Percona ClusterSync for MongoDB (PCSM) 0.9.0 adds cross-version replication support, enabling near-zero-downtime migrations from MongoDB 6.0 directly to 8.0 without requiring an intermediate same-version step. The engineering team discovered that the expected complexity — a change-stream event translation layer between major versions — was unnecessary, as MongoDB 6.0 and 8.0 produce identical change-stream events for the operations PCSM handles. The real problem was a single swallowed DDL error that caused cascading failures. Key fixes include surfacing DDL errors to halt diverged replication, a version-compatibility gate that blocks downgrades, a capped-collection size rounding fix specific to 6.x behavior, and a TTL index recreation workaround for 8.0's stricter index-options validation. The supported matrix now covers all lower-to-higher pairs among 6.0, 7.0, and 8.0 on both replica-set and sharded topologies.
352 Impressions1 Comment