@kapa.ai what does this mean: 2026-10-21 081642 source ERROR pool-2-thread-1 i.d.e.a.AsyncEmbeddedEngine(startSourceTasks):510 1 task(s) out of 1 failed to start. 2026-10-21 081642 source ERROR pool-2-thread-1 i.d.e.a.AsyncEmbeddedEngine(closeEngineWithException):335 Engine has failed with java.lang.InterruptedException: Time out while waiting for source task to start. at io.debezium.embedded.async.AsyncEmbeddedEngine.startSourceTasks(AsyncEmbeddedEngine.java:488) ~[debezium-embedded-3.6.2.Final.jar:3.6.2.Final] at io.debezium.embedded.async.AsyncEmbeddedEngine.run(AsyncEmbeddedEngine.java:228) ~[debezium-embedded-3.6.2.Final.jar:3.6.2.Final] at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144) ~[?:?] at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642) ~[?:?] at java.base/java.lang.Thread.run(Thread.java:1583) [?:?] Stack Trace: java.lang.InterruptedException: Time out while waiting for source task to start. at io.debezium.embedded.async.AsyncEmbeddedEngine.startSourceTasks(AsyncEmbeddedEngine.java:488) at io.debezium.embedded.async.AsyncEmbeddedEngine.run(AsyncEmbeddedEngine.java:228) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642) at java.base/java.lang.Thread.run(Thread.java:1583)

Thinking completed The knowledge sources don't explain this exact error ("Time out while waiting for source task to start"), so I can't say definitively what caused it in your case. Here is what the log itself shows, plus related cases from the sources. What the log says • The embedded Debezium engine, which Airbyte's CDC database sources use, tried to start its single source task. • The task didn't start within the engine's allowed time, so the engine gave up. It raised an

InterruptedException

and shut down with the message "1 task(s) out of 1 failed to start." • This is a startup failure. No records were read, and the sync fails. The stack trace only shows Debezium's engine code. It doesn't reveal the underlying cause. Possible causes from similar reports These are not confirmed for your error: • A Postgres startup bug. An open issue describes Debezium failing during startup in its own thread. The connector doesn't fail fast and only surfaces a timeout message after waiting. The cause there was an empty enum type (

CREATE TYPE ... AS ENUM ()

) in the source database. The source also warns about replication slot WAL accumulating while this happens. [Postgres enum issue] • Other startup failures in the same place. A MSSQL issue shows the same "1 task(s) out of 1 failed to start" line, but with a different underlying exception: "Could not find existing redo log information". [MSSQL redo log issue] What to check • Look earlier in the full job logs for another exception from the Debezium task start, such as a

Caused by:

line or a connection error. • Confirm the source is reachable and its CDC prerequisites are met: the replication slot and publication for Postgres, or CDC enabled for MSSQL. • If this is Postgres, run the detection query from the issue to check for empty enum types. If you tell me which connector and version you're using, and share the log lines just before this error, I can help narrow it down. 👍 0 button 👎 0 button ℹ️ Tip: Mention @kapa.ai in the thread for follow-ups or DM the app for 1-to-1 help.

I use a mongo connector: 2026-10-21 081642 source ERROR pool-2-thread-1 i.d.e.a.AsyncEmbeddedEngine(startSourceTasks):510 1 task(s) out of 1 failed to start. 2026-10-21 081642 source ERROR pool-2-thread-1 i.d.e.a.AsyncEmbeddedEngine(closeEngineWithException):335 Engine has failed with java.lang.InterruptedException: Time out while waiting for source task to start. at io.debezium.embedded.async.AsyncEmbeddedEngine.startSourceTasks(AsyncEmbeddedEngine.java:488) ~[debezium-embedded-3.6.2.Final.jar:3.6.2.Final] at io.debezium.embedded.async.AsyncEmbeddedEngine.run(AsyncEmbeddedEngine.java:228) ~[debezium-embedded-3.6.2.Final.jar:3.6.2.Final] at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144) ~[?:?] at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642) ~[?:?] at java.base/java.lang.Thread.run(Thread.java:1583) [?:?] Stack Trace: java.lang.InterruptedException: Time out while waiting for source task to start. at io.debezium.embedded.async.AsyncEmbeddedEngine.startSourceTasks(AsyncEmbeddedEngine.java:488) at io.debezium.embedded.async.AsyncEmbeddedEngine.run(AsyncEmbeddedEngine.java:228) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642) at java.base/java.lang.Thread.run(Thread.java:1583) 2026-10-21 081642 source INFO pool-2-thread-1 i.d.e.a.AsyncEmbeddedEngine(setEngineState):845 Engine state has changed from 'STARTING_TASKS' to 'STOPPING' 2026-10-21 081644 source INFO pool-3-thread-1 i.d.c.m.c.MongoDbConnection(lambda$isValidResumeToken$10):220 Valid resume token present, so no snapshot will be performed' 2026-10-21 081644 source INFO pool-3-thread-1 i.d.c.m.MongoDbConnectorTask(start):163 Guardrail validation skipped 2026-10-21 081644 source INFO pool-3-thread-1 i.d.u.Threads(threadFactory):296 Requested thread factory for component MongoDbConnector, id = mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary named = change-event-source-coordinator 2026-10-21 081644 source INFO pool-3-thread-1 i.d.u.Threads(threadFactory):296 Requested thread factory for component MongoDbConnector, id = mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary named = blocking-snapshot 2026-10-21 081644 source INFO pool-3-thread-1 i.d.u.Threads$3(newThread):313 Creating thread debezium-mongodbconnector-mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary-change-event-source-coordinator 2026-10-21 081644 source INFO pool-3-thread-1 i.d.c.c.BaseSourceTask(stop):527 Stopping down connector 2026-10-21 081645 source INFO debezium-mongodbconnector-mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary-change-event-source-coordinator i.d.p.ChangeEventSourceCoordinator(lambda$start$0):140 Metrics registered 2026-10-21 081645 source INFO debezium-mongodbconnector-mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary-change-event-source-coordinator i.d.p.ChangeEventSourceCoordinator(lambda$start$0):143 Context created 2026-10-21 081645 source INFO debezium-mongodbconnector-mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary-change-event-source-coordinator i.d.c.m.MongoDbSnapshotChangeEventSource(getSnapshottingTask):145 A previous offset indicating a completed snapshot has been found. 2026-10-21 081645 source INFO debezium-mongodbconnector-mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary-change-event-source-coordinator i.d.c.m.MongoDbSnapshotChangeEventSource(getSnapshottingTask):152 According to the connector configuration, no snapshot will occur. 2026-10-21 081645 source INFO debezium-mongodbconnector-mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary-change-event-source-coordinator i.d.p.ChangeEventSourceCoordinator(doSnapshot):319 Snapshot ended with SnapshotResult [status=SKIPPED, offset=MongoDbOffsetContext [sourceInfo=SourceInfo [initialSync=false, collectionId=null, position=Position [ts=Timestamp{value=7698592070486720518, seconds=1792468147, inc=6}, changeStreamSessionTxnId=null, resumeToken=826AD6E4B3000000062B042C0100296E5A100415EC1A6E43CB4D47910D3BF132F5B9EF463C6F7065726174696F6E54797065003C7570646174650046646F63756D656E744B65790046645F696400646AD606138DD97B036971AD57000004]]]] 2026-10-21 081645 source INFO debezium-mongodbconnector-mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary-change-event-source-coordinator i.d.p.ChangeEventSourceCoordinator(streamingConnected):524 Connected metrics set to 'false' 2026-10-21 081645 source INFO pool-3-thread-1 i.d.u.Threads$3(newThread):313 Creating thread debezium-mongodbconnector-mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary-SignalProcessor 2026-10-21 081645 source INFO pool-3-thread-1 i.d.p.s.SignalProcessor(stop):138 SignalProcessor stopped 2026-10-21 081645 source INFO pool-3-thread-1 i.d.s.DefaultServiceRegistry(close):105 Debezium ServiceRegistry stopped. 2026-10-21 081645 source INFO pool-2-thread-1 i.d.e.a.AsyncEmbeddedEngine(stopSourceTasks):742 Stopped task #1 out of 1 tasks (it took 2741 ms to stop the task). 2026-10-21 081645 source INFO pool-2-thread-1 i.a.c.i.d.i.DebeziumRecordPublisher$start$3(taskStopped):91 DebeziumEngine notify: task stopped 2026-10-21 081645 source INFO pool-2-thread-1 o.a.k.c.s.FileOffsetBackingStore(stop):71 Stopped FileOffsetBackingStore 2026-10-21 081645 source INFO pool-2-thread-1 i.d.c.m.MongoDbConnector(stop):87 Stopping MongoDB connector 2026-10-21 081645 source INFO pool-2-thread-1 i.d.c.m.MongoDbConnector(stop):91 Stopped MongoDB connector 2026-10-21 081645 source INFO pool-2-thread-1 i.a.c.i.d.i.DebeziumRecordPublisher$start$3(connectorStopped):83 DebeziumEngine notify: connector stopped 2026-10-21 081645 source INFO pool-2-thread-1 i.d.e.a.AsyncEmbeddedEngine(finishShutDown):363 Engine is stopped. 2026-10-21 081645 source INFO pool-2-thread-1 i.d.e.a.AsyncEmbeddedEngine(setEngineState):845 Engine state has changed from 'STOPPING' to 'STOPPED' 2026-10-21 081645 source INFO pool-2-thread-1 i.a.c.i.d.i.DebeziumRecordPublisher(start$lambda$1):60 Debezium engine shutdown. Engine terminated successfully : false 2026-10-21 081645 source INFO pool-2-thread-1 i.a.c.i.d.i.DebeziumRecordPublisher(start$lambda$1):63 Time out while waiting for source task to start.

Thinking completed Your last message contained only a caret (^) and no question, so I'm not sure what you'd like to know. If you're following up on the Debezium error "Time out while waiting for source task to start", I can help narrow it down. Please share: • Which connector you're using (for example Postgres or MSSQL) and its version. • The log lines just before the error, especially any

Caused by:

line or connection error. • Whether the sync is in CDC mode and whether it's the first sync (initial snapshot) or an incremental one. For Postgres CDC, the knowledge sources note that the connector waits for an initial wait time of 20 minutes by default, with a valid range of 120 to 2400 seconds. If the connector can't read changes you know exist, increasing this wait time can help test whether insufficient waiting time is the cause. [Initial CDC wait time] What would you like to ask? 👍 0 button 👎 0 button ℹ️ Tip: Mention @kapa.ai in the thread for follow-ups or DM the app for 1-to-1 help.

@kapa.ai 2026-10-21 081642 source ERROR pool-2-thread-1 i.d.e.a.AsyncEmbeddedEngine(startSourceTasks):510 1 task(s) out of 1 failed to start. 2026-10-21 081642 source ERROR pool-2-thread-1 i.d.e.a.AsyncEmbeddedEngine(closeEngineWithException):335 Engine has failed with java.lang.InterruptedException: Time out while waiting for source task to start. at io.debezium.embedded.async.AsyncEmbeddedEngine.startSourceTasks(AsyncEmbeddedEngine.java:488) ~[debezium-embedded-3.6.2.Final.jar:3.6.2.Final] at io.debezium.embedded.async.AsyncEmbeddedEngine.run(AsyncEmbeddedEngine.java:228) ~[debezium-embedded-3.6.2.Final.jar:3.6.2.Final] at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144) ~[?:?] at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642) ~[?:?] at java.base/java.lang.Thread.run(Thread.java:1583) [?:?] Stack Trace: java.lang.InterruptedException: Time out while waiting for source task to start. at io.debezium.embedded.async.AsyncEmbeddedEngine.startSourceTasks(AsyncEmbeddedEngine.java:488) at io.debezium.embedded.async.AsyncEmbeddedEngine.run(AsyncEmbeddedEngine.java:228) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642) at java.base/java.lang.Thread.run(Thread.java:1583) 2026-10-21 081642 source INFO pool-2-thread-1 i.d.e.a.AsyncEmbeddedEngine(setEngineState):845 Engine state has changed from 'STARTING_TASKS' to 'STOPPING' 2026-10-21 081644 source INFO pool-3-thread-1 i.d.c.m.c.MongoDbConnection(lambda$isValidResumeToken$10):220 Valid resume token present, so no snapshot will be performed' 2026-10-21 081644 source INFO pool-3-thread-1 i.d.c.m.MongoDbConnectorTask(start):163 Guardrail validation skipped 2026-10-21 081644 source INFO pool-3-thread-1 i.d.u.Threads(threadFactory):296 Requested thread factory for component MongoDbConnector, id = mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary named = change-event-source-coordinator 2026-10-21 081644 source INFO pool-3-thread-1 i.d.u.Threads(threadFactory):296 Requested thread factory for component MongoDbConnector, id = mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary named = blocking-snapshot 2026-10-21 081644 source INFO pool-3-thread-1 i.d.u.Threads$3(newThread):313 Creating thread debezium-mongodbconnector-mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary-change-event-source-coordinator 2026-10-21 081644 source INFO pool-3-thread-1 i.d.c.c.BaseSourceTask(stop):527 Stopping down connector 2026-10-21 081645 source INFO debezium-mongodbconnector-mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary-change-event-source-coordinator i.d.p.ChangeEventSourceCoordinator(lambda$start$0):140 Metrics registered 2026-10-21 081645 source INFO debezium-mongodbconnector-mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary-change-event-source-coordinator i.d.p.ChangeEventSourceCoordinator(lambda$start$0):143 Context created 2026-10-21 081645 source INFO debezium-mongodbconnector-mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary-change-event-source-coordinator i.d.c.m.MongoDbSnapshotChangeEventSource(getSnapshottingTask):145 A previous offset indicating a completed snapshot has been found. 2026-10-21 081645 source INFO debezium-mongodbconnector-mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary-change-event-source-coordinator i.d.c.m.MongoDbSnapshotChangeEventSource(getSnapshottingTask):152 According to the connector configuration, no snapshot will occur. 2026-10-21 081645 source INFO debezium-mongodbconnector-mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary-change-event-source-coordinator i.d.p.ChangeEventSourceCoordinator(doSnapshot):319 Snapshot ended with SnapshotResult [status=SKIPPED, offset=MongoDbOffsetContext [sourceInfo=SourceInfo [initialSync=false, collectionId=null, position=Position [ts=Timestamp{value=7698592070486720518, seconds=1792468147, inc=6}, changeStreamSessionTxnId=null, resumeToken=826AD6E4B3000000062B042C0100296E5A100415EC1A6E43CB4D47910D3BF132F5B9EF463C6F7065726174696F6E54797065003C7570646174650046646F63756D656E744B65790046645F696400646AD606138DD97B036971AD57000004]]]] 2026-10-21 081645 source INFO debezium-mongodbconnector-mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary-change-event-source-coordinator i.d.p.ChangeEventSourceCoordinator(streamingConnected):524 Connected metrics set to 'false' 2026-10-21 081645 source INFO pool-3-thread-1 i.d.u.Threads$3(newThread):313 Creating thread debezium-mongodbconnector-mongodb_srv___miter-prod.ptjem.mongodb.net__readPreference_secondary-SignalProcessor 2026-10-21 081645 source INFO pool-3-thread-1 i.d.p.s.SignalProcessor(stop):138 SignalProcessor stopped 2026-10-21 081645 source INFO pool-3-thread-1 i.d.s.DefaultServiceRegistry(close):105 Debezium ServiceRegistry stopped. 2026-10-21 081645 source INFO pool-2-thread-1 i.d.e.a.AsyncEmbeddedEngine(stopSourceTasks):742 Stopped task #1 out of 1 tasks (it took 2741 ms to stop the task). 2026-10-21 081645 source INFO pool-2-thread-1 i.a.c.i.d.i.DebeziumRecordPublisher$start$3(taskStopped):91 DebeziumEngine notify: task stopped 2026-10-21 081645 source INFO pool-2-thread-1 o.a.k.c.s.FileOffsetBackingStore(stop):71 Stopped FileOffsetBackingStore 2026-10-21 081645 source INFO pool-2-thread-1 i.d.c.m.MongoDbConnector(stop):87 Stopping MongoDB connector 2026-10-21 081645 source INFO pool-2-thread-1 i.d.c.m.MongoDbConnector(stop):91 Stopped MongoDB connector 2026-10-21 081645 source INFO pool-2-thread-1 i.a.c.i.d.i.DebeziumRecordPublisher$start$3(connectorStopped):83 DebeziumEngine notify: connector stopped 2026-10-21 081645 source INFO pool-2-thread-1 i.d.e.a.AsyncEmbeddedEngine(finishShutDown):363 Engine is stopped. 2026-10-21 081645 source INFO pool-2-thread-1 i.d.e.a.AsyncEmbeddedEngine(setEngineState):845 Engine state has changed from 'STOPPING' to 'STOPPED' 2026-10-21 081645 source INFO pool-2-thread-1 i.a.c.i.d.i.DebeziumRecordPublisher(start$lambda$1):60 Debezium engine shutdown. Engine terminated successfully : false 2026-10-21 081645 source INFO pool-2-thread-1 i.a.c.i.d.i.DebeziumRecordPublisher(start$lambda$1):63 Time out while waiting for source task to start.

Thinking completed The knowledge sources don't contain enough information to say definitively why this MongoDB sync failed. Below is what the new logs show, based on the log content itself. What the logs show • This is a MongoDB CDC source, so the connector is Debezium's

MongoDbConnector

running in Airbyte's embedded engine. • The first error is a timeout: the engine waited for the source task to start, gave up, and began shutting down (

STARTING_TASKS

→

STOPPING

). • The MongoDB task was not broken. About two seconds later it logged that a valid resume token was present, so no snapshot would run. It also logged that a previous offset showing a completed snapshot was found, and the snapshot ended as

SKIPPED

. • The task then reached the streaming phase (

Connected metrics set to 'false'

), but by then the engine was already stopping it, and it was shut down ("Stopping down connector"). • The final line says the engine did not terminate successfully (

Engine terminated successfully : false

) and repeats the timeout message. Likely interpretation The task was slow to start rather than failing outright. The engine's startup timeout was reached before the MongoDB task finished initializing. This is my reading of the log sequence, not something confirmed by the documentation. The connection string suggests you're reading from a secondary (

readPreference=secondary

) on MongoDB Atlas. Connecting to and validating the resume token on a secondary can be slow, which could contribute to a slow startup. This is a hypothesis only. What to try • Retry the sync to see whether the timeout is intermittent. • Check network latency and the health of the Atlas cluster, especially the secondary node, at the time of the failure. • Check whether the MongoDB connector has an initial wait or timeout setting you can raise. I can't confirm from the sources that one exists for MongoDB. • Share the connector version and whether the failure repeats on every sync. If it does, it's worth opening an issue on the Airbyte GitHub repository with these logs. 👍 0 button 👎 0 button ℹ️ Tip: Mention @kapa.ai in the thread for follow-ups or DM the app for 1-to-1 help.

@kapa.ai I am working using

readPreference=secondary

everytime I retry sync, I get the same error

Thinking completed The knowledge sources don't describe this exact startup timeout, so I can't confirm the cause. A failure on every retry does suggest something persistent rather than a one-off slowdown, and

readPreference=secondary

is the most obvious thing to test. Isolate the read preference • Temporarily remove

readPreference=secondary

from your connection string, or switch to

readPreference=secondaryPreferred

. The Airbyte docs list both as valid options for routing reads away from the primary. [Other alternatives] • If the sync succeeds without

secondary

, the secondary is probably slow to serve the change stream when the task starts. If it still fails, the read preference isn't the cause. Related reports, which don't match exactly • An open issue describes a MongoDB CDC sync where the Debezium change-stream fetcher blocks while establishing the cursor, most likely on low-traffic collections. It reproduced both with and without a read preference, so a secondary isn't necessarily the culprit. Its symptom was a forced exit at shutdown, not a startup timeout. [Cursor establishment issue] • Another open issue uses

readPreference=secondary

with a raised

initial_waiting_seconds

(1200). It reports that this setting doesn't govern every timeout path in the connector. [Frozen resume token] Next steps • Try raising

initial_waiting_seconds

, but it may not affect this particular startup timeout. • Check the health and replication lag of the secondary in Atlas. The sources don't cover this, so it's general troubleshooting. • If it still fails, open a GitHub issue with your connector version, the full logs, and whether the failure happens with and without

readPreference=secondary

. If you share your connector version and the full log from the start of the sync, I can look for more clues. 👍 0 button 👎 0 button ℹ️ Tip: Mention @kapa.ai in the thread for follow-ups or DM the app for 1-to-1 help.