19.2.4.1 Configuring the Change Stream Applier

The Change Stream Applier requires all of the following:

• The source uses row-based binary logging.

• gtid_mode=ON

• SOURCE_AUTO_POSITION=1 for the channel.

• GTID_ONLY=1 for the channel.

• REQUIRE_ROW_FORMAT=1 for the channel.

• SOURCE_DELAY=0 for the channel.

A MySQL 26.7 replica using the Change Stream Applier can replicate transactions from a MySQL 9.7 source if these requirements are satisfied.

The replication applier must be stopped before changing APPLIER_VERSION, APPLIER_WORKER_COUNT, or APPLIER_EVENT_MEMORY_LIMIT. The following example configures eight CSA workers for channel channel_1:

STOP REPLICA FOR CHANNEL 'channel_1';

CHANGE REPLICATION SOURCE TO
    APPLIER_VERSION = 2,
    APPLIER_WORKER_COUNT = 8,
    APPLIER_EVENT_MEMORY_LIMIT = 2147483648,
    SOURCE_AUTO_POSITION = 1,
    GTID_ONLY = 1,
    REQUIRE_ROW_FORMAT = 1,
    SOURCE_DELAY = 0
    FOR CHANNEL 'channel_1';

START REPLICA FOR CHANNEL 'channel_1';

• APPLIER_VERSION: Selects the applier implementation. 1 for the MTA or 2 for the CSA.

• APPLIER_WORKER_COUNT: Specifies the number of CSA worker threads for the channel. The permitted range is 1 through 1024. If the option is omitted when a channel is created, the value of replica_parallel_workers initializes the channel's worker count. Changing replica_parallel_workers later does not change the worker count of an existing CSA channel.

• APPLIER_EVENT_MEMORY_LIMIT: Specifies the per-channel memory limit for caching binary log events. The effective limit is the greater of this value and replica_max_allowed_packet. If a smaller value is specified, the statement succeeds with a warning and replica_max_allowed_packet is used as the effective limit.

  Memory used while decompressing events is accounted for separately and is not included in this limit. Commit events can exceed the limit when necessary to avoid blocking commit-order processing.