November 22, 2014

Using MySQL 5.6 Performance Schema in multi-tenant environments

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 higher, Performance Schema is already enabled (with minimum set of “instrumentation” thou) and ready to use. In this post I will share examples of using Performance Schema for multi-tenant environments.

Overview

If you want to use Performance Schema, make sure it is enabled (enabled by default starting with MySQL 5.6.6):

Performance_schema provides you with the “raw” metrics and it may be difficult to select data from it. The good news is that you can use the “sys” schema project by Mark Leith. The “sys” schema (old name: ps_helper) is a collection of views and stored procedures which will provide you with reports in human readable format. The installation is easy, download it from github and run:

(it will only create database “sys” and a set of views and stored procedures/stored functions in it)

Examples

For the multi-tenant environment the most interesting is resource utilization breakdown. Lets say you want to “charge per IO” similar to Amazon RDS for MySQL model. You can now run this simple query against “sys” schema, which will use Performance Schema in MySQL 5.6 to generate report (in my example all users starts with “a”):

If you need more extensive metrics you can use this report:

Or a breakdown per user per statement:

If you are using  “schema per customer” approach you get get the per-schema resource utilization using sys.schema_table_statistics. Example (from Peter Zaitsev’s webinar):

This report may be really slow if you have lots of tables. If you are only interested in disk utilization per database you can directly query the performance_schema:

Edit: if you also need to get a quick “hot tables” report with focus on disk utilization (io requests) you can use this query:

This will give you a breakdown per table (and will include system files as well).

Conclusion

Performance_schema in MySQL 5.6 is very useful tool and can help you to get better visualization in MySQL multi-user (multi-tenant) installations. It can also do much more, i.e. find all queries with temporary tables or profile locks and mutex. “sys” schema provide you with the useful pre-defined reports, the table (view) names are almost self explanatory:

If you are using MySQL 5.6, performance_schema will give a additional valuable inside.

About Alexander Rubin

Alexander joined Percona in 2013. Alexander worked with MySQL since 2000 as DBA and Application Developer. Before joining Percona he was doing MySQL consulting as a principal consultant for over 7 years (started with MySQL AB in 2006, then Sun Microsystems and then Oracle). He helped many customers design large, scalable and highly available MySQL systems and optimize MySQL performance. Alexander also helped customers design Big Data stores with Apache Hadoop and related technologies.

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