How to do one-off profiling for dogfood and production using pprof

Go has built-in support for a sampling profiler pprof, which can be used to investigate CPU usage, heap usage and more.

You can obtain and examine a profile from a running Sourcegraph instance as follows:

Select the right Kubernetes context using kubectx or kubectl.
Set up port-forwarding for the pod you're interested in profiling using k9s or kubectl. For example:
```
kubectl port-forward precise-code-intel-worker-0000000000-00000 6061:6060
```
This will map port 6060 on the pod to port 6061 on your machine.

Record a profile.

# Sample CPU usage for 60 seconds
go tool pprof -seconds 60 http://localhost:6061/debug/pprof/profile
# Sample heap usage for 60 seconds
go tool pprof -seconds 60 http://localhost:6061/debug/pprof/heap

This will save the output to a temporary file. (Or you can specify a path using -output <path>.)

Examine the generated using go tool pprof:
```
# in the web UI
go tool pprof -http :9999 /path/to/profile.pb.gz
# in a REPL
go tool pprof /path/to/profile.pb.gz
```
The web UI supports visualizing the output as a flamegraph, as a call graph with weighted edges, and more.

Other resources: