It’s been way too long since I’ve posted anything here, so I’ve decided to resume again with what I’ve been busy with lately.
We’ve been using Logstash for quite a while now, and one of the annoyances I’ve had is that with the default configuration we threw together we only got second resolution on our timestamps. 99% of the time this has been good enough for the simple things we’ve been trying to keep an eye on, but now and again it’s resulted trouble stitching together the exact sequence of events when trying to diagnose a problem.
Rsyslog is the primary tool we use to get data into Logstash in the first place. As we don’t have the luxury of using anything cloud oriented we need to care about our hardware too, and using syslog makes this very easy. Add to this how simple it is to get most applications to log via syslog too and it makes using it a no brainer.
Getting the high resolution timestamps into your rsyslog messages is actually really simple. Just make sure you have the following configuration option set in your rsyslog configuration:
I’ve just release Ecks into the wild, a Python library for accessing SNMP data from a server without having to deal with the pain of knowing about what a MIB or OID is. SNMP stands for Simple Network Management Protocol, but for most people it is anything but simple. It’s pretty straight forward once you understand what’s going on, but most people are daunted by the learning curve.
What results from this resistance is that when your average developer decides he wants to monitor CPU usage or disk space on his machine he or she ends up doing it in the most obtrusive way possible – SSH. While I’m a big fan of small shell scripts, this is one place they do not belong. Let me give you an example:
I set up a new server here in London for one of our Chicago teams. Being a conscientious team, the first thing they did was wire in some monitoring that wrote for their servers. It checks things like disk space, memory usage, CPU load and the state of various processes that they care about. They need pretty fine grained checking intervals, so they check these every minute. The easiest way they know how to do this though is to SSH in to their machines and run df, free, netstat,etc and scrape the output. Every minute. Which on this nice shiny server consumed almost 20% of the CPU right off the bat. Educating them on the use of SSH ControlMaster helped, but it’s still doing a lot of work on the machine.
This was the last straw that lead to the creation of Ecks. People will always follow the path of least resistance, so if you want people to do the right thing, you need to make it the easiest thing to do. SNMP has all this information available, modern snmpd implementations are stable, have a tiny footprint and are more secure than providing SSH access to your machine.
The hardest part of all though is what to name this little library. When discussing the problem with Julian Simpson (the @builddoctor), he pointed out that MIB always reminded him of the Men in Black. Reading the Wikipedia article on the original comic book series had some interesting snippets:
The Men in Black are a secret organization that monitors and suppresses paranormal activity on Earth…
Replace “Earth” with “a computer” and you’re starting to get somewhere. Then I noticed this gem:
An agent named Ecks went rogue after learning the truth behind the MiB: they seek to manipulate and reshape the world in their own image by keeping the supernatural hidden.
Many people think that the complexity of the MIB keeps SNMP data hidden. And so the name was chosen…
With the price of storage dropping all the time, there is a constant perception from people who don’t deal with it every day that “disk space is cheap”, especially when it comes to developers. The problem is that so called “Enterprise” storage costs are still astronomical compared to what people are used to paying for home storage – even when using SATA disks.
A lot of this extra cost comes from a perceived requirement for the highest available capacity, availability and performance. Achieving all three characteristics is expensive, but if you’re willing to sacrifice one of them then costs start to fall considerably. Lowering requirements on two of the three drops it even more.
One of the teams I work with has a requirement primarily on capacity. Performance and availability are nice, but capacity is the key. We generate gigabytes worth of log files every day, but didn’t have one place to store it all for easy analysis. Just before I joined the team they’d purchased the cheapest “Enterprise” storage system the IT team at the time would allow – it ended up costing in the region of £12k for 12TB of raw storage. That’s £1000 per TB!
In addition to the price, the other problems were accessibility and management of the data and managing growth. This inspired a hunt for something that would provide a cheaper and more flexible solution.
Our requirements were:
- *nix based system. The current storage solution was based on Windows Storage Server, but all our systems and tools for this team are Linux based. Yes, Windows does technically provide things like an NFS server, but fighting with the file system permissions and overall performance are two things that impacted us.
- Cheap to expand. We need to have a clear path to grow the storage in the server easily by simply adding more disks.
- Large filesystems. There’s nothing more wasteful from a storage point of view than having lots of small filesystems. Besides the management overhead, there’s also many wasted blocks lying around un-used.
- Cheap to build. This inevitably means commodity hardware.
- Reasonable availability. We don’t need 99.999% uptime, but would be happy with somewhere in the region of 90%+
- Reasonable performance. Primary access to the data on this machine is via gigabit Ethernet. As long as it can keep up with the network card we’re happy…
When I got back from DevOpsDays in Hamburg this year I felt the need to explain my journey to the “DevOps” world and my view on where it’s headed. I started writing a State of the Nation paper to lay it all out. A couple of weeks in I got a message from Matthias Marschall asking if I’d like to do a guest post as part of their DevOps series. I agreed, and after a lot of effort (and help from a couple of great editors) you can now read it here.
It’s by far the longest article I’ve ever written, and I was amazed at how ideas that had been floating around in my head for a while crystalized through the processes of writing them down. I found I got so passionate talking to people about what was in it that I’ve decided to make a talk out of it, the first iteration of which will be in Chicago on Tuesday (see previous post).
I’ll be in Chicago next week and I’ll be speaking at the local DevOps group meetup on the 7th of December. Places are limited, so please sign up here if you’d like to attend.
Julian Simpson, aka The Build Doctor, has been working away at a nice web based Build Status Monitor called XFD for a while now. One of my complaints for years has been that there’s no nice build status tool that’s easy to use, but I think he’s on to something.
It’s entered in the Ultimate Wallboard Challenge, and you can vote for it here.