Performance benchmarking for Concourse releases

[ddadlani]

As a Concourse dev, it would be nice to know the impact that a particular release has on the overall performance of Concourse. @jama22 pointed out that since a lot of the runtime backlog revolves around stability, this would help us understand whether the changes made in a particular release improve stability or have unforeseen consequences that impact resiliency or efficiency.

Here are some of the benchmarking metrics that we would like to measure against some predefined workload:

Worker:

1. CPU load
2. Memory usage
3. Disk utilization
4. System load average
5. Min, max and average number of containers
6. Min, max and average number of volumes
7. Network I/O
8. Standard deviation of the above values among all workers (esp. containers and volumes)

Web:

1. HTTP response duration
2. Number of DB connections
3. Time taken to schedule a build

This issue is to discuss and track work related to building out a benchmarking tool or process.

[ddadlani]

We plan to use concourse/concourse/drills to create a performance environment. We can use https://linux.die.net/man/1/stress to simulate high load for CPU, memory and disk I/O.

For containers, volumes and network I/O we need to design a pipeline with several heavy get steps.

[jamieklassen]

Bumping @jchesterpivotal's wise observation that stddev loses its prediction power in the absence of normally-distributed data: #2874 (comment)

[jchesterpivotal]

I'd also add Brendan Gregg's book, Systems Performance: Enterprise and the Cloud to a reading list. It's very good at breaking down the way different components and systems can manifest performance problems.