[cpp client] Bugfix prevent dup consumer for same topic subscription (a…

…pache#3748)

Same fix as apache#3746 but for cpp client.

  - Filter consumers for the same topic name.
  - Add test to verify that same subscription names with different topics are
    allowed to be different consumers subscription instead of reused.

pulsar-client-cpp/lib/ClientImpl.cc

@@ -344,7 +344,8 @@ void ClientImpl::subscribeAsync(const std::string& topic, const std::string& con
             ConsumersList consumers(consumers_);
             for (auto& weakPtr : consumers) {
                 ConsumerImplBasePtr consumer = weakPtr.lock();
-                if (consumer && consumer->getSubscriptionName() == consumerName && !consumer->isClosed()) {
+                if (consumer && consumer->getSubscriptionName() == consumerName &&
+                    consumer->getTopic() == topic && !consumer->isClosed()) {
                     lock.unlock();
                     LOG_INFO("Reusing existing consumer instance for " << topic << " -- " << consumerName);
                     callback(ResultOk, Consumer(consumer));

pulsar-client-cpp/tests/BasicEndToEndTest.cc

@@ -2909,4 +2909,34 @@ TEST(BasicEndToEndTest, testNegativeAcksWithPartitions) {
     ASSERT_FALSE(res != 204 && res != 409);
 
     testNegativeAcks(topicName, true);
-}
+}
+
+TEST(BasicEndToEndTest, testPreventDupConsumersAllowSameSubForDifferentTopics) {
+    ClientConfiguration config;
+    Client client(lookupUrl);
+    std::string subsName = "my-only-sub";
+    std::string topicName =
+        "persistent://public/default/testPreventDupConsumersAllowSameSubForDifferentTopics";
+    ConsumerConfiguration consumerConf;
+    consumerConf.setConsumerType(ConsumerShared);
+
+    Consumer consumerA;
+    Result resultA = client.subscribe(topicName, subsName, consumerConf, consumerA);
+    ASSERT_EQ(ResultOk, resultA);
+    ASSERT_EQ(consumerA.getSubscriptionName(), subsName);
+
+    Consumer consumerB;
+    Result resultB = client.subscribe(topicName, subsName, consumerConf, consumerB);
+    ASSERT_EQ(ResultOk, resultB);
+    ASSERT_EQ(consumerB.getSubscriptionName(), subsName);
+
+    Consumer consumerC;
+    Result resultC = client.subscribe(topicName + "-different-topic", subsName, consumerConf, consumerC);
+    ASSERT_EQ(ResultOk, resultB);
+    ASSERT_EQ(consumerB.getSubscriptionName(), subsName);
+    ASSERT_EQ(ResultOk, consumerA.close());
+    ASSERT_EQ(ResultAlreadyClosed, consumerB.close());
+
+    // consumer C should be a different instance from A and B and should be with open state.
+    ASSERT_EQ(ResultOk, consumerC.close());
+}