In MariaDB 10.2.12, these two don’t yet work together. GTID = Global Transaction ID.  In the master-slave asynchronous replication realm, this means that you can reconnect a slave to another server (change its master) and it’ll happily continue replicating from the correct point.  No more fussing with filenames and offsets (which of course will both differ on different machines).

So in concept the GTIID is “globally” unique – that means it’s consistent across an entire infra: a binlogged write transaction will have the same GTID no matter on which machine you look at it.

• OK: if you are transitioning from async replication to Galera cluster, and have a cluster as slave of the old infra, then GTID will work fine.
• PROBLEM: if you want to run an async slave in a Galera cluster, GTID will currently not work. At least not reliably.

The overview issue is …

In Amazon space, any EC2 or Service instance can “disappear” at any time.  Depending on which service is affected, the service will be automatically restarted.  In EC2 you can choose whether an interrupted instance will be restarted, or left shutdown.

For an Aurora instance, an interrupted instance is always restarted. Makes sense.

The restart timing, and other consequences during the process, are noted in our post on Aurora Failovers.

Aurora Testing Limitations

As mentioned earlier, we love testing “uncontrolled” failovers.  That is, we want to be able to pull any plug on any service, and see that the environment as a whole continues to do its job.  We can’t do that with Aurora, because we can’t control the essentials:

• power button;
• reset switch;
…

Right now Aurora only allows a single master, with up to 15 read-only replicas.

Master/Replica Failover

We love testing failure scenarios, however our options for such tests with Aurora are limited (we might get back to that later).  Anyhow, we told the system, through the RDS Aurora dashboard, to do a failover. These were our observations:

Role Change Method

Both master and replica instances are actually restarted (the MySQL uptime resets to 0).

This is quite unusual these days, we can do a fully controlled role change in classic asynchronous replication without a restart (CHANGE MASTER TO …), and Galera doesn’t have read/write roles as such (all instances are technically writers) so it doesn’t need role changes at all.

Failover Timing

Failover between running instances takes about 30 seconds.  This is in line with information provided in the …

Our clients operate on a variety of platforms, and RDS (Amazon Relational Database Service) Aurora has received quite a bit of attention in recent times. On behalf of our clients, we look beyond the marketing, and see what the technical architecture actually delivers.  We will address specific topics in individual posts, this time checking out what the Aurora architecture means for write and caching behaviour (and thus performance).

What is RDS Aurora?

First of all, let’s declare the baseline.  MySQL Aurora is not a completely new RDBMS. It comprises a set of Amazon modifications on top of stock Oracle MySQL 5.6 and 5.7, implementing a different replication mechanism and some other changes/additions.  While we have some information (for instance from the “deep dive” by AWS VP Anurag Gupta), the source code of the Aurora modifications …

Open Source is a whole-of-process approach to development that can produce high-quality products better tailored to users’ real world needs.  A key reason for this is the early feedback cycle built into that complete process.

Simply publishing something under an Open Source license (while not applying Open Source development processes) does not yield the same quality and other benefits.  So, not all Open Source is the same.

Publishing source of a product “later” (for instance when the monetary benefit has diminished for the company) is meaningless.  In this scenario, there is no “Open Source benefit” to users whatsoever, it’s simply a proprietary product. There is no opportunity for the client to make custom modifications or improvements, or ask a third party to work on such matters – neither is there any third party opportunity to verify and validate either code …

You may not be aware that the mechanism used to fingerprint the SSL certificates that  keep your access to websites encrypted and secure is changing. The old method, known as SHA1 is being deprecated – meaning it will no longer be supported. As per January 2016 various vendors will no longer support creating certificates with SHA1, and browsers show warnings when they encounter an old SHA1 certificate. Per January 2017 browsers will reject old certificates.

The new signing method, known as SHA2, has been available for some time. Users have had a choice of signing methods up until now, but there are still many sites using old certificates out there. You may want to check the security on any SSL websites you own or run!

To ensure your users’ security and privacy, force https across your entire website, not just e-commerce or other sections. You may have noticed this move on major websites over the last …

Some time ago, Peter Boros at Percona wrote this post: Rotating MySQL slow logs safely. It contains good info, such as that one should use the rename method for rotation (rather than copytruncate), and then connect to mysqld and issue a FLUSH LOGS (rather than send a SIGHUP signal).

So far so good. What I do not agree with is the additional construct to prevent slow queries from being written during log rotation. The author’s rationale is that if too many items get written while the rotation is in process, this can block threads. I understand this, but let’s review what actually happens.

Indeed, if one were to do lots of writes to the slow query log in a short space of time, a write could block while waiting.

Is the risk of this occurring greater during a logrotate operation? I doubt it. A FLUSH LOGS has to …

https://lkml.org/lkml/2015/2/9/534

Building on the original kSplice idea and combining the efforts of the work done at Red Hat and SuSE, common infrastructure is now ready to be put into the Linux 3.20 mainline kernel – Red Hat and SuSE have already committed to using this.

I still reckon it’s freaky trickery, but heck – it works, and it’s great for server environments that have no redundancy (I prefer to fix that issue!) and can’t afford any downtime.

While there are many graphing tools out there and we’ve used Munin for a while now.

The MySQL plugin for Munin had fallen out of date and the show engine innodb status output changed in 5.5 making some bits of the plugin simply not work any more. Also the show global status has some extra variables so there was a need to create new graphs.

All of these are now in the 2.1.8+ development releases of Munin.

Here are samples of the new/updated graphs.

Tables

Table …

Chuck Bell, one of my former colleague from MySQL AB, has created a connector for Arduino to MySQL. So this allows Arduino code to be a direct client of a MySQL or MariaDB server, with Ethernet and WiFi shields supported.

With Arduino boards being used more and more, this can come in really handy – not only for retrieving (for instance) centralised configuration data, but also for logging. Useful stuff. Thanks Chuck!

Links

• Introducing MySQL Connector/Arduino 1.0.0 beta (original article)
• MySQL Connector/Arduino on Launchpad
• Freetronics (Arduino gear)