[
https://issues.apache.org/jira/browse/FLINK-9083?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16691813#comment-16691813
]
ASF GitHub Bot commented on FLINK-9083:
---------------------------------------
azagrebin commented on a change in pull request #6782: [FLINK-9083][Cassandra
Connector] Add async backpressure support to Cassandra Connector
URL: https://github.com/apache/flink/pull/6782#discussion_r234653055
##########
File path:
flink-connectors/flink-connector-cassandra/src/main/java/org/apache/flink/streaming/connectors/cassandra/CassandraSinkBase.java
##########
@@ -43,70 +48,82 @@
*/
public abstract class CassandraSinkBase<IN, V> extends RichSinkFunction<IN>
implements CheckpointedFunction {
protected final Logger log = LoggerFactory.getLogger(getClass());
- protected transient Cluster cluster;
- protected transient Session session;
- protected transient volatile Throwable exception;
- protected transient FutureCallback<V> callback;
+ // ------------------------ Default Configurations
------------------------
+
+ /**
+ * The default maximum number of concurrent requests. By default,
{@code Integer.MAX_VALUE}.
+ */
+ public static final int DEFAULT_MAX_CONCURRENT_REQUESTS =
Integer.MAX_VALUE;
+
+ /**
+ * The default timeout duration when acquiring a permit to execute. By
default, {@code Long.MAX_VALUE}.
+ */
+ public static final long DEFAULT_MAX_CONCURRENT_REQUESTS_TIMEOUT =
Long.MAX_VALUE;
+
+ /**
+ * The default timeout unit when acquiring a permit to execute. By
default, milliseconds.
+ */
+ public static final TimeUnit
DEFAULT_MAX_CONCURRENT_REQUESTS_TIMEOUT_UNIT = TimeUnit.MILLISECONDS;
+
+ // ------------------------- Configuration Fields
-------------------------
+
+ private int maxConcurrentRequests = DEFAULT_MAX_CONCURRENT_REQUESTS;
+ private long maxConcurrentRequestsTimeout =
DEFAULT_MAX_CONCURRENT_REQUESTS_TIMEOUT;
+ private TimeUnit maxConcurrentRequestsTimeoutUnit =
DEFAULT_MAX_CONCURRENT_REQUESTS_TIMEOUT_UNIT;
+
+ // --------------------------- Cassandra Fields
---------------------------
private final ClusterBuilder builder;
- private final AtomicInteger updatesPending = new AtomicInteger();
+ protected transient Cluster cluster;
+ protected transient Session session;
+
+ // ------------------------ Synchronization Fields
------------------------
+
+ private AtomicReference<Throwable> throwable;
+ private Semaphore semaphore;
+ private Phaser phaser;
CassandraSinkBase(ClusterBuilder builder) {
this.builder = builder;
ClosureCleaner.clean(builder, true);
}
- @Override
- public void open(Configuration configuration) {
- this.callback = new FutureCallback<V>() {
- @Override
- public void onSuccess(V ignored) {
- int pending = updatesPending.decrementAndGet();
- if (pending == 0) {
- synchronized (updatesPending) {
- updatesPending.notifyAll();
- }
- }
- }
+ // ----------------------------- Sink Methods
-----------------------------
+ @Override
+ public void open(Configuration parameters) {
+ cluster = createCluster();
+ session = createSession();
+
+ throwable = new AtomicReference<>();
+ semaphore = new Semaphore(maxConcurrentRequests);
+ /*
+ * A Phaser is a flexible and reusable synchronization barrier
similar to CyclicBarrier and CountDownLatch.
+ *
+ * This Phaser is configured to support "1 + N" parties.
+ * - "1" for the CassandraSinkBase to arrive and to await at
the Phaser during a flush() call.
+ * - "N" for the varying number of invoke() calls that
register and de-register with the Phaser.
+ *
+ * The Phaser awaits the completion of the advancement of a
phase prior to returning from a register() call.
+ * This behavior ensures that no backlogged invoke() calls
register to execute while the Semaphore's permits
+ * are being released during a flush() call.
+ */
+ phaser = new Phaser(1) {
Review comment:
If I understand correctly:
> The only feature we would miss given the streaming and back-pressured
nature of Flink, is the Phaser preventing invoke() calls backed up on the
semaphore from delaying the flush()
I think `invoke()` is not supposed to be called concurrently with
`snapshotState()/flush()`or after `close()`.
Anyways, I see some space advantage in using `Phaser`.
----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on GitHub and use the
URL above to go to the specific comment.
For queries about this service, please contact Infrastructure at:
us...@infra.apache.org
> Add async backpressure support to Cassandra Connector
> -----------------------------------------------------
>
> Key: FLINK-9083
> URL: https://issues.apache.org/jira/browse/FLINK-9083
> Project: Flink
> Issue Type: Improvement
> Components: Cassandra Connector
> Reporter: Jacob Park
> Assignee: Jacob Park
> Priority: Minor
> Labels: pull-request-available
>
> As the CassandraSinkBase derivatives utilize async writes, they do not block
> the task to introduce any backpressure.
> I am currently using a semaphore to provide backpressure support by blocking
> at a maximum concurrent requests limit like how DataStax's Spark Cassandra
> Connector functions:
> [https://github.com/datastax/spark-cassandra-connector/blob/v2.0.7/spark-cassandra-connector/src/main/scala/com/datastax/spark/connector/writer/AsyncExecutor.scala#L18]
> This improvement has greatly improved the fault-tolerance of our Cassandra
> Sink Connector implementation on Apache Flink in production. I would like to
> contribute this feature back upstream.
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
