org.apache.druid.segment.realtime.appenderator

Interface Appenderator

All Superinterfaces:

QuerySegmentWalker

All Known Implementing Classes:

AppenderatorImpl, BatchAppenderator, StreamAppenderator

public interface Appenderator
extends QuerySegmentWalker

An Appenderator indexes data. It has some in-memory data and some persisted-on-disk data. It can serve queries on both of those. It can also push data to deep storage. But, it does not decide which segments data should go into. It also doesn't publish segments to the metadata store or monitor handoff; you have to do that yourself!

You can provide a Committer or a Supplier of one when you call one of the methods that add(org.apache.druid.segment.realtime.appenderator.SegmentIdWithShardSpec, org.apache.druid.data.input.InputRow, com.google.common.base.Supplier<org.apache.druid.data.input.Committer>), persistAll(org.apache.druid.data.input.Committer), or push(java.util.Collection<org.apache.druid.segment.realtime.appenderator.SegmentIdWithShardSpec>, org.apache.druid.data.input.Committer, boolean). The Committer should represent all data you have given to the Appenderator so far. This Committer will be used when that data has been persisted to disk. Concurrency: all methods defined in this class directly, including close() and closeNow(), i. e. all methods of the data appending and indexing lifecycle except drop(org.apache.druid.segment.realtime.appenderator.SegmentIdWithShardSpec) must be called from a single thread. Methods inherited from QuerySegmentWalker can be called concurrently from multiple threads.

Important note: For historical reasons there was a single implementation for this interface (AppenderatorImpl) but that since has been split into two classes: StreamAppenderator and BatchAppenderator. With this change all the query support & concurrency has been removed/changed in BatchAppenderator therefore this class no longer makes sense to have as an Appenderator. In the future we may want to refactor away the Appenderator interface from BatchAppenderator.

Nested Class Summary

Nested Classes

Modifier and Type

Interface and Description

static class

Appenderator.AppenderatorAddResult Result of add(org.apache.druid.segment.realtime.appenderator.SegmentIdWithShardSpec, org.apache.druid.data.input.InputRow, com.google.common.base.Supplier<org.apache.druid.data.input.Committer>) containing following information - SegmentIdWithShardSpec - identifier of segment to which rows are being added - int - positive number indicating how many summarized rows exist in this segment so far and - boolean - true if is set to false and persist is required; false otherwise

Method Summary

Modifier and Type	Method and Description
default Appenderator.AppenderatorAddResult	add(SegmentIdWithShardSpec identifier, InputRow row, com.google.common.base.Supplier<Committer> committerSupplier) Same as add(SegmentIdWithShardSpec, InputRow, Supplier, boolean), with allowIncrementalPersists set to true
Appenderator.AppenderatorAddResult	add(SegmentIdWithShardSpec identifier, InputRow row, com.google.common.base.Supplier<Committer> committerSupplier, boolean allowIncrementalPersists) Add a row.
void	clear() Drop all in-memory and on-disk data, and forget any previously-remembered commit metadata.
void	close() Stop any currently-running processing and clean up after ourselves.
void	closeNow() Stop all processing, abandoning current pushes, currently running persist may be allowed to finish if they persist critical metadata otherwise shutdown immediately.
com.google.common.util.concurrent.ListenableFuture<?>	drop(SegmentIdWithShardSpec identifier) Schedule dropping all data associated with a particular pending segment.
String	getDataSource() Return the name of the dataSource associated with this Appenderator.
String	getId() Return the identifier of this Appenderator; useful for log messages and such.
int	getRowCount(SegmentIdWithShardSpec identifier) Returns the number of rows in a particular pending segment.
List<SegmentIdWithShardSpec>	getSegments() Returns a list of all currently active segments.
int	getTotalRowCount() Returns the number of total rows in this appenderator of all segments pending push.
com.google.common.util.concurrent.ListenableFuture<Object>	persistAll(Committer committer) Persist any in-memory indexed data to durable storage.
com.google.common.util.concurrent.ListenableFuture<SegmentsAndCommitMetadata>	push(Collection<SegmentIdWithShardSpec> identifiers, Committer committer, boolean useUniquePath) Merge and push particular segments to deep storage.
Object	startJob() Perform any initial setup.

Methods inherited from interface org.apache.druid.query.QuerySegmentWalker

getQueryRunnerForIntervals, getQueryRunnerForSegments

Method Detail

getId

String getId()

Return the identifier of this Appenderator; useful for log messages and such.

getDataSource

String getDataSource()

Return the name of the dataSource associated with this Appenderator.

startJob

Object startJob()

Perform any initial setup. Should be called before using any other methods.

Returns:

currently persisted commit metadata

add

default Appenderator.AppenderatorAddResult add(SegmentIdWithShardSpec identifier,
                                               InputRow row,
                                               com.google.common.base.Supplier<Committer> committerSupplier)
                                        throws IndexSizeExceededException,
                                               SegmentNotWritableException

Same as add(SegmentIdWithShardSpec, InputRow, Supplier, boolean), with allowIncrementalPersists set to true

Throws:

IndexSizeExceededException

SegmentNotWritableException

add

Appenderator.AppenderatorAddResult add(SegmentIdWithShardSpec identifier,
                                       InputRow row,
                                       @Nullable
                                       com.google.common.base.Supplier<Committer> committerSupplier,
                                       boolean allowIncrementalPersists)
                                throws IndexSizeExceededException,
                                       SegmentNotWritableException

Add a row. Must not be called concurrently from multiple threads.

If no pending segment exists for the provided identifier, a new one will be created.

This method may trigger a persistAll(Committer) using the supplied Committer. If it does this, the Committer is guaranteed to be *created* synchronously with the call to add, but will actually be used asynchronously.

If committer is not provided, no metadata is persisted.

Parameters:

identifier - the segment into which this row should be added

row - the row to add

committerSupplier - supplier of a committer associated with all data that has been added, including this row if allowIncrementalPersists is set to false then this will not be used as no persist will be done automatically

allowIncrementalPersists - indicate whether automatic persist should be performed or not if required. If this flag is set to false then the return value should have Appenderator.AppenderatorAddResult.isPersistRequired set to true if persist was skipped because of this flag and it is assumed that the responsibility of calling persistAll(Committer) is on the caller.

Returns:

Appenderator.AppenderatorAddResult

Throws:

IndexSizeExceededException - if this row cannot be added because it is too large

SegmentNotWritableException - if the requested segment is known, but has been closed

getSegments

List<SegmentIdWithShardSpec> getSegments()

Returns a list of all currently active segments.

getRowCount

int getRowCount(SegmentIdWithShardSpec identifier)

Returns the number of rows in a particular pending segment.

Parameters:

identifier - segment to examine

Returns:

row count

Throws:

IllegalStateException - if the segment is unknown

getTotalRowCount

int getTotalRowCount()

Returns the number of total rows in this appenderator of all segments pending push.

Returns:

total number of rows

clear

void clear()
    throws InterruptedException

Drop all in-memory and on-disk data, and forget any previously-remembered commit metadata. This could be useful if, for some reason, rows have been added that we do not actually want to hand off. Blocks until all data has been cleared. This may take some time, since all pending persists must finish first.

Throws:

InterruptedException

drop

com.google.common.util.concurrent.ListenableFuture<?> drop(SegmentIdWithShardSpec identifier)

Schedule dropping all data associated with a particular pending segment. Unlike clear()), any on-disk commit metadata will remain unchanged. If there is no pending segment with this identifier, then this method will do nothing.

You should not write to the dropped segment after calling "drop". If you need to drop all your data and re-write it, consider clear() instead. This method might be called concurrently from a thread different from the "main data appending / indexing thread", from where all other methods in this class (except those inherited from QuerySegmentWalker) are called. This typically happens when drop() is called in an async future callback. drop() itself is cheap and relays heavy dropping work to an internal executor of this Appenderator.

Parameters:

identifier - the pending segment to drop

Returns:

future that resolves when data is dropped

persistAll

com.google.common.util.concurrent.ListenableFuture<Object> persistAll(@Nullable
                                                                      Committer committer)

Persist any in-memory indexed data to durable storage. This may be only somewhat durable, e.g. the machine's local disk. The Committer will be made synchronously with the call to persistAll, but will actually be used asynchronously. Any metadata returned by the committer will be associated with the data persisted to disk.

If committer is not provided, no metadata is persisted.

Parameters:

committer - a committer associated with all data that has been added so far

Returns:

future that resolves when all pending data has been persisted, contains commit metadata for this persist

push

com.google.common.util.concurrent.ListenableFuture<SegmentsAndCommitMetadata> push(Collection<SegmentIdWithShardSpec> identifiers,
                                                                                   @Nullable
                                                                                   Committer committer,
                                                                                   boolean useUniquePath)

Merge and push particular segments to deep storage. This will trigger an implicit persistAll(Committer) using the provided Committer.

After this method is called, you cannot add new data to any segments that were previously under construction.

If committer is not provided, no metadata is persisted.

Parameters:

identifiers - list of segments to push

committer - a committer associated with all data that has been added so far

useUniquePath - true if the segment should be written to a path with a unique identifier

Returns:

future that resolves when all segments have been pushed. The segment list will be the list of segments that have been pushed and the commit metadata from the Committer.

close

void close()

Stop any currently-running processing and clean up after ourselves. This allows currently running persists and pushes to finish. This will not remove any on-disk persisted data, but it will drop any data that has not yet been persisted.

closeNow

void closeNow()

Stop all processing, abandoning current pushes, currently running persist may be allowed to finish if they persist critical metadata otherwise shutdown immediately. This will not remove any on-disk persisted data, but it will drop any data that has not yet been persisted. Since this does not wait for pushes to finish, implementations have to make sure if any push is still happening in background thread then it does not cause any problems.