JRuby support: pooled application manager (instead of fork) - used if fork if not supported

Author: mrbrdo

lib/spring/application.rb

@@ -1,9 +1,17 @@
 require "spring/boot"
 require "set"
 require "pty"
+require "spring/platform"
 
 module Spring
   class Application
+    if Spring.fork?
+      require 'spring/application/fork_strategy'
+      include ForkStrategy
+    else
+      require 'spring/application/pool_strategy'
+      include PoolStrategy
+    end
     attr_reader :manager, :watcher, :spring_env, :original_env
 
     def initialize(manager, original_env)
@@ -114,13 +122,9 @@ def preload
       end
     end
 
-    def eager_preload
-      with_pty { preload }
-    end
-
     def run
       state :running
-      manager.puts
+      manager.puts Process.pid
 
       loop do
         IO.select [manager, @interrupt.first]
@@ -134,6 +138,7 @@ def run
     end
 
     def serve(client)
+      app_started = [false]
       log "got client"
       manager.puts
 
@@ -153,7 +158,7 @@ def serve(client)
         ActionDispatch::Reloader.prepare!
       end
 
-      pid = fork {
+      start_app(client, streams, app_started) {
         IGNORE_SIGNALS.each { |sig| trap(sig, "DEFAULT") }
         trap("TERM", "DEFAULT")
 
@@ -184,24 +189,18 @@ def serve(client)
 
         command.call
       }
-
-      disconnect_database
-      reset_streams
-
-      log "forked #{pid}"
-      manager.puts pid
-
-      wait pid, streams, client
     rescue Exception => e
+      Kernel.exit if exiting? && e.is_a?(SystemExit)
+
       log "exception: #{e}"
-      manager.puts unless pid
+      manager.puts unless app_started[0]
 
       if streams && !e.is_a?(SystemExit)
         print_exception(stderr, e)
         streams.each(&:close)
       end
 
-      client.puts(1) if pid
+      client.puts(1) if app_started[0]
       client.close
     end
 
@@ -282,39 +281,11 @@ def print_exception(stream, error)
       rest.each { |line| stream.puts("\tfrom #{line}") }
     end
 
-    def with_pty
-      PTY.open do |master, slave|
-        [STDOUT, STDERR, STDIN].each { |s| s.reopen slave }
-        Thread.new { master.read }
-        yield
-        reset_streams
-      end
-    end
-
     def reset_streams
       [STDOUT, STDERR].each { |stream| stream.reopen(spring_env.log_file) }
       STDIN.reopen("/dev/null")
     end
 
-    def wait(pid, streams, client)
-      @mutex.synchronize { @waiting << pid }
-
-      # Wait in a separate thread so we can run multiple commands at once
-      Thread.new {
-        begin
-          _, status = Process.wait2 pid
-          log "#{pid} exited with #{status.exitstatus}"
-
-          streams.each(&:close)
-          client.puts(status.exitstatus)
-          client.close
-        ensure
-          @mutex.synchronize { @waiting.delete pid }
-          exit_if_finished
-        end
-      }
-    end
-
     private
 
     def active_record_configured?

lib/spring/application/boot.rb

@@ -3,8 +3,15 @@
 
 require "spring/application"
 
+remote_socket =
+  if ENV["SPRING_SOCKET"]
+    UNIXSocket.open(ENV.delete("SPRING_SOCKET"))
+  else
+    UNIXSocket.for_fd(3)
+  end
+
 app = Spring::Application.new(
-  UNIXSocket.for_fd(3),
+  remote_socket,
   Spring::JSON.load(ENV.delete("SPRING_ORIGINAL_ENV").dup)
 )
 

lib/spring/application/fork_strategy.rb

@@ -0,0 +1,50 @@
+module Spring
+  class Application
+    module ForkStrategy
+      def eager_preload
+        with_pty { preload }
+      end
+
+      def with_pty
+        PTY.open do |master, slave|
+          [STDOUT, STDERR, STDIN].each { |s| s.reopen slave }
+          Thread.new { master.read }
+          yield
+          reset_streams
+        end
+      end
+
+      def wait(pid, streams, client)
+        @mutex.synchronize { @waiting << pid }
+
+        # Wait in a separate thread so we can run multiple commands at once
+        Thread.new {
+          begin
+            _, status = Process.wait2 pid
+            log "#{pid} exited with #{status.exitstatus}"
+
+            streams.each(&:close)
+            client.puts(status.exitstatus)
+            client.close
+          ensure
+            @mutex.synchronize { @waiting.delete pid }
+            exit_if_finished
+          end
+        }
+      end
+
+      def start_app(client, streams, app_started)
+        pid = fork { yield }
+        app_started[0] = true
+
+        disconnect_database
+        reset_streams
+
+        log "forked #{pid}"
+        manager.puts pid
+
+        wait pid, streams, client
+      end
+    end
+  end
+end

lib/spring/application/pool_strategy.rb

@@ -0,0 +1,30 @@
+module Spring
+  class Application
+    module PoolStrategy
+      def eager_preload
+        reset_streams
+        preload
+      end
+
+      def start_app(client, streams, app_started)
+        app_started[0] = true
+        exitstatus = 0
+        manager.puts Process.pid
+        begin
+          log "started #{Process.pid}"
+          yield
+        rescue SystemExit => ex
+          exitstatus = ex.status
+        end
+
+        log "#{Process.pid} exited with #{exitstatus}"
+
+        streams.each(&:close)
+        client.puts(exitstatus)
+        client.close
+
+        exit
+      end
+    end
+  end
+end

lib/spring/application_manager.rb

@@ -1,138 +1,7 @@
 module Spring
-  class ApplicationManager
-    attr_reader :pid, :child, :app_env, :spring_env, :status
-
-    def initialize(app_env)
-      @app_env    = app_env
-      @spring_env = Env.new
-      @mutex      = Mutex.new
-      @state      = :running
-    end
-
-    def log(message)
-      spring_env.log "[application_manager:#{app_env}] #{message}"
-    end
-
-    # We're not using @mutex.synchronize to avoid the weird "<internal:prelude>:10"
-    # line which messes with backtraces in e.g. rspec
-    def synchronize
-      @mutex.lock
-      yield
-    ensure
-      @mutex.unlock
-    end
-
-    def start
-      start_child
-    end
-
-    def restart
-      return if @state == :stopping
-      start_child(true)
-    end
-
-    def alive?
-      @pid
-    end
-
-    def with_child
-      synchronize do
-        if alive?
-          begin
-            yield
-          rescue Errno::ECONNRESET, Errno::EPIPE
-            # The child has died but has not been collected by the wait thread yet,
-            # so start a new child and try again.
-            log "child dead; starting"
-            start
-            yield
-          end
-        else
-          log "child not running; starting"
-          start
-          yield
-        end
-      end
-    end
-
-    # Returns the pid of the process running the command, or nil if the application process died.
-    def run(client)
-      with_child do
-        child.send_io client
-        child.gets or raise Errno::EPIPE
-      end
-
-      pid = child.gets.to_i
-
-      unless pid.zero?
-        log "got worker pid #{pid}"
-        pid
-      end
-    rescue Errno::ECONNRESET, Errno::EPIPE => e
-      log "#{e} while reading from child; returning no pid"
-      nil
-    ensure
-      client.close
-    end
-
-    def stop
-      log "stopping"
-      @state = :stopping
-
-      if pid
-        Process.kill('TERM', pid)
-        Process.wait(pid)
-      end
-    rescue Errno::ESRCH, Errno::ECHILD
-      # Don't care
-    end
-
-    private
-
-    def start_child(preload = false)
-      @child, child_socket = UNIXSocket.pair
-
-      Bundler.with_clean_env do
-        @pid = Process.spawn(
-          {
-            "RAILS_ENV"           => app_env,
-            "RACK_ENV"            => app_env,
-            "SPRING_ORIGINAL_ENV" => JSON.dump(Spring::ORIGINAL_ENV),
-            "SPRING_PRELOAD"      => preload ? "1" : "0"
-          },
-          "ruby",
-          "-I", File.expand_path("../..", $LOADED_FEATURES.grep(/bundler\/setup\.rb$/).first),
-          "-I", File.expand_path("../..", __FILE__),
-          "-e", "require 'spring/application/boot'",
-          3 => child_socket
-        )
-      end
-
-      start_wait_thread(pid, child) if child.gets
-      child_socket.close
-    end
-
-    def start_wait_thread(pid, child)
-      Process.detach(pid)
-
-      Thread.new {
-        # The recv can raise an ECONNRESET, killing the thread, but that's ok
-        # as if it does we're no longer interested in the child
-        loop do
-          IO.select([child])
-          break if child.recv(1, Socket::MSG_PEEK).empty?
-          sleep 0.01
-        end
-
-        log "child #{pid} shutdown"
-
-        synchronize {
-          if @pid == pid
-            @pid = nil
-            restart
-          end
-        }
-      }
-    end
+  module ApplicationManager
   end
 end
+
+require 'spring/application_manager/fork_strategy'
+require 'spring/application_manager/pool_strategy'