Update Alertmanager to latest master (8b584eb2265e).

[pstibrany]

What this PR does: This PR updates alertmanager to latest master (prometheus/alertmanager@f686ff3).

Which issue(s) this PR fixes:
Fixes #4234

Checklist

• [na] Tests updated
• [na] Documentation added
• [na] CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[pstibrany]

Integration tests currently failing due to bug in JSON-marshalling of URL wrapper. PRs with the fix:

• Fix marshalling of URL wrapper with nil value. prometheus/common#303
• Fix mashaling of URL, Regex wrappers with nil value, and empty Matchers. prometheus/alertmanager#2607

[stevesg]

Looks good assuming the upstream fixes are merged.

[pracucci]

I checked the changes in alertmanager and common: LGTM (modulo the URL marshalling issue you've found).

A nit, non blocking: while looking at the code I've noticed a TODO at integration/e2ecortex/client.go:211. Can we fix it?

[pstibrany]

I checked the changes in alertmanager and common: LGTM (modulo the URL marshalling issue you've found).

A nit, non blocking: while looking at the code I've noticed a TODO at integration/e2ecortex/client.go:211. Can we fix it?

I don't see what struct to use here. Alertmanager v1 api uses inline struct to send the response:

cortex/vendor/github.com/prometheus/alertmanager/api/v1/api.go

Line 171 in 5e496f4

func (api *API) status(w http.ResponseWriter, req *http.Request) {

[pracucci]

I checked the changes in alertmanager and common: LGTM (modulo the URL marshalling issue you've found).
A nit, non blocking: while looking at the code I've noticed a TODO at integration/e2ecortex/client.go:211. Can we fix it?

I don't see what struct to use here. Alertmanager v1 api uses inline struct to send the response:

cortex/vendor/github.com/prometheus/alertmanager/api/v1/api.go

Line 171 in 5e496f4

func (api *API) status(w http.ResponseWriter, req *http.Request) {

I think it was added by @jtlisi: do you remember it?

In any case, this is definitely not a blocker, so please merge this PR as soon as ready.

[bboreham]

Since this added features and deprecated others, it really needed a CHANGELOG comment.
From the issue: "Updating alertmanager adds new functionality such as negative matches/timebased routing...."
match, match_re are deprecated.

[bboreham]

The new feature side was added to CHANGELOG in #4325.