What is Config Servers in MongoDB? well, config server MongoDB is basically used when you go for sharding of your data, what does it mean? for a sharded cluster, you require config servers. If you use a replica set for the config server it means you basically improve consistency across the config server MongoDB.
Overview of Config Servers in MongoDB
Following are the restriction which apply to a replica set configuration when used for config servers MongoDB:
- Must have zero arbiters.
- Must have no delayed members.
- must build indexes, it means , no members should have
buildIndexessetting to false
- Standalone and identical mongod servers.
- There are not all created equal (config string passed to mongos). The first config server in the list is important. in 3 node config server, if you lose 1 or 2 config servers, the cluster continues to function. In this case you can’t modify any metadata or chunksize, etc in the sharded enviroment.
Useful Commands on mongos for config server mongodb
db.chunks()on config server mongodb
- It’s important to remember that all operations over configs, need to be done through the mongos and not directly.
Availability of Config Server mongoDB
If config server in MongoDB replica set loses its primary , it this case , can not elect a primary, it means cluster metadata become read-only. You can read and write data from shards , but no chunck migration or chunk split will ocuur until the replic set can elect primary.
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