Elastic Expansion

Last updated: 2021-01-05 15:45:53

    Overview

    TDSQL for MySQL supports real-time expansion in the console. There are two capacity expansion methods: adding shards and expanding the existing shards. The entire expansion process is completely imperceptible to your business without downtime. Only a fraction of shards become read-only for seconds (or are interrupted) during the expansion, while the entire cluster will not be affected.

    Capacity Expansion Process

    TDSQL for MySQL achieves automatic expansion and ensures stability with Tencent's automatic rebalancing technology.

    Adding a new shard

    1. Scale node A in the TDSQL for MySQL console.
    2. According to the configuration of new node G, some data of node A will be migrated (from secondary) to node G.
    3. After the data is completely synchronized, TDSQL will verify the data in node A and node G (read-only for one to tens of seconds), but the entire service is not suspended.
    4. The scheduling system notifies proxy to switch routing.

    Expanding an existing shard

    The expansion based on existing shards is actually to replace the old one with a larger physical shard.

    Note:

    The expansion based on existing shards does not add any shard and will not change the logic rules of sharding or the number of shards.

    1. Assign a new physical shard (hereinafter referred to as "new shard") based on required configuration.
    2. Synchronize the data and configuration of the physical shard to be upgraded (hereinafter referred to as "old shard") to the new shard.
    3. After the data sync is completed, switch the route in the Tencent Cloud gateway to the new shard, and then you can use the new shard.

    References

    A distributed database contains multiple shards. To upgrade the specification of an existing TDSQL for MySQL instance, please see Purchase and Upgrade.