calyptia-fluentd instance will be up and running with a predefined template configuration file.
The default path for this configuration file is:
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/etc/calyptia-fluentd/calyptia-fluentd.conf
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You may edit this configuration file according to your own use case.
After editing the configuration file, restart calyptia-fluentd using systemctl command:
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$ sudo systemctl restart calyptia-fluentd
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Logging
By default, calyptia-fluentd writes its operation logs to the following file:
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/var/log/calyptia-fluentd/calyptia-fluentd.log
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For more verbose logs, read the article on Troubleshooting.
Connect to the Other Services
How It Works
In Fluentd, the most important part of data input/output is managed by plugins. Each plugin knows how to interface with an external endpoint and is solely responsible for managing one pipeline to forward data streams.
Plugins use a certain naming convention. For example, if it receives data and interfaces with Apache Kafka, it is called in_kafka. In the same way, if it publishes data and connects to MongoDB, it is called out_mongo.
The following configuration uses the in_forward plugin as an input source and out_file plugin as an output endpoint:
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<source>
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  @type forward
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  port 9999
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</source>
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<match app.**>
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  @type file
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  path /var/log/app/data.log
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  compress gzip
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</match>
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Plugin Management
Fluentd manages plugins as Ruby gems but stores them in their dedicated directory separated from the normal Ruby gems.
td-agent
A special program td-agent-gem is used to manage plugin gems. For example, the following command installs a plugin to connect to S3 (including both in_s3 and out_s3 plugins):
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 $ sudo /usr/sbin/td-agent-gem install fluent-plugin-s3
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calyptia-fluentd
A special program calyptia-fluentd-gem is used to manage plugin gems. For example, the following command installs a plugin to connect to S3 (including both in_s3 and out_s3 plugins):
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 $ sudo /usr/sbin/calyptia-fluentd-gem install fluent-plugin-s3
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Available Plugins
See the List Of All Plugins to explore the available third-party plugins.
Note that a number of plugins are bundled with the standard distribution of td-agent so you do not need to install them manually.
Configuration Syntax
Data Source
A configuration file consists of a number of setting blocks or sections e.g. <source>. Each block contains a set of options for a specific data endpoint.
For example, if you want to create an endpoint to receive data from syslog, you need to add a <source> block and set up its settings like this:
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<source>
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  @type syslog
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  port 5140
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  tag system
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</source>
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The @type parameter specifies which plugin to use. Note that the plugin type prefix i.e. in_, out_, etc. is not needed here. In this example, the input plugin is specified as syslog, not in_syslog.
Output Endpoint
To add an output endpoint for the data stream, you need to define a <match> block. Syntactically, <match> is slightly different from <source> in the sense that it requires a filter expression as an argument.
For example, if you want to output events tagged with debug.log, you need to mention this tag as an argument in <match> like this:
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<match debug.log>
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  @type kafka2
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  port 5140
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  brokers kafka-server:9092
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  tag system
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  # ...
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</match>
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The wildcard character * can be used in the filter expression. For example, debug.* matches debug.log, debug.foo, etc.
To catch all the descendent tags, use double asterisks **. For example, debug.** matches not only debug.log, but also debug.log.bar or debug.log.level.critical, etc.
Further Reading
​Configuration File Syntax​
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.