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Recentemente respondi algumas questões referente a lag(atraso) na replicação, o que percebi é que muita gente não intende corretamente como este processo funciona internamente no MySQL e o porque do lag acontecer:

• MySQL replication: most important config parameters for performance on slave server?
• mysql replication delay very serious

Veja a figura abaixo, ela representa replicação assíncrona no MySQL, recomendo que você leia meu outro post sobre o assunto:

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These days I’ve answer some questions about replication lag, and I realized that most of people does not correctly understand how this process works internally on MySQL, and why does delays happen:

• MySQL replication: most important config parameters for performance on slave server?
• mysql replication delay very serious

See the bellow image, it represents asynchronous replication on MySQL, I highly recommend you to read my other post:

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See the bellow image, it represents how asynchronous replication works on MySQL

Bearing in mind the number on the image, let’s see how the process works:

• Item 1 in the image represents the clients executing queries on master, note that the master is capable to handle multiple simultaneous connections (it can be configurable by max_connections variable). 
• Master process these queries, and save it to his binary log(item number 2 in the image), then it can later on be replied on the slave.
• The slave has 2 threads reubuntu mount ext4 partitionsponsible to deal with replication :
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MySQL Connector/J 5.1.25 has been released, and is available in Community and Enterprise flavors on dev.mysql.com and My Oracle Support, respectively.  I’ve already noted the addition of support for connection attributes for MySQL 5.6 – 5.1.25 adds this functionality.  This release also includes a fix for Bug#68733, which caused the special light-weight ping operation to execute only against the master and currently-selected slave, rather than …

I was reviewing the Percona Live sponsors list the other day and pondering the potential success stories associated with this product or that one…. and as I was preparing to put more thought on the topic, a PlanetMySQL post caught my eye. It was penned by Mike Hogan and titled, “Thoughts on Xeround and Free!”

For some reason the author of that post makes a connection between a free account in a cloud-based service and Open Source software. I think it’s an incorrect analogy, as they are two totally different things. A “free account” in this case is really just a marketing tool. Well, I admit there are companies that also use the “Open …

This week again, the Log Buffer Edition covers the exciting and ever-evolving galaxies of Oracle, MySQL and SQL Server.

Oracle:

When does an Oracle process know it’s on Exadata?

MobaXterm 6.3 has been released. You can find the download and changelog in the usual place.

A new major release (version 3.0) of Randolf’s XPLAN_ASH tool is available for download.

Important !! Clustering Factor Calculation Improvement

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Having an InnoDB table without a PRIMARY KEY is not good. Many have known this for years, but exact opinions as to why have differed. From observation, it was clear to me that it impacted performance.

InnoDB stores its row data in the leaf nodes of the primary key B+tree structure, that means that it can’t work without… so if you don’t specify a PK, it makes one up. Seems pretty innocuous and shouldn’t actually perform any worse than an auto-inc field. Except that in reality the performance can be much much worse. Annoying. Naturally we recommend clients to always have a PK (auto-inc, a composite of foreign keys, or if need be a natural key) but production systems cannot always be quickly changed, depending on the app code adding a column is not something you can just do at the DBA level.

Recently my good friend and former colleague Jeremy Cole, who has been delving into the depths of InnoDB, asked me if I had any …

It's now safe to backup InnoDB with mysqldumpBefore MySQL 5.6, running mysqldump to make backup of InnoDB tables could cause your backup to 'loose' some data. The problem is described in our manual  here.

In latest MySQL 5.6 this is no longer a problem, this means you no longer risk 'loosing' data when using mysqlbackup together with DDL statements on your InnoDB tables. If you are interested in metadata-locking (MDL) you can read more about MDL  here.

To test this we need to create a few tables and also look at which order mysqldump processes tables.

mysql> CREATE DATABASE ted;
mysql> USE ted;
mysql> CREATE TABLE `a` (`i` int(11) DEFAULT NULL) ENGINE=InnoDB
mysql> CREATE …

Replication is a hot topic in MySQL 5.6, and for good reason: There are many excellent features that make it a strong well-supported feature, from the new Global Transaction Identifiers (GTIDs), to simplified replication configuration and automated failover using MySQL Utilities (now available in alpha as a separate download).

Circular Replication

The simplest topology consists of a master server that accepts changes, and slaves that replicate those changes from the master. A common requirement is for a network to have multiple servers that accept changes and replicate to each other. This is possible by means of circular …