What does MySQL replication do?

What does MySQL replication do?

Replication enables data from one MySQL database server (known as a source) to be copied to one or more MySQL database servers (known as replicas). Replication is asynchronous by default; replicas do not need to be connected permanently to receive updates from a source.

How reliable is MySQL replication?

MySQL replication is reasonably stable, and no less so than other solutions. But there are a variety of failures that can happen, without it being MySQL’s fault. Binlogs can develop corrupted packets in transit due to network glitches. MySQL 5.6 introduced binlog checksums to detect this.

How do I fix MySQL replication lag?

To minimize slave SQL_THREAD lag, focus on query optimization. My recommendation is to enable the configuration option log_slow_slave_statements so that the queries executed by slave that take more than long_query_time will be logged to the slow log.

How make MySQL replicate faster?

Speed up slave replication on large database / quickly spawn…

1. Create a slave server.
2. Load in a mysql dump of the master.
3. Start the slave.
4. Wait for slave replication to sync w/ master.
5. Place slave server in production.

What causes replication lag MySQL?

Replication lag is caused when either the I/O Thread or SQL Thread cannot cope with the demands placed upon it. If the I/O Thread is suffering, this means that the network connection between the master and its slaves is slow. There may be long-running transactions or too much I/O activity.

How do you deal with lag replication?

To mitigate replication lag for large operations we use batching. We never apply a change to 100,000 rows all at once. Any big update is broken into small segments, subtasks, of some 50 or 100 rows each. As an example, say our app needs to purge some rows that satisfy a condition from a very large table.

How does replication work in azure database for MySQL?

Those updates are saved on a replica server, in a local log called the relay log. The SQL thread reads the relay log and then applies the data changes on replica servers. Azure Database for MySQL provides the metric for replication lag in seconds in Azure Monitor.

How does MySQL replication improve performance and latency?

This setup reduces the pressure on the source server. It also improves overall performance and latency of the application as it scales. Replicas are updated asynchronously by using the MySQL engine’s native binary log (binlog) file position-based replication technology.

When to use row based replication in MySQL?

Row-based replication allows extra columns to exist at the end of the table, so as long as it is able to write the first columns it will be fine. First apply the change to all slaves, then failover to one of the slaves and then apply the change to the master and attach that as a slave.

Why does MySQL replication stall the replication stream?

This has to do with the fact that a DDL change will most of the time lock a table and only release this lock once the DDL change has been applied. It even gets worse once you start replicating these DDL changes through MySQL replication, where it will in addition stall the replication stream.