github-fast-envd/github-fast-envd.rb

#!/usr/bin/env ruby

require "base64"
require "socket"

class ClientError < StandardError
	def initialize(message)
		super(message)
	end
end

class ClientScriptError < StandardError
	def initialize(source)
		super(source.message)
		@source = source
	end

	def source
		@source
	end
end

control_socket_path = "/tmp/github-fast-envd.sock"

if File.exist?(control_socket_path) and File.socket?(control_socket_path)
	File.unlink(control_socket_path)
end

control_server = UNIXServer.new(control_socket_path)
File.chmod 0700, control_socket_path

#at_exit do
#	control_server.close
#end

$stderr.puts "serving control socket"

connection_id = 0

def open_pipe(connection_id, name)
	pipe_path = "/tmp/github-fast-envd.#{connection_id}.#{name}"

	if File.exist?(pipe_path) and File.pipe?(pipe_path)
		File.unlink(pipe_path)
	end

	File.mkfifo(pipe_path, mode = 0600)

	pipe_path
end

def read_command(control_socket)
	ready_ios = IO.select([control_socket], [], [], 10)

	if not ready_ios
		log "error", "timeout while communicating with github-fast-envd"
		exit 1
	end

	response = control_socket.readline.strip.split(" ", 2)

	if response.empty?
		log "error", "malformed response from github-fast-envd"
		exit 1
	end

	command = response[0]

	if command == "error"
		if response.length < 2
			log "error", "malformed error response from github-fast-envd"
			exit 1
		end

		error_message = response[1]

		log "error", "#{error_message}"
		exit 1
	end

	arguments = response[1].nil? ? [] : response[1].split(" ")

	return command, arguments
end

while true
	control_socket = control_server.accept
	$stderr.puts "- new connection"

	begin
		command, arguments = read_command(control_socket)

		if command != "new"
			raise ClientError.new "unexpected command"
		end

		if arguments.length != 2
			raise ClientError.new "malformed command"
		end

		if arguments[0] != "v1"
			raise ClientError.new "unsupported protocol version"
		end

		connection_id += 1

		child_process = fork {
			original_stdin = $stdin.dup
			original_stdout = $stdout.dup
			original_stderr = $stderr.dup

			exit_code = "unknown"

			begin
				stdin = open_pipe(connection_id, "stdin")
				control_socket.puts "stdin #{stdin}"
				stdin = File::open(stdin, "r")
				# TODO: reconsider
				stdin.sync = true

				stdout = open_pipe(connection_id, "stdout")
				control_socket.puts "stdout #{stdout}"
				stdout = File::open(stdout, "w")
				stdout.sync = true

				stderr = open_pipe(connection_id, "stderr")
				control_socket.puts "stderr #{stderr}"
				stderr = File::open(stderr, "w")
				stderr.sync = true

				$stderr.puts "  set up pipes"
				control_socket.puts "ready"

				response = control_socket.readline.strip

				if response != "ready"
					raise ClientError.new "invalid command"
					Kernel.exit!
				end

				script_path = Base64.decode64(arguments[1])
				$stderr.puts "  executing script " + script_path

				$stdin.reopen(stdin)
				$stdout.reopen(stdout)
				$stderr.reopen(stderr)

				begin
					load script_path, true
				rescue SystemExit => error
					original_stderr.puts "  exit code: #{error.status}"
					exit_code = error.status
				rescue => error
					$stdin = original_stdin
					$stdout = original_stdout
					$stderr = original_stderr

					raise ClientScriptError.new error
				end
			rescue ClientScriptError => error
				# TODO: Restore pipes to make sure that syntax errors are caught
				encoded_error_output = Base64.encode64(error.source.full_message).delete("\n")
				original_stderr.puts "  error executing script, ignoring request"
				# TODO: if the begin/rescue blog has syntax errors, these go unnoticed
				begin
					control_socket.puts "script_error #{encoded_error_output}"
				rescue
				end
			rescue ClientError => error
				original_stderr.puts "  error communicating with client, ignoring request (#{error})"
				begin
					control_socket.puts "error #{error}"
				rescue
				end
			rescue StandardError => error
				original_stderr.puts "  error, ignoring request (#{error})"
				begin
					control_socket.puts "error internal server error"
				rescue
				end
			end

			begin
				control_socket.puts "done #{exit_code}"
			rescue
			end
			control_socket.close

			original_stderr.puts "  finished handling request"

			Kernel.exit!
		}

		Process.detach(child_process)
	rescue ClientError => error
		$stderr.puts "  error communicating with client, ignoring request (#{error})"
		begin
			control_socket.puts "error #{error}"
		rescue
		end
	rescue StandardError => error
		$stderr.puts "  error, ignoring request (#{error})"
		begin
			control_socket.puts "error internal server error"
		rescue
		end
	end

	control_socket.close
end