Release Notes for mongosync 1.7

1.7.3 Release

June 4, 2024

Issues Fixed:

• Fixed bug introduced in v1.0.0 where the destination may have missing or extra indexes after mongosync is committed. This is an unlikely edge case.

• Fixed bug introduced in v1.0.0 where mongosync may miss change events for a document. This is an unlikely edge case that is only possible if the destination server version is MongoDB 5.0 or earlier.

• Fixed bug introduced in v1.7.0 that could result in size mismatches between source and destination capped collections. This can only affect migrations if all of the following conditions are met:

  • The source cluster is MongoDB 6.0 or earlier.

  • The destination cluster is MongoDB 7.0 or later.

  • A capped collection's size was modified during a migration.

• Fixed bug introduced in v1.0.0 where mongosync ignored the changeStreamPreAndPostImages field in modify change events. This could result in a destination collection having a different value for this field compared to its source collection. mongosync now correctly handles this field.

• Mitigated bug introduced in v1.0.0 that could result in missed change events when mongosync is interrupted and resumed. This is an unlikely edge case.

Other Changes:

• Adds a two minute delay when restarting and resuming sync operations.

Limitations:

• You must stop the balancer on both the source and destination sharded clusters for the entire lifetime of a migration. If you try to start mongosync while the balancer is still running, it throws an error.

• You must not run the moveChunk or moveRange commands on the destination cluster. If you try to run these commands on the source cluster, mongosync throws an error.

• mongosync reads from the destination cluster using the primary read preference. If you try to start mongosync with a different read preference, it throws an error.

1.7.2 Release

April 4, 2024

Issues Fixed:

• Fixed bug introduced in v1.5.0 where mongosync could miss change events when reading documents from a lagging secondary node by disabling the Oplog Rollover Resilience mechanism.

• Fixed bug introduced in v1.1.0 where mongosync could miss copying documents during long running reads in the initial copying phase if the source cluster is sharded and the source balancer is enabled.

• Fixed bug introduced in v1.5.0 that could result in data inconsistencies when mongosync is killed or paused during the initial collection copy phase and then resumed.

  This can only affect migrations if:

  • The migration includes mixed _id types and the destination cluster runs MongoDB 4.4 or earlier.

  • The migration includes capped collections and the destination cluster runs MongoDB 6.0 or later.

• Fixed bug introduced in v1.0.0 where indexes could be created on the destination cluster that were dropped on the source cluster during migration.

  This can only affect migrations where the given index is both created and dropped while mongosync is running.

• Fixed bug introduced in v1.0.0 that could result in collections being created on the destination cluster with incorrect types, options, or indexes.

  This can only affect migrations where collections are dropped or renamed while mongosync is running and the source or destination cluster runs MongoDB 6.0.0 to 6.0.12 or MongoDB 7.0.0 or 7.0.3.

• Fixed bug introduced in v1.1.0 that could result in a mongosync crash if shard key indexes on the source cluster have inconsistent values across shards for the "background" index build option.

  This can only affect migrations that involve sharded collections and source clusters older than MongoDB 6.0.

Other Changes:

• Disables the Oplog Rollover Resilience mechanism.

• Live upgrade to mongosync 1.7.2 is not allowed.

• Reduces latency of the mongosync API.

Limitations:

• mongosync must read from the source cluster using the primary read preference. If you try to start mongosync with a different read preference, it throws an error.

• You must stop the balancer on a sharded source cluster until mongosync finishes the collection copy phase. If you try to start mongosync while the balancer is still running, it throws an error.

• You must not run the moveChunk or moveRange commands on the source cluster. If these are run on the source cluster, mongosync throws an error.

1.7.1 Release

November 9, 2023

Issues Fixed:

• Fixed a bug that caused mongosync to crash when attempting to live upgrade from version 1.6. The bug does not result in modified user data and doesn't preclude the sync from being continued using version 1.7.1.

Live Upgrade

Starting in mongosync 1.7.0, you can upgrade mongosync without restarting data synchronization operations from the beginning. You can only live upgrade to mongosync 1.7.3 or later from mongosync 1.7.2 or later.

For details, see Live Upgrade.

Synchronize Data Between Clusters with Different MongoDB Server Major Versions

Starting in 1.7.0, mongosync can perform version migration from certain lower major version source clusters to certain higher major version destination clusters.

Cross-version migration requires additional preparation and configuration when migrating from a pre-6.0 release. To perform a cross-version migration from a pre-6.0 version of the MongoDB Server using mongosync, please contact your account team to inquire about Professional Services.

Other Notes

New Features:

• mongosync now truncates logged fields that contain more than 1,024 characters.

Issues Fixed:

• Fixed bug introduced in mongosync 1.5.0 that may cause ORR to insert capped collection documents out of order. That is, documents on the source and destination cluster may not be deleted from the capped collection in the same order. This bug is only triggered if documents are inserted into a capped collection during migration, before or while the Collection Copy phase is working on the same capped collection.

• Fixed bug introduced in 1.6 that caused mongosync to fail during initialization if the user specified only an exclusion filter and there were no fully excluded databases.