Priority: Major - P3
Affects Version/s: 3.0.3
Kernel Tools Iteration 4, Kernel Tools Iteration 5
I have a job exporting a set of documents from collections on a sharded cluster using mongodump to BSON files which are later imported on other type of DBs.
Since maintaining a strong consistency from our mongodb cluster and the other DBs is important to us, we implemented a three way check on the number of exported documents :
- count the targeted documents using a normal query
- parse and count the mongodump exported documents count
- count the number of imported documents from the BSON files into the other DBs
- everything is okay when all counts match obviously !
We are migrating this cluster to 3.0.3. It was doing okay while the primaries and secondaries were still running under MMAPv1 : the number of documents extracted by mongodump was the same as the number found in the bson.
But since the migration to mongodb 3.0.3 wiredTiger on the SECONDARIES (primaries still run MMAPv1), a difference is visible between the total number of documents than mongodump said to have extracted, and the actual number of records found in the bson!
- mongodump reports exporting 4314985 documents.
- bsondump reports exporting 4314084 documents.
- restored documents count is 4314084 !