Release Notes
Announcements
Node | Feature | Description |
Primary node | It is responsible for handling read/write operations. | There can be only one primary node in each replica set instance. |
Secondary node | It replicates the data of the primary node by periodically polling the oplogs of the primary node with data consistency guaranteed. When the original primary node fails, a new primary node will be elected from multiple secondary nodes to ensure the high availability. | When a client connects to a secondary node, it has read-only access and cannot write data. A secondary node can be expanded as described in Adding Secondary Node. A secondary node can be promoted to primary node as described in Promoting Secondary Node to Primary Node. |
Hidden node | A secondary node will be designated as the hidden node by default for each newly purchased instance. It serves as an invisible replica node to back up data. When a secondary or a read-only node fails, this hidden node and the faulty secondary node can be switched to new secondary nodes, thereby achieving high availability. | There can be only one hidden node in each replica set instance. It is not possible to delete a secondary node that has been designated as a hidden node. A hidden node is not included in the "Primary Node's Replica List" and will not be elected as the primary node. However, it can participate in the voting process to elect the primary node. |
Read-only node | If the read-only replica feature is enabled, the system will set one or more secondary nodes as read-only nodes. Read-only nodes are primarily used in scenarios with a large volume of read requests. They synchronize data from the primary or secondary nodes through the operation log. The system automatically routes read requests to the read-only nodes to reduce the access pressure on the primary node. | Read-only nodes do not participate in the election of the primary node. There can be multiple read-only nodes in each replica set instance. For more information, see Adding Read-Only Node. |
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