Package org.apache.druid.frame.processor
Interface FrameProcessor<T>
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- All Known Implementing Classes:
FrameChannelBatcher
,FrameChannelHashPartitioner
,FrameChannelMerger
,FrameChannelMixer
public interface FrameProcessor<T>
A FrameProcessor is like an incremental version of Runnable that operates onReadableFrameChannel
andWritableFrameChannel
. It is designed to enable interleaved non-blocking work on a fixed-size thread pool. Typically, this is done using an instance ofFrameProcessorExecutor
.
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description void
cleanup()
Closes resources used by this worker.List<ReadableFrameChannel>
inputChannels()
List of input channels.List<WritableFrameChannel>
outputChannels()
List of output channels.ReturnOrAwait<T>
runIncrementally(it.unimi.dsi.fastutil.ints.IntSet readableInputs)
Runs some of the algorithm, without blocking, and either returns a value or a set of input channels to wait for.
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Method Detail
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inputChannels
List<ReadableFrameChannel> inputChannels()
List of input channels. The positions of channels in this list are used to build thereadableInputs
set provided torunIncrementally(it.unimi.dsi.fastutil.ints.IntSet)
.
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outputChannels
List<WritableFrameChannel> outputChannels()
List of output channels.
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runIncrementally
ReturnOrAwait<T> runIncrementally(it.unimi.dsi.fastutil.ints.IntSet readableInputs) throws InterruptedException, IOException
Runs some of the algorithm, without blocking, and either returns a value or a set of input channels to wait for. This method is called byFrameProcessorExecutor.runFully(org.apache.druid.frame.processor.FrameProcessor<T>, java.lang.String)
when all output channels are writable. Therefore, it is guaranteed that each output channel can accept at least one frame. This method must not read more than one frame from each readable input channel, and must not write more than one frame to each output channel.- Parameters:
readableInputs
- channels frominputChannels()
that are either finished or ready to read. That is: eitherReadableFrameChannel.isFinished()
orReadableFrameChannel.canRead()
are true.- Returns:
- either a final return value or a set of input channels to wait for. Must be nonnull.
- Throws:
InterruptedException
IOException
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cleanup
void cleanup() throws IOException
Closes resources used by this worker. Exact same concept asCloseable.close()
. This interface does not extend Closeable, in order to make it easier to find all places where cleanup happens. (Static analysis tools can lose the thread when Closeables are closed in generic ways.) Implementations typically callReadableFrameChannel.close()
andWritableFrameChannel.close()
on all input and output channels, as well as releasing any additional resources that may be held, such asFrameWriter
. In cases of cancellation, this method may be called even ifrunIncrementally(it.unimi.dsi.fastutil.ints.IntSet)
has not yet returned a result viaReturnOrAwait.returnObject(T)
.- Throws:
IOException
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