Fix for the hang during deletion of engine=Kafka (one more time) (#11145)

* Added flag for safer rdkafka destruction, but more testing detected another hang case, which has no straigt solutions and can be workarounded currenly only by draining the consumer queue, so destructor is back

* After review fixes

* After review fixes2

* After review fixes3

contrib/cppkafka

@@ -1 +1 @@
-Subproject commit 9b184d881c15cc50784b28688c7c99d3d764db24
+Subproject commit f555ee36aaa74d17ca0dab3ce472070a610b2966

src/Storages/Kafka/ReadBufferFromKafkaConsumer.cpp

@@ -15,6 +15,7 @@ namespace ErrorCodes
 
 using namespace std::chrono_literals;
 const auto MAX_TIME_TO_WAIT_FOR_ASSIGNMENT_MS = 15000;
+const auto DRAIN_TIMEOUT_MS = 5000ms;
 
 
 ReadBufferFromKafkaConsumer::ReadBufferFromKafkaConsumer(
@@ -80,9 +81,72 @@ ReadBufferFromKafkaConsumer::ReadBufferFromKafkaConsumer(
     });
 }
 
-// NOTE on removed desctuctor: There is no need to unsubscribe prior to calling rd_kafka_consumer_close().
+ReadBufferFromKafkaConsumer::~ReadBufferFromKafkaConsumer()
-// check: https://github.com/edenhill/librdkafka/blob/master/INTRODUCTION.md#termination
+{
-// manual destruction was source of weird errors (hangs during droping kafka table, etc.)
+    try
+    {
+        if (!consumer->get_subscription().empty())
+        {
+            try
+            {
+                consumer->unsubscribe();
+            }
+            catch (const cppkafka::HandleException & e)
+            {
+                LOG_ERROR(log, "Error during unsubscribe: " << e.what());
+            }
+            drain();
+        }
+    }
+    catch (const cppkafka::HandleException & e)
+    {
+        LOG_ERROR(log, "Error while destructing consumer: " << e.what());
+    }
+
+}
+
+// Needed to drain rest of the messages / queued callback calls from the consumer
+// after unsubscribe, otherwise consumer will hang on destruction
+// see https://github.com/edenhill/librdkafka/issues/2077
+//     https://github.com/confluentinc/confluent-kafka-go/issues/189 etc.
+void ReadBufferFromKafkaConsumer::drain()
+{
+    auto start_time = std::chrono::steady_clock::now();
+    cppkafka::Error last_error(RD_KAFKA_RESP_ERR_NO_ERROR);
+
+    while (true)
+    {
+        auto msg = consumer->poll(100ms);
+        if (!msg)
+            break;
+
+        auto error = msg.get_error();
+
+        if (error)
+        {
+            if (msg.is_eof() || error == last_error)
+            {
+                break;
+            }
+            else
+            {
+                LOG_ERROR(log, "Error during draining: " << error);
+            }
+        }
+
+        // i don't stop draining on first error,
+        // only if it repeats once again sequentially
+        last_error = error;
+
+        auto ts = std::chrono::steady_clock::now();
+        if (std::chrono::duration_cast<std::chrono::milliseconds>(ts-start_time) > DRAIN_TIMEOUT_MS)
+        {
+            LOG_ERROR(log, "Timeout during draining.");
+            break;
+        }
+    }
+}
+
 
 void ReadBufferFromKafkaConsumer::commit()
 {

src/Storages/Kafka/ReadBufferFromKafkaConsumer.h

@@ -28,7 +28,7 @@ public:
         const std::atomic<bool> & stopped_,
         const Names & _topics
     );
-
+    ~ReadBufferFromKafkaConsumer() override;
     void allowNext() { allowed = true; } // Allow to read next message.
     void commit(); // Commit all processed messages.
     void subscribe(); // Subscribe internal consumer to topics.
@@ -75,6 +75,8 @@ private:
     cppkafka::TopicPartitionList assignment;
     const Names topics;
 
+    void drain();
+
     bool nextImpl() override;
 };
 

src/Storages/Kafka/StorageKafka.cpp

@@ -293,6 +293,7 @@ ConsumerBufferPtr StorageKafka::createReadBuffer()
 
     // Create a consumer and subscribe to topics
     auto consumer = std::make_shared<cppkafka::Consumer>(conf);
+    consumer->set_destroy_flags(RD_KAFKA_DESTROY_F_NO_CONSUMER_CLOSE);
 
     // Limit the number of batched messages to allow early cancellations
     const Settings & settings = global_context.getSettingsRef();

tests/integration/test_storage_kafka/test.py

@@ -246,6 +246,50 @@ def test_kafka_consumer_hang(kafka_cluster):
     # 'dr'||'op' to avoid self matching
     assert int(instance.query("select count() from system.processes where position(lower(query),'dr'||'op')>0")) == 0
 
+@pytest.mark.timeout(180)
+def test_kafka_consumer_hang2(kafka_cluster):
+
+    instance.query('''
+        DROP TABLE IF EXISTS test.kafka;
+
+        CREATE TABLE test.kafka (key UInt64, value UInt64)
+            ENGINE = Kafka
+            SETTINGS kafka_broker_list = 'kafka1:19092',
+                     kafka_topic_list = 'consumer_hang2',
+                     kafka_group_name = 'consumer_hang2',
+                     kafka_format = 'JSONEachRow';
+
+        CREATE TABLE test.kafka2 (key UInt64, value UInt64)
+            ENGINE = Kafka
+            SETTINGS kafka_broker_list = 'kafka1:19092',
+                     kafka_topic_list = 'consumer_hang2',
+                     kafka_group_name = 'consumer_hang2',
+                     kafka_format = 'JSONEachRow';
+        ''')
+
+    # first consumer subscribe the topic, try to poll some data, and go to rest
+    instance.query('SELECT * FROM test.kafka')
+
+    # second consumer do the same leading to rebalance in the first
+    # consumer, try to poll some data
+    instance.query('SELECT * FROM test.kafka2')
+
+#echo 'SELECT * FROM test.kafka; SELECT * FROM test.kafka2; DROP TABLE test.kafka;' | clickhouse client -mn &
+#    kafka_cluster.open_bash_shell('instance')
+
+    # first consumer has pending rebalance callback unprocessed (no poll after select)
+    # one of those queries was failing because of
+    # https://github.com/edenhill/librdkafka/issues/2077
+    # https://github.com/edenhill/librdkafka/issues/2898
+    instance.query('DROP TABLE test.kafka')
+    instance.query('DROP TABLE test.kafka2')
+
+
+    # from a user perspective: we expect no hanging 'drop' queries
+    # 'dr'||'op' to avoid self matching
+    assert int(instance.query("select count() from system.processes where position(lower(query),'dr'||'op')>0")) == 0
+
+
 @pytest.mark.timeout(180)
 def test_kafka_csv_with_delimiter(kafka_cluster):
     instance.query('''
@@ -1130,6 +1174,7 @@ def test_kafka_rebalance(kafka_cluster):
 
     print(instance.query('SELECT count(), uniqExact(key), max(key) + 1 FROM test.destination'))
 
+    # Some queries to debug...
     # SELECT * FROM test.destination where key in (SELECT key FROM test.destination group by key having count() <> 1)
     # select number + 1 as key from numbers(4141) left join test.destination using (key) where  test.destination.key = 0;
     # SELECT * FROM test.destination WHERE key between 2360 and 2370 order by key;
@@ -1137,6 +1182,18 @@ def test_kafka_rebalance(kafka_cluster):
     # select toUInt64(0) as _partition, number + 1 as _offset from numbers(400) left join test.destination using (_partition,_offset) where test.destination.key = 0 order by _offset;
     # SELECT * FROM test.destination WHERE _partition = 0 and _offset between 220 and 240 order by _offset;
 
+    # CREATE TABLE test.reference (key UInt64, value UInt64) ENGINE = Kafka SETTINGS kafka_broker_list = 'kafka1:19092',
+    #             kafka_topic_list = 'topic_with_multiple_partitions',
+    #             kafka_group_name = 'rebalance_test_group_reference',
+    #             kafka_format = 'JSONEachRow',
+    #             kafka_max_block_size = 100000;
+    #
+    # CREATE MATERIALIZED VIEW test.reference_mv Engine=Log AS
+    #     SELECT  key, value, _topic,_key,_offset, _partition, _timestamp, 'reference' as _consumed_by
+    # FROM test.reference;
+    #
+    # select * from test.reference_mv left join test.destination using (key,_topic,_offset,_partition) where test.destination._consumed_by = '';
+
     result = int(instance.query('SELECT count() == uniqExact(key) FROM test.destination'))
 
     for consumer_index in range(NUMBER_OF_CONSURRENT_CONSUMERS):