By default, Fluentd only uses a single CPU core on the system. The in_multiprocess Input plugin enables Fluentd to use multiple CPU cores by spawning multiple child processes. One Fluentd user is using this plugin to handle 10+ billion records / day.


in_multiprocess is NOT included in td-agent by default. td-agent users must install fluent-plugin-multiprocess manually.

  • Fluentd: fluent-gem install fluent-plugin-multiprocess

  • td-agent v2:

    /usr/sbin/td-agent-gem install fluent-plugin-multiprocess

  • td-agent v1:

    /usr/lib/fluent/ruby/bin/fluent-gem install fluent-plugin-multiprocess

Example Configuration

  @type multiprocess

    cmdline -c /etc/fluent/fluentd_child1.conf --log /var/log/fluent/fluentd_child1.log
    sleep_before_start 1s
    sleep_before_shutdown 5s
    cmdline -c /etc/fluent/fluentd_child2.conf --log /var/log/fluent/fluentd_child2.log
    sleep_before_start 1s
    sleep_before_shutdown 5s
    cmdline -c /etc/fluent/fluentd_child3.conf --log /var/log/fluent/fluentd_child3.log
    sleep_before_start 1s
    sleep_before_shutdown 5s

Please see the Config File article for the basic structure and syntax of the configuration file.

Especially for daemonized fluentd (ex: td-agent), `--log` option MUST be specified to put logs of child processes.


type (required)

The value must be multiprocess.


The interval to send the signal to gracefully shut down the process (default: 2sec).


The increment time, when graceful shutdown fails (default: 3sec).


The timeout, to identify the failure of graceful shutdown (default: 60sec).

process (required)

The process section sets the command line arguments of a child process. This plugin creates one child process for each section.

cmdline (required)

The cmdline option is required in a section


This parameter sets the wait time before starting the process (default: 0sec).


This parameter sets the wait time before shutting down the process (default: 0sec).

log_level option

The log_level option allows the user to set different levels of logging for each plugin. The supported log levels are: fatal, error, warn, info, debug, and trace.

Please see the logging article for further details.

If this article is incorrect or outdated, or omits critical information, please let us know. Fluentd is a open source project under Cloud Native Computing Foundation (CNCF). All components are available under the Apache 2 License.

Last updated