Blog

We have been looking at the WebScaleSQL project with great excitement. As with any new enhancements to the MySQL world, we need to test extensively to ensure we can give PSCE customers the best advice possible. Since this project is source only, we decided to add WebScaleSQL builds to our repo, so we could examine the changes being introduced by all the different collaborators.

Qualys announced they had found an exploit in one of the Linux core libraries - glibc - using a buffer overflow technique in gethostbyname(). They have developed a proof-of-concept in which simply sending a specially created e-mail to a mail server enabled them to create a remote shell to the Linux machine. According to Qualys, "This bypasses all existing protections (like ASLR, PIE and NX) on both 32-bit and 64-bit systems.". How does it affect MySQL servers? Read on!

Long running transactions can be problematic for OLTP workloads, particularly where we would expect most to be completed in less than a second. In some cases a transaction staying open just a few seconds can cause behaviour that is entirely unexpected, with the developers at a loss as to why a transaction remained open. There are a number of ways to find long running transactions, luckily versions of MySQL from 5.6 onwards provide some very insightful instrumentation.

On a recent consulting engagement, the PSCE team were charged with what can be considered a fairly common task of synchronising tables between master and slave in MySQL Replication. On this occasion the schema contained both foreign key constraints and triggers, this post describes how we avoided the potential problems related to such an operation.

Recently we faced an issue when Nagios reported significant amount of "Locked" queries. To investigate and debug the issue we needed to get more insight about the state of MySQL and the OS at the time the locks occurred. This is how we got the much needed information.