server helper manages various types of servers.

Here is the code example with server helper:

require 'fluent/plugin/input'
​
module Fluent::Plugin
  class ExampleInput < Input
    Fluent::Plugin.register_input('example', self)
​
    # 1. load server helper
    helpers :server
​
    # omit configure, shutdown and other plugin API
​
    def start
      # 2. create server
      server_create(:title, @port) do |data|
        #3. process data
      end
    end
  end
end

Launched server is managed by the plugin. No need server shutdown code in plugin's shutdown. The plugin shutdowns launched servers automatically.

For more details about configuration, see Transport section.

Methods

server_create_connection(title, port, proto: nil, bind: '0.0.0.0', shared: true, backlog: nil, tls_options: nil, **socket_options, &block)

This method creates server instance for various protocols.

The block will be invoked with connection as a parameter on connection.

• title: unique symbol

• port: the port to listen to

• proto: protocol type. :tcp, :tls

• bind: the bind address to listen to

• shared: if true, share socket via serverengine for multiple

  workers

• backlog: the maximum length of the queue for pending connections

• tls_options: options for TLS

  • version: set TLS version :'TLSv1_1' or :'TLSv1_2'.

    Default: :'TLSv1_2'

  • ciphers: set the list of available cpher suites. Default:

    "ALL:!aNULL:!eNULL:!SSLv2"

  • insecure: if true, set TLS verify mode NONE

  • cert_verifier: if specified, pass evaluated object to openssl's verify_callback. See also "cert_verifier example" section.

  • verify_fqdn: if true, check the server certificate is valid

    for the hostname

  • fqdn: set FQDN

  • enable_system_cert_store: if true, enable system default cert

    store

  • allow_self_signed_cert: if true, allow self signed certificate

  • cert_paths: files contain PEM-encoded certificates

• socket_options: options for socket

  • resolve_name: if true, resolve hostname

  • connect: if true, connect to host

  • nonblock: if true, use non-blocking I/O

  • linger_timeout: the timeout time in seconds used to set

    SO_LINGER

  • recv_timeout: the timeout time in seconds used to set

    SO_RECVTIMEO

  • send_timeout: the timeout time in seconds used to set

    SO_SNDTIMEO

  • send_keepalive_packet: if true, enable TCP keepalive via SO_KEEPALIVE. See also socket article​

Code example:

# TCP
server_create_connection(:title, @port) do |conn|
  # on connection
  # conn is Fluent::PluginHelper::Server::TCPCallbackSocket
  source_addr = conn.remote_host
  source_port = conn.remote_port
  conn.data do |data|
    conn.write(something)
  end
end

server_create(title, port, proto: nil, bind: '0.0.0.0', shared: true, socket: nil, backlog: nil, tls_options: nil, max_bytes: nil, flags: 0, **socket_options, &callback)

This method creates server instance for various protocols.

The block will be invoked with parameter(s) on data.

• title: unique symbol

• port: the port to listen to

• proto: protocol type. :tcp, :udp, :tls

• bind: the bind address to listen to

• shared: if true, share socket via serverengine for multiple

  workers.

• socket: socket instance for UDP. this is available only for UDP.

• backlog: the maximum length of the queue for pending connections

• tls_options: options for TLS

  • version: set TLS version :'TLSv1_1' or :'TLSv1_2'.

    Default: :'TLSv1_2'

  • ciphers: set the list of available cpher suites. Default:

    "ALL:!aNULL:!eNULL:!SSLv2"

  • insecure: if true, set TLS verify mode NONE

  • cert_verifier: if specified, pass evaluated object to openssl's verify_callback. See also "cert_verifier example" section.

  • verify_fqdn: if true, check the server certificate is valid

    for the hostname

  • fqdn: set FQDN

  • enable_system_cert_store: if true, enable system default cert

    store

  • allow_self_signed_cert: if true, allow self signed certificate

  • cert_paths: files contain PEM-encoded certificates

• max_bytes: the maximum number of bytes to receive from the socket.

  This is required only for UDP.

• flags: zero or more of the MSG_ options. This is available only

  for UDP.

• socket_options: options for socket

  • resolve_name: if true, resolve hostname

  • connect: if true, connect to host

  • nonblock: if true, use non-blocking I/O

  • linger_timeout: the timeout time in seconds used to set

    SO_LINGER

  • recv_timeout: the timeout time in seconds used to set

    SO_RECVTIMEO

  • send_timeout: the timeout time in seconds used to set

    SO_SNDTIMEO

  • send_keepalive_packet: if true, enable TCP keepalive via SO_KEEPALIVE. See also socket article​

Code example:

# UDP (w/o socket)
server_create(:title, @port, proto: :udp, max_bytes: 2048) do |data|
  # data is received data
end
​
# UDP (w/ socket)
server_create(:title, @port, proto: :udp, max_bytes: 2048) do |data, sock|
  # data is received data
  # sock is UDPSocket
end
​
# TCP (w/o connection)
server_create(:title, @port) do |data|
  # data is received data
end
​
# TCP (w/ connection)
server_create(:title, @port) do |data, conn|
  # data is received data
  # conn is Fluent::PluginHelper::Server::TCPCallbackSocket
end
​
# TLS (w/o connection)
server_create(:title, @port, proto: :tls) do |data|
  # data is received data
end
​
# TLS (w/ connection)
server_create(:title, @port, proto: :tls) do |data, conn|
  # data is received data
  # conn is Fluent::PluginHelper::Server::TLSCallbackSocket
end

Configuration example

Here is TLS configuration example with server helper used plugin.

<source>
  @type forward
  # other plugin parameters
  <transport tls>
    version TLSv1_2
    ciphers ALL:!aNULL:!eNULL:!SSLv2
    insecure false
​
    # For Cert signed by public CA
    ca_path /path/to/ca_file
    cert_path /path/to/cert_path
    private_key_path /path/to/priv_key
    private_key_passphrase "passphrase"
    client_cert_auth false
​
    # For Cert generated and signed by private CA Certificate
    ca_cert_path /path/to/ca_cert
    ca_private_key_path /path/to/ca_priv_key
    ca_private_key_passphrase "ca_passphrase"
​
    # For generating certs by private CA certs or self-signed
    generate_private_key_length 2048
    generate_cert_country US
    generate_cert_state CA
    generate_cert_locality Mountain View
    generate_cert_common_name "Common Name"
    generate_cert_expiration "#{10 * 365 * 86400}"
    generate_cert_digest sha256
  <transport>
<source>

cert_verifier example

cert_verifier is supported since v1.10.0.

• Configuration example

<source>
  @type forward
  <transport tls>
    # other parameters
    client_cert_auth true
    cert_verifier /path/to/my_verifier.rb
  </transport>
</source>

• my_verifier.rb example

Code must be return callable object which has call method with 2 arguments. This object is used as openssl's verify_callback​

Proc or lambda object for simple case

Proc.new { |ok, ctx|
  # check code
​
  if cond
    true
  else
    false
  end
}

Use class for complicated case

This is CN check example..

module Fluent
  module Plugin
    class InForwardCNChecker
      def initialize
        # Modify for actual common names
        @allow_list = ['fluentd', 'fluentd-client', 'other-org']
      end
​
      def call(ok, ctx)
        subject = ctx.chain.first.subject.to_a.find { |entry| entry.first == 'CN' }
        if subject
          @allow_list.include?(subject[1])
        else
          false
        end
      end
    end
  end
end
​
Fluent::Plugin::InForwardCNChecker.new

server used plugins

• ​Forward input​

• ​Syslog input​

• ​TCP input​

• ​UDP input​

• ​Forward output​

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.