Implement end-to-end ruler test for AlertManager HTTP Client.

[idoqo]

We need to test that Thanos Ruler is able to send alerts to AlertManager(AM) in different setups such as:

• Plain HTTP
• HTTPS with custom CA
• API with a prefix
• API protected by a bearer token authentication.

Because AlertManager supports HTTP only and no authentication, we had to initially use a mocked AM server instead of a “real” one:

thanos/test/e2e/rule_test.go

Line 237 in 98e369d

func TestRule_AlertmanagerHTTPClient(t *testing.T) {

That didn’t work though, because having docker containers reach out to services running on the host would be hacky.

It will make sense to have a test implementation that will cater to those different setups, without the downsides of the initial implementation.

Possible solutions include putting the mocked server in a container, or putting AlertManager and a proxy in a container so services can reach them.

[stale]

Hello 👋 Looks like there was no activity on this issue for the last two months.
Do you mind updating us on the status? Is this still reproducible or needed? If yes, just comment on this PR or push a commit. Thanks! 🤗
If there will be no activity in the next two weeks, this issue will be closed (we can always reopen an issue if we need!). Alternatively, use remind command if you wish to be reminded at some point in future.

[idoqo]

Still valid.

[stale]

Hello 👋 Looks like there was no activity on this issue for the last two months.
Do you mind updating us on the status? Is this still reproducible or needed? If yes, just comment on this PR or push a commit. Thanks! 🤗
If there will be no activity in the next two weeks, this issue will be closed (we can always reopen an issue if we need!). Alternatively, use remind command if you wish to be reminded at some point in future.

[stale]

Closing for now as promised, let us know if you need this to be reopened! 🤗