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What should the delay be for replicas in MongoDB?
The duration should be less than the capacity of the operation log, which for the WiredTiger, MMAPv1 and In-Memory storage engines is 50GB. Otherwise, the delayed member cannot successfully replicate operations. The delay duration should be equal or slightly greater than your expected maintenance window durations.
When to use majority write concern in MongoDB?
The operation specifies “majority” write concern and a 5 second timeout using the wtimeout write concern parameter so that the operation does not block indefinitely. The application waits until the primary returns write concern acknowledgment, indicating that a calculated majority of the data-bearing voting members acknowledged the write operation.
What does a write concern for a replica set mean?
Write concern for replica sets describe the number of data-bearing members (i.e. the primary and secondaries, but not arbiters) that must acknowledge a write operation before the operation returns as successful. A member can only acknowledge a write operation after it has received and applied the write successfully.
Why is it important to have a fast MongoDB database?
MongoDB often involves working with a large set of data including embedded arrays and array objects. Therefore, it is always important to ensure your database processing rate is as fast as possible to enhance read and write operations.
How long does it take to set a primary in MongoDB?
The median time before a cluster elects a new primary should not typically exceed 12 seconds, assuming default replica configuration settings. This includes time required to mark the primary as unavailable and call and complete an election .
Can you change the number of votes in a replica set?
Do not alter the number of votes to control which members will become primary. Instead, modify the members [n].priority option. Only alter the number of votes in exceptional cases. For example, to permit more than seven members. To configure a non-voting member, see Configure Non-Voting Replica Set Member.
Can a replica set member become a primary member?
Members with a priority value of 0 cannot become primary and do not seek election. For details, see Priority 0 Replica Set Members. Starting in version 4.4, MongoDB provides mirrored reads to pre-warm electable secondary members’ cache with the most recently accessed data.