Chapter 12. Connecting to a Replica Set from Your Application
This chapter covers how applications interact with replica sets, including:
How connections and failovers work
Waiting for replication on writes
Routing reads to the correct member
Client−to−Replica Set Connection Behavior
MongoDB client libraries (“drivers” in MongoDB parlance) are designed to manage communication with MongoDB servers, regardless of whether the server is a standalone MongoDB instance or a replica set. For replica sets, by default, drivers will connect to the primary and route all traffic to it. Your application can perform reads and writes as though it were talking to a standalone server while your replica set quietly keeps hot standbys ready in the background.
Connections to a replica set are similar to connections to a single
server. Use the
MongoClient class (or equivalent) in your driver and provide a
seed list for the driver to connect to. A seed list is simply a list
of server addresses. Seeds are members of the replica
set your application will read from and write data to. You do not need to
list all members in the seed list (although you can). When the driver
connects to the seeds, it will discover the other members from them. A
connection string usually looks something like this:
See your driver’s documentation for details.
To provide further resilience, you should also use the DNS Seedlist Connection format to specify how your applications connect ...