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Showing entries 1 to 10 of 23 10 Older Entries

Displaying posts with tag: Stéphane Combaudon (reset)

Making HAProxy 1.5 replication lag aware in MySQL
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HAProxy is frequently used as a software load balancer in the MySQL world. Peter Boros, in a past post, explained how to set it up with Percona XtraDB Cluster (PXC) so that it only sends queries to available nodes. The same approach can be used in a regular master-slaves setup to spread the read load across multiple slaves. However with MySQL replication, another factor comes into play: replication lag. In this case the approach mentioned for  …

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Faster restarts for MySQL and Percona Server 5.6.21+
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By default in MySQL 5.6, each time MySQL is started (regular start or crash recovery), it iterates through all the binlog files when GTIDs are not enabled. This can take a very long time if you have a large number of binary log files. MySQL and Percona Server 5.6.21+ have a fix with the simplified-binlog-gtid-recovery option. Let’s explore this issue.

Understanding the issue

It was first reported by Yoshinori @ Facebook (bug …

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Schema changes in MySQL for OpenStack Trove users
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People using OpenStack Trove instances can hit a common issue in the MySQL world: how to perform schema change operations while minimizing the impact on the database server? Let’s explore the options that can allow online schema changes.

Summary

With MySQL 5.5, pt-online-schema-change from Percona Toolkit is your best option for large tables while regular ALTER TABLE statements are only acceptable for small tables. Also beware of metadata locks.

With MySQL 5.6, almost all types of …

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Typical misconceptions on Galera Replication for MySQL
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Even if a Galera node looks like a regular MySQL server, the underlying replication mechanism is very different. This implies some changes in the way you have to configure the Galera nodes. Here are some of the most common misconceptions about Galera when using Percona XtraDB Cluster.

Q: Why should I enable binary logging as it is not needed by Galera replication?
Unlike for regular asynchronous MySQL replication, it is true that …

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Data inconsistencies on MySQL replicas: Beyond pt-table-checksum
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Percona Toolkit’s pt-table-checksum is a great tool to find data inconsistencies between a MySQL master and its replicas. However it is sometimes not enough to know that there are inconsistencies and let pt-table-sync fix the issue: you may want to know which exact rows are different to identify the statements that created the inconsistency. This post shows one way to achieve that goal.

The issue

Let’s assume …

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MySQL ring replication: Why it is a bad option
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I’ve recently worked with customers using replication rings with 4+ servers; several servers accepting writes. The idea behind this design is always the same: by having multiple servers, you get high availability and by having multiple writer nodes, you get write scalability. Alas, this is simply not true. Here is why.

High Availability

Having several servers is a necessary condition to have high availability, but it’s far from sufficient. What happens if for instance C suddenly disappears?

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HAProxy: Give me some logs on CentOS 6.5!
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HAProxy is frequently used as a load-balancer in front of a Galera cluster. While diagnosing an issue with HAProxy configuration, I realized that logging doesn’t work out of the box on CentOS 6.5. Here is a simple recipe to fix the issue.

If you look at the top of /etc/haproxy/haproxy.cfg, you will see something like:

global
    log         127.0.0.1 local2
[...]

This means that HAProxy will send its messages to rsyslog on 127.0.0.1. But by default, rsyslog doesn’t listen on any …

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MySQL & OpenStack: How to overcome issues as your dataset grows
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MySQL is the database of choice for most OpenStack components (Ceilometer is a notable exception). If you start with a small deployment, it will probably run like a charm. But as soon as the dataset grows, you will suddenly face several challenges. We will write a series of blog posts explaining the issues you may hit and how to overcome them.

Where is MySQL used in OpenStack?

Have a look at the logical diagram of OpenStack below (click the image for a larger view).

 

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Using MySQL 5.6 Global Transaction IDs (GTIDs) in production: Q&A
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Thank you to all of you who attended my webinar last week about Global Transaction IDs (GTIDs), which were introduced in MySQL 5.6 to make the reconfiguration of replication straightforward. If you missed my webinar, you can still listen to the recording and download the sides …

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How to use MySQL Global Transaction IDs (GTIDs) in production
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Reconfiguring replication has always been a challenge with MySQL. Each time the replication topology has to be changed, the process is tedious and error-prone because finding the correct binlog position is not straightforward at all. Global Transaction IDs (GTIDs) introduced in MySQL 5.6 aim at solving this annoying issue.

The idea is quite simple: each transaction is associated with a unique identifier shared by all servers in a given replication topology. Now reconfiguring replication is easy as the correct binlog position can be automatically calculated by the server.

Awesome? Yes it is! However GTIDs …

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Showing entries 1 to 10 of 23 10 Older Entries

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