17.2.2.3 Startup Options and Replication Channels

This section describes startup options which are impacted by the addition of replication channels.

The master_info_repository and relay_log_info_repository system variables must not be set to FILE when you use replication channels. In MySQL 8.0, the FILE setting is deprecated, and TABLE is the default, so the system variables can be omitted. From MySQL 8.0.23, they must be omitted because their use is deprecated from that release. If these system variables are set to FILE, attempting to add more sources to a replica fails with ER_SLAVE_NEW_CHANNEL_WRONG_REPOSITORY.

The following startup options now affect all channels in a replication topology.

--log-slave-updates
All transactions received by the replica (even from multiple sources) are written in the binary log.
--relay-log-purge
When set, each channel purges its own relay log automatically.
--slave_transaction_retries
The specified number of transaction retries can take place on all applier threads of all channels.
--skip-slave-start
No replication threads start on any channels.
--slave-skip-errors
Execution continues and errors are skipped for all channels.

The values set for the following startup options apply on each channel; since these are mysqld startup options, they are applied on every channel.

--max-relay-log-size=size
Maximum size of the individual relay log file for each channel; after reaching this limit, the file is rotated.
--relay-log-space-limit=size
Upper limit for the total size of all relay logs combined, for each individual channel. For N channels, the combined size of these logs is limited to relay_log_space_limit * N.
--slave-parallel-workers=value
Number of replication applier threads per channel.
slave_checkpoint_group
Waiting time by an I/O thread for each source.
--relay-log-index=filename
Base name for each channel's relay log index file. See Section 17.2.2.4, “Replication Channel Naming Conventions”.
--relay-log=filename
Denotes the base name of each channel's relay log file. See Section 17.2.2.4, “Replication Channel Naming Conventions”.
--slave_net-timeout=N
This value is set per channel, so that each channel waits for N seconds to check for a broken connection.
--slave-skip-counter=N
This value is set per channel, so that each channel skips N events from its source.