Package org.apache.druid.frame.channel

Interface WritableFrameChannel

All Superinterfaces:

AutoCloseable, Closeable

All Known Implementing Classes:

ComposingWritableFrameChannel, WritableFrameFileChannel

public interface WritableFrameChannel
extends Closeable

Interface for writing a sequence of result batches. Supports nonblocking writes through the writabilityFuture() method. May be implemented using an in-memory queue, disk file, stream, etc. Channels implementing this interface are used by a single writer; they do not support concurrent writes. Despite its name, instances of this class can typically accept any RowsAndColumns through the write(RowsAndColumns) method.

Field Summary

Fields

Modifier and Type	Field	Description
static final int	NO_PARTITION	Partition number used when there is no meaningful partition to associate with a batch of data.

Method Summary

Modifier and Type	Method	Description
void	close()	Finish writing to this channel.
void	fail(Throwable cause)	Called prior to close() if the writer has failed.
boolean	isClosed()	Whether close() has been called on this channel.
com.google.common.util.concurrent.ListenableFuture<?>	writabilityFuture()	Returns a future that resolves when write(org.apache.druid.query.rowsandcols.RowsAndColumns, int) is able to receive a new batch of data without blocking or throwing an exception.
default void	write(Frame frame)	Writes a frame without an attached partition number.
default void	write(Frame frame, int partitionNumber)	Writes a frame with an attached partition number.
default void	write(RowsAndColumns rac)	Writes a batch of data without an attached partition number.
void	write(RowsAndColumns rac, int partitionNumber)	Writes a batch of data with an attached partition number.

Field Details

NO_PARTITION

static final int NO_PARTITION

Partition number used when there is no meaningful partition to associate with a batch of data.

See Also:

• Constant Field Values

Method Details

write

void write(RowsAndColumns rac,
 int partitionNumber)
    throws IOException

Writes a batch of data with an attached partition number. May throw an exception if writabilityFuture() is unresolved.

Throws:

IOException

write

default void write(RowsAndColumns rac)
            throws IOException

Writes a batch of data without an attached partition number. May throw an exception if writabilityFuture() is unresolved.

Throws:

IOException

write

default void write(Frame frame,
 int partitionNumber)
            throws IOException

Writes a frame with an attached partition number. Equivalent to calling write(RowsAndColumns, int) with Frame.asRAC(). May throw an exception if writabilityFuture() is unresolved.

Throws:

IOException

write

default void write(Frame frame)
            throws IOException

Writes a frame without an attached partition number. Equivalent to calling write(RowsAndColumns) with Frame.asRAC(). May throw an exception if writabilityFuture() is unresolved.

Throws:

IOException

fail

void fail(@Nullable
 Throwable cause)
   throws IOException

Called prior to close() if the writer has failed. Must be followed by a call to close().

Parameters:

cause - optional cause of failure. Used by the in-memory channel BlockingQueueFrameChannel.Writable to propagate exeptions to downstream processors. Most other channels ignore the provided cause.

Throws:

IOException

close

void close()
    throws IOException

Finish writing to this channel. When this method is called without fail(Throwable) having previously been called, the writer is understood to have completed successfully. After calling this method, no additional calls to write(org.apache.druid.query.rowsandcols.RowsAndColumns, int), fail(Throwable), or this method are permitted.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException

isClosed

boolean isClosed()

Whether close() has been called on this channel.

writabilityFuture

com.google.common.util.concurrent.ListenableFuture<?> writabilityFuture()

Returns a future that resolves when write(org.apache.druid.query.rowsandcols.RowsAndColumns, int) is able to receive a new batch of data without blocking or throwing an exception. The future never resolves to an exception.