It is just plain fun to run parallel workflows and builds and watch the activities and build steps light up the workflow monitor in real time like a Christmas tree. See this flash demo to see what I mean.

As customers go to machines with more and more cores, fewer machines are needed in the application lifecycle infrastructure, particularly for builds and code retrievals - the most resource intensive functions. This is helping to simplify the infrastructure, reduce maintenance and administration and drive down costs.

Several of our customers are running around 5000 builds and non-build workflows per month on two machines. The primary reason for two machines, in fact, is for disaster recovery, and the goal is to run both machines at less than half capacity so that in the event that one machine (or datacenter) fails, all the current capacity can be run as a contingency on the one machine that’s left.

Thread control is very simple with Meister and Mojo. Both use the omsubmit dependency manager program to handle this. Meister’s om program translates build events into workflow steps using omsubmit. The OMSUBMIT_MAX_USER_PROC value sets the maximum allowed number of threads.

You might think that if you are running dual, quad-core build machines that you should set the max threads at 8. However, Meister posts build operations to one thread and the associated logging operation to another. Compile operations notoriously use a lot of memory and CPU resources, but the logging operation posts to a server and waits for the operation to complete. There is really no disadvantage to setting the max threads higher than 16 in this case, so go ahead and do it.

As a non-build workflow example, I worked on JBoss deployments to 48 Linux machines. The workflow was parallelized into 48 activities each of which deployed to a single machine in parallel. The deployment activity was largely a remote execute operation that extracted archives on the remote machine. The extraction took about a second for a medium sized application. Again, this is a waiting situation where machine resources are essentially idle while the thread is in use, so use more threads. The machine was a dual, dual-core build machine and we set OMSUBMIT_MAX_USER_PROC to 50.

Watching the workflow monitor as the deployment ran, we could see roughly half of the machines light up (meaning actively running) at any one time and the entire deployment process synchronized all 48 machines in a little over two seconds.

So, don’t simply match your machine’s CPU threading capabilities - overclock! Aim high for max threads and try to determine where your performance is optimized. I’d love to provide you with some metrics as a function of thread count, but usually once something is working it’s on to the next project. I barely have enough time to blog!