16.2.2.3 Startup Options and Replication Channels

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

The following startup settings must be configured correctly to use multi-source replication.

• relay_log_info_repository.

  This must be set to TABLE. If this variable is set to FILE, attempting to add more sources to a replica fails with ER_SLAVE_NEW_CHANNEL_WRONG_REPOSITORY.

• master_info_repository

  This must be set to TABLE. If this variable is 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

  Applier threads of all channels retry transactions.

• --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 worker 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 16.2.2.4, “Replication Channel Naming Conventions”.

• --relay-log=filename

  Denotes the base name of each channel's relay log file. See Section 16.2.2.4, “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.