MongoDB handles replication through an implementation called “replication sets”. Replication sets in their basic form are somewhat similar to nodes in a master-slave configuration. A single primary member is used as the base for applying changes to secondary members.
- Primary member: The primary member is the default access point for transactions with the replication set. It is the only member that can accept write operations.
- Secondary members: A replication set can contain multiple secondary members. Secondary members reproduce changes from the oplog on their own data.
- Arbiter: An arbiter is an optional member of a replication set that does not take part in the actual replication process. It is added to the replication set to participate in only a single, limited function: to act as a tie-breaker in elections.
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