In this post I would like to review how my dumper for MySQL works from the point of view of locks. Since 0.6 serie we have different options, so I will try to explain how they work

As you may know mydumper is multithreaded and this adds a lot of complexity compared with other logical backup tools as it also needs to coordinate all threads with the same snapshot to be consistent. So let review how mydumper does this with the default settings.

By default mydumper uses 4 threads to dump data and 1 main thread

Main Thread

• FLUSH TABLES WITH READ LOCK

Dump Thread X

• START TRANSACTION WITH CONSISTENT SNAPSHOT;
• dump non-InnoDB tables

Main Thread

• UNLOCK TABLES

Dump Thread X

• dump InnoDB tables

As you can see in this case we need FTWRL for two things, coordinate transaction’s snapshots …

When you make a change to your MySQL configuration in production it would be great to know the impact (a “before and after” type of picture). Some changes are obvious. For many variables proper values can be determined beforehand, i.e. innodb_buffer_pool_size or innodb_log_file_size. However, there is 1 configuration variable which is much less obvious for many people working with MySQL: query_cache.

The idea of query cache is great, however, there are a lot of issues with MySQL query …

Hosting a shared MySQL instance for your internal or external clients (“multi-tenant”) was always a challenge. Multi-tenants approach or a “schema-per-customer” approach is pretty common nowadays to host multiple clients on the same MySQL sever. One of issues of this approach, however, is the lack of visibility: it is hard to tell how many resources (queries, disk, cpu, etc) each user will use.

Percona Server contains userstats Google patch, which will allow you to get the resource utilization per user. The new MySQL 5.6 performance_schema has even more instrumentation which can give you a better visibility on per-user or per-schema/per-database level. And if you are running MySQL 5.6.6 or …

I’ve been running a benchmark today on my old test box with conventional hard drives (no raid with BBU) and noticed something unusual in the CPU utilization statistics being reported.

The benchmark was run like this:

sysbench --num-threads=64 --max-requests=0 --max-time=600000 --report-interval=10 --test=oltp --db-driver=mysql --oltp-dist-type=special  --oltp-table-size=1000000   --mysql-user=root --mysql-password=password  run

Which means: create 64 threads and hammer the database with queries as quickly as possible. As the test was run on the localhost I would expect the benchmark to completely saturate the system – being either using CPU or being blocked on IO nature of this benchmark so it does not spend a lot on database locks, especially as this system has just 2 cores.

Looking at VMSTAT however I noticed this:

[root@smt1 mysql]# vmstat 10
procs -----------memory---------- ---swap-- -----io---- …

This is the third post in our MySQL Fabric series. If you missed the previous two, we started with an overall introduction, and then a discussion of MySQL Fabric’s high-availability (HA) features. MySQL Fabric was RC when we started this series, but it went GA recently. You can read the press release here, and see this blog post from Oracle’s Mats Kindahl for more details. In our previous post, we showed a simple HA setup managed with MySQL Fabric, including some basic failure scenarios. …

MySQL has status variables “questions” and “queries” which are rather close but also a bit different, making it confusing for many people. The manual describing it might not be very easy to understand:

Queries
The number of statements executed by the server. This variable includes statements executed within stored programs, unlike the Questions variable. It does not count COM_PING or COM_STATISTICS commands.
 Questions
The number of statements executed by the server. This includes only statements sent to the server by clients and not statements executed within stored programs, unlike the Queries variable. This variable does not count COM_PING, COM_STATISTICS, COM_STMT_PREPARE, COM_STMT_CLOSE, or COM_STMT_RESET commands.

In a nutshell if you’re not using prepared statements the big difference between those is what …

First, I would like to invite you to my webinar, “Monitoring All (Yes, All!) MySQL Metrics with Percona Cloud Tools,” on Wednesday, June 25 at 10 a.m. Pacific Daylight Time, where I will talk on the
new features in Percona Cloud Tools, including monitoring capabilities.

In this post I’d like to show the cool and interesting things we’ve implemented in Percona Cloud Tools, including the recently released agent that Daniel also talks about here in this post.

Basically our agent allows users to collect ALL MySQL metrics plus important …

There is one new feature in MySQL 5.6 that didn’t get the attention it deserved (at least from me ) : “DATA DIRECTORY” for InnoDB tables.

This is implemented since MySQL 5.6.6 and can be used only at the creation of the table. It’s not possible to change the DATA DIRECTORY with an ALTER for a normal table (but it’s in some case with partitioned ones as you will see below). If you do so, the option will be just ignored:

mysql> CREATE TABLE `sales_figures` (
    ->   `region_id` int(11) DEFAULT NULL,
    ->   `sales_date` date DEFAULT NULL,
    ->   `amount` int(11) DEFAULT NULL
    -> ) ENGINE=InnoDB DEFAULT CHARSET=latin1
    -> DATA DIRECTORY = '/tb1/';
Query OK, 0 rows affected (0.11 sec)
mysql> alter table sales_figures engine=innodb data directory='/tb2/';
Query OK, 0 rows affected, 1 warning (0.21 sec)
Records: 0  Duplicates: 0  Warnings: 1
mysql> show warnings; …

In my previous post, I blogged about using Percona Server with Docker and have shown you how fast and easy it was to create a virtual environment with just a few commands.

This time I will be showing you how to setup a three-node Percona XtraDB Cluster (PXC) 5.6 on the Docker open-source engine. Just to review Docker… “is an open-source engine that automates the deployment of any application as a lightweight, portable, self-sufficient container that will run virtually anywhere.”

In this case we will make use of a Dockerfile, think of this more like the Vagrantfile, it is a build script with a set of commands automating the creation of a new docker container.

For this case, we will use the …

There are many cool, new things happening with Percona Cloud Tools.  To avoid “tl;dr” I will highlight only one new feature after a brief, general announcement.  The new feature is a 3-minute MySQL monitor.  I’ll blog later about other features.

The general announcement is: Last week we quietly released a brand-new agent called percona-agent, and we added MySQL and system monitoring to Percona Cloud Tools.  We also wrote a brand-new API from the ground up.  We call it all “PCT v2″.  For you it means a better experience and more features, all still free while we’re in beta.

One new feature in Percona Cloud Tools v2 is MySQL monitoring in 3 minutes, i.e. a 3-minute MySQL monitor.  Let’s be honest about monitoring: We …