Package org.apache.cassandra.net

Class AsyncChannelOutputPlus

  • All Implemented Interfaces:
    java.io.Closeable, java.io.DataOutput, java.io.Flushable, java.lang.AutoCloseable, DataOutputPlus
    Direct Known Subclasses:
    AsyncMessageOutputPlus, AsyncStreamingOutputPlus
    public abstract class AsyncChannelOutputPlus
extends BufferedDataOutputStreamPlus
    A DataOutputStreamPlus that writes ASYNCHRONOUSLY to a Netty Channel. The close() and flush() methods synchronously wait for pending writes, and will propagate any exceptions encountered in writing them to the wire. The correctness of this class depends on the ChannelPromise we create against a Channel always being completed, which appears to be a guarantee provided by Netty so long as the event loop is running. There are two logical threads accessing the state in this class: the eventLoop of the channel, and the writer (the writer thread may change, so long as only one utilises the class at any time). Each thread has exclusive write access to certain state in the class, with the other thread only viewing the state, simplifying concurrency considerations.

    • Constructor Detail

      • AsyncChannelOutputPlus

        public AsyncChannelOutputPlus​(io.netty.channel.Channel channel)

    • Method Detail

      • beginFlush

        protected io.netty.channel.ChannelPromise beginFlush​(long byteCount,
                                                     long lowWaterMark,
                                                     long highWaterMark)
                                              throws java.io.IOException
        Create a ChannelPromise for a flush of the given size.

        This method will not return until the write is permitted by the provided watermarks and in flight bytes, and on its completion will mark the requested bytes flushed.

        If this method returns normally, the ChannelPromise MUST be writtenAndFlushed, or else completed exceptionally.

        Throws:
        java.io.IOException

      • parkUntilFlushed

        protected void parkUntilFlushed​(long wakeUpWhenFlushed,
                                long signalWhenFlushed)
        Utility method for waitUntilFlushed, which actually parks the current thread until the necessary number of bytes have been flushed This may only be invoked by the writer thread, never by the eventLoop.

      • releaseSpace

        protected void releaseSpace​(long bytesFlushed)
        Update our flushed count, and signal any waiters. This may only be invoked by the eventLoop, never by the writer thread.

      • position

        public abstract long position()
        Description copied from interface: DataOutputPlus
        Returns the current position of the underlying target like a file-pointer or the position withing a buffer. Not every implementation may support this functionality. Whether or not this functionality is supported can be checked via the DataOutputPlus.hasPosition().

      • flushed

        public long flushed()

      • flushedToNetwork

        public long flushedToNetwork()

      • flush

        public void flush()
           throws java.io.IOException
        Perform an asynchronous flush, then waits until all outstanding flushes have completed
        Specified by:
        flush in interface java.io.Flushable
        Overrides:
        flush in class BufferedDataOutputStreamPlus
        Throws:
        java.io.IOException - if any flush fails

      • close

        public void close()
           throws java.io.IOException
        Flush any remaining writes, and release any buffers. The channel is not closed, as it is assumed to be managed externally. WARNING: This method requires mutual exclusivity with all other producer methods to run safely. It should only be invoked by the owning thread, never the eventLoop; the eventLoop should propagate errors to flushFailed, which will propagate them to the producer thread no later than its final invocation to close() or flush() (that must not be followed by any further writes).
        Specified by:
        close in interface java.lang.AutoCloseable
        Specified by:
        close in interface java.io.Closeable
        Overrides:
        close in class BufferedDataOutputStreamPlus
        Throws:
        java.io.IOException

      • discard

        public abstract void discard()
        Discard any buffered data, and the buffers that contain it. May be invoked instead of close() if we terminate exceptionally.