From 6430c541dc3971f58a26b915a8458812a646fe40 Mon Sep 17 00:00:00 2001
From: lipenghui <penghui@apache.org>
Date: Sun, 27 Jun 2021 20:30:15 +0800
Subject: [PATCH] Fix race condition of the
 SystemTopicBasedTopicPoliciesService (#11097)

### Motivation

Currently, we are triggering the reader to read more messages not waiting for the init policies cache to complete,
This might lead to the init process got hasMessages=true but not able to read the message since the message has been
consumed by the read more entries process will lead to the `topic policy cache not init` exception.

Here are the details of the race condition:

https://github.com/apache/pulsar/blob/0b67438d23bbbc46b500e896a18aad715a514fd9/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/SystemTopicBasedTopicPoliciesService.java#L190

https://github.com/apache/pulsar/blob/0b67438d23bbbc46b500e896a18aad715a514fd9/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/SystemTopicBasedTopicPoliciesService.java#L248

https://github.com/apache/pulsar/blob/0b67438d23bbbc46b500e896a18aad715a514fd9/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/SystemTopicBasedTopicPoliciesService.java#L275

(cherry picked from commit 81063c04870ba7fa26222e57e4d4e94145e0a1e0)
---
 .../broker/service/SystemTopicBasedTopicPoliciesService.java | 5 +++--
 .../org/apache/pulsar/broker/admin/TopicPoliciesTest.java    | 5 +++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/SystemTopicBasedTopicPoliciesService.java b/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/SystemTopicBasedTopicPoliciesService.java
index 87ff3b8710f04..e2d2e7450f03b 100644
--- a/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/SystemTopicBasedTopicPoliciesService.java
+++ b/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/SystemTopicBasedTopicPoliciesService.java
@@ -188,7 +188,7 @@ public CompletableFuture<Void> addOwnedNamespaceBundleAsync(NamespaceBundle name
                         result.completeExceptionally(ex);
                     } else {
                         initPolicesCache(reader, result);
-                        readMorePolicies(reader);
+                        result.thenRun(() -> readMorePolicies(reader));
                     }
                 });
             }
@@ -254,6 +254,7 @@ private void initPolicesCache(SystemTopicClient.Reader<PulsarEvent> reader, Comp
                         readerCaches.remove(reader.getSystemTopic().getTopicName().getNamespaceObject());
                     }
                     refreshTopicPoliciesCache(msg);
+                    notifyListener(msg);
                     if (log.isDebugEnabled()) {
                         log.debug("[{}] Loop next event reading for system topic.",
                                 reader.getSystemTopic().getTopicName().getNamespaceObject());
@@ -264,9 +265,9 @@ private void initPolicesCache(SystemTopicClient.Reader<PulsarEvent> reader, Comp
                 if (log.isDebugEnabled()) {
                     log.debug("[{}] Reach the end of the system topic.", reader.getSystemTopic().getTopicName());
                 }
-                future.complete(null);
                 policyCacheInitMap.computeIfPresent(
                         reader.getSystemTopic().getTopicName().getNamespaceObject(), (k, v) -> true);
+                future.complete(null);
             }
         });
     }
diff --git a/pulsar-broker/src/test/java/org/apache/pulsar/broker/admin/TopicPoliciesTest.java b/pulsar-broker/src/test/java/org/apache/pulsar/broker/admin/TopicPoliciesTest.java
index f66f464490aa4..ecd53b276c6c7 100644
--- a/pulsar-broker/src/test/java/org/apache/pulsar/broker/admin/TopicPoliciesTest.java
+++ b/pulsar-broker/src/test/java/org/apache/pulsar/broker/admin/TopicPoliciesTest.java
@@ -947,8 +947,9 @@ public void testRestart() throws Exception {
                 new InactiveTopicPolicies(InactiveTopicDeleteMode.delete_when_no_subscriptions,200,false);
         admin.topics().setInactiveTopicPolicies(topic, inactiveTopicPolicies);
 
+        InactiveTopicPolicies finalInactiveTopicPolicies = inactiveTopicPolicies;
         Awaitility.await()
-                .untilAsserted(() -> Assert.assertNotNull(admin.topics().getInactiveTopicPolicies(topic)));
+                .untilAsserted(() -> Assert.assertEquals(admin.topics().getInactiveTopicPolicies(topic), finalInactiveTopicPolicies));
 
         // restart broker, policy should still take effect
         restartBroker();
@@ -956,7 +957,7 @@ public void testRestart() throws Exception {
         // Trigger the cache init.
         Producer<byte[]> producer = pulsarClient.newProducer().topic(topic).create();
 
-        InactiveTopicPolicies finalInactiveTopicPolicies = inactiveTopicPolicies;
+
         Awaitility.await()
                 .untilAsserted(() -> {
                     PersistentTopic persistentTopic = (PersistentTopic) pulsar.getBrokerService().getTopicIfExists(topic).get().get();