[exporter/clickhouse] Fix data race that caused panic in integration tests

[lim123123123]

Description

clickhouse exporter tests use their own sql drivers to validate the queries sent during the tests.
Each driver has a unique name (which is the same as the test name). This name must be passed to the sql.Open function during database initialization.

Unfortunately, instead of explicitly passing the driver name into the buildDB function, it was passed implicitly through a global variable. This approach works in production but leads to data races when tests are executed in parallel because each test writes its own name to driverName. As a result, integration tests expected driverName to be set to the standard "clickhouse", but instead, it retained the value set by the previous test. This caused the validation callbacks to be triggered incorrectly, leading to test failures (panics).

There were two possible solutions to fix this issue:

1. Hardcode the "clickhouse" constant in integration tests.
2. Pass driverName explicitly into sql.Open.
   Although the first option might work, I believe it is not a careful way to write tests and code. A global variable that changes during tests introduces bugs that are difficult to debug and reproduce. Therefore, I prefer the second option.

Link to tracking issue

Fixes
Close #32530

[SpencerTorres]

I have a branch where I'm refactoring some of the driver code, this won't be a problem anymore in that version but this is a good fix to get the integration tests running again. Thanks!

[lim123123123]

Hello, could somebody else review this mr pls? There are 40 loc and it blocks another fix(because it adds an integration test). @dmitryax @Frapschen @hanjm

[Frapschen]

I am little confuse, please give more examplianation about :

This approach works in production but leads to data races when tests are executed in parallel because each test writes its own name to driverName.

[Frapschen]

what is the different use of a const string clickhouse between a var string clickhouse

[lim123123123]

It was a variable because some tests set this variable with mock names to record their actions. However, this behavior wasn't safe for concurrent use, especially for integration tests. If they were executed after other tests, they used the mock instead of 'clickhouse'. Now, this is a constant, and nobody changes it. Tests that need to use the mock pass it explicitly with the driverName, so this issue no longer occurs. You can read the description of the PR for more details

[lim123123123]

The logical issue here is that integration tests might use mock drivers from other tests instead of the real Clickhouse driver because those tests set the mock names in driverName. The main fix is to avoid setting mock names in driverName and instead pass these names explicitly in the configuration
Hope that the problem is clear now

[Frapschen]

like this code, right?

opentelemetry-collector-contrib/exporter/clickhouseexporter/exporter_logs_test.go

Lines 261 to 266 in 4e84b33

	func initClickhouseTestServer(t *testing.T, recorder recorder) {
	driverName = t.Name()
	sql.Register(t.Name(), &testClickhouseDriver{
	recorder: recorder,
	})
	}

[lim123123123]

Yes . driverName = t.Name() is the problem

[lim123123123]

I am little confuse, please give more examplianation about :

This approach works in production but leads to data races when tests are executed in parallel because each test writes its own name to driverName.

In production, nobody sets the names of their mocks in driverName, so it always defaults to 'Clickhouse'. This works fine, and it would also work if the other tests (those that set this variable) were disabled.

[lim123123123]

@atoulme Do I understand right that we need a review from @dmitryax to merge this?