Over the last few weeks, I’ve been sharing the bits and pieces that went into our construction of an ELB logs processing pipeline using AWS Lambda.

As I said in the introduction, the body of work around the processor can be broken down into three pieces:

I’ve gone through each of these components in detail in the posts I’ve linked above, so this last post is really just to tie it all together and reflect on the process, as well as provide a place to mention a few things that didn’t neatly fit into any of the buckets above.

Also, I’ll obviously be continuing the pattern of naming every sub-header after a chapter title in the original Half-Life, almost all of which have proven to be surprisingly apt for whatever topic is being discussed. I mean seriously, look at this next one? How is that not perfectly fitting for a conclusion/summary post.

Residue Processing

It took a fair amount of effort for us to get to the solution we have in place now, and a decent amount of time. The whole thing was put together over the course of a few weeks by one of the people I work with, with some guidance and feedback from other members of the team from time to time. This timeframe was to develop, test and then deploy the solution into a real production environment, by a person with little to no working knowledge of the AWS toolset, so I think it was a damn good effort.

The most time consuming part was the long turnaround on environment builds, because each build needs to run a suite of tests which involve creating and destroying at least one environment, sometimes more. In reality, this means a wait time or something like 30-60 minutes per build, which is so close to eternity as to be effectively indistinguishable from it. I’ll definitely have to come up with some sort of way to tighten this feedback loop, but being that most of it is actually just waiting for AWS resources, I’m not really sure what I can do.

The hardest part of the whole process was probably just working with Lambda for the first time outside of the AWS management website.

As a team, we’d used Lambda before (back when I tried to make something to clone S3 buckets more quickly), but we’d never tried to manage the various Lambda bits and pieces through CloudFormation.

It turns out that the AWS website does a hell of a lot of things in order to make sure that your Lambda function runs, including dealing with profiles and permissions, network interfaces, listeners and so on. Having to do all of that explicitly through CloudFormation was something of a learning process.

Speaking of CloudFormation and Lambda, we ran into a nasty bug with Elastic Network Interfaces and VPC hosted Lambda functions created through CloudFormation, where the CloudFormation stack doesn’t delete cleanly because the ENI is still in use. It looks like its a known issue, so I assume it will be fixed at some point in the future, but as a result we had to include some additional cleanup in the Powershell that wraps our environment management to check the stack for Lambda functions and manually remove and delete the ENI before we try to delete the stack.

This isn’t the first time we’ve had to manually cleanup resources “managed” by CloudFormation. We do the same thing with S3 buckets because CloudFormation won’t delete a bucket with anything in it (and some of our buckets, like the ELB logs ones, are constantly being written to by other AWS services).

The only other difficult part of the whole thing I’ve already mentioned in the deployment post, which was figuring out how we could incorporate non-machine based Octopus deployments into our environments. For now they just happen after the actual AWS stack is created (as part of the Powershell scripts wrapping the entire process) and rely on having an Octopus tentacle registered in each environment on the Octopus Server machine, used as a script execution point.


Having put this whole system in place, the obvious question is “Was it worth it?”.

For me, the answer is “definitely”.

We’ve managed to retire a few hacky components (a Windows service running Powershell scripts via NSSM to download files from an S3 bucket, for example) and removed an entire machine from every environment that needs to process ELB logs. Its not often that you get to reduce both running and maintenance costs in one blow, so it was nice to get that accomplished.

Ignoring the reduced costs to the business for a second, we’ve also decreased the latency for receiving our ELB logs for analysis because rather than relying on a polling system, we’re now triggering the processing directly when the ELB writes the log file into S3.

Finally, we’ve gained some more experience with systems and services that we haven’t really had a chance to look into, allowing us to leverage that knowledge and tooling for other, potentially more valuable purposes.

All in all, I consider this exercise a resounding success, and I’m happy I was able to dedicate some time to improving an existing process, even though it was already “working”.

Improving existing engineering like this is incredibly valuable to the morale of a development time, which is an important and limited resource.