Previously we’ve talked about how we use Nagios / Icinga for three broad types of monitoring at LMAX Exchange: alerting, metrics, and validation. The difference between our definitions of alerting and validation is a fine one and it more has to do with the impo…
At LMAX Exchange we use LVM for snapshotting volumes for two use cases
1. Take a snapshot of a slave database so it can catch up quickly while the work happens on the snapshotted volume.
2. Backups in case we need to roll back.
Every now and then in our CI environment as we soak tested the integration of this with our in house deployment tool – scotty – we found that we would get a merge error.journal: Merging snapshot invalidated. Aborting merge.
At LMAX Exchange Nagios is one of our essential tools for monitoring and verifying the operation of our systems. We use it for three distinct purposes.
- Alerting when things break.
- Recording trends so that we can predict when problems will occur and then mitigate them.
- Using Nagios to verify the overall structure of our environments.
Things have broken
Using Nagios to monitor things breaking down is perhaps the most common use case. These checks need to run often, perhaps every few seconds. Let us look at an example, a web server, and some of the tests we might [...]
Building great stuff fast
I’ll be writing some posts over the coming weeks about how we run our technology department including the processes and procedures we use to keep moving fast but continue to work within our regulatory constraints and the demands we put upon ourselves for operational excellence. This post will be covering how we get things done in IT using an agile mentality with minimal process.
Before talking about stories, iterations and retrospectives (processes) or boards and cards (tools) [...]
Just before New Year 2017 a leap second was inserted into Coordinated Universal Time (UTC). At LMAX Exchange we had some luxury to play with how we handled the leap second. January 1st is a public holiday, there’s no trading, so we are free to do recovery if so…
In part one, we discovered that our multicast receipt thread was being stalled by page faults.
In part two, we’ll dig down into the causes of those page faults, and with some help from our friends at Informatica, get to the bottom of things.
We recently fixed a long standing performance issue at LMAX.
The path we followed to fixing it was sufficiently windy to merit a couple of posts.
In this first post we’ll define our issue and then attempt to figure out its cause.
One reason that automated UI tests can be unreliable is that they tend to be sensitive to what else is on screen at the time and even things like the current screen size. Developers running the tests locally also find it annoying to have windows openin…
A month or two ago I was asked by someone in our Operations team what clock synchronisation is and why we need to do it. I gave them a very basic few sentence answer. That got me thinking that I never read an easy explanation when I myself got started …
Ever since I read some initial blogs posts about the upcoming eBPF tracing functionality in the 4.x Linux kernel, I have been looking for an excuse to get to grips with this technology.With a planned kernel upgrade in progress at LMAX, I now have acc…
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