Are there hidden members in MongoDB replica set?
Hidden members are good for workloads with different usage patterns from the other members in the replica set. Hidden members must always be priority 0 members and so cannot become primary. The db.isMaster () method does not display hidden members. Hidden members, however, may vote in elections.
When to use a hidden node in MongoDB?
The most common use of hidden nodes is to support delayed members. If you only need to prevent a member from becoming primary, configure a priority 0 member. If the settings.chainingAllowed setting allows secondary members to sync from other secondaries, MongoDB by default prefers non-hidden members over hidden members when selecting a sync target.
When to change arbiter priority in MongoDB 3.6?
Changed in version 3.6: Starting in MongoDB 3.6, arbiters have priority 0. When you upgrade a replica set to MongoDB 3.6, if the existing configuration has an arbiter with priority 1, MongoDB 3.6 reconfigures the arbiter to have priority 0. Adjust priority settings during a scheduled maintenance window.
Can a replica set member have a priority greater than 0?
Members with priority greater than 0 cannot have 0 votes. As such, increasing a non-voting member’s priority requires setting votes to 1 and increases the number of voting replica set members. Before increasing the priority of a non-voting member, consider the following:
How are write operations applied in MongoDB replica set?
MongoDB applies write operations on the primary and then records the operations on the primary’s oplog. Secondary members replicate this log and apply the operations to their data sets. In the following three-member replica set, the primary accepts all write operations.
What’s the purpose of secondary members in MongoDB?
You can configure a secondary member for a specific purpose. You can configure a secondary to: Prevent it from becoming a primary in an election, which allows it to reside in a secondary data center or to serve as a cold standby. See Priority 0 Replica Set Members.