The in_udp Input plugin enables Fluentd to accept UDP payload.

Example Configuration

in_udp is included in Fluentd's core. No additional installation process is required.

  @type udp
  tag mytag # required
  format /^(?<field1>\d+):(?<field2>\w+)$/ # required
  port 20001 # optional. 5160 by default
  bind # optional. by default
  body_size_limit 1MB # optional. 4096 bytes by default

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

We've observed the drastic performance improvements on Linux, with proper kernel parameter settings (e.g. `net.core.rmem_max` parameter). If you have high-volume UDP traffic, please make sure to follow the instruction described at Before Installing Fluentd.


type (required)

The value must be udp.

tag (required)

tag of output events.


The port to listen to. Default Value = 5160


The bind address to listen to. Default Value =


The field name of the client's hostname. If set the value, the client's hostname will be set to its key. The default is nil (no adding hostname).

If you set following configuration:

source_hostname_key client_host

then the client's hostname is set to client_host field.

    "foo": "bar",
    "client_host": "client.hostname.org"

format (required)

The format of the UDP payload. in_udp uses parser plugin to parse the payload. See parser article for more detail.

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.


How to prevent request drop?

If in_udp gots lots of packets within 1 sec, some packets are dropped. For example, you can see bigger RcvbufErrors number via netstat -su.

This means in_udp with one process can't handle such traffic. Try fluent-plugin-multiprocess to resolve the problem. See issue 1334 for more detail.

If this article is incorrect or outdated, or omits critical information, please let us know.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.

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