DNS based service discovery plugin for Fluentd

The dns service discovery plugin updates target services by DNS list.

This plugin uses Socket.getaddrinfo internally.

Requirements

• Fluentd v1.8 or later

Installation

Use RubyGems:

fluent-gem install fluent-plugin-sd-dns --no-document

Configuration

Use @type dns in <service_discovery>.

<match pattern>
  @type forward

  <service_discovery>
    @type dns
    <entry>
      host host1.domain
      port 24224
    </entry>
    <entry>
      host host2.domain
      port 24225
    </entry>
  </service_discovery>
</match>

If host1.domain returns 3 addresses and host2.domain returns 2 addresses, sd_dns generates 5 address entries with given port.

e.g.

• host1.domain returns 1.2.3.4, 1.2.3.5 and 1.2.3.6
• host2.domain returns 2.2.3.4 and 2.2.3.5

sd_dns generates 1.2.3.4:24224, 1.2.3.5:24224, 1.2.3.6:24224, 2.2.3.4:24225 and 2.2.3.5:24225.

section

Specify host and additional information. Each entry has the following parameters:

• host
• port
• address_family
• shared_key
• username
• password
• weight

host

• Type: string

Hostname for service lookup. This is required parameter

port

• Type: integer

Port of service. This is required parameter

address_family

• Type: string (ipv4 or ipv6)
• Default: nil (both)

Specify the desired address family. By default, sd_dns gets IPv4 and IPv6 addresses. If you want to get only IPv4 or IPv6, set it.

<entry>
  host host1.domain
  port 24224
  address_family ipv4
</entry>

shared_key

• Type: string
• Default: nil

The shared_key per entry

username

• Type: string
• Default: empty string

The username for authentication.

password

• Type: string
• Default: empty string

The password for authentication

weight

• Type: Integer
• Default: 60

The load balancing weight

shared_key, username, password and weight are mainly for out_forward.

<match pattern>
  @type forward

  <service_discovery>
    @type dns
    <entry>
      host host1.domain
      port 24224
      username user1
      password pass1
      shared_key key1
      weight 80
    </entry>
    <entry>
      host host2.domain
      port 24225
      username user2
      password pass2
      shared_key key2
      weight 20
    </entry>
  </service_discovery>
</match>

interval

• Type: time
• Default: nil (no update)

Interval for updating the service list. By default, sd_dns keeps to use first service list. If you want to update the service list periodically, set interval parameter.

<match pattern>
  @type forward

  <service_discovery>
    @type dns
    interval 60s
    <entry>
      host host.domain
      port 80
    </entry>
  </service_discovery>
</match>

ignore_dns_error

• Type: bool
• Default: false

Ignore DNS related error or not. This parameter is for multiple <entry> case. By default, sd_dns will stop the update process when raises an error in DNS resolution.

If you want to contine the update process, set ignore_dns_error true

<match pattern>
  @type forward

  <service_discovery>
    @type dns
    interval 60
    ignore_dns_error true
    <entry>
      host host1.domain
      port 24224
    </entry>
    <entry>
      host host2.domain
      port 24225
    </entry>
  </service_discovery>
</match>

When error happens, sd_dns generates following warning message:

failed to get service list from host1.domain

More information

• Copyright: 2020- Fluentd Authors
• License: Apache License, Version 2.0