What is the exact difference between mongod and mongos

Question

While I was looking into the MongoDB documentation, I found two different terms mongod and mongos.

While starting the server, I am using ./mongod --dbpath <path to mongodb> and I am running ./mongo to connect to the server.

Can someone please clarify the differences between these two terms.

Answer 1

The difference between mongod and mongoose is as follows: 

mongod is the daemon, mongo is the client, mongos is the 'MongoDB Shard Utility'. Take a look at man mongos.

Answer 2

Mongos is the MongoDB Shard Utility which is considered to be the controller and query router for sharded clusters. Sharding helps in partitioning the data-set into discrete parts.

Mongod is the primary daemon method for the MongoDB system. It helps in handling the data requests, managing the data access, and performing background management operations.

Answer 3

In MongoDB, there are mongod and mongos, that are two totally different objects.

- `mongod` - the main server process, commonly also known as the Mongo Daemon. This daemon performs storage and queries data handling, even carries out all the actions of a database. Thus, launching MongoDB with `/./mongod --dbpath <path to mongodb>`, you start one run of the instance of the database server listening for incoming requests and connections.

- `mongos`: This term refers to Mongo Shard Router. The application is used with a sharded cluster. It provides for the role of being a query router. It routes requests by the client to proper instances of `mongod`, which hold the related data. Clients do not need to connect directly to servers running `mongod`, but instead connect to instances of `mongos`.