mongodb - maintenance, scaling, monitoring

mongo_scale.md

Scale

• replica sets scales reads
• sharding scales read and writes

replica sets

• backup
• primary and secondary members
• oplog requires a replica set

primary member

• only one

secondary member

• multiple
• copies-, and repeats the primary oplog after a set delay
• priority 0 will not become a primary
• use "hidden" to avoid interference. Suitable for analytics and offline reads. Rquired to be priority 0.

arbiter

• only required if even number-, or only one secondary

sharded cluster

• Cluster of shards. Each shard is a mongod
• Each shard should be a replica set
• Requires: shardKey, router mongos, config server

TODOs

• try replica sets on DO
• try sharded cluster on DO
• checkout datadog for monitoring
• read tal the oplog