PIP 68: Exclusive Producer #8685

merlimat · 2020-11-24T15:59:45Z

Motivation

Implementation of https://github.com/apache/pulsar/wiki/PIP-68%3A-Exclusive-Producer

This is the first part of the implementation of exclusive producer. It adds support for ProducerAccessMode.Exclusive.

The 2nd mode, ProducerAccessMode.WaitForExclusive, will be added in separate PR.

rdhabalia

LGTM.. few minor comments.

pulsar-broker/src/main/java/org/apache/pulsar/broker/service/AbstractTopic.java

rdhabalia · 2020-11-25T07:54:17Z

pulsar-broker/src/main/java/org/apache/pulsar/broker/service/AbstractTopic.java

+    }
+
+    protected CompletableFuture<Optional<Long>> incrementTopicEpochIfNeeded(Producer producer) {
+        lock.writeLock().lock();


can we avoid locking for normal producer usecase?

if (producers.isEmpty() && producer.getAccessMode() == Shared) { return CompletableFuture.completedFuture(topicEpoch); }

+1 to @rdhabalia suggestion

I'm not sure that we can avoid the locking, and I'm not sure that it's something to worry about in the context of adding a producer.
Actually, in the specific case there's still a race condition between updating the producers map, since the update to hasExclusiveProducer and the insertion into producers map should be atomic as well.

pulsar-broker/src/main/java/org/apache/pulsar/broker/service/AbstractTopic.java

rdhabalia · 2020-11-25T07:59:50Z

pulsar-broker/src/main/java/org/apache/pulsar/broker/service/AbstractTopic.java

+                    return future;
+                }
+
+           // case WaitForExclusive:


I have one suggestion. I am sure you must have thought about it but can't we rename WaitForExclusive with FailOver as it will be consistent to subscription type name and it will need no explanation and easy to understand.

The problem I see is that it's not exactly the same thing and that can confuse people:

The semantic of creating a WaitForExclusive is different because the newProducer()....create() call is hanging until that particular producer is selected, unlike in consumers where it's created immediately but it will not receive messages.

The use case is mostly different from "failover" for reliability purpose, since you can use WaitForExclusive to do leader election

rdhabalia · 2020-11-25T08:02:26Z

pulsar-broker/src/main/java/org/apache/pulsar/broker/service/AbstractTopic.java

+        checkArgument(producer.getTopic() == this);
+
+        if (producers.remove(producer.getProducerName(), producer)) {
+            handleProducerRemoved(producer);


shouldn't we need lock here else it may create a race condition and producer with WaitForExclusive may wait forever.

No lock needed there so far. Other changes are needed for WaitForExclusive, it's not implemented in this PR

eolivelli

Great work!
I left a few little suggestions

eolivelli · 2020-11-25T08:07:58Z

pulsar-broker/src/main/java/org/apache/pulsar/broker/service/AbstractTopic.java

+    }
+
+    protected CompletableFuture<Optional<Long>> incrementTopicEpochIfNeeded(Producer producer) {
+        lock.writeLock().lock();


+1 to @rdhabalia suggestion

pulsar-broker/src/main/java/org/apache/pulsar/broker/service/AbstractTopic.java

pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentTopic.java

merlimat · 2020-12-01T18:54:18Z

Rebased and addressed comments

eolivelli

LGTM
Great work

One question, with an Exclusive Producer, what happens if I delete and recreate a topic?

create a topic
start ex producer and write
delete/create the same topic
is the producer still valid?
I expect the ex producer to be fenced out.
Is this the case?

eolivelli · 2020-12-02T05:56:34Z

pulsar-broker/src/test/java/org/apache/pulsar/broker/service/BrokerTestBase.java

@@ -86,5 +88,11 @@ void runMessageExpiryCheck() {
        }
    }

+    private static final Random random = new Random();


What about setting a fixed seed? In order to have reproducible tests execution.

This is just to get random topic names. We don't really need it to be reproducible.

merlimat · 2020-12-02T06:32:05Z

One question, with an Exclusive Producer, what happens if I delete and recreate a topic?

create a topic

start ex producer and write

delete/create the same topic

is the producer still valid?
I expect the ex producer to be fenced out.
Is this the case?

Deleting the topic will delete all the state associated with the topic. If the topic is re-created, it's effectively a different topic. All the state associated with the topic is gone: subscriptions, dedup state, fencing.

The topic epoch will be reset after the deletion, so it should allow the producer. I will add specific test for this.

eolivelli

Great. Thank you

* PIP 68: Exclusive Producer * Added missing enums cases in C++ * Addressed comments * Moved constant to top of file * Fix mistake in previous update * Added handling for topic deletion

merlimat added the type/feature The PR added a new feature or issue requested a new feature label Nov 24, 2020

merlimat added this to the 2.8.0 milestone Nov 24, 2020

merlimat requested review from ivankelly, sijie, srkukarni, rdhabalia, jerrypeng, codelipenghui and massakam November 24, 2020 15:59

merlimat self-assigned this Nov 24, 2020

merlimat force-pushed the exclusive-producer branch from 0ceb670 to e6f7c8e Compare November 24, 2020 16:17

rdhabalia reviewed Nov 25, 2020

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eolivelli reviewed Nov 25, 2020

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jerrypeng approved these changes Nov 30, 2020

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merlimat force-pushed the exclusive-producer branch from 6ef1fc1 to c2d57bc Compare December 1, 2020 18:54

eolivelli approved these changes Dec 2, 2020

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rdhabalia approved these changes Dec 2, 2020

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merlimat added 6 commits December 2, 2020 15:42

PIP 68: Exclusive Producer

a60156f

Added missing enums cases in C++

3524cc0

Addressed comments

1f86250

Moved constant to top of file

69a0a8f

Fix mistake in previous update

9c0dda2

Added handling for topic deletion

eba7bbe

merlimat force-pushed the exclusive-producer branch from f6aecc3 to eba7bbe Compare December 2, 2020 23:42

merlimat merged commit d12486b into apache:master Dec 3, 2020

merlimat deleted the exclusive-producer branch December 3, 2020 01:38

Lanayx mentioned this pull request Jun 26, 2021

Support exclusive producer fsprojects/pulsar-client-dotnet#172

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PIP 68: Exclusive Producer #8685

PIP 68: Exclusive Producer #8685

merlimat commented Nov 24, 2020

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rdhabalia Nov 25, 2020

eolivelli Nov 25, 2020

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PIP 68: Exclusive Producer #8685

PIP 68: Exclusive Producer #8685

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merlimat commented Nov 24, 2020

Motivation

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