chore(e2e): better port selection

[Lazar955]

Sometimes due to parallel tests, we could end up with the same port allocated. In this PR I try to introduce a small timeout when testing port availability by opening it for a short time which should decrease the chance of collision.

Tested with no collision couple of times with:

go test -mod=readonly -failfast -timeout=15m -v $(PACKAGES_E2E) -count=30 --parallel 12 --tags=e2e

References issue

[RafilxTenfen]

this seems hacky...
I would feel better by setting a specific port range for each test, but also doesn't seem too good
Any other idea to solve this? @babylonlabs-io/core-dev

[KonradStaniec]

If we assume there is no other processes using our test ports we could probably:

1. have global map of used ports
2. change semantics of this function to be more like acquirePort i.e each call generates port, checks if it is not used (stored in map), and if it is not used it stores it in this map. (of course this operations must be behind mutex)
3. at the end of the test port is released (removed from map) . This can by accomplished by t.Cleanup(..) and of course it also must be protected by mutex

[Lazar955]

Right, but tests do not share state, so having a mutex or a map here doesn't help. One way would be to have a test which would be ran first (e.g called 01Setup and without parallel flag), which would create a file and a lockfile, then all other parallel tests startup and read/write port that they are acquiring to this shared file (locking and unlocking).
I feel like this is a bit much, but if we start having collisions I would implement it.
Thoughts @KonradStaniec @RafilxTenfen

[Lazar955]

Also reason for needing to have a test called 01Setup (or something like that), is that because all tests start in parallel so they would also be having race condition for the initial file creation

[Lazar955]

Not super hard to implement, I'll try it, see if it works and is worth the extra code. Thorugh this was clever and a nice hack :D

[KonradStaniec]

Right, but tests do not share state, so having a mutex or a map here doesn't help.

They do not share it now but we could introduce it. You could create file port_map.go in our e2etest package have there var port_map = map[int]bool and protect access to it. It seems simpler that having file with lock file.

Or do I miss something about how go shares state between tests ?

[Lazar955]

Actually, you're right, pushed a new version

[KonradStaniec]

probably not critical right now becouse there is not much tests but we should also have here:

		t.Cleanup(func() {
			portMutex.Lock()
			defer portMutex.Unlock()
			delete(allocatedPorts, port)
		})