Info

In HELP-35620 AutoSplitVector was called by the create collection coordinator and generated a response with too many split points. So when the response was serialized to a BSONObject the command failed with a BSONObjectTooLarge error. The AutoSplitVector has a logic in place to prevent this. In fact, while building the split points array, it tries to predict the final BSON object size and stops in case the maximum size is reached. As demonstrated in HELP-35620 this logic is somehow broken. From the customer's log we can see that the AutoSplitVector failed with BSONObjectTooLarge: 2022-07-06T11:40:55.206-05:00 E COMMAND 4879802 [conn124862] "Failed to handle request","attr":{"error":"BSONObjectTooLarge: BSON size limit hit while building Message. Size: 17973680 (0x11241B0); maxSize: 16793600(16MB)"} From the collection entry we can derive the ShardKey pattern for the collection: {"_id":"","lastmodEpoch":{"$oid":"62c70e4d59dd43b776579a8c"},"lastmod":{"$date":{"$numberLong":"1657212494323"}},"timestamp":{"$timestamp":{"t":1657212495,"i":218}},"uuid":{"$binary":{"base64":"pMa3VhfSS2ChFp59zYnnTg==","subType":"04"}},"key":{"ne_unique_id":{"$numberInt":"1"},"area-2":{"$numberInt":"1"},"cnum":{"$numberInt":"1"},"timestamp":{"$numberInt":"1"}},"unique":true,"noBalance":false} And from the chunks we can derive a possible split point structure: { "_id": { "$oid": "62c740258c72e513f017a59c" }, "uuid": { "$binary": { "base64": "pMa3VhfSS2ChFp59zYnnTg==", "subType": "04" } }, "min": { "ne_unique_id": "AFK_247123", "area-2": { "$numberInt": "247" }, "cnum": { "$numberInt": "45" }, "timestamp": { "$date": { "$numberLong": "1627797600000" } } }, "max": { "ne_unique_id": "AFK_247123", "area-2": { "$numberInt": "247" }, "cnum": { "$numberInt": "55" }, "timestamp": { "$date": { "$numberLong": "1636117200000" } } }, "shard": "myShard_0", "lastmod": { "$timestamp": { "t": 1540, "i": 40 } }, "history": [ { "validAfter": { "$timestamp": { "t": 1657212495, "i": 218 } }, "shard": "myShard_0" } ] }

Top User Comments

xgen-internal-githook commented on Wed, 27 Jul 2022 13:26:08 +0000: Author: {'name': 'Pierlauro Sciarelli', 'email': 'pierlauro.sciarelli@mongodb.com', 'username': 'pierlauro'} Message: SERVER-68130 adjust autoSplitVector's estimatedAdditionalBytesPerItemInBSONArray Branch: v4.2 https://github.com/mongodb/mongo/commit/7438eb5acd7f99ad7e1a618eb13598f3e5e5cff4 xgen-internal-githook commented on Wed, 27 Jul 2022 13:24:18 +0000: Author: {'name': 'Pierlauro Sciarelli', 'email': 'pierlauro.sciarelli@mongodb.com', 'username': 'pierlauro'} Message: SERVER-68130 adjust autoSplitVector's estimatedAdditionalBytesPerItemInBSONArray Branch: v4.4 https://github.com/mongodb/mongo/commit/daa784ee5f0deb97b15c78fd1adb6b9186fed414 xgen-internal-githook commented on Wed, 27 Jul 2022 12:53:44 +0000: Author: {'name': 'Pierlauro Sciarelli', 'email': 'pierlauro.sciarelli@mongodb.com', 'username': 'pierlauro'} Message: SERVER-68130 adjust autoSplitVector's estimatedAdditionalBytesPerItemInBSONArray Branch: v5.0 https://github.com/mongodb/mongo/commit/c42b4e0287cee7894cc4fc6d295a28c03f49baaa xgen-internal-githook commented on Tue, 26 Jul 2022 14:44:50 +0000: Author: {'name': 'Pierlauro Sciarelli', 'email': 'pierlauro.sciarelli@mongodb.com', 'username': 'pierlauro'} Message: SERVER-68130 adjust autoSplitVector's estimatedAdditionalBytesPerItemInBSONArray Branch: v6.0 https://github.com/mongodb/mongo/commit/5f5940439f371d712670567ef117c0dd5bfe7fba xgen-internal-githook commented on Mon, 25 Jul 2022 13:17:42 +0000: Author: {'name': 'Pierlauro Sciarelli', 'email': 'pierlauro.sciarelli@mongodb.com', 'username': 'pierlauro'} Message: SERVER-68130 adjust autoSplitVector's estimatedAdditionalBytesPerItemInBSONArray Branch: master https://github.com/mongodb/mongo/commit/c0e3f3796a417747ccd1a8a97cb4fc21d78f2fc5

Steps to Reproduce