Elias Levy created FLINK-9731:
---------------------------------
Summary: Kafka source subtask begins to consume from earliest
offset
Key: FLINK-9731
URL: https://issues.apache.org/jira/browse/FLINK-9731
Project: Flink
Issue Type: Bug
Components: Kafka Connector
Affects Versions: 1.4.2
Reporter: Elias Levy
On Jun 30th 2018, at 9:35 am UTC, the Kafka source in subtask 7 in a Flink job
instance began consuming records from the earliest offsets available in Kafka
for the partitions assigned to it. Other subtasks did not exhibit this behavior
and continued operating normally.
Previous to the event the job exhibited no Kafka lag. The job showed no failed
checkpoints and the job did not restore or restart. Flink logs show no
indication of anything amiss. There were no errors in the or Kafka related
messages in the Flink logs.
The job is configured with checkpoints at 1 minute intervals. The Kafka
connector consumer is configured to start from group offsets if it is not
started from a savepoint via `setStartFromGroupOffsets()`, and the Kafka
consumer is configured to fallback to the earliest offsets is no group offsets
are committed by setting `auto.offset.reset` to `earliest` in the Kafka
consumer config.
Right before the event a Kafka broker (kafka-broker-b5-int) lost leadership of
its partitions for around 30 seconds as a result of losing its connection to
ZooKeeper.
{noformat}
[2018-06-30 09:34:54,799] INFO Unable to read additional data from server
sessionid 0x161305b7bd81a09, likely server has closed socket, closing socket
connection and attempting reconnect (org.apache.zookeeper.ClientCnxn)
[2018-06-30 09:34:54,899] INFO zookeeper state changed (Disconnected)
(org.I0Itec.zkclient.ZkClient)
[2018-06-30 09:34:55,384] ERROR [ReplicaFetcherThread-3-1002]: Error for
partition [cloud_ioc_events,32] to broker
1002:org.apache.kafka.common.errors.NotLeaderForPartitionException: This server
is not the leader for that topic-partition. (kafka.server.ReplicaFetcherThread)
{noformat}
The broker immediately reconnected to after a few tries ZK:
{noformat}
[2018-06-30 09:34:55,462] INFO Opening socket connection to server
10.210.48.187/10.210.48.187:2181 (org.apache.zookeeper.ClientCnxn)
[2018-06-30 09:34:55,462] INFO zookeeper state changed (AuthFailed)
(org.I0Itec.zkclient.ZkClient)
[2018-06-30 09:34:55,463] INFO Socket connection established to
10.210.48.187/10.210.48.187:2181, initiating session
(org.apache.zookeeper.ClientCnxn)
[2018-06-30 09:34:55,464] WARN Unable to reconnect to ZooKeeper service,
session 0x161305b7bd81a09 has expired (org.apache.zookeeper.ClientCnxn)
[2018-06-30 09:34:55,465] INFO zookeeper state changed (Expired)
(org.I0Itec.zkclient.ZkClient)
[2018-06-30 09:34:55,465] INFO Initiating client connection,
connectString=10.210.48.187:2181,10.210.43.200:2181,10.210.16.102:2181/kafka
sessionTimeout=6000 watcher=org.I0Itec.zkclient.ZkClient@5c33f1a9
(org.apache.zookeeper.ZooKeeper)
[2018-06-30 09:34:55,465] INFO Unable to reconnect to ZooKeeper service,
session 0x161305b7bd81a09 has expired, closing socket connection
(org.apache.zookeeper.ClientCnxn)
[2018-06-30 09:34:55,466] INFO EventThread shut down for session:
0x161305b7bd81a09 (org.apache.zookeeper.ClientCnxn)
[2018-06-30 09:34:55,467] INFO zookeeper state changed (AuthFailed)
(org.I0Itec.zkclient.ZkClient)
[2018-06-30 09:34:55,468] INFO Opening socket connection to server
10.210.43.200/10.210.43.200:2181 (org.apache.zookeeper.ClientCnxn)
[2018-06-30 09:34:55,468] INFO Socket connection established to
10.210.43.200/10.210.43.200:2181, initiating session
(org.apache.zookeeper.ClientCnxn)
[2018-06-30 09:34:55,471] INFO Session establishment complete on server
10.210.43.200/10.210.43.200:2181, sessionid = 0x163934fa09d1baa, negotiated
timeout = 6000 (org.apache.zookeeper.ClientCnxn)
[2018-06-30 09:34:55,471] INFO zookeeper state changed (SyncConnected)
(org.I0Itec.zkclient.ZkClient)
[2018-06-30 09:34:55,472] INFO re-registering broker info in ZK for broker 2005
(kafka.server.KafkaHealthcheck$SessionExpireListener)
[2018-06-30 09:34:55,472] INFO Creating /brokers/ids/2005 (is it secure? false)
(kafka.utils.ZKCheckedEphemeral)
[2018-06-30 09:34:55,476] INFO Result of znode creation is: OK
(kafka.utils.ZKCheckedEphemeral)
[2018-06-30 09:34:55,476] INFO Registered broker 2005 at path /brokers/ids/2005
with addresses:
EndPoint(kafka-broker-b5-int,9092,ListenerName(PLAINTEXT),PLAINTEXT),EndPoint(kafka-broker-b5,19092,ListenerName(PUBLIC),SASL_PLAINTEXT)
(kafka.utils.ZkUtils)
[2018-06-30 09:34:55,476] INFO done re-registering broker
(kafka.server.KafkaHealthcheck$SessionExpireListener)
[2018-06-30 09:34:55,476] INFO Subscribing to /brokers/topics path to watch for
new topics (kafka.server.KafkaHealthcheck$SessionExpireListener)
{noformat}
By 9:35:02 partitions had returned to the broker.
It appears this it the broker that the subtask was consuming from, as outgoing
network traffic from it spiked after the broker recovered leadership of its
partitions, which is consistent with the subtask starting to consuming from the
earliest offset.
This may have been related to this [Kafka issue
5600](https://issues.apache.org/jira/browse/KAFKA-5600), which affects
0.11.0.0, the version we are running, and that was fixed in 0.11.0.1. But that
seems unlikely as the Flink Kafka connector consumer shouldn't make use of the
offsets committed in Kafka when operating with checkpoints enabled, nor when
the job is not restarting or being restored.
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