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https://issues.apache.org/jira/browse/CAMEL-25679?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Work on CAMEL-25679 started by shashank.
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> camel-mongodb - the tailable and change streams consumers stop consuming for
> good (route still started) when the server is unreachable for longer than the
> server selection timeout
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: CAMEL-25679
> URL: https://issues.apache.org/jira/browse/CAMEL-25679
> Project: Camel
> Issue Type: Bug
> Components: camel-mongodb
> Reporter: shashank
> Assignee: shashank
> Priority: Major
>
> The tailable cursor consumer ({{consumerType=tailable}}, the default) and the
> change streams consumer ({{consumerType=changeStreams}}) read from a cursor
> on one thread, {{MongoAbstractConsumerThread.run()}}. When reading fails (for
> example the connection to the server is lost), the loop logs a WARN ("Will
> try again on next poll"), closes the cursor, waits
> {{cursorRegenerationDelay}} (1000 ms by default) and opens a new cursor
> ({{initializeCursor()}}).
> At main cd2ce899764e the new cursor is opened at line 130, after the {{try}}
> of the loop (101-115). While the server is still unreachable, opening the
> cursor fails: the driver gives up after its server selection timeout (30
> seconds by default) with {{MongoTimeoutException: Timed out while waiting for
> a server}}. The exception leaves {{run()}}, the consumer thread ends, and:
> * the route stays started and the consumer never reads again, also long after
> the server is back; only a restart of the route helps;
> * the only trace is the uncaught exception printed on stderr by the thread
> ({{Exception in thread "Camel (camel-1) thread #1 - mongodb://..."
> com.mongodb.MongoTimeoutException ...}}), not through the logging framework.
> Trigger: default options, a MongoDB server (or replica set) that cannot be
> reached for longer than about 31 seconds (server selection timeout plus the
> regeneration delay): a restart, a failover that takes long, a network outage,
> maintenance. A long-running tailing or change stream consumer will see such
> an outage.
> h3. Reproduction
> New {{MongoDbConsumerCursorRegenerationTest}} with Mockito mocks of the
> driver objects (no server): the cursor of the start fails its read
> ({{MongoSocketReadException}}), the first new cursor cannot be opened
> ({{MongoTimeoutException}}), the next one returns a document. On main:
> * tailable consumer: {{mock://result Received message count. Expected: <1>
> but was: <0>}}, and the test output shows {{Exception in thread "Camel
> (camel-1) thread #1 - mongodb://myDb" com.mongodb.MongoTimeoutException:
> Timed out while waiting for a server}};
> * change streams consumer: the same.
> * A third test (the tailing thread run directly, stopped while it opens a new
> cursor) pins a related small leak of the same lines: a cursor opened while
> the consumer is being stopped was neither read nor closed on main ({{Wanted
> but not invoked: mongoCursor.close()}}).
> h3. Proposed fix
> Open the new cursor at the start of the next iteration of the loop, inside
> its {{try}}: a failure is logged like a failed read ("Exception from
> consuming from MongoDB caused by ... Will try again on next poll.") and tried
> again after {{cursorRegenerationDelay}}, until the server is back or the
> consumer is stopped. A cursor opened while the consumer was being stopped is
> closed instead of read (stop() could not close it). The {{cursor}} field
> becomes volatile, as {{stop()}} reads it from another thread.
> While the server is down there is one WARN with stack trace per attempt,
> every server selection timeout plus {{cursorRegenerationDelay}} (about 31
> seconds by default), like the WARN that main already logs for every failed
> read. No option or default changes, so no upgrade guide entry.
> camel-mongodb unit tests with the fix: 21 run, 0 failures, 0 skipped. Not
> run: the module's integration tests (they need a MongoDB container), a real
> outage.
> How it was found: reading the consumers' loop during a sweep of reconnect
> paths; the test confirmed it.
> Not changed: the tailable consumer still ends quietly when the driver throws
> {{IllegalStateException}} from {{hasNext()}} (meant for a cursor closed by
> {{stop()}}); the change streams consumer logs a failed read at DEBUG only
> (CAMEL-16025).
> Affected: main (cd2ce899764e; tested). camel-4.23.x (line 130), camel-4.22.x,
> camel-4.18.x and camel-4.14.x (line 94) open the new cursor outside the
> {{try}} the same way (read, not run).
> Duplicate check (2026-10-15): JIRA text "MongoAbstractConsumerThread"
> (CAMEL-16025, CAMEL-16024, CAMEL-25024, CAMEL-25025, CAMEL-17121 retry logic
> consolidation; none about the regeneration), "MongoTimeoutException"
> (CAMEL-24257, camel export; CAMEL-12142, tests), component camel-mongodb with
> "tailable cursor" (CAMEL-11977 stop on shutdown, 2017); GitHub pull requests
> "MongoAbstractConsumerThread" (#26961, failure handling of the route, did not
> touch the regeneration), "mongodb tailable cursor", "mongodb change streams
> reconnect" (nothing related).
> _Filed with Claude Code on behalf of allthingssecurity._
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