Operational Defect Database
BugZero found this defect 48 days ago.
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MongoDB | 2628023
clusterTime values are duplicated in change stream events
Last update date:
4/1/2024
Affected products:
MongoDB Server
Affected releases:
No affected releases provided.
Fixed releases:
No fixed releases provided.
Description:
Info
Two change stream events, generated from the execution of an insert command containing two documents, both having the same clusterTime value. {"cursor": {"nextBatch": [ {"_id": {"_data": "82660AF114000000022B042C0100296E5A10043DA2BBD326BC4B7798739AC6DA4FE305463C6F7065726174696F6E54797065003C696E736572740046646F63756D656E744B657900461E5F6964002B02000004"}, "operationType": "insert", "clusterTime": {"$timestamp": {"t": 1711993108, "i": 2}}, "wallTime": {"$date": "2024-04-01T17:38:28.212Z"}, "fullDocument": {"_id": 1, "a": 1}, "ns": {"db": "JavaDriverTest", "coll": "com.mongodb.internal.operation.ChangeStreamOperationSpecification"}, "documentKey": {"_id": 1}}, {"_id": {"_data": "82660AF114000000022B042C01002B026E5A10043DA2BBD326BC4B7798739AC6DA4FE305463C6F7065726174696F6E54797065003C696E736572740046646F63756D656E744B657900461E5F6964002B04000004"}, "operationType": "insert", "clusterTime": {"$timestamp": {"t": 1711993108, "i": 2}}, "wallTime": {"$date": "2024-04-01T17:38:28.212Z"}, "fullDocument": {"_id": 2, "a": 2}, "ns": {"db": "JavaDriverTest", "coll": "com.mongodb.internal.operation.ChangeStreamOperationSpecification"}, ... This was found via an integration test of startAtOperationTime for change streams, in the Java driver. The test assumes that, at least outside of a transaction, that: 1. clusterTime values are unique 2. clusterTime values are ascending If this assumption is false, then we will need to re-write the test. It has held true from 4.0 until now.
Top User Comments
jeff.yemin commented on Mon, 1 Apr 2024 19:00:25 +0000: Not a problem at all. Now that I know we will just update the Java driver test to reflect this. Easy to do by just inserting the two documents in two commands instead of in bulk.
Steps to Reproduce
Start a change stream Insert two documents in a single insert command Wait for change stream to deliver events for the two documents Expected result: Each event includes a unique value for clusterTime, and the value is ascending. I observe this behavior testing against: "version": "8.0.0-alpha1-29-g1a70849", "gitVersion": "1a70849e14f429693786ea53168d660c686ca622", and all prior server releases. Actual result: The value of clusterTime is identical for the two events I observe this behavior testing against "version": "8.0.0-alpha2-76-g80adfd2", "gitVersion": "80adfd256dd70ed903f84f4f8985a832355bfdcd", Evergreen patch demonstrating the failure: https://spruce.mongodb.com/task/mongo_java_driver_tests_jdk_secure__version~latest_os~linux_topology~replicaset_auth~auth_ssl~ssl_jdk~jdk17_test_patch_9a02f8102531ed1fbce140cef4668f52844facca_660af005e6cd580007699eca_24_04_01_17_34_19?execution=0&sortBy=STATUS&sortDir=ASC
