Class: BgService::Server

Inherits:
Object
  • Object
show all
Defined in:
lib/bg_service/server.rb

Overview

A network server that listens for incoming connections to be run as a background process.

Constant Summary collapse

DEFAULT_BOOT_TIMEOUT =

Wait this long for the server to start listening before giving up

10
DEFAULT_TERM_TIMEOUT =

After sending a TERM signal, wait this long for the process to exit before sending a KILL signal

1
SLEEP_INTERVAL =

5ms (while waiting for the server to start or stop)

0.005

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(cmd, port:, env: {}, boot_timeout: DEFAULT_BOOT_TIMEOUT, term_timeout: DEFAULT_TERM_TIMEOUT) ⇒ Server

Returns a new instance of Server.



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# File 'lib/bg_service/server.rb', line 18

def initialize(cmd, port:, env: {}, boot_timeout: DEFAULT_BOOT_TIMEOUT, term_timeout: DEFAULT_TERM_TIMEOUT)
  @cmd = cmd
  @env = env
  @port = port
  @tmpdir = Dir.mktmpdir
  @out = File.join(@tmpdir, 'out')
  @err = File.join(@tmpdir, 'err')
  @boot_timeout = boot_timeout
  @term_timeout = term_timeout
end

Instance Attribute Details

#cmd ⇒ Object (readonly)

Returns the value of attribute cmd.



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# File 'lib/bg_service/server.rb', line 16

def cmd
  @cmd
end

#exit_status ⇒ Object (readonly)

Returns the value of attribute exit_status.



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# File 'lib/bg_service/server.rb', line 16

def exit_status
  @exit_status
end

Instance Method Details

#block_until_ready ⇒ Object

Raises:



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# File 'lib/bg_service/server.rb', line 47

def block_until_ready
  while (now - @started_at) < @boot_timeout
    s=status
    if s == :starting
      sleep SLEEP_INTERVAL
    elsif s == :listening
      return
    elsif s == :not_running
      raise CrashedOnStartup.new("process exited before listening on port #{@port}", self)
    else
      raise UnexpectedStatus.new("invariant violated: status was #{s.inspect}", self)
    end
  end
  stop
  raise TimedOut.new("not listening after #{@boot_timeout} seconds", self)
end

#cleanup ⇒ Object 



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# File 'lib/bg_service/server.rb', line 102

def cleanup
  @final_out = logs
  FileUtils.remove_entry @tmpdir
end

#listening? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/bg_service/server.rb', line 107

def listening?
  TCPSocket.open('127.0.0.1', @port).close
  true
rescue Errno::ECONNREFUSED
  false
end

#logs ⇒ Object 



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# File 'lib/bg_service/server.rb', line 64

def logs
  return @final_out if @final_out
  out = prefix_log(@out, 'out') 
  err = prefix_log(@err, 'err')
  "#{out}#{err.chomp}"
end

#now ⇒ Object 



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# File 'lib/bg_service/server.rb', line 43

def now
  Process.clock_gettime(Process::CLOCK_MONOTONIC)
end

#prefix_log(path, msg) ⇒ Object 



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# File 'lib/bg_service/server.rb', line 71

def prefix_log(path, msg)
  lines = File.readlines(path)
  padding = lines.size.to_s.size
  lines.map.with_index { |line, i| "  #{msg} #{i.to_s.rjust(padding, "0")}: #{line}" }.join.tap do |str|
    return "#{msg}: <empty>\n" if str.empty?
  end
rescue Errno::ENOENT
  return "#{msg}: <missing>\n"
end

#running? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/bg_service/server.rb', line 114

def running?
  return false unless @pid

  wait_status.nil?
end

#start ⇒ Object 



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# File 'lib/bg_service/server.rb', line 29

def start
  if @start_attempted
    raise InvalidState.new("cannot start a server that has already been stopped", self)
  end
  @start_attempted = now
  if listening?
    raise AlreadyRunning, "port #{@port} is already in use, refusing to start #{@cmd.inspect}"
  end

  @pid = spawn(@env, *@cmd, out: @out, err: @err)
  @started_at = now
  block_until_ready
end

#status ⇒ Object 



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# File 'lib/bg_service/server.rb', line 120

def status
  return :not_running if !running?
  listening? ? :listening : :starting
end

#stop ⇒ Object 



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# File 'lib/bg_service/server.rb', line 81

def stop
  if @pid
    wait_for_exit
    cleanup
    freeze # prevent further use
  end
end

#wait_for_exit ⇒ Object

Give the process @kill_timeout seconds to exit after sending a TERM signal and then forcibly terminate it with SIGKILL.



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# File 'lib/bg_service/server.rb', line 91

def wait_for_exit
  Process.kill 'TERM', @pid
  termed_at = now
  loop do
    break if wait_status
    if (now - termed_at) > @term_timeout
      Process.kill 'KILL', @pid
    end
  end
end

#wait_status ⇒ Object 



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# File 'lib/bg_service/server.rb', line 125

def wait_status
  @wait_status ||= begin
    _, status = Process.wait2(@pid, Process::WNOHANG)
    if status
      @pid = nil
      @exit_status = status
    end
  end
end