Plugin Helper: Http Server

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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. If async-http gem is not installed, this helper uses the standard webrick server instead.
Here is an example:
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require 'fluent/plugin/input'
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​
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module Fluent::Plugin
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  class ExampleInput < Input
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    Fluent::Plugin.register_output('example', self)
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​
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    # 1. Load http_server helper
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    helpers :http_server
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​
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    config_param :bind, :string
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    config_param :port, :integer
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​
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    def start
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      super
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​
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      # 2. Create and start HTTP server
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      create_http_server(:example_http_server, addr: @bind, port: @port, logger: log) do |serv|
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        # Define endpoint `/hello` with GET method
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        serv.get('/hello') { [200, { 'Content-Type' => 'text/plain' }, 'hello!'] }
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      end
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    end
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  end
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end
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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
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create_http_server(:example_http_server, addr: @bind, port: @port, logger: log) do |serv|
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  # define POST method `/hello`
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  serv.post('/hello') { [200, { 'Content-Type' => 'text/plain' }, 'hello!'] }
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​
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  # define HEAD method `/hello`
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  serv.head('/hello') { [200, { 'Content-Type' => 'text/plain' }, nil] }
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end
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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
Response
The http_server helper expects an array as the return value i.e.:
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[${response_status}, ${headers}, ${body}]
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${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:
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create_http_server(:example_json_http_server, addr: @bind, port: @port, logger: log) do |serv|
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  serv.post('/hello.json') do |req|
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    body = JSON.parse(req.body)
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    log.info(body)
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​
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    [code, { 'Content-Type' => 'application/json' }, { 'status' => 'success' }.to_json]
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  end
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end
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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.