Plugin Helper: Socket

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The socket plugin helper creates various types of socket instances.
Here is an example:
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require 'fluent/plugin/output'
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​
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module Fluent::Plugin
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  class ExampleOutput < Output
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    Fluent::Plugin.register_output('example', self)
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​
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    # 1. Load socket helper
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    helpers :socket
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​
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    config_param :host, :string
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    config_param :port, :integer
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​
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    # Omit `configure`, `shutdown` and other plugin APIs
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​
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    def try_write(chunk)
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      # 2. Create socket
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      socket = socket_create(:tcp, @host, @port)
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      chunk.each do |time, record|
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        # 3. Write data to socket
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        socket.write(record.to_json)
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      end
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    ensure
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      # 4. Close socket
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      socket.close if socket
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    end
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  end
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end
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The socket plugin helper does not manage the lifecycle of the socket. User must close the socket when it is no longer needed.
Methods
socket_create(proto, host, port, **kwargs, &block)
This method creates a socket instance with the given protocol type.
If the block is given, it will be invoked with the socket instance as a parameter, and the socket will automatically be closed when the block terminates.
proto: protocol type. { :tcp, :udp, :tls }
host: host name or IP address
port: port number
kwargs: extra options. For more details, see methods below.
block: customize socket
Code example:
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# TCP
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socket = socket_create(:tcp, 'example.com', 12340)
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socket.write(data)
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socket.close
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​
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# UDP
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socket = socket_create(:udp, 'example.com', 12341)
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socket.write(data)
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socket.close
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​
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# TLS
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socket = socket_create(:tls, 'example.com', 12342, insecure: true)
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socket.write(data)
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socket.close
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​
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# close socket automatically
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socket_create(:udp, 'example.com', 12341) do |sock|
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  sock.write(data)
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end
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socket_create_tcp(host, port, **kwargs, &block)
This method creates socket instance for TCP.
If the block is given, it will be invoked with the socket instance as a parameter, and the socket will automatically be closed when the block terminates.
host: hostname or IP address
port: port number
kwargs: extra options
resolve_name: if true, resolve the hostname
nonblock: if true, use non-blocking I/O
linger_timeout: the timeout (seconds) to set SO_LINGER
recv_timeout: the timeout (seconds) to set SO_RECVTIMEO
send_timeout: the timeout (seconds) to set SO_SNDTIMEO
send_keepalive_packet: if true, enable TCP keep-alive via SO_KEEPALIVE
connect_timeout: the timeout for socket connect. When the connection
timed out during establishment, Errno::ETIMEDOUT is raised.
send_keepalive_packet Use Case
If you set true to send_keepalive_packet, you also need to configure keep-alive related kernel parameters:
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net.ipv4.tcp_keepalive_intvl = 75
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net.ipv4.tcp_keepalive_probes = 5
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net.ipv4.tcp_keepalive_time = 7200
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This parameter mitigates half-open connection issue with load balancers. Check also this issue for AWS NLB case.
socket_create_udp(host, port, **kwargs, &block)
This method creates socket instance for UDP.
If block is given, it will be invoked with the socket instance as a parameter, and socket will automatically be closed when the block terminates.
host: host name or IP address
port: port number
kwargs: extra options
resolve_name: if true, resolve the hostname
connect: if true, connect to host
nonblock: if true, use non-blocking I/O
linger_timeout: the timeout (seconds) to set SO_LINGER
recv_timeout: the timeout (seconds) to set SO_RECVTIMEO
send_timeout: the timeout (seconds) to set SO_SNDTIMEO
socket_create_tls(host, port, **kwargs, &block)
This method creates socket instance for TLS.
If block is given, it will be invoked with the socket instance as a parameter, and socket will automatically be closed when the block terminates.
host: host name or IP address
port: port number
kwargs: extra options
version: set TLS version :TLSv1_1 or :TLSv1_2. (default: :TLSv1_2)
ciphers: set the list of available cipher suites. (default:
"ALL:!aNULL:!eNULL:!SSLv2")
insecure: if true, set TLS verify mode NONE
verify_fqdn: if true, validate the server certificate 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
private_key_path: set the client private key path
private_key_passphrase: set the client private key passphrase
cert_thumbprint: set the certificate thumbprint for searching from Windows system certstore
cert_logical_store_name: set the certificate logical store name on Windows system certstore
cert_use_enterprise_store: if true, enable to use certificate enterprise store on Windows system certstore
Support more parameters same as socket_create_tcp's kwargs
Plugins using socket
​out_forward​
If this article is incorrect or outdated, or omits critical information, please let us know. Fluentd is an open-source project under Cloud Native Computing Foundation (CNCF). All components are available under the Apache 2 License.

Plugin Helper: Server

Plugin Helper: Storage

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Contents

Methods

socket_create(proto, host, port, **kwargs, &block)

socket_create_tcp(host, port, **kwargs, &block)

socket_create_udp(host, port, **kwargs, &block)

socket_create_tls(host, port, **kwargs, &block)

Plugins using socket

Methods

`socket_create(proto, host, port, **kwargs, &block)`

`socket_create_tcp(host, port, **kwargs, &block)`

`send_keepalive_packet` Use Case

`socket_create_udp(host, port, **kwargs, &block)`

`socket_create_tls(host, port, **kwargs, &block)`

Plugins using `socket`