Overview The Skinny

From time to time we are asked how to check whether or not there are data discrepancies between Master/Slave nodes within a MySQL (or MariaDB) cluster that’s managed with Tungsten Clustering. This is always a challenging task, not least because we hope and believe that our replication mechanism would avoid such occurrences, that said there can be factors outside of our control that can appear to “corrupt” data – such as inadvertent execution of DML against a slave using a root level user account.

Tungsten Replicator, the core replication component in our Tungsten Clustering solution for MySQL (& MariaDB), is just that, a replicator – it takes transactions from the binary logs and replicates them around. The replicator isn’t a data synchronisation tool in that respect, the …

GTID Replication (Skip Transaction using empty transaction) To skip SQL thread's error in GTID replication setup, Insert empty transaction. PROBLEM :  db-test (none)> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: xxxxx
                  Master_User: rep_user
                  Master_Port: 3306
        …

MySQL 8.0.16 has been released last Thursday. In it, you can find some new replication features. Here is a quick summary. Follow-up blog posts will provide details about these features.

• Large Messages Fragmentation Layer for Group Replication. Tiago Vale’s work, introduces message fragmentation to the Group Communication Framework.

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So over the years, we all learn more and more about what we like and use often in MySQL. 

Currently, I step in and out of a robust about of different systems. I love it being able to see how different companies use MySQL.  I also see several aspect and settings that often get missed. So here are a few things I think should always be set and they not impact your MySQL database. 

At a high level:

• >Move the Slow log to a table 
• Set report_host_name 
• Set master & slaves to use tables
• Turn off log_queries_not_using_indexes until needed 
• Side note -- USE  ALGORITHM=INPLACE
• Side note -- USE mysql_config_editor
• Side note -- USE  mysql_upgrade  --upgrade-system-tables

Move the Slow log to a …

Just about a month ago, Pavel Ivanov released Ripple under the Apache-2.0 license. Ripple is a MySQL binlog server: software which receives binary logs from MySQL or MariaDB servers and delivers them to another MySQL or MariaDB server. Practically ,this is an intermediary master which does not store any data, except the binary logs themselves, and does not apply events. This solution allows saving of a lot of resources on the server, which acts only as a middle-man between the master and its actual slave(s).

The intermediary server, keeping binary logs only and not doing any other job, is a prevalent use case which allows us to remove IO (binlog read) and network (binlog retrieval via network) load from the actual …

Recently, we had an edge case where a MySQL slave went out-of-sync but it couldn’t be rebuilt from scratch. The slave was acting as a master server to some applications and it had data was being written to it. It was a design error, and this is not recommended, but it happened. So how do you synchronize the data in this circumstance? This blog post describes the steps taken to recover from this situation. The tools used to recover the slave were pt-slave-restart, pt-table-checksum, pt-table-sync and mysqldiff.

Scenario

To illustrate this …

On previous posts about Group Replication consistency we:

1. introduced consistency levels;
2. explained how to configure the primary failover consistency;
3. presented how to configure transaction consistency levels to achieve the consistency required by your applications.

In blog 3. we presented the consistency levels: EVENTUAL, BEFORE, AFTER and BEFORE_AND_AFTER; their scopes: SESSION, GLOBAL; and their context: whether they only impact the ongoing transaction or all concurrent transactions.…

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This was not on the radar. I have never been proficient in Galera clusters and related technologies, and thus I hadn’t given much thought to Percona Xtradb Cluster (PXC), until Alkin approached me at FOSDEM, and proposed to extend dbdeployer features to support PXC. He mentioned that many support engineers at Percona use dbdeployer) on a daily basis and that the addition of PXC would be welcome.

I could not follow up …

• Replication used to replicate data from the Master node to a slave node[Replica].
• By default Replication is asynchronous.
• It uses binary logs for reading data from the Master node and relay log on slave[Replica].
• Depending on the configuration, you can replicate all databases, selected databases, or even selected tables within a database.

Replication Methods:

• File-based Replication:

The traditional method is based on replicating events from the master’s binary log, and requires the log files and positions in them to be synchronized between master and slave.

• GTID Replication:

The newer method based on global transaction identifiers (GTIDs) is transactional and therefore does not require working with log files or positions within …

Some months ago, Shlomi Noach published a series about Service Discovery.  In his posts, Shlomi describes many ways for an application to find the master.  He also gives detail on how these solutions cope with failing-over to a slave, including their integration with Orchestrator.

This is a great series, and I recommend its reading for everybody implementing master failover, with or without