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Displaying posts with tag: Software and tools (reset)
On Open Source and Business Choices

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 …

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Choosing Whether to Migrate to Another Database: Uber

Uber Engineering explains the technical reasoning behind its switch in database technologies, from Postgres to MySQL:

These things are always an interesting read, because it looks at one company’s decision making process and operational steps.

At Open Query we’re not a fan of migrations – it doesn’t matter from what brand to what brand, migrations tend to be expensive and painful.  Any application tends to be more suited to a particular brand – because of design and implementation choices. This is neither good nor bad, it’s just a fact that has to be acknowledged when considering these things.

Similarly, infrastructure (what hardware there is and how it’s set up and connected) tends to be dependent on the brand choice, as different databases have different needs in that space, …

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Web Security: SHA1 SSL Deprecated

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 …

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Slow Query Log Rotation

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 …

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LKML: Live patching for 3.20

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.

Munin graphing of MySQL

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.


Table …

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MySQL Connector/Arduino

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!


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Storage caching options in Linux 3.9 kernel

dm-cache is (albeit still classified “experimental”) is in the just released Linux 3.9 kernel. It deals with generic block devices and uses the device mapper framework. While there have been a few other similar tools flying around, since this one has been adopted into the kernel it looks like this will be the one that you’ll be seeing the most in to the future. It saves sysadmins the hassle of compiling extra stuff for a system.

A typical use is for an SSD to cache a HDD. Similar to a battery backed RAID controller, the objective is to insulate the application from latency caused by the mechanical device, the most laggy part of which is seek time (measured in milliseconds). Giventhe  relatively high storage capacity of an SSD (in the hundreds of GBs), this allows you to mostly disregard the mechanical latency for writes and that’s very useful for database systems such as MariaDB.

That covers writes (for the moment), but …

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Optimising Web Servers

I was lucky enough to attend PyCon-AU recently and one talk in particular highlighted the process of web server optimisation.

Graham Dumpleton’s add-in talk Web Server Bottlenecks And Performance Tuning available on YouTube (with the majority of PyCon-AU talks)

The first big note at the beginning is that the majority of the delay in user’s perception of a website is caused by the browser rendering the page. Though not covered in the talk for those that haven’t used the tool YSlow (for Firefox and Chrome) or Google’s Developer Tools (ctrl-alt-I in Chrome), both tools will …

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Jetpants: a toolkit for huge MySQL topologies

From a Tumblr engineering blog post:

Tumblr is one of the largest users of MySQL on the web. At present, our data set consists of over 60 billion relational rows, adding up to 21 terabytes of unique relational data. Managing over 200 dedicated database servers can be a bit of a handful, so naturally we engineered some creative solutions to help automate our common processes.

Today, we’re happy to announce the open source release of Jetpants, Tumblr’s in-house toolchain for managing huge MySQL database topologies. Jetpants offers a command suite for easily cloning replicas, rebalancing shards, and performing master …

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