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Previous 30 Newer Entries Showing entries 31 to 60 of 332 Next 30 Older Entries

Displaying posts with tag: Insight for DBAs (reset)

High Availability with MySQL Fabric: Part I
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In our previous post, we introduced the MySQL Fabric utility and said we would dig deeper into it. This post is the first part of our test of MySQL Fabric’s High Availability (HA) functionality.

Today, we’ll review MySQL Fabric’s HA concepts, and then walk you through the setup of a 3-node cluster with one Primary and two Secondaries, doing a few basic tests with it. In a second post, we will spend more time generating failure scenarios and documenting how Fabric handles them. (MySQL Fabric is an extensible framework to manage large farms of MySQL servers, with support for high-availability and sharding.)

Before we begin, we recommend you read 

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Why ALTER TABLE runs faster on Percona Server 5.5 vs. MySQL 5.5
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Some of us Perconians are at OpenStack summit this week in Atlanta. Matt Griffin, our director of product management, tweeted about the turbo-hipster CI talk about their experience of ALTER TABLEs running faster on Percona Server. Oracle’s Morgan Tocker then

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max_allowed_packet and binary log corruption in MySQL
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The combination of max_allowed_packet variable and replication in MySQL is a common source of headaches. In a nutshell, max_allowed_packet is the maximum size of a MySQL network protocol packet that the server can create or read. It has a default value of 1MB (<= 5.6.5) or 4MB (>= 5.6.6) and a maximum size of 1GB. This adds some constraints in our replication environment:

  • The master server shouldn’t write events to the binary log larger than max_allowed_packet
  • All the slaves in the replication chain should have the same max_allowed_packet as the master server

Sometimes, even following those two basic rules we can have problems.

For example, there are situations (also called

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Practical MySQL performance optimization: May 14 Webinar
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Achieving the best possible MySQL Performance doesn’t have to be complicated. It’s all about knowing which tools are designed for the task at hand – along with some basic (yet often overlooked) best practices.

Join me Wednesday, May 14 at 10 a.m. Pacific for a free webinar titled, “Practical MySQL performance optimization.” I’ll be sharing the main areas for improving MySQL performance – along with what to specifically focus on in each. These will

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GTIDs in MySQL 5.6: New replication protocol; new ways to break replication
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One of the MySQL 5.6 features many people are interested in is Global Transactions IDs (GTIDs). This is for a good reason: Reconnecting a slave to a new master has always been a challenge while it is so trivial when GTIDs are enabled. However, using GTIDs is not only about replacing good old binlog file/position with unique identifiers, it is also using a new replication protocol. And if you are not aware of it, it can bite.

Replication protocols: old vs new

The old protocol is pretty straightforward: the slave connects to a given binary log file at a specific offset, and the master sends all the transactions from there.

The new protocol is slightly different: the slave first sends the range of GTIDs it has

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MySQL Audit Plugin now available in Percona Server 5.5 and 5.6
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The new Percona Server 5.5.37-35.0 and Percona Server 5.6.17-65.0-56, announced yesterday (May 6), both include the open source version of the MySQL Audit Plugin. The MySQL Audit Plugin is used to log all queries or connections (“audit” MySQL usage). Until yesterday’s release, the MySQL Audit Plugin was only available in

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The top 9 Percona Toolkit tools that can make your job easier: May 7 Webinar
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Tools for MySQL are a vital part of any deployment, so it’s important to use ones that are reliable and well-designed. Percona Toolkit is a collection of more than 30 command-line tools for MySQL, Percona Server, and MariaDB that can help database administrators automate a variety of database and system tasks. With so many available tools, however, it can be difficult knowing where to start.

For this reason I invite you to join me on Wednesday, May 7 at 10 a.m. Pacific time for a free webinar titled, “

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How to identify and cure MySQL replication slave lag
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Here on the Percona MySQL Support team, we often see issues where a customer is complaining about replication delays – and many times the problem ends up being tied to MySQL replication slave lag. This of course is nothing new for MySQL users and we’ve had a few posts here on the MySQL Performance Blog on this topic over the years (two particularly popular post in the past were: “Reasons for MySQL Replication Lag” and “

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Parallel Query for MySQL with Shard-Query
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While Shard-Query can work over multiple nodes, this blog post focuses on using Shard-Query with a single node.  Shard-Query can add parallelism to queries which use partitioned tables.  Very large tables can often be partitioned fairly easily. Shard-Query can leverage partitioning to add paralellism, because each partition can be queried independently. Because MySQL 5.6 supports the partition hint, Shard-Query can add parallelism to any partitioning method (even subpartioning) on 5.6 but it is limited to RANGE/LIST partitioning methods on early versions.

The output from Shard-Query is from the commandline client, but you can use MySQL proxy to communicate with Shard-Query too.

In the examples I am going to use the schema from the Star Schema Benchmark.  I generated data for scale factor 10, which means about 6GB of data in the largest

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ScaleArc: Real-world application testing with WordPress (benchmark test)
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ScaleArc recently hired Percona to perform various tests on its database traffic management product. This post is the outcome of the benchmarks carried out by me and ScaleArc co-founder and chief architect, Uday Sawant.

The goal of this benchmark was to identify ScaleArc’s overhead using a real-world application – the world’s most popular (according to wikipedia) content management system and blog engine: WordPress.

The tests also sought to identify the benefit of caching for this type of workload. The caching parameters represent more real-life circumstances than we applied in the sysbench performance tests

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OOM relation to vm.swappiness=0 in new kernel
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I have recently been involved in diagnosing the reasons behind OOM invocation that would kill the MySQL server process. Of course these servers were primarily running MySQL. As such the MySQL server process was the one with the largest amount of memory allocated.

But the strange thing was that in all the cases, there was no swapping activity seen and there were enough pages in the page cache. Ironically all of these servers were CentOS 6.4 running kernel version 2.6.32-358. Another commonality was the fact that vm.swappiness was set to 0. This is a pretty much standard practice and one that is applied on nearly every server that runs MySQL.

Looking into this further I realized that there was a change introduced in kernel 3.5-rc1 that altered the swapping behavior when “vm.swappiness=0″.

Below is the description of the commit that

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Managing farms of MySQL servers with MySQL Fabric
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While built-in replication has been a major cause for MySQL’s wide adoption, official tools to help DBAs manage replication topologies have typically been missing from the picture. The community has produced many good products to fill in this gap, but recently, Oracle has been filling it too with the addition of MySQL Utilities to the mix.

One part of the Utilities that has been generating interest recently is MySQL Fabric, and we will be discussing this project in an upcoming series of blog

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How to find bugs in MySQL
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Finding bugs in MySQL is not only fun, it’s also something I have been doing the last four years of my life.

Whether you want to become the next Shane Bester (who is generally considered the most skilled MySQL bug hunter worldwide), or just want to prove you can outsmart some of the world’s best programmers, finding bugs in MySQL is a skill not reserved anymore to top QA engineers armed with a loads of scripts, expensive flash storage and top-range server hardware. Off course, for professionals that’s still the way to go, but now anyone with an average laptop and a standard HDD can have a lot of fun trying to find that

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Heartbleed: Separating FAQ From FUD
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If you’ve been following this blog (my colleague, David Busby, posted about it yesterday) or any tech news outlet in the past few days, you’ve probably seen some mention of the “Heartbleed” vulnerability in certain versions of the OpenSSL library.

So what is ‘Heartbleed’, really?

In short, Heartbleed is an information-leak issue. An attacker can exploit this bug to retrieve the contents of a server’s memory without any need for local access. According to the researchers that discovered it, this can be done without leaving any trace of compromise on the system. In other words, if you’re vulnerable, they can steal your keys and you won’t even notice that they’ve gone missing. I use the word

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OpenSSL heartbleed CVE-2014-0160 – Data leaks make my heart bleed
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The heartbleed bug was introduced in OpenSSL 1.0.1 and is present in

  • 1.0.1
  • 1.0.1a
  • 1.0.1b
  • 1.0.1c
  • 1.0.1d
  • 1.0.1e
  • 1.0.1f

The bug is not present in 1.0.1g, nor is it present in the 1.0.0 branch nor the 0.9.8 branch of OpenSSL some sources report 1.0.2-beta is also affected by this bug at the time of writing, however it is a beta product and I would really recommend not to use beta quality releases for something as fundamentally important as OpenSSL in production.

The bug itself is within the heartbeat extension of OpenSSL (RFC6520). The bug allows an attacker to leak the memory in up to 64k chunks, this is not to say the data being leaked is limited to 64k as the attacker can continually abuse this bug to leak data, until they are satisfied with

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Optimizing MySQL Performance: Choosing the Right Tool for the Job
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Next Wednesday, I will present a webinar about MySQL performance profiling tools that every MySQL DBA should know.

Application performance is a key aspect of ensuring a good experience for your end users. But finding and fixing performance bottlenecks is difficult in the complex systems that define today’s web applications. Having a method and knowing how to use the tools available can significantly reduce the amount of time between problems manifesting and fixes being deployed.

In the webinar, titled “Optimizing MySQL Performance: Choosing the Right Tool for the Job,” we’ll start with the basic top, iostat, and vmstat then move onto advanced tools like GDB, Oprofile, and Strace.

I’m looking forward to this webinar and invite you to join us April 16th at 10 a.m. Pacific time. You can learn more

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Facebook’s Yoshinori Matsunobu on MySQL, WebScaleSQL & Percona Live
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Facebook’s Yoshinori Matsunobu

I spoke with Facebook database engineer Yoshinori Matsunobu here at Percona Live 2014 today about a range of topics, including MySQL at Facebook, the company’s recent move to WebScaleSQL, new MySQL flash storage technologies – and why attending the Percona Live MySQL Conference and Expo each year is very important to him.

Facebook engineers are hosting several sessions at

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How to add an existing Percona XtraDB Cluster to Percona ClusterControl
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In my last blog post I explained how to use Percona ClusterControl to create a new Percona XtraDB Cluster from scratch. That’s a good option when you want to create a testing environment in just some mouse clicks. In this case I’m going to show you how to add your existing cluster to Percona ClusterControl so you can manage and monitor it on the web interface.

The environment will be pretty similar, we will have UI, CMON and 3 XtraDB Cluster nodes. The cluster should be already running and Percona ClusterControl also installed.

Adding an existing Cluster

The

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ScaleArc: Benchmarking with sysbench
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ScaleArc recently hired Percona to perform various tests on its database traffic management product. This post is the outcome of the benchmarks carried out by Uday Sawant (ScaleArc) and myself. You can also download the report directly as a PDF here.

The goal of these benchmarks is to identify the potential overhead of the ScaleArc software itself and the potential benefits of caching. The benchmarks were carried out with the trunk version of sysbench. For this reason, we used a very small set of data, so the measurements will be fast, and it’s known that caching has huge benefits when the queries themselves are rather expensive. We decided that we would rather show that benefit with a real-world application, which is coming later is this series.

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Innodb redo log archiving
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Percona Server 5.6.11-60.3 introduces a new “log archiving” feature. Percona XtraBackup 2.1.5 supports “apply archived logs.” What does it mean and how it can be used?

Percona products propose three kinds of incremental backups. The first is full scan of data files and comparison the data with backup data to find some delta. This approach provides a history of changes and saves disk space by storing only data deltas. But the disadvantage is a full-data file scan that adds load to the disk subsystem. The second kind of incremental

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7 Key MySQL clustering technologies – A joint webinar with 451 Research
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I’m looking forward to Wednesday’s joint webinar on MySQL clustering technologies with Matt Aslett, research director of data management and analytics over at 451 Research. We’ll be participating in a live, in-depth discussion of MySQL Clustering for High Availability and Scalability.

Matt will present an overview of the trends driving adoption of clustering technology. He’ll also discuss the key technologies and criteria that developers and administrators need

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How to log slow queries on Slave in MySQL 5.0 with pt-query-digest
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Working as a Percona Support Engineer, every day we are seeing lots of issues related to MySQL replication. One very common issue is slave lagging. There are many reasons for slave lag but one common reason is that queries are taking more time on slave then master. How to check and log those long-running queries?  From MySQL 5.1, log-slow-slave-statements variable was introduced, which you can enable on slave and log slow queries. But what if you want to log slow queries on slave in earlier versions like MySQL 5.0?  There is a good solution/workaround:

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Tools and tips for analysis of MySQL’s Slow Query Log
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MySQL has a nice feature, slow query log, which allows you to log all queries that exceed a predefined about of time to execute. Peter Zaitsev first wrote about this back in 2006 – there have been a few other posts here on the MySQL Performance Blog since then (check this and

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Open Source Appreciation Day at the Percona Live MySQL Conference
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I am very pleased to announce a new event in conjunction with the Percona Live MySQL Conference and Expo this year: Open Source Appreciation Day on Monday, March 31st in the Santa Clara Convention Center! We are pleased to announce two separate groups holding events this year under this new umbrella. We are hosting an event called “OpenStack Today” for those interested in learning more about developments in the OpenStack world. CentOS is holding the “

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Introducing backup locks in Percona Server
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TL;DR version: The backup locks feature introduced in Percona Server 5.6.16-64.0 is a lightweight alternative to FLUSH TABLES WITH READ LOCK and can be used to take both physical and logical backups with less downtime on busy servers. To employ the feature with mysqldump, use mysqldump --lock-for-backup --single-transaction. The next release of Percona XtraBackup will also be using backup locks automatically if the target server supports the feature.

Now on to the gory details, but let’s start with some history.

In the beginning…

In the beginning there was FLUSH TABLES, and users messed with their MyISAM tables under a live server and were not ashamed. Users could do nice things like:

mysql> FLUSH TABLES;
# execute myisamchk, myisampack, backup / restore some


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Many-table joins in MySQL 5.6
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I recently worked on an uncommon slow query: less than 100 rows were read and returned, the whole dataset was fitting in memory but the query took several seconds to run. Long story short: the query was a join involving 21 tables, running on MySQL 5.1. But by default MySQL 5.1 is not good at handling joins with such a large number of tables. The good news is that MySQL 5.6 brings welcome improvements.

Isolating the problem

As always with a slow query, finding the execution plan with EXPLAIN is the 1st step to understand where time is spent. Here the plan was very good with almost all joins using the primary key or a unique key, but perhaps the most interesting part was that EXPLAIN was very slow as well. This indicates that the optimizer takes a lot of time finding the optimal execution plan. To double check, we can run SHOW

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Oracle’s Mats Kindahl to weave MySQL Fabric into Percona Live session
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Mats Kindahl of Oracle is lead developer of MySQL Fabric

MySQL Fabric is an integrated framework for managing farms of MySQL servers with support for both high-availability and sharding. Its development has been spearheaded by Mats Kindahl, senior principal software developer in MySQL at Oracle.

Mats is leading the MySQL Scaling and High-Availability effort covering the newly released MySQL Fabric and the MySQL Applier for Hadoop. He is also the architect and implementer of several features (mostly replication features), including the row-based replication available in 5.1 and the binary log group commit available in MySQL 5.6. Before starting MySQL he earned a doctoral degree in the area of automated

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How rows_sent can be more than rows_examined?
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When looking at queries that are candidates for optimization I often recommend that people look at rows_sent and rows_examined values as available in the slow query log (as well as some other places). If rows_examined is by far larger than rows_sent, say 100 larger, then the query is a great candidate for optimization. Optimization could be as simple as adding a few indexes or much more complicated as in generating summary tables so you do not need to rely on large aggregations for your real-time queries.

Just to be clear this is a great rule for your “real time” queries need to be handled very quickly and in high volumes. Batch jobs, reporting queries often will have to scan through millions of rows to get few rows of result set and it is fine.

So it is all clear with rows_sent being smaller than

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DBA 101: Sometimes forgotten functionality in the MySQL client
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The MySQL client has some functionalities some of us never use. Why would you use them and what is the added value of this?

Every DBA and developer has had a moment when he or she needs to connect to a MySQL database using the command line tool. Therefore I’ve written down an explanation of some command line commands you can insert in the CLI, most of them give added value and make your experience with the cli more enjoyable.

prompt

Who has never witnessed the scary feeling of not being connected to the write database when having several terminals open. I do, due to the fact I use the prompt functionality.

mysql >\R Production >
PROMPT set to 'Production > '

Or you can go a bit further and visualise the user, host and active database in:

mysql > \R \u@\h [\d]>
PROMPT set
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The MySQL ARCHIVE storage engine – Alternatives
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In my previous post I pointed out that the existing ARCHIVE storage engine in MySQL may not be the one that will satisfy your needs when it comes to effectively storing large and/or old data. But are there any good alternatives? As the primary purpose of this engine is to store rarely accessed data in disk space efficient way, I will focus here on data compression abilities rather then on performance.

The InnoDB engine provides compressed row format, but is it’s efficiency even close to the one from that available in archive engine? You can also compress MyISAM tables by using myisampack tool, but that also means a table will be read only after such operation.

Moreover, I don’t trust MyISAM nor Archive when it comes to data

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