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Displaying posts with tag: Percona XtraDB Cluster (reset)

keepalived with reader and writer VIPs for Percona XtraDB Cluster
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This is a followup to Jay Janssen’s October post, “Using keepalived for HA on top of Percona XtraDB Cluster.” We got a request recently where the customer has 2 VIPs (Virtual IP addresses), one for reader and one for a writer for a cluster of 3 nodes. They wanted to keep it simple, with low latency and does not require an external node resource like HaProxy would.

keepalived is a simple load balancer with HA capabilities, which means it can proxy TCP services behind it and at the same time, keep itself

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Upcoming Webinar: What’s new in Percona XtraDB Cluster 5.6
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I’ve been blogging a lot about some of the new things you can expect with 

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The use of Iptables ClusterIP target as a load balancer for PXC, PRM, MHA and NDB
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Most technologies achieving high-availability for MySQL need a load-balancer to spread the client connections to a valid database host, even the Tungsten special connector can be seen as a sophisticated load-balancer. People often use hardware load balancer or software solution like haproxy. In both cases, in order to avoid having a single point of failure, multiple load balancers must be used. Load balancers have two drawbacks: they increase network latency and/or they add a validation check load on the database servers. The increased network latency is obvious in the case of standalone load balancers where you must first connect to the load balancer which then completes the request by connecting to one of the database servers. Some workloads like reporting/adhoc queries are not affected by a small increase of latency but other workloads like oltp processing

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Finding a good IST donor in Percona XtraDB Cluster 5.6
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Gcache and IST

The Gcache is a memory-based cache of recent Galera transactions that is local to each node in a cluster.  If a node leaves and rejoins the cluster, it can use the gcache from another node that stayed in the cluster (i.e., its donor node) to fetch the transactions it missed (IST) as opposed to doing a full state snapshot transfer (SST).  However, there are a few nuances that are not obvious to the beginner:

  • The Gcache is lost when a node restarts
  • The Gcache is fixed size and implemented as a LRU.  Once it is full, older transactions roll off.
  • Donor selection is made irregardless of the gcache state
  • If the given donor for a restarting node doesn’t have all transactions needed, a full SST (read: full backup) is done instead
  • Until recent developments, there was no way to tell what,
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Automatic replication relaying in Galera 3.x (available with PXC 5.6)
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A decade ago MySQL folks were in love with the concept of a relay slave for MySQL high availability across data centers.  A relay is a single slave in a remote data center that receives replication from the global master and, in turn, replicates to all the other local slaves in that data center.  This saved a lot of bandwidth, especially back in the days before memcached when scaling reads meant lots of slaves.  Sending 20 copies of your replication stream cross-WAN gets expensive.

In Galera and Percona XtraDB Cluster (PXC), by default when a transaction commits on a given node it is sent to every other node in the cluster from that node.  That is, the actual writeset payload (the RBR events) are sent over the network to every other node, so the bandwidth to

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Percona XtraDB Cluster 5.5.34-25.9 is now available
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Percona is glad to announce the release of Percona XtraDB Cluster 5.5.34-25.9 on December 4, 2013. Binaries are available from the downloads area or from our software repositories.

Based on Percona Server 5.5.34-32.0 including all the bug fixes in it, Galera Replicator and on Codership wsrep API 5.5.34-25.9, Percona XtraDB Cluster

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Useful MySQL 5.6 features you get for free in PXC 5.6
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I get a lot of questions about Percona XtraDB Cluster 5.6 (PXC 5.6), specifically about whether such and such MySQL 5.6 Community Edition feature is in PXC 5.6.  The short answer is: yes, all features in community MySQL 5.6 are in Percona Server 5.6 and, in turn, are in PXC 5.6.  Whether or not the new feature is useful in 5.6 really depends on how useful it is in general with Galera.

I thought it would be useful to highlight a few features and try to show them working:

Innodb Fulltext Indexes

Yes, FTS works in Innodb in 5.6, so why wouldn’t it work in PXC 5.6?  To test this I used the Sakila database , which contains a single table with FULLTEXT.  In the

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New wsrep_provider_options in Galera 3.x and Percona XtraDB Cluster 5.6
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Now that Percona XtraDB Cluster 5.6 is out in beta, I wanted to start a series talking about new features in Galera 3 and PXC 5.6.  On the surface, Galera 3 doesn’t reveal a lot of new features yet, but there has been a lot of refactoring of the system in preparation for great new features in the future.

Galera vs MySQL options

wsrep_provider_options is a semi-colon separated list of key => value configurations that set low-level Galera library configuration.  These tweak the actual cluster communication and replication in the group communication system.  By contrast, other PXC global variables (like ‘wsrep%’)

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Percona XtraDB Cluster 5.6.14-25.1 Beta is now available
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Percona is glad to announce the first Beta release of Percona XtraDB Cluster 5.6 on November 21st, 2013. Binaries are available from downloads area or from our software repositories.

Based on Percona Server 5.6.14-62.0 including all the bug fixes in it, Galera Replicator 3.1 and on Codership wsrep API 5.6.14-25.1

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How to add VIPs to Percona XtraDB Cluster or MHA with Pacemaker
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It is a rather frequent problem to have to manage Virtual IP addresses (VIPs) with a Percona XtraDB Cluster (PXC) or with MySQL master HA (MHA). In order to help solving these problems, I wrote a Pacemaker agent, mysql_monitor that is a simplified version of the mysql_prm agent. The mysql_monitor agent only monitors MySQL and set attributes according to the state of MySQL, the read-only variable, the slave status and/or the output of the clustercheck script for PXC. The agent can operate in 3 modes or cluster types: replication (default), pxc and read-only.

The simplest mode is read-only, only the state of the read_only variable is looked at. If the node has the read_only variable set to OFF, then the writer is set to 1 and reader attributes

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Percona XtraDB Cluster/ Galera with Percona Monitoring Plugins
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The Percona Monitoring Plugins (PMP) provide some free tools to make it easier to monitor PXC/Galera nodes.  Monitoring broadly falls into two categories: alerting and historical graphing, and the plugins support Nagios and Cacti, respectively, for those purposes.

Graphing

An update to the PMP this summer (thanks to our Remote DBA team for supporting this!) added a Galera-specific host template that includes a variety of Galera-related stats,

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High-availability options for MySQL, October 2013 update
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The technologies allowing to build highly-available (HA) MySQL solutions are in constant evolution and they cover very different needs and use cases. In order to help people choose the best HA solution for their needs, we decided, Jay Janssen and I, to publish, on a regular basis (hopefully, this is the first), an update on the most common technologies and their state, with a focus on what type of workloads suite them best. We restricted ourselves to the open source solutions that provide automatic failover. Of course, don’t simply look at the number of Positives/Negatives items, they don’t have the same values. Should you pick any of these technologies, heavy testing is mandatory, HA is never beyond scenario that have been tested.

Percona XtraDB  [Read more...]

Measuring Max Replication Throughput on Percona XtraDB Cluster with wsrep_desync
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Checking throughput with async MySQL replication

Replication throughput is the measure of just how fast the slaves can apply replication (at least by my definition).  In MySQL async replication this is important to know because the single-threaded apply nature of async replication can be a write performance bottleneck.  In a production system, we can tell how fast the slave is currently running (applying writes), and we might have historical data to check for the most throughput ever seen, but that doesn’t give us a solid way of determining where we stand right NOW().

An old consulting trick to answer this question is to simply stop replicating on your slave for a minute, (usually just the SQL_THREAD), restart it and watch how long it takes to catch up.  We can also watch the slave thread apply rate during this interval

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Using keepalived for HA on top of Percona XtraDB Cluster
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Percona XtraDB Cluster (PXC) itself manages quorum and node failure.  Minorities of nodes in a network partition situation will move themselves into a Non-primary state and not allow any DB activity.  Nodes in such a state will be easily detectable via SHOW GLOBAL STATUS variables.

It’s common to use HAproxy with PXC for load balancing purposes, but what if you are

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Taking backups on Percona XtraDB Cluster (without stalls!)
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I occasionally see customers who are taking backups from their PXC clusters that complain that the cluster “stalls” during the backup.  As I wrote about in a previous blog post, often these stalls are really just Flow Control.  But why would a backup cause Flow control?

Most backups I know of (even Percona XtraBackup) take a FLUSH TABLES WITH READ LOCK (FTWRL) at some point in the backup process.  This can be disabled in XtraBackup (in certain circumstances), but it is enabled by

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Percona XtraDB Cluster: Setting up a simple cluster
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Percona XtraDB Cluster (PXC) is different enough from async replication that it can be a bit of a puzzle how to do things the Galera way.  This post will attempt to illustrate the basics of setting up 2 node PXC cluster from scratch.

Requirements

Two servers (could be VMs) that can talk to each other.  I’m using CentOS for this post.  Here’s a dirt-simple Vagrant setup: https://github.com/jayjanssen/two_centos_nodes to make this easy (on Virtualbox).

These servers are talking over the 192.168.70.0/24 internal network for our example.

jayj@~/Src $ git clone https://github.com/jayjanssen/two_centos_nodes.git
jayj@~/Src $ cd two_centos_nodes
jayj@~/Src/two_centos_nodes $
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OSS4B – Presenting in Italy on MySQL and Percona XtraDB Cluster
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I will be in Prato (Firenze), Italy Thursday and Friday (September 19th and 20th) to deliver 2 presentations at OSS4B:

If you want to learn about these projects or discuss anything related to MySQL and Percona, join the conference and don’t hesitate to come to talk to me. I will be very happy to answer your questions.

I  also want to share a list of tracks I would like to attend (there is also another one but it’s at the same time as mine

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Switching between versions using yum
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One type of question we get very often (even in the form of filed bugs!) is how to switch from stock MySQL to Percona Server or switch from Percona Server 5.5 to Percona XtraDB Cluster using yum, but à la apt-get, i.e. having yum handle the replace.

In its simplest form, yum cannot replace a package¹ for another like apt-get does:

 

# yum -q -q install Percona-XtraDB-Cluster-server
Error: Percona-XtraDB-Cluster-server conflicts with Percona-Server-server-55
Error: Percona-XtraDB-Cluster-client conflicts with Percona-Server-client-55
Error: Percona-XtraDB-Cluster-shared


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Percona Server 5.6 Webinar follow-up and Q&A
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Good news everyone! I recently presented a webinar: Percona Server 5.6: Enterprise Grade MySQL. It was also recorded so you can watch along or view the slide deck. As with all my talks, I am not simply reading the slides so it really is worth to listen to the audio rather than just glance through the slide deck.

There were a number of great questions asked which I’ll answer below:

Q: How does Stewart feel about this version of 5.6 taking into consideration “Stewart’s .20 rule?” (ref 2013 Percona Live Conference).

A: For those who aren’t familiar with it, I have a rule which I call “Stewart’s dot twenty rule” which I’ve posted a few times about on

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MySQL Webinar: 5 proactive measures to help minimize MySQL downtime, July 17
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Failure is an unavoidable part of IT life, but it does not always have to imply MySQL service downtime. In the years I have been working at Percona, I have been involved in many customer emergency cases, and I have seen a good number of problems that could have been avoided or alleviated if relatively simple proactive measures were taken.

On July 17th 2013, at 10 a.m. PDT, I will be delivering a webinar focused on presenting the Top 5 such measures, with the objective of helping you assess your current situation, and implement any needed changes to avoid production downtime in the future. The webinar is titled:

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Percona XtraDB Cluster operations MySQL Webinar follow-up questions anwsered
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Thanks to all who attended my PXC Operations webinar last week.  If you missed it you can watch the video here.

I wanted to take some time to answer the questions I didn’t get to during the broadcast.

Is there an easy way to leverage the xtrabackup SST and IST in an xtradb cluster to take your full and incremental backups of the cluster’s databases?

An SST is a full backup of one of the nodes in your database already.  If you want

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2 new features added to Percona XtraDB Cluster (PXC) since 5.5.31
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With the last Percona XtraDB Cluster (PXC) release, two major features were added:

* a new command to bootstrap the cluster was added to the init script
* SST via Xtrabackup now supports Xtrabackup 2.1 features

In this post, I want to explain the benefits of these added features and how to use them.

If you follow the mysqlperformanceblog regularly, you’ve already noticed that there are several ways to start a node and that it’s not always easy to start the node


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Changing an async slave of a PXC cluster to a new Master
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Async and PXC

A common question I get about Percona XtraDB Cluster is if you can mix it with asynchronous replication, and the answer is yes!  You can pick any node in your cluster and it can either be either a slave or a master just like any other regular MySQL standalone server (Just be sure to use log-slave-updates in both cases on the node in question!).  Consider this architecture:

However, there are some caveats to be aware of.  If you slave from a cluster node, there is no built in mechanism to fail that slave over automatically to another master node in your cluster.  You cannot assume that the binary log positions are the same on all nodes in

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Percona XtraDB Cluster (PXC) in the real world: Share your use cases!
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The aim of this post is to enumerate real-world usage of Percona XtraDB Cluster (PXC), and also to solicit use cases from the readers. One of the prominent usages in the production environment that we have come across (and our Percona consultants have assisted) is that of HP Cloud. There is a post about it here by Patrick Galbraith of HP. The post focuses on their deployment of PXC for HP Cloud DNS. The post focuses on the key aspects of

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Is Synchronous Replication right for your app?
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I talk with lot of people who are really interested in Percona XtraDB Cluster (PXC) and mostly they are interested in PXC as a high-availability solution.  But, what they tend not to think too much about is if moving from async to synchronous replication is right for their application or not.

Facts about Galera replication

There’s a lot of different facts about Galera that come into play here, and it isn’t always obvious how they will affect your database workload.  For example:

  • Transaction commit takes approximately the worst packet round trip time (RTT) between any two nodes in your cluster.
  • Transaction apply on slave nodes is still asynchronous from client commit (except on the original node where the transaction is
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Follow these basics when migrating to Percona XtraDB Cluster for MySQL
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Galera/Percona XtraDB Cluster (PXC) for MySQL is a hot thing right now and some users jump right in without enough testing. Consequently, they’re more likely to either suffer failure or issues that prevent them from moving forward. If you are thinking of migrating your workload to Percona XtraDB Cluster, make sure to go through these basics.

log_slave_updates is REQUIRED

You need to have log_slave_updates enabled on the cluster node acting as async slave for replicated events from the async master to be applied to the other

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Percona XtraDB Cluster 5.5.30-23.7.4 for MySQL now available
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Percona is glad to announce the release of Percona XtraDB Cluster 5.5.30-23.7.4 for MySQL on April 17, 2013. Binaries are available from the downloads area or from our software repositories.

New Features:

  • Percona XtraDB Cluster has implemented initial implementation of weighted quorum. Weight for node can be assigned via pc.weight option in the wsrep_provider_options variable. Accepted values are in the range [0, 255] (inclusive). Quorum is computed using weighted
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Keynotes, BOFs, and the Community Networking Reception at Percona Live MySQL Conference and Expo
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The Percona Live MySQL Conference and Expo begins next Monday and runs April 22-25, 2013. Attendees will see great keynotes from leaders in the industry including representatives from Oracle, Amazon Web Services, HP, Continuent, and Percona. They can also participate in thought provoking Birds of a Feather sessions on Tuesday night and the Wednesday night Community Networking Reception will be fun and entertaining with the presentation of the Community Awards and the Lightning Talks.

If you

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Percona MySQL University coming to Toronto this Friday!
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Percona CEO Peter Zaitsev leads a track at Percona MySQL University in Raleigh, N.C. on Jan. 29, 2013.

Percona MySQL University, Toronto is taking place this Friday and I’m very excited about this event because it is a special opportunity to fit a phenomenal number of specific and focused MySQL technical talks all into one day, for free.

Over the course of the day we will cover some of the hottest topics in the MySQL space. There will be talks covering topics like MySQL 5.6, MySQL in the Cloud and High Availability for MySQL, as well as

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Accessing Percona XtraDB Cluster nodes in parallel from PHP using MySQL asynchronous queries
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Accessing Percona XtraDB Cluster nodes in parallel with MySQL asynchronous calls

This post is followup to Peter’s recent post, “Investigating MySQL Replication Latency in Percona XtraDB Cluster,” in which a question was raised as to whether we can measure latency to all nodes at the same time. It is an interesting question: If we have N nodes, can we send queries to nodes to be executed in parallel?

To answer it, I decided to try a new asynchronous call to send a

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