Replace Webrick with custom simple http server (#1030)

This commit removes Webrick and replaces it with a (simple) custom
HttpServer.

This is a single-process/singe-thread server that behaves simmilary to
webrick.

.rubocop.yml

@@ -47,6 +47,9 @@ Layout/ParameterAlignment:
 Lint/AmbiguousBlockAssociation:
   Enabled: false
 
+Lint/IncompatibleIoSelectWithFiberScheduler:
+  Enabled: false
+
 Metrics:
   Enabled: false
 

Gemfile.lock

@@ -18,7 +18,6 @@ PATH
       fugit (>= 1.1)
       railties (>= 6.0.0)
       thor (>= 0.14.1)
-      webrick (>= 1.3)
 
 GEM
   remote: https://rubygems.org/
@@ -454,7 +453,6 @@ GEM
     unparser (0.6.8)
       diff-lcs (~> 1.3)
       parser (>= 3.2.0)
-    webrick (1.8.1)
     websocket (1.2.9)
     websocket-driver (0.7.5)
       websocket-extensions (>= 0.1.0)

good_job.gemspec

@@ -57,7 +57,6 @@ Gem::Specification.new do |spec|
   spec.add_dependency "fugit", ">= 1.1"
   spec.add_dependency "railties", ">= 6.0.0"
   spec.add_dependency "thor", ">= 0.14.1"
-  spec.add_dependency "webrick", ">= 1.3"
 
   spec.add_development_dependency "benchmark-ips"
   spec.add_development_dependency "capybara"

lib/good_job.rb

@@ -29,6 +29,7 @@
 require "good_job/multi_scheduler"
 require "good_job/notifier"
 require "good_job/poller"
+require "good_job/http_server"
 require "good_job/probe_server"
 require "good_job/scheduler"
 require "good_job/shared_executor"

lib/good_job/http_server.rb

@@ -0,0 +1,75 @@
+# frozen_string_literal: true
+
+module GoodJob
+  class HttpServer
+    SOCKET_READ_TIMEOUT = 5 # in seconds
+
+    def initialize(app, options = {})
+      @app    = app
+      @port   = options[:port]
+      @logger = options[:logger]
+
+      @running = Concurrent::AtomicBoolean.new(false)
+    end
+
+    def run
+      @running.make_true
+      start_server
+      handle_connections if @running.true?
+    rescue StandardError => e
+      @logger.error "Server encountered an error: #{e}"
+    ensure
+      stop
+    end
+
+    def stop
+      @running.make_false
+      @server&.close
+    end
+
+    def running?
+      @running.true?
+    end
+
+    private
+
+    def start_server
+      @server = TCPServer.new('0.0.0.0', @port)
+    rescue StandardError => e
+      @logger.error "Failed to start server: #{e}"
+      @running.make_false
+    end
+
+    def handle_connections
+      while @running.true?
+        begin
+          ready_sockets, = IO.select([@server], nil, nil, SOCKET_READ_TIMEOUT)
+          return unless ready_sockets
+
+          client = @server.accept_nonblock(exception: false)
+          request = client.gets
+
+          status, headers, body = @app.call(parse_request(request))
+          respond(client, status, headers, body)
+
+          client.close
+        rescue IO::WaitReadable, Errno::EINTR
+          retry
+        end
+      end
+    end
+
+    def parse_request(request)
+      method, full_path = request.split
+      path, query = full_path.split('?')
+      { 'REQUEST_METHOD' => method, 'PATH_INFO' => path, 'QUERY_STRING' => query || '' }
+    end
+
+    def respond(client, status, headers, body)
+      client.write "HTTP/1.1 #{status}\r\n"
+      headers.each { |key, value| client.write "#{key}: #{value}\r\n" }
+      client.write "\r\n"
+      body.each { |part| client.write part.to_s }
+    end
+  end
+end

lib/good_job/probe_server.rb

@@ -2,8 +2,6 @@
 
 module GoodJob
   class ProbeServer
-    RACK_SERVER = 'webrick'
-
     def self.task_observer(time, output, thread_error) # rubocop:disable Lint/UnusedMethodArgument
       return if thread_error.is_a? Concurrent::CancelledOperationError
 
@@ -15,20 +13,18 @@ def initialize(port:)
     end
 
     def start
-      @handler = Rack::Handler.get(RACK_SERVER)
-      @future = Concurrent::Future.new(args: [@handler, @port, GoodJob.logger]) do |thr_handler, thr_port, thr_logger|
-        thr_handler.run(self, Port: thr_port, Host: '0.0.0.0', Logger: thr_logger, AccessLog: [])
-      end
+      @handler = HttpServer.new(self, port: @port, logger: GoodJob.logger)
+      @future = Concurrent::Future.new { @handler.run }
       @future.add_observer(self.class, :task_observer)
       @future.execute
     end
 
     def running?
-      @handler&.instance_variable_get(:@server)&.status == :Running
+      @handler&.running?
     end
 
     def stop
-      @handler&.shutdown
+      @handler&.stop
       @future&.value # wait for Future to exit
     end