MySQL Connector - Issue with Message Flushing After Initial Operation

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Kaua Rodrigues

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4:00 PM (7 hours ago) 4:00 PM

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Hi all,

We're experiencing an issue with our AWS MSK Connector (Debezium) connected to a MySQL RDS instance, with multiple large databases (~20GB/week data volume). After running successfully for a few hours or days, the connector stops flushing/committing messages to Kafka (0 messages sent), despite no errors or warnings appearing in CloudWatch Logs, the connector remaining alive and connected to MySQL, the source tables being actively updated and MySQL binlog continuing to grow.

[Worker-0989ee99c536b29b0] [2026-02-02 20:27:51,011] INFO [mysql|task-0|offsets] WorkerSourceTask{id=mysql-0} flushing 0 outstanding messages for offset commit (org.apache.kafka.connect.runtime.WorkerSourceTask:507)
[Worker-0989ee99c536b29b0] [2026-02-02 20:27:56,012] INFO [mysql|task-0|offsets] WorkerSourceTask{id=mysql-extractor-0} Committing offsets (org.apache.kafka.connect.runtime.WorkerSourceTask:490)

Our current configuration is:
database_server_id = "5401"
max_batch_size = 128
max_queue_size = 2048
mcu_count = 1
worker_count = 1
connect_timeout_ms = 30000
offset_flush_timeout_ms = 1200000 # 20min
offset_flush_interval_ms = 5000 # 5s
errors_log_enable = true
errors_tolerance = "all"
errors_log_include_messages = true
producer_buffer_memory_bytes = 16777216 # 16MB
snapshot_mode = "schema_only"
snapshot.locking.mode = "none"
tasks.max = "1"
key.converter = "org.apache.kafka.connect.json.JsonConverter"
value.converter = "org.apache.kafka.connect.json.JsonConverter"
transforms = "unwrap,addVersion,underscoreRemover"
transforms.unwrap.type = "io.debezium.transforms.ExtractNewRecordState"
transforms.unwrap.delete.handling.mode = "rewrite"

Destroying and recreating the connector via Terraform resolves the issue temporarily, but it recurs after some time. Besides, when the connector reaches this stale state the Kafka offset topic stops receiving new messages, which implies the offsets stop advancing even though the binlog keeps growing.

We have also investigated the binlog positions where the connector stopped processing, considering two cases in which it reached this ghost state. In both scenarios, the last offset corresponded to an Xid (transaction BEGIN) and the transactions involved multiple tables with INSERT operations. In case 1, one table was in the connector exclude list. In case 2, all 3 tables were in the include list, with tables 2 and 3 being, actually, the same table.

We have, finally, attempted to enable DEBUG logs but discovered that, apparently, AWS MSK only supports INFO level logging.

We're using Debizium MySQK Connector Plug-In (2.7.1) and Kafka Connect (2.7.1).

I'd really appreciate any insights into potential root causes or recommended troubleshooting steps.