update documentation

Signed-off-by: Simon Pasquier <[email protected]>

CHANGELOG.md

@@ -19,7 +19,6 @@ We use *breaking* word for marking changes that are not backward compatible (rel
 - [#1852](https://github.com/thanos-io/thanos/pull/1852) Add support for `AWS_CONTAINER_CREDENTIALS_FULL_URI` by upgrading to minio-go v6.0.44
 - [#1854](https://github.com/thanos-io/thanos/pull/1854) Update Rule UI to support alerts count displaying and filtering.
 - [#1838](https://github.com/thanos-io/thanos/pull/1838) Ruler: Add TLS and authentication support for Alertmanager with the `--alertmanagers.config` and `--alertmanagers.config-file` CLI flags. See [documentation](docs/components/rule.md/#configuration) for further information.
-
 - [#1838](https://github.com/thanos-io/thanos/pull/1838) Ruler: Add a new `--alertmanagers.sd-dns-interval` CLI option to specify the interval between DNS resolutions of Alertmanager hosts.
 
 ## [v0.9.0](https://github.com/thanos-io/thanos/releases/tag/v0.9.0) - 2019.12.03

cmd/thanos/rule.go

@@ -328,7 +328,7 @@ func runRule(
 		dns.ResolverType(dnsSDResolver),
 	)
 	for _, cfg := range alertingCfg.Alertmanagers {
-		// Each Alertmanager client needs its own DNS provider.
+		// Each Alertmanager client has a different list of targets thus each needs its own DNS provider.
 		am, err := alert.NewAlertmanager(logger, cfg, amProvider.Clone())
 		if err != nil {
 			return err

docs/service-discovery.md

@@ -33,7 +33,7 @@ The repeatable flag `--store=<store>` can be used to specify a `StoreAPI` that `
 
 The repeatable flag `--query=<query>` can be used to specify a `QueryAPI` that `Thanos Rule` should use.
 
-The repeatable flag `--alertmanagers.url=<alertmanager>` can be used to specify a `Alertmanager API` that `Thanos Rule` should use.
+`Thanos Rule` also supports the configuration of Alertmanager endpoints using YAML with the `--alertmanagers.config=<content>` and `--alertmanagers.config-file=<path>` flags in the `StaticAddress` section.
 
 ## File Service Discovery
 
@@ -77,7 +77,7 @@ Again, the `<path>` can be a glob pattern.
 
 The flag `--query.sd-interval=<5m>` can be used to change the fallback re-read interval.
 
-`Thanos Rule` also supports the configuration of Alertmanager endpoints using YAML with the `--alertmanagers.config=<content>` and `--alertmanagers.config-file=<path>` flags.
+`Thanos Rule` also supports the configuration of Alertmanager endpoints using YAML with the `--alertmanagers.config=<content>` and `--alertmanagers.config-file=<path>` flags in the `FileSDfiles` section..
 
 ## DNS Service Discovery
 

test/e2e/rule_test.go

@@ -157,6 +157,17 @@ func (m *mockAlertmanager) ServeHTTP(resp http.ResponseWriter, req *http.Request
 	m.mtx.Unlock()
 }
 
+// TestRuleAlertmanagerHTTPClient verifies that Thanos Ruler can send alerts to
+// Alertmanager in various setups:
+// * Plain HTTP.
+// * HTTPS with custom CA.
+// * API with a prefix.
+// * API protected by bearer token authentication.
+//
+// Because Alertmanager supports HTTP only and no authentication, the test uses
+// a mocked server instead of the "real" Alertmanager service.
+// The other end-to-end tests exercise against the "real" Alertmanager
+// implementation.
 func TestRuleAlertmanagerHTTPClient(t *testing.T) {
 	a := newLocalAddresser()