mongodb : Unable to acquire buffer lock, buffer queue is likely full

## Bug report

**What Debezium connector do you use and what version?**

Version: DebeziumServer3.2.5
Connector: mongodb connect for mongodb8

---

**What is the connector configuration?**

debezium.source.name=wechat_pro
debezium.source.connector.class=io.debezium.connector.mongodb.MongoDbConnector
debezium.source.mongodb.connection.string=mongodb://server1,server2/admin?replicaSet=mgset-92139473
debezium.source.mongodb.name=wechat
debezium.source.mongodb.user=debezium
debezium.source.mongodb.password=debezium123
debezium.source.mongodb.authsource=admin
debezium.source.mongodb.ssl.enabled=false
debezium.source.mongodb.connection.timeout.ms=30000
debezium.source.mongodb.socket.timeout.ms=30000
debezium.source.mongodb.poll.interval.ms=1000
debezium.source.database.include.list=wechat
debezium.source.collection.include.list=wechat.collection1,wechat.collection2
debezium.source.max.batch.size=1000
debezium.source.max.queue.size=32768
debezium.source.topic.prefix=pro
debezium.source.capture.mode=change_streams_update_full
debezium.source.capture.scope=database
debezium.source.capture.target=wechat
debezium.source.skipped.operations=t
debezium.source.snapshot.mode=when_needed
debezium.source.snapshot.max.threads=4
debezium.source.tombstones.on.delete=false

debezium.source.key.converter=org.apache.kafka.connect.json.JsonConverter
debezium.source.key.converter.schemas.enable=false
debezium.source.value.converter=org.apache.kafka.connect.json.JsonConverter
debezium.source.value.converter.schemas.enable=false
debezium.source.decimal.handling.mode=string

# offset file
debezium.source.offset.storage.file.filename=./data/mongodb.data
#1s
debezium.source.heartbeat.interval.ms=5000
debezium.source.offset.flush.interval.ms=5000

---

**What is the captured database version and mode of deployment?**

_E.g. on-premises, with a specific cloud provider, etc._

mongodb8
aliyun cloud

---

**What behavior do you expect?**

---

**What behavior do you see?**

WARN [io.deb.con.mon.eve.BufferingChangeStreamCursor] (debezium-mongodbconnector-pro-replicator-fetcher-0) Unable to acquire buffer lock, buffer queue is likely full

---

**Do you see the same behaviour using the latest released Debezium version?**

yes

---

**Do you have the connector logs, ideally from start till finish?**

_You might be asked later to provide [DEBUG/TRACE](https://debezium.io/documentation/reference/stable/operations/logging.html) level log._

{"timestamp":"2025-11-27T15:38:33.467712391+08:00","sequence":792,"loggerClassName":"org.slf4j.impl.Slf4jLogger","loggerName":"io.debezium.connector.mongodb.events.BufferingChangeStreamCursor","level":"WARN","message":"Unable to acquire buffer lock, buffer queue is likely full","threadName":"debezium-mongodbconnector-pro-replicator-fetcher-0","threadId":90,"mdc":{"dbz.connectorLogicalName":"pro","dbz.taskId":"0","dbz.connectorType":"MongoDB","dbz.connectorContext":"streaming"},"ndc":"","hostName":"sync","processName":"/usr/lib/jvm/jdk-21-oracle-x64/bin/java","processId":2926039}
{"timestamp":"2025-11-27T15:38:33.5708462+08:00","sequence":793,"loggerClassName":"org.slf4j.impl.Slf4jLogger","loggerName":"io.debezium.connector.mongodb.events.BufferingChangeStreamCursor","level":"WARN","message":"Unable to acquire buffer lock, buffer queue is likely full","threadName":"debezium-mongodbconnector-pro-replicator-fetcher-0","threadId":90,"mdc":{"dbz.connectorLogicalName":"pro","dbz.taskId":"0","dbz.connectorType":"MongoDB","dbz.connectorContext":"streaming"},"ndc":"","hostName":"sync","processName":"/usr/lib/jvm/jdk-21-oracle-x64/bin/java","processId":2926039}
{"timestamp":"2025-11-27T15:38:33.651107205+08:00","sequence":794,"loggerClassName":"org.slf4j.impl.Slf4jLogger","loggerName":"io.debezium.connector.common.BaseSourceTask","level":"INFO","message":"19639 records sent during previous 00:10:37.192, last recorded offset of {server_id=pro} partition is {sec=1764228556, ord=8311, resume_token=zQAAAAJfZGF0YQC9AAAAODI2OTI3RkRDQzAwMDAyMDc3MkIwNDJDMDEwMDI5NkU1QTEwMDQxMjE3MjRBMzUwRjY0QkE2QUQyMUJCMDJEOEUxQkEyQjQ2M0M2RjcwNjU3MjYxNzQ2OTZGNkU1NDc5NzA2NTAwM0M3NTcwNjQ2MTc0NjUwMDQ2NjQ2RjYzNzU2RDY1NkU3NDRCNjU3OTAwNDY2NDVGNjk2NDAwNjQ2OTI3RkRDN0JBOEQyQjkyRTRERDY3QjkwMDAwMDQAAA==}","threadName":"pool-10-thread-1","threadId":65,"mdc":{},"ndc":"","hostName":"sync","processName":"/usr/lib/jvm/jdk-21-oracle-x64/bin/java","processId":2926039}
{"timestamp":"2025-11-27T15:38:35.806577048+08:00","sequence":795,"loggerClassName":"org.slf4j.impl.Slf4jLogger","loggerName":"io.debezium.connector.mongodb.events.BufferingChangeStreamCursor","level":"WARN","message":"Unable to acquire buffer lock, buffer queue is likely full","threadName":"debezium-mongodbconnector-pro-replicator-fetcher-0","threadId":90,"mdc":{"dbz.connectorLogicalName":"pro","dbz.taskId":"0","dbz.connectorType":"MongoDB","dbz.connectorContext":"streaming"},"ndc":"","hostName":"sync","processName":"/usr/lib/jvm/jdk-21-oracle-x64/bin/java","processId":2926039}
{"timestamp":"2025-11-27T15:38:36.391156985+08:00","sequence":796,"loggerClassName":"org.slf4j.impl.Slf4jLogger","loggerName":"io.debezium.connector.mongodb.events.BufferingChangeStreamCursor","level":"WARN","message":"Unable to acquire buffer lock, buffer queue is likely full","threadName":"debezium-mongodbconnector-pro-replicator-fetcher-0","threadId":90,"mdc":{"dbz.connectorLogicalName":"pro","dbz.taskId":"0","dbz.connectorType":"MongoDB","dbz.connectorContext":"streaming"},"ndc":"","hostName":"sync","processName":"/usr/lib/jvm/jdk-21-oracle-x64/bin/java","processId":2926039}
{"timestamp":"2025-11-27T15:38:37.643012278+08:00","sequence":797,"loggerClassName":"org.slf4j.impl.Slf4jLogger","loggerName":"io.debezium.connector.mongodb.events.BufferingChangeStreamCursor","level":"WARN","message":"Unable to acquire buffer lock, buffer queue is likely full","threadName":"debezium-mongodbconnector-pro-replicator-fetcher-0","threadId":90,"mdc":{"dbz.connectorLogicalName":"pro","dbz.taskId":"0","dbz.connectorType":"MongoDB","dbz.connectorContext":"streaming"},"ndc":"","hostName":"sync","processName":"/usr/lib/jvm/jdk-21-oracle-x64/bin/java","processId":2926039}