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MySQL Replication  /  Configuring Replication  /  MySQL Multi-Source Replication

2.4 MySQL Multi-Source Replication

MySQL multi-source replication enables a replication slave to receive transactions from multiple immediate masters in parallel. In a multi-source replication topology, a slave creates a replication channel for each master that it should receive transactions from. For more information on how replication channels function, see Section 5.3, “Replication Channels”.

You might choose to implement multi-source replication to achieve goals like these:

  • Backing up multiple servers to a single server.

  • Merging table shards.

  • Consolidating data from multiple servers to a single server.

Multi-source replication does not implement any conflict detection or resolution when applying transactions, and those tasks are left to the application if required.

Note

Each channel on a multi-source replication slave must replicate from a different master. You cannot set up multiple replication channels from a single slave to a single master. This is because the server IDs of replication slaves must be unique in a replication topology. The master distinguishes slaves only by their server IDs, not by the names of the replication channels, so it cannot recognize different replication channels from the same slave.

A rmulti-source replication slave can also be set up as a multi-threaded replication slave, by setting the slave_parallel_workers system variable to a value greater than 0. When you do this on a multi-source replication slave, each channel on the slave has the specified number of applier threads, plus a coordinator thread to manage them. You cannot configure the number of applier threads for individual channels.

From MySQL 8.0, multi-source replication slaves can be configured with replication filters on specific replication channels. Channel specific replication filters can be used when the same database or table is present on multiple masters, and you only need the slave to replicate it from one master. For more information, see Section 5.5.4, “Replication Channel Based Filters”.

This section provides tutorials on how to configure masters and slaves for multi-source replication, how to start, stop and reset multi-source slaves, and how to monitor multi-source replication.