5.2.3 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_REPLICA_NEW_CHANNEL_WRONG_REPOSITORY.

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

• --log-replica-updates or --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.

• --replica-transaction-retries or --slave-transaction-retries

  The specified number of transaction retries can take place on all applier threads of all channels.

• --skip-replica-start or --skip-slave-start (or skip_replica_start or skip_slave_start system variable set)

  No replication threads start on any channels.

• --replica-skip-errors or --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.

• --replica-parallel-workers=value or --slave-parallel-workers=value

  Number of replication applier threads per channel.

• replica_checkpoint_group or slave_checkpoint_group

  Waiting time by an receiver thread for each source.

• --relay-log-index=filename

  Base name for each channel's relay log index file. See Section 5.2.4, “Replication Channel Naming Conventions”.

• --relay-log=filename

  Denotes the base name of each channel's relay log file. See Section 5.2.4, “Replication Channel Naming Conventions”.

• --replica-net-timeout=N or --slave-net-timeout=N

  This value is set per channel, so that each channel waits for N seconds to check for a broken connection.

• --replica-skip-counter=N or --slave-skip-counter=N

  This value is set per channel, so that each channel skips N events from its source.