Package pl.allegro.tech.hermes.consumers.consumer.batch

Class DirectBufferPool

  • public final class DirectBufferPool
extends java.lang.Object
    A pool of ByteBuffers kept under a given memory limit. This class is fairly specific to the needs of the producer. In particular it has the following properties:
    1. There is a special "poolable size" and buffers of this size are kept in a free list and recycled
    2. It is fair. That is all memory is given to the longest waiting thread until it has sufficient memory. This prevents starvation or deadlock when a thread asks for a large chunk of memory and needs to block until multiple buffers are deallocated.

    • Constructor Summary

      Constructors 
      Constructor Description
      DirectBufferPool​(long memory, int poolableSize, boolean blockOnExhaustion)
      Create a new buffer pool

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      java.nio.ByteBuffer allocate​(int size)
      Allocate a buffer of the given size.
      long availableMemory()
      the total free memory both unallocated and in the free list
      void deallocate​(java.nio.ByteBuffer buffer)  
      void deallocate​(java.nio.ByteBuffer buffer, int size)
      Return buffers to the pool.
      int poolableSize()
      The buffer size that will be retained in the free list after use
      int queued()
      The number of threads blocked waiting on memory
      long totalMemory()
      The total memory managed by this pool
      long unallocatedMemory()
      Get the unallocated memory (not in the free list or in use)

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • DirectBufferPool

        public DirectBufferPool​(long memory,
                        int poolableSize,
                        boolean blockOnExhaustion)
        Create a new buffer pool
        Parameters:
        memory - The maximum amount of memory that this buffer pool can allocate
        poolableSize - The buffer size to cache in the free list rather than deallocating
        blockOnExhaustion - This controls the behavior when the buffer pool is out of memory. If true the allocate(int) call will block and wait for memory to be returned to the pool. If false allocate(int) will throw an exception if the buffer is out of memory.

    • Method Detail

      • allocate

        public java.nio.ByteBuffer allocate​(int size)
                             throws java.lang.InterruptedException
        Allocate a buffer of the given size. This method blocks if there is not enough memory and the buffer pool is configured with blocking mode.
        Parameters:
        size - The buffer size to allocate in bytes
        Returns:
        The buffer
        Throws:
        java.lang.InterruptedException - If the thread is interrupted while blocked
        java.lang.IllegalArgumentException - if size is larger than the total memory controlled by the pool (and hence we would block forever)
        java.nio.BufferOverflowException - if the pool is in non-blocking mode and size exceeds the free memory in the pool

      • deallocate

        public void deallocate​(java.nio.ByteBuffer buffer,
                       int size)
        Return buffers to the pool. If they are of the poolable size add them to the free list, otherwise just mark the memory as free.
        Parameters:
        buffer - The buffer to return
        size - The size of the buffer to mark as deallocated, note that this maybe smaller than buffer.capacity since the buffer may re-allocate itself during in-place compression

      • deallocate

        public void deallocate​(java.nio.ByteBuffer buffer)

      • availableMemory

        public long availableMemory()
        the total free memory both unallocated and in the free list

      • unallocatedMemory

        public long unallocatedMemory()
        Get the unallocated memory (not in the free list or in use)

      • queued

        public int queued()
        The number of threads blocked waiting on memory

      • poolableSize

        public int poolableSize()
        The buffer size that will be retained in the free list after use

      • totalMemory

        public long totalMemory()
        The total memory managed by this pool