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What is query router in MongoDB?
The query router, also known as mongos process, acts as the interface and entry point to our MongoDB cluster. Applications connect to it instead of connecting to the underlying shards and replica sets; mongos executes queries, gathers results, and passes them to our application.
What is Query router?
Query routing is a process of directing user queries to appropriate servers by constraining the search space through query refinement and source selection.
What is sharding and replication in MongoDB?
Replication: A replica set in MongoDB is a group of mongod processes that maintain the same data set. Sharding: Sharding is a method for storing data across multiple machines.
What is mongos instance?
Synopsis. For a sharded cluster, the mongos instances provide the interface between the client applications and the sharded cluster. The mongos instances route queries and write operations to the shards. From the perspective of the application, a mongos instance behaves identically to any other MongoDB instance.
How does sharding work in a MongoDB cluster?
The query router processes and targets the operations to shards and then returns results to the clients. A sharded cluster can contain more than one query router to divide the client request load. A client sends requests to one query router. Generally, a sharded cluster have many query routers.
How does a query router work in MongoDB?
The query router uses this metadata to target operations to specific shards. In production environment, sharded clusters have exactly 3 config servers. Query Routers − Query routers are basically mongo instances, interface with client applications and direct operations to the appropriate shard.
What do you need to know about shards in Mongo?
Shards are required to be deployed in the replica set. Mongos is a Mongo instance and acts as an interface between a client application and a sharded cluster. It works as a query router to shards. Config Server is a Mongo instance which stores metadata information and configuration details of cluster.
How many query routers are in a shardid cluster?
In production environment, sharded clusters have exactly 3 config servers. Query Routers − Query routers are basically mongo instances, interface with client applications and direct operations to the appropriate shard.