The spawn manager is capable of spawning Ruby on Rails or Rack application instances. It acts like a simple fascade for the rest of the spawn manager system.
Note: SpawnManager may only be started synchronously with AbstractServer#start_synchronously. Starting asynchronously has not been tested. Don‘t forget to call cleanup after the server‘s main loop has finished.
Ruby on Rails optimizations ===
Spawning a Ruby on Rails application is usually slow. But SpawnManager will preload and cache Ruby on Rails frameworks, as well as application code, so subsequent spawns will be very fast.
Internally, SpawnManager uses Railz::FrameworkSpawner to preload and cache Ruby on Rails frameworks. Railz::FrameworkSpawner, in turn, uses Railz::ApplicationSpawner to preload and cache application code.
In case you‘re wondering why the namespace is "Railz" and not "Rails": it‘s to work around an obscure bug in ActiveSupport‘s Dispatcher.
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# File lib/passenger/spawn_manager.rb, line 48 48: def initialize 49: super() 50: @spawners = {} 51: @lock = Mutex.new 52: @cond = ConditionVariable.new 53: @cleaner_thread = Thread.new do 54: cleaner_thread_main 55: end 56: define_message_handler(:spawn_application, :handle_spawn_application) 57: define_message_handler(:reload, :handle_reload) 58: define_signal_handler('SIGHUP', :reload) 59: 60: GC.start 61: if GC.copy_on_write_friendly? 62: # Preload libraries for copy-on-write semantics. 63: require 'base64' 64: require 'passenger/application' 65: require 'passenger/railz/framework_spawner' 66: require 'passenger/railz/application_spawner' 67: require 'passenger/rack/application_spawner' 68: require 'passenger/html_template' 69: require 'passenger/platform_info' 70: require 'passenger/exceptions' 71: 72: # Commonly used libraries. 73: ['mysql', 'sqlite3'].each do |lib| 74: begin 75: require lib 76: rescue LoadError 77: # Do nothing; ignore if not present. 78: end 79: end 80: end 81: end
Cleanup resources. Should be called when this SpawnManager is no longer needed.
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# File lib/passenger/spawn_manager.rb, line 173 173: def cleanup 174: @lock.synchronize do 175: @cond.signal 176: end 177: @cleaner_thread.join 178: @lock.synchronize do 179: @spawners.each_value do |spawner| 180: if spawner.started? 181: spawner.stop 182: end 183: end 184: @spawners.clear 185: end 186: end
Remove the cached application instances at the given application root. If nil is specified as application root, then all cached application instances will be removed, no matter the application root.
Long description: Application code might be cached in memory. But once it a while, it will be necessary to reload the code for an application, such as after deploying a new version of the application. This method makes sure that any cached application code is removed, so that the next time an application instance is spawned, the application code will be freshly loaded into memory.
Raises AbstractServer::SpawnError if something went wrong.
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# File lib/passenger/spawn_manager.rb, line 144 144: def reload(app_root = nil) 145: if app_root 146: begin 147: app_root = normalize_path(app_root) 148: rescue ArgumentError 149: end 150: end 151: @lock.synchronize do 152: if app_root 153: # Delete associated ApplicationSpawner. 154: key = "app:#{app_root}" 155: spawner = @spawners[key] 156: if spawner 157: if spawner.started? 158: spawner.stop 159: end 160: @spawners.delete(key) 161: end 162: end 163: @spawners.each_value do |spawner| 164: # Reload FrameworkSpawners. 165: if spawner.respond_to?(:reload) 166: spawner.reload(app_root) 167: end 168: end 169: end 170: end
Spawn a RoR application When successful, an Application object will be returned, which represents the spawned RoR application.
See Railz::ApplicationSpawner.new for an explanation of the lower_privilege, lowest_user and environment parameters.
The spawn_method argument may be one of "smart" or "conservative". When "smart" is specified (the default), SpawnManager will internally cache the code of applications, in order to speed up future spawning attempts. This implies that, if you‘ve changed the application‘s code, you must do one of these things:
- Restart this SpawnManager by calling AbstractServer#stop, then AbstractServer#start.
- Reload the application by calling reload with the correct app_root argument.
Caching however can be incompatible with some applications.
The "conservative" spawning method does not involve any caching at all. Spawning will be slower, but is guaranteed to be compatible with all applications.
Raises:
- ArgumentError: app_root doesn‘t appear to be a valid Ruby on Rails application root.
- VersionNotFound: The Ruby on Rails framework version that the given application requires is not installed.
- AbstractServer::ServerError: One of the server processes exited unexpectedly.
- FrameworkInitError: The Ruby on Rails framework that the application requires could not be loaded.
- AppInitError: The application raised an exception or called exit() during startup.
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# File lib/passenger/spawn_manager.rb, line 107 107: def spawn_application(app_root, lower_privilege = true, lowest_user = "nobody", 108: environment = "production", spawn_method = "smart", 109: app_type = "rails") 110: if app_type == "rack" 111: if !defined?(Rack::ApplicationSpawner) 112: require 'passenger/rack/application_spawner' 113: end 114: return Rack::ApplicationSpawner.spawn_application(app_root, 115: lower_privilege, lowest_user, environment) 116: elsif app_type == "wsgi" 117: require 'passenger/wsgi/application_spawner' 118: return WSGI::ApplicationSpawner.spawn_application(app_root, 119: lower_privilege, lowest_user, environment) 120: else 121: if !defined?(Railz::FrameworkSpawner) 122: require 'passenger/application' 123: require 'passenger/railz/framework_spawner' 124: require 'passenger/railz/application_spawner' 125: end 126: return spawn_rails_application(app_root, lower_privilege, lowest_user, 127: environment, spawn_method) 128: end 129: end