Package io.debezium.connector.mongodb.events

Class BufferingChangeStreamCursor<TResult>

java.lang.Object

io.debezium.connector.mongodb.events.BufferingChangeStreamCursor<TResult>

Type Parameters:

TResult - the type of documents the cursor contains

All Implemented Interfaces:

com.mongodb.client.MongoChangeStreamCursor<BufferingChangeStreamCursor.ResumableChangeStreamEvent<TResult>>, com.mongodb.client.MongoCursor<BufferingChangeStreamCursor.ResumableChangeStreamEvent<TResult>>, Closeable, AutoCloseable, Iterator<BufferingChangeStreamCursor.ResumableChangeStreamEvent<TResult>>

@NotThreadSafe
public class BufferingChangeStreamCursor<TResult>
extends Object
implements com.mongodb.client.MongoChangeStreamCursor<BufferingChangeStreamCursor.ResumableChangeStreamEvent<TResult>>

An implementation of MongoChangeStreamCursor which immediately starts consuming available events into a buffer.

Internally this cursor starts a BufferingChangeStreamCursor.EventFetcher as a separate thread on provided executor. Although the implementation is internally thread safe the cursors is not meant to be accessed concurrently from multiple threads.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final class	BufferingChangeStreamCursor.EventFetcher<TResult>	Runnable responsible for fetching events from ChangeStreamIterable and buffering them in provided queue;
static final class	BufferingChangeStreamCursor.ResumableChangeStreamEvent<TResult>	Combination of change stream event and resume token

Field Summary

Fields

Modifier and Type	Field	Description
private final ExecutorService	executor
private final BufferingChangeStreamCursor.EventFetcher<TResult>	fetcher
static final int	FETCHER_SHUTDOWN_TIMEOUT
private org.bson.BsonDocument	lastResumeToken
private static final org.slf4j.Logger	LOGGER
static final int	THROTTLE_NO_MESSAGE_BEFORE_PAUSE
private final DelayStrategy	throttler

Constructor Summary

Constructors

Constructor	Description
BufferingChangeStreamCursor(BufferingChangeStreamCursor.EventFetcher<TResult> fetcher, ExecutorService executor, DelayStrategy throttler)	Creates new prefetching cursor
BufferingChangeStreamCursor(BufferingChangeStreamCursor.EventFetcher<TResult> fetcher, ExecutorService executor, Duration throttleMaxSleep)

Method Summary

Modifier and Type	Method	Description
int	available()	See BufferingChangeStreamCursor.EventFetcher.size()
void	close()
static <TResult> BufferingChangeStreamCursor<TResult>	fromIterable(com.mongodb.client.ChangeStreamIterable<TResult> stream, MongoDbTaskContext taskContext, MongoDbStreamingChangeEventSourceMetrics metrics, Clock clock)
org.bson.BsonDocument	getResumeToken()
com.mongodb.ServerAddress	getServerAddress()
com.mongodb.ServerCursor	getServerCursor()
boolean	hasNext()
BufferingChangeStreamCursor.ResumableChangeStreamEvent<TResult>	next()	Returns next event in buffer.
private BufferingChangeStreamCursor.ResumableChangeStreamEvent<TResult>	pollWithDelay()	Repeatedly polling fetcher for new event, exponentially waiting between polls until limit is reached
BufferingChangeStreamCursor<TResult>	start()
BufferingChangeStreamCursor.ResumableChangeStreamEvent<TResult>	tryNext()

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Iterator

remove

Methods inherited from interface com.mongodb.client.MongoCursor

forEachRemaining

Field Details

LOGGER

private static final org.slf4j.Logger LOGGER

THROTTLE_NO_MESSAGE_BEFORE_PAUSE

public static final int THROTTLE_NO_MESSAGE_BEFORE_PAUSE

See Also:

• Constant Field Values

FETCHER_SHUTDOWN_TIMEOUT

public static final int FETCHER_SHUTDOWN_TIMEOUT

See Also:

• Constant Field Values

fetcher

private final BufferingChangeStreamCursor.EventFetcher<TResult> fetcher

executor

private final ExecutorService executor

throttler

private final DelayStrategy throttler

lastResumeToken

private org.bson.BsonDocument lastResumeToken

Constructor Details

BufferingChangeStreamCursor

public BufferingChangeStreamCursor(BufferingChangeStreamCursor.EventFetcher<TResult> fetcher,
 ExecutorService executor,
 DelayStrategy throttler)

Creates new prefetching cursor

Parameters:

fetcher - MongoDB change event fetcher

executor - executor used to dispatch buffering thread

throttler - throttling mechanism

BufferingChangeStreamCursor

public BufferingChangeStreamCursor(BufferingChangeStreamCursor.EventFetcher<TResult> fetcher,
 ExecutorService executor,
 Duration throttleMaxSleep)

Method Details

fromIterable

public static <TResult>
BufferingChangeStreamCursor<TResult> fromIterable(com.mongodb.client.ChangeStreamIterable<TResult> stream,
 MongoDbTaskContext taskContext,
 MongoDbStreamingChangeEventSourceMetrics metrics,
 Clock clock)

start

public BufferingChangeStreamCursor<TResult> start()

tryNext

public BufferingChangeStreamCursor.ResumableChangeStreamEvent<TResult> tryNext()

Specified by:

tryNext in interface com.mongodb.client.MongoCursor<TResult>

next

public BufferingChangeStreamCursor.ResumableChangeStreamEvent<TResult> next()

Returns next event in buffer. Not that unlike other Mongo implementation this method does not block

Specified by:

next in interface Iterator<TResult>

Specified by:

next in interface com.mongodb.client.MongoCursor<TResult>

Returns:

event

Throws:

NoSuchElementException - when no element is available

pollWithDelay

private BufferingChangeStreamCursor.ResumableChangeStreamEvent<TResult> pollWithDelay()

Repeatedly polling fetcher for new event, exponentially waiting between polls until limit is reached

Returns:

event or null if not available within time limit

hasNext

public boolean hasNext()

Specified by:

hasNext in interface Iterator<TResult>

Specified by:

hasNext in interface com.mongodb.client.MongoCursor<TResult>

available

public int available()

See BufferingChangeStreamCursor.EventFetcher.size()

Specified by:

available in interface com.mongodb.client.MongoCursor<TResult>

getResumeToken

public org.bson.BsonDocument getResumeToken()

Specified by:

getResumeToken in interface com.mongodb.client.MongoChangeStreamCursor<TResult>

getServerCursor

public com.mongodb.ServerCursor getServerCursor()

Specified by:

getServerCursor in interface com.mongodb.client.MongoCursor<TResult>

getServerAddress

public com.mongodb.ServerAddress getServerAddress()

Specified by:

getServerAddress in interface com.mongodb.client.MongoCursor<TResult>

close

public void close()

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in interface com.mongodb.client.MongoCursor<TResult>