This section describes startup options which are impacted by the addition of replication channels.
Themaster_info_repository
andrelay_log_info_repository
system variables mustnotbe set toFILE
when you use replication channels. In MySQL 8.0, theFILE
setting is deprecated, andTABLE
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 toFILE
, attempting to add more sources to a replica fails withER_SLAVE_NEW_CHANNEL_WRONG_REPOSITORY
.
The following startup options now affectallchannels in a replication topology.
All transactions received by the replica (even from multiple sources) are written in the binary log.
When set, each channel purges its own relay log automatically.
The specified number of transaction retries can take place on all applier threads of all channels.
--skip-slave-start
(orskip_slave_start
system variable set)No replication threads start on any channels.
Execution continues and errors are skipped for all channels.
The values set for the following startup options apply on each channel; since these aremysqldstartup 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 torelay_log_space_limit *
.N
--slave-parallel-workers=
value
Number of replication applier threads per channel.
Waiting time by an I/O thread for each source.
--relay-log-index=filename
Base name for each channel's relay log index file. SeeSection 17.2.2.4, “Replication Channel Naming Conventions”.
--relay-log=filename
Denotes the base name of each channel's relay log file. SeeSection 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.