Package org.apache.tomcat.util.threads

Class LimitLatch

  • public class LimitLatch
extends java.lang.Object
    Shared latch that allows the latch to be acquired a limited number of times after which all subsequent requests to acquire the latch will be placed in a FIFO queue until one of the shares is returned.

    • Constructor Summary

      Constructors 
      Constructor Description
      LimitLatch​(long limit)
      Instantiates a LimitLatch object with an initial limit.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      long countDown()
      Releases a shared latch, making it available for another thread to use.
      void countUpOrAwait()
      Acquires a shared latch if one is available or waits for one if no shared latch is current available.
      long getCount()
      Returns the current count for the latch
      long getLimit()
      Obtain the current limit.
      java.util.Collection<java.lang.Thread> getQueuedThreads()
      Provide access to the list of threads waiting to acquire this limited shared latch.
      boolean hasQueuedThreads()
      Returns true if there is at least one thread waiting to acquire the shared lock, otherwise returns false.
      boolean releaseAll()
      Releases all waiting threads and causes the limit to be ignored until reset() is called.
      void reset()
      Resets the latch and initializes the shared acquisition counter to zero.
      void setLimit​(long limit)
      Sets a new limit.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • LimitLatch

        public LimitLatch​(long limit)
        Instantiates a LimitLatch object with an initial limit.
        Parameters:
        limit - - maximum number of concurrent acquisitions of this latch

    • Method Detail

      • getCount

        public long getCount()
        Returns the current count for the latch
        Returns:
        the current count for latch

      • getLimit

        public long getLimit()
        Obtain the current limit.
        Returns:
        the limit

      • setLimit

        public void setLimit​(long limit)
        Sets a new limit. If the limit is decreased there may be a period where more shares of the latch are acquired than the limit. In this case no more shares of the latch will be issued until sufficient shares have been returned to reduce the number of acquired shares of the latch to below the new limit. If the limit is increased, threads currently in the queue may not be issued one of the newly available shares until the next request is made for a latch.
        Parameters:
        limit - The new limit

      • countUpOrAwait

        public void countUpOrAwait()
                    throws java.lang.InterruptedException
        Acquires a shared latch if one is available or waits for one if no shared latch is current available.
        Throws:
        java.lang.InterruptedException - If the current thread is interrupted

      • countDown

        public long countDown()
        Releases a shared latch, making it available for another thread to use.
        Returns:
        the previous counter value

      • releaseAll

        public boolean releaseAll()
        Releases all waiting threads and causes the limit to be ignored until reset() is called.
        Returns:
        true if release was done

      • reset

        public void reset()
        Resets the latch and initializes the shared acquisition counter to zero.
        See Also:
        releaseAll()

      • hasQueuedThreads

        public boolean hasQueuedThreads()
        Returns true if there is at least one thread waiting to acquire the shared lock, otherwise returns false.
        Returns:
        true if threads are waiting

      • getQueuedThreads

        public java.util.Collection<java.lang.Thread> getQueuedThreads()
        Provide access to the list of threads waiting to acquire this limited shared latch.
        Returns:
        a collection of threads