Last night I wrote about trending data with a moving average, and then after I went to bed, I realized I made a mistake on the chart I showed. I calculated α for the exponentially weighted moving average so that the average age of metrics approaches 60 samples as time approaches infinity, and I plotted that on the same chart with a 60-sample simple moving average.

I’ve made this mistake several times before. The mistake is that the average age of the metrics in the 60-sample simple moving average is 30, not 60.

Here’s what the chart looks like if I change the exponential moving average to a 30-second average age:

If you compare this with yesterday’s chart, you’ll see that today’s red line …

In my recent talk at Surge and Percona Live about adaptive fault detection (slides), I claimed that hardcoded thresholds for alerting about error conditions are usually best to avoid in favor of dynamic or adaptive thresholds. (I actually went much further than that and said that it’s possible to detect faults with great confidence in many systems like MySQL, without setting any thresholds at all.)

In this post I want to explain a little more about the moving averages I used for determining “normal” behavior in the examples I gave. There are two obvious candidates for moving averages: straightforward moving averages and exponentially weighted moving averages.

A straightforward moving average just computes the average (mean) over the last N samples of data. In my case, I used 60 samples. This requires keeping an array …

I feel like I just got back home from Oracle OpenWorld (check out my pictures) and some vacation, but I'll be on the road again next week to attend LinuxCon Europe in Barcelona. I'll be there from Monday (Nov. 5th) until Wednesday evening. Oracle is sponsoring the event and we'll have a booth at the exhibition area (booth #19), handing out free Oracle Linux and Oracle VM DVDs. I'll be at the booth every now and then and plan to give a short introduction and live demo of Ksplice rebootless updates on Monday evening (6:00pm).

Two …

MySQL’s SHOW STATUS and SHOW VARIABLES commands (or queries against the corresponding INFORMATION_SCHEMA tables) don’t always show what they say. In particular, SHOW STATUS contains several rows that aren’t status-related, but are really configuration variables in my opinion (and it is an opinion – sometimes the difference isn’t black and white). Here’s a short list of some status counters that I think are really better off as configuration variables: Innodb_page_size Replica_heartbeat_period Ssl_cipher Ssl_cipher_list Ssl_ctx_verify_depth Ssl_ctx_verify_mode Ssl_default_timeout Ssl_session_cache_mode Ssl_verify_depth Ssl_verify_mode Ssl_version Most of those are legacy, but Replica_heartbeat_period is a recent addition.

Tungsten Replicator version 2.0.6 was released today.

You can get both the binaries and the source code at the project's downloads page.

This release contains many bug fixes, and various improvements. All of them are listed in the Release Notes. The most interesting ones are the improvement in multi-master topologies. Using this release with star topologies you will get less traffic than before, because we have reduced some duplication of transaction history logs that were sent between servers.

And speaking of multi-master topologies, this release includes the cookbook recipes mentioned in this blog …

High Availability (HA) ensures all important business information is available for your application even when there is no database failure. This includes:

How about when you are upgrading your database schema? What if you need to add memory to a database server or reconfigure/restart MySQL? If your apps want to read data from a MySQL slave, how can you be sure they are not reading stale data

Join us at this MySQL community event with Continuent database rockstars. "State of the art of MySQL High Availability and Replication" in Barcelona, November 13th at 7pm. Reserve your seat at http://mysql-high-availability.eventbrite.es.

MySQL is the world’s most popular open-source database, and powers websites and applications of numerous leading and fast-growing organizations. In this

MySQL command line utilities have an interesting property – if you only use the prefix of the option or command it will go over the list of available command and if there is only one command with matching prefix it will execute it with no warnings or any kind, otherwise it will report the error. For example mysqladmin e works as there is only one command “extended-status” which starts with “e” mysqladmin f however does not work because there are multiple commands which start with “f”.

This behavior can cause all kings of issues especially if you make a typo. I made one today (thankfully on the test box). MySQL init Scripts use “stop” and “start” commands to start and stop the server while mysqladmin uses “shutdown”. I mixed this while trying to stop Percona Server:

root@smt2:/var/lib/mysql# mysqladmin stop …

While we were at MySQL Connect last month, we interviewed long-time MySQL developer JD Duncan about integrating NoSQL and JavaScript with MySQL. His team developed the Node.js API for MySQL. This week, we present the interview we did. In Ear Candy, we discuss what makes a senior DBA, and in At the Movies we present a ScaleBase webinar.

Events
Oracle's "Scale with MySQL" seminars:
Bucharest Romania, Tuesday 13 November
Madrid, Tuesday 27 November

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Within hours of my post about meeting the MySQL community in Barcelona, we got several offers to help, and within one day, an event was created and agreed upon.

Thanks!

Today the event was posted at Evenbrite. It will take place on Tuesday, November 13th, at 7pm. It will be a one hour talk about State of the art in MySQL high availability and replication, followed by one hour of Q&A, networking, beer, and snacks.

Registration is necessary, because the seats are limited. If you want to attend, you should register as soon as possible!