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. If async-http gem is not installed, this helper uses the standard webrick server instead.

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

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

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.