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.

<source>
  @type udp
  tag mytag # required
  <parse>
    @type regexp
    expression /^(?<field1>\d+):(?<field2>\w+)$/
  </parse>
  port 20001               # optional. 5160 by default
  bind 0.0.0.0             # optional. 0.0.0.0 by default
  message_length_limit 1MB # optional. 4096 bytes by default
</source>

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

• ​server​

• ​parser​

• ​extract​

• ​compat_parameters​

Parameters

​Common Parameters​

@type

The value must be udp.

tag

tag of output events.

port

The port to listen to. Default Value = 5160

bind

The bind address to listen to.

source_hostname_key

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": "client.hostname.org"
}

source_address_key

The field name for the client's IP address. If you set this option, Fluentd automatically adds the remote address to each data record.

For example, if you have the following configuration:

@type udp source_address_key client_addr ...

you will get something like below:

:::text
{
    ...
    "client_addr": "192.168.10.10"
    ...
}

message_length_limit

The max bytes of message

remove_newline

Remove newline from the end of incoming payload

<parse> section

in_tcp uses parser plugin to parse the payload.

For more details about parser plugin, see followings:

• ​Parser Plugin Overview​

• ​Parse section configurations​

Code example

Here is ruby example to send event to in_udp.

require 'socket'
​
us = UDPSocket.open
sa = Socket.pack_sockaddr_in(5160, '127.0.0.1')
​
# 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)
us.close

FAQ

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.

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.