Add fixture-based e2e tests with sample apps

[damemi]

Fixes #39

This adds an e2e test matrix (largely based on collector-contrib's tests) that does the following:

1. Builds the auto-instrumentation agent, launcher (to be removed with Allocate memory without launcher #40), and sample apps using each supported library
2. Spins up a kind cluster
3. Starts an otel collector with trace receiver and file exporter
4. Starts the sample app for that library
5. The sample app calls itself to generate trace data
6. Copies the file exporter output to a local fixture
7. Checks for changes to the current fixture, ignoring/removing timestamps

I used a k8s cluster instead of just running the binaries for a couple reasons: First, I wanted to just use a collector image from upstream rather than building it ourselves. Second, k8s gives some nice orchestration around starting up and stopping these processes that works well as a Github action. I couldn't find a good way to build local binaries and have those run in the background, while moving on to the next Workflow step, and checking that everything had completed successfully.

The steps are basically copied to a new make fixture-$LIBRARY target that lets you generate these fixtures. Eg, make fixture-nethttp will run all the steps from above. Failures in these tests could indicate a legitimate update to the fixtures, so updating them locally will be useful.

I added sample apps for gorillamux and net/http. If someone else wants to add a gRPC app, I think the first 2 serve as a good example. New libraries should be able to drop in similarly.

[pellared]

This is a comment rather for future improvment. I do not want to block this PR as we need to start with something 😉

Based on my experience in https://github.com/open-telemetry/opentelemetry-dotnet-instrumentation (where I am a maintainer) I find testing against a "test fake collector" makes the tests more maintainable:

• spinning up a a httptest server or by setting up a gRPC server in tests is faster than running a real collector [image]
• you get more flexibility in assertion logic

Here you can find an example implementation and usage of a "test fake collector" in Go: https://github.com/signalfx/splunk-otel-go/blob/main/distro/otel_test.go

[damemi]

@pellared that's a great suggestion, but I agree on not blocking this PR right now (especially because I want to unblock #40). I'll make a new issue from your comment to track that for a refactor in the future.

Right now I just want to figure out the empty labels from above which I'm trying a couple things for. Maybe an issue with context propagation from the request?

[damemi]

It looks like #55 broke auto-instrumentation due to a change in v0.9.1 that updated UprobeOptions.Offset to be relative, with Address now being absolute. Updated this in dddbb7e and running e2es locally now seem to work again, hopefully they pass in CI too

[damemi]

They're green! 🎉 🎉