Plugin Helper: Http Server

The http_server helper creates an HTTP server. This helper was introduced in v1.6.0.

It supports async-http-based server to improve the performance.

Here is an example:

require 'fluent/plugin/input'

module Fluent::Plugin
  class ExampleInput < Input
    Fluent::Plugin.register_output('example', self)

    # 1. Load http_server helper
    helpers :http_server

    config_param :bind, :string
    config_param :port, :integer

    def start
      super

      # 2. Create and start HTTP server
      create_http_server(:example_http_server, addr: @bind, port: @port, logger: log) do |serv|
        # Define endpoint `/hello` with GET method
        serv.get('/hello') { [200, { 'Content-Type' => 'text/plain' }, 'hello!'] }
      end
    end
  end
end

NOTE: The launched plugin itself is managed by its plugin helper which stops it automatically. No need to stop it in the stop method.

Methods

create_http_server(title, addr:, port:, logger:, default_app: nil, &block) (deprecated)

This method is deprecated! Use http_server_create_http_server method instead.

http_server_create_http_server(title, addr:, port:, logger:, default_app: nil, proto: nil, tls_opts: nil, &block)

It creates and starts an HTTP server with the given routes defined in &block.

• title: The name of the listening thread. Must be unique!

• addr: The address to listen to.

• port: The port to listen to.

• logger: The logger used in the server helper.

• default_app: The object to handle the requests with unregistered paths. This

  object must have a #call method or must be a Proc object.

• proto: Protocol type. Supported values: {:tcp, :tls} (default: :tcp)

• tls_opts: TLS options. Same as the Server Helper's

  server_create_connection tls_options.

http_server_create_https_server(title, addr:, port:, logger:, default_app: nil, tls_opts: nil, &block)

It creates and starts an HTTPS server with the given routes defined in &block.

• title: The name of the listening thread. Must be unique!

• addr: The address to listen to.

• port: The port to listen to.

• logger: The logger used in the server helper.

• default_app: The object to handle the requests with unregistered paths. This

  object must have a #call method or must be a Proc object.

• tls_opts: TLS options. Same as the Server Helper's

  server_create_connection tls_options.

Handling of other HTTP Methods

create_http_server(:example_http_server, addr: @bind, port: @port, logger: log) do |serv|
  # define POST method `/hello`
  serv.post('/hello') { [200, { 'Content-Type' => 'text/plain' }, 'hello!'] }

  # define HEAD method `/hello`
  serv.head('/hello') { [200, { 'Content-Type' => 'text/plain' }, nil] }
end

Request and Response

Request

Request supports these following methods:

• query_string: returns query string like hoge=v1&fuga=v2

• query: returns query which is query_string parsed by CGI.parse

• body: returns the request body

• path: returns the request path

• headers: returns Protocol::HTTP::Headers object to read the request headers (since v1.19.0)

Response

The http_server helper expects an array as the return value i.e.:

[${response_status}, ${headers}, ${body}]

• ${response_status} should be an Integer

• ${headers} should be a Hash

• ${body} should be a String or nil

Example

Here is an example of request and response in JSON format:

create_http_server(:example_json_http_server, addr: @bind, port: @port, logger: log) do |serv|
  serv.post('/hello.json') do |req|
    body = JSON.parse(req.body)
    log.info(body)

    [code, { 'Content-Type' => 'application/json' }, { 'status' => 'success' }.to_json]
  end
end

Plugins using http_server

• in_monitor_agent

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.