Package com.google.appengine.api

Class ThreadManager

java.lang.Object
com.google.appengine.api.ThreadManager
public final class ThreadManager extends Object
ThreadManager exposes a ThreadFactory that allows App Engine applications to spawn new threads. Refer to this discussion of threads for drawbacks of thread usage and possible alternatives.

  • Constructor Details

    • ThreadManager

      public ThreadManager()

  • Method Details

    • currentRequestThreadFactory

      public static ThreadFactory currentRequestThreadFactory()
      Returns a ThreadFactory which will create threads scoped to the current request. These threads will be interrupted at the end of the current request and must complete within the request deadline. If they fail to, the instance containing them may be terminated.

      The principal reason to use this method is so that the created threads can make App Engine API calls (com.google.appengine.api.*). In general, threads not associated with a request cannot make these API calls.

      The returned factory is typically used with a call like Executors.newCachedThreadPool(ThreadFactory). Do not use the ExecutorService returned by this call after the request that created it has completed.

      Note that calling ThreadFactory.newThread(java.lang.Runnable) on the returned instance may throw any of the unchecked exceptions mentioned by createBackgroundThread(java.lang.Runnable).

      Throws:
      NullPointerException - if the calling thread is not associated with a request.

    • currentRequestThreadFactoryOptional

      public static Optional<ThreadFactory> currentRequestThreadFactoryOptional()
      Returns an Optional ThreadFactory which will create threads scoped to the current request. These threads will be interrupted at the end of the current request and must complete within the request deadline. If they fail to, the instance containing them may be terminated.

      If this method is not called from an App Engine request thread, returns an empty Optional instance.

      The principal reason to use this method is so that the created threads can make App Engine API calls (com.google.appengine.api.*). In general, threads not associated with a request cannot make these API calls.

      The returned factory is typically used with a call like Executors.newCachedThreadPool(ThreadFactory). Do not use the ExecutorService returned by this call after the request that created it has completed.

      Note that calling ThreadFactory.newThread(java.lang.Runnable) on the returned instance may throw any of the unchecked exceptions mentioned by createBackgroundThread(java.lang.Runnable).

    • createThreadForCurrentRequest

      public static Thread createThreadForCurrentRequest(Runnable runnable)
      Create a new Thread that executes runnable for the duration of the current request. Calling this method is equivalent to invoking ThreadFactory.newThread(java.lang.Runnable) on the ThreadFactory returned from currentRequestThreadFactory(). This thread will be interrupted at the end of the current request and must complete within the request deadline. If it fails to, the instance containing it may be terminated.
      Throws:
      IllegalStateException - if you try to create more than 50 threads in a single request.
      NullPointerException - if the calling thread is not associated with a request.
      com.google.apphosting.api.ApiProxy.FeatureNotEnabledException - If this application cannot use this feature.

    • backgroundThreadFactory

      public static ThreadFactory backgroundThreadFactory()
      Returns a ThreadFactory that will create threads that are independent of the current request.

      This ThreadFactory can currently only be used by backends.

      Note that calling ThreadFactory.newThread(java.lang.Runnable) on the returned instance may throw any of the unchecked exceptions mentioned by createBackgroundThread(java.lang.Runnable).

    • createBackgroundThread

      public static Thread createBackgroundThread(Runnable runnable)
      Create a new Thread that executes runnable independent of the current request. Calling this method is equivalent to invoking ThreadFactory.newThread(java.lang.Runnable) on the ThreadFactory returned from backgroundThreadFactory().

      This method can currently only be used by backends.

      Throws:
      com.google.apphosting.api.ApiProxy.FeatureNotEnabledException - If this application cannot use this feature.
      com.google.apphosting.api.ApiProxy.CancelledException - If the request was interrupted while creating the new thread.
      com.google.apphosting.api.ApiProxy.ApiDeadlineExceededException - If creation of the new thread took too long.