mongodb - 使用 Arbiter 将两个节点的副本集升级到 3.6 后出现 Arbiter 功能兼容性问题

Question

我已按照此说明将 MongoDB 副本集升级到 3.6 https://docs.mongodb.com/manual/release-notes/3.6-upgrade-replica-set/ .当我执行命令时

db.adminCommand( { setFeatureCompatibilityVersion: "3.6" } )

Primary 和 Secondary 都将功能兼容性更新到 3.6，但 Arbiter 功能兼容性保持在 3.4。

为什么它仍然是 3.4 以及如何使 Arbiter 具有与 Primary 和 Secondary 相同的功能兼容性？

Answer 1

来自 MongoDB 3.6.7 arbiters continuously log "Using sessions while not fully upgraded to FCV3.6" even though replset is FCV3.6 :

Arbiters always have the downgrade value of FCV, regardless of the FCV of the replica set. So if the arbiter has binary version 3.6, it will always have FCV=3.4. They never learn the FCV, since they do not replicate the admin.system.version collection. Arbiters' behavior is not allowed to depend on FCV for this reason.