Cluster¶
Each DDS cluster consists of a config node, and multiple mongos and shard nodes. The following diagram shows the node relationships.
Figure 1 Diagram of node relationships¶
mongos¶
A mongos is a router for reading and writing data, providing a unified interface for accessing DB instances.
Each DB instance has 2 to 32 mongos. You can specify the quantity.
A mongos reads configuration settings from configs and allocates read and write requests to shards. You can connect to a mongos directly.
config¶
A config stores configuration settings for DB instances and consists of one replica set.
The availability of a config is the prerequisite to deploying a DB instance or modifying the instance information.
You cannot connect to a config directly.