Versions | v1.0 (td-agent3) | v0.12 (td-agent2)

UDP Input Plugin

The in_udp Input plugin enables Fluentd to accept UDP payload.

Table of Contents

Example Configuration

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

  @type udp
  tag mytag # required
    @type regexp
    expression /^(?<field1>\d+):(?<field2>\w+)$/
  port 20001               # optional. 5160 by default
  bind             # optional. by default
  message_length_limit 1MB # optional. 4096 bytes by default
Please see the Config File article for the basic structure and syntax of the configuration file. For <parse> section, please check Parse section cofiguration.
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.

Plugin helpers


Common Parameters


The value must be udp.


type default version
string required parameter 0.14.0

tag of output events.


type default version
integer 5160 0.14.0

The port to listen to. Default Value = 5160


type default version
string (all addresses) 0.14.0

The bind address to listen to.


type default version
string nil (no adding hostname) 0.14.10

The field name of the client’s hostname. If set the value, the client’s hostname will be set to its key.

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": ""


type default version
size 4096 0.14.14

The max bytes of message


type default version
bool true 0.14.23

Remove newline from the end of incoming payload

<parse> section

required multi version
true false 0.14.10

in_tcp uses parser plugin to parse the payload.

For more details about parser plugin, see followings:

Code example

Here is ruby example to send event to in_udp.

require 'socket'

us =
sa = Socket.pack_sockaddr_in(5160, '')

# This example uses json payload.
# In in_udp configuration, need to configure "@type json" in "<parse>"
us.send('{"k":"v1"}', 0, sa)
us.send('{"k":"v2"}', 0, sa)


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 multi workers.

Last updated: 2019-03-22 16:55:20 +0000

Versions | v1.0 (td-agent3) | v0.12 (td-agent2)

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.