Alerting: Allow hooking into request handler functions. (#67000)

* Alerting: Allow hooking into request handler functions.

Adds a facility to AlertNG for hooking into API handlers, allowing the
replacement of request handlers for specific paths. One of goals of this
approach was to allow hooking as late as possible in the request, e.g.
after all middleware has been applied, to simplfiy usage.

* Update pkg/services/ngalert/api/hooks.go

Co-authored-by: gotjosh <josue.abreu@gmail.com>

* Update pkg/services/ngalert/api/hooks.go

Co-authored-by: gotjosh <josue.abreu@gmail.com>

* Update pkg/services/ngalert/ngalert.go

Co-authored-by: gotjosh <josue.abreu@gmail.com>

* Fixes to review comments

* Fix passing logger in

---------

Co-authored-by: gotjosh <josue.abreu@gmail.com>

pkg/services/ngalert/api/api.go

@@ -85,6 +85,9 @@ type API struct {
 	Historian            Historian
 
 	AppUrl *url.URL
+
+	// Hooks can be used to replace API handlers for specific paths.
+	Hooks *Hooks
 }
 
 // RegisterAPIEndpoints registers API handlers

pkg/services/ngalert/api/generated_base_api_alertmanager.go

@@ -190,7 +190,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/alertmanager/grafana/api/v2/silences",
-				srv.RouteCreateGrafanaSilence,
+				api.Hooks.Wrap(srv.RouteCreateGrafanaSilence),
 				m,
 			),
 		)
@@ -200,7 +200,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/alertmanager/{DatasourceUID}/api/v2/silences",
-				srv.RouteCreateSilence,
+				api.Hooks.Wrap(srv.RouteCreateSilence),
 				m,
 			),
 		)
@@ -210,7 +210,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodDelete,
 				"/api/alertmanager/{DatasourceUID}/config/api/v1/alerts",
-				srv.RouteDeleteAlertingConfig,
+				api.Hooks.Wrap(srv.RouteDeleteAlertingConfig),
 				m,
 			),
 		)
@@ -220,7 +220,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodDelete,
 				"/api/alertmanager/grafana/config/api/v1/alerts",
-				srv.RouteDeleteGrafanaAlertingConfig,
+				api.Hooks.Wrap(srv.RouteDeleteGrafanaAlertingConfig),
 				m,
 			),
 		)
@@ -230,7 +230,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodDelete,
 				"/api/alertmanager/grafana/api/v2/silence/{SilenceId}",
-				srv.RouteDeleteGrafanaSilence,
+				api.Hooks.Wrap(srv.RouteDeleteGrafanaSilence),
 				m,
 			),
 		)
@@ -240,7 +240,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodDelete,
 				"/api/alertmanager/{DatasourceUID}/api/v2/silence/{SilenceId}",
-				srv.RouteDeleteSilence,
+				api.Hooks.Wrap(srv.RouteDeleteSilence),
 				m,
 			),
 		)
@@ -250,7 +250,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/alertmanager/{DatasourceUID}/api/v2/alerts/groups",
-				srv.RouteGetAMAlertGroups,
+				api.Hooks.Wrap(srv.RouteGetAMAlertGroups),
 				m,
 			),
 		)
@@ -260,7 +260,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/alertmanager/{DatasourceUID}/api/v2/alerts",
-				srv.RouteGetAMAlerts,
+				api.Hooks.Wrap(srv.RouteGetAMAlerts),
 				m,
 			),
 		)
@@ -270,7 +270,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/alertmanager/{DatasourceUID}/api/v2/status",
-				srv.RouteGetAMStatus,
+				api.Hooks.Wrap(srv.RouteGetAMStatus),
 				m,
 			),
 		)
@@ -280,7 +280,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/alertmanager/{DatasourceUID}/config/api/v1/alerts",
-				srv.RouteGetAlertingConfig,
+				api.Hooks.Wrap(srv.RouteGetAlertingConfig),
 				m,
 			),
 		)
@@ -290,7 +290,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/alertmanager/grafana/api/v2/alerts/groups",
-				srv.RouteGetGrafanaAMAlertGroups,
+				api.Hooks.Wrap(srv.RouteGetGrafanaAMAlertGroups),
 				m,
 			),
 		)
@@ -300,7 +300,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/alertmanager/grafana/api/v2/alerts",
-				srv.RouteGetGrafanaAMAlerts,
+				api.Hooks.Wrap(srv.RouteGetGrafanaAMAlerts),
 				m,
 			),
 		)
@@ -310,7 +310,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/alertmanager/grafana/api/v2/status",
-				srv.RouteGetGrafanaAMStatus,
+				api.Hooks.Wrap(srv.RouteGetGrafanaAMStatus),
 				m,
 			),
 		)
@@ -320,7 +320,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/alertmanager/grafana/config/api/v1/alerts",
-				srv.RouteGetGrafanaAlertingConfig,
+				api.Hooks.Wrap(srv.RouteGetGrafanaAlertingConfig),
 				m,
 			),
 		)
@@ -330,7 +330,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/alertmanager/grafana/config/history",
-				srv.RouteGetGrafanaAlertingConfigHistory,
+				api.Hooks.Wrap(srv.RouteGetGrafanaAlertingConfigHistory),
 				m,
 			),
 		)
@@ -340,7 +340,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/alertmanager/grafana/config/api/v1/receivers",
-				srv.RouteGetGrafanaReceivers,
+				api.Hooks.Wrap(srv.RouteGetGrafanaReceivers),
 				m,
 			),
 		)
@@ -350,7 +350,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/alertmanager/grafana/api/v2/silence/{SilenceId}",
-				srv.RouteGetGrafanaSilence,
+				api.Hooks.Wrap(srv.RouteGetGrafanaSilence),
 				m,
 			),
 		)
@@ -360,7 +360,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/alertmanager/grafana/api/v2/silences",
-				srv.RouteGetGrafanaSilences,
+				api.Hooks.Wrap(srv.RouteGetGrafanaSilences),
 				m,
 			),
 		)
@@ -370,7 +370,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/alertmanager/{DatasourceUID}/api/v2/silence/{SilenceId}",
-				srv.RouteGetSilence,
+				api.Hooks.Wrap(srv.RouteGetSilence),
 				m,
 			),
 		)
@@ -380,7 +380,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/alertmanager/{DatasourceUID}/api/v2/silences",
-				srv.RouteGetSilences,
+				api.Hooks.Wrap(srv.RouteGetSilences),
 				m,
 			),
 		)
@@ -390,7 +390,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/alertmanager/{DatasourceUID}/api/v2/alerts",
-				srv.RoutePostAMAlerts,
+				api.Hooks.Wrap(srv.RoutePostAMAlerts),
 				m,
 			),
 		)
@@ -400,7 +400,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/alertmanager/{DatasourceUID}/config/api/v1/alerts",
-				srv.RoutePostAlertingConfig,
+				api.Hooks.Wrap(srv.RoutePostAlertingConfig),
 				m,
 			),
 		)
@@ -410,7 +410,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/alertmanager/grafana/config/api/v1/alerts",
-				srv.RoutePostGrafanaAlertingConfig,
+				api.Hooks.Wrap(srv.RoutePostGrafanaAlertingConfig),
 				m,
 			),
 		)
@@ -420,7 +420,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/alertmanager/grafana/config/history/{id}/_activate",
-				srv.RoutePostGrafanaAlertingConfigHistoryActivate,
+				api.Hooks.Wrap(srv.RoutePostGrafanaAlertingConfigHistoryActivate),
 				m,
 			),
 		)
@@ -430,7 +430,7 @@ func (api *API) RegisterAlertmanagerApiEndpoints(srv AlertmanagerApi, m *metrics
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/alertmanager/grafana/config/api/v1/receivers/test",
-				srv.RoutePostTestGrafanaReceivers,
+				api.Hooks.Wrap(srv.RoutePostTestGrafanaReceivers),
 				m,
 			),
 		)

pkg/services/ngalert/api/generated_base_api_configuration.go

@@ -55,7 +55,7 @@ func (api *API) RegisterConfigurationApiEndpoints(srv ConfigurationApi, m *metri
 			metrics.Instrument(
 				http.MethodDelete,
 				"/api/v1/ngalert/admin_config",
-				srv.RouteDeleteNGalertConfig,
+				api.Hooks.Wrap(srv.RouteDeleteNGalertConfig),
 				m,
 			),
 		)
@@ -65,7 +65,7 @@ func (api *API) RegisterConfigurationApiEndpoints(srv ConfigurationApi, m *metri
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/v1/ngalert/alertmanagers",
-				srv.RouteGetAlertmanagers,
+				api.Hooks.Wrap(srv.RouteGetAlertmanagers),
 				m,
 			),
 		)
@@ -75,7 +75,7 @@ func (api *API) RegisterConfigurationApiEndpoints(srv ConfigurationApi, m *metri
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/v1/ngalert/admin_config",
-				srv.RouteGetNGalertConfig,
+				api.Hooks.Wrap(srv.RouteGetNGalertConfig),
 				m,
 			),
 		)
@@ -85,7 +85,7 @@ func (api *API) RegisterConfigurationApiEndpoints(srv ConfigurationApi, m *metri
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/v1/ngalert",
-				srv.RouteGetStatus,
+				api.Hooks.Wrap(srv.RouteGetStatus),
 				m,
 			),
 		)
@@ -95,7 +95,7 @@ func (api *API) RegisterConfigurationApiEndpoints(srv ConfigurationApi, m *metri
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/v1/ngalert/admin_config",
-				srv.RoutePostNGalertConfig,
+				api.Hooks.Wrap(srv.RoutePostNGalertConfig),
 				m,
 			),
 		)

pkg/services/ngalert/api/generated_base_api_history.go

@@ -32,7 +32,7 @@ func (api *API) RegisterHistoryApiEndpoints(srv HistoryApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/v1/rules/history",
-				srv.RouteGetStateHistory,
+				api.Hooks.Wrap(srv.RouteGetStateHistory),
 				m,
 			),
 		)

pkg/services/ngalert/api/generated_base_api_prometheus.go

@@ -49,7 +49,7 @@ func (api *API) RegisterPrometheusApiEndpoints(srv PrometheusApi, m *metrics.API
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/prometheus/{DatasourceUID}/api/v1/alerts",
-				srv.RouteGetAlertStatuses,
+				api.Hooks.Wrap(srv.RouteGetAlertStatuses),
 				m,
 			),
 		)
@@ -59,7 +59,7 @@ func (api *API) RegisterPrometheusApiEndpoints(srv PrometheusApi, m *metrics.API
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/prometheus/grafana/api/v1/alerts",
-				srv.RouteGetGrafanaAlertStatuses,
+				api.Hooks.Wrap(srv.RouteGetGrafanaAlertStatuses),
 				m,
 			),
 		)
@@ -69,7 +69,7 @@ func (api *API) RegisterPrometheusApiEndpoints(srv PrometheusApi, m *metrics.API
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/prometheus/grafana/api/v1/rules",
-				srv.RouteGetGrafanaRuleStatuses,
+				api.Hooks.Wrap(srv.RouteGetGrafanaRuleStatuses),
 				m,
 			),
 		)
@@ -79,7 +79,7 @@ func (api *API) RegisterPrometheusApiEndpoints(srv PrometheusApi, m *metrics.API
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/prometheus/{DatasourceUID}/api/v1/rules",
-				srv.RouteGetRuleStatuses,
+				api.Hooks.Wrap(srv.RouteGetRuleStatuses),
 				m,
 			),
 		)

pkg/services/ngalert/api/generated_base_api_provisioning.go

@@ -212,7 +212,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodDelete,
 				"/api/v1/provisioning/alert-rules/{UID}",
-				srv.RouteDeleteAlertRule,
+				api.Hooks.Wrap(srv.RouteDeleteAlertRule),
 				m,
 			),
 		)
@@ -222,7 +222,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodDelete,
 				"/api/v1/provisioning/contact-points/{UID}",
-				srv.RouteDeleteContactpoints,
+				api.Hooks.Wrap(srv.RouteDeleteContactpoints),
 				m,
 			),
 		)
@@ -232,7 +232,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodDelete,
 				"/api/v1/provisioning/mute-timings/{name}",
-				srv.RouteDeleteMuteTiming,
+				api.Hooks.Wrap(srv.RouteDeleteMuteTiming),
 				m,
 			),
 		)
@@ -242,7 +242,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodDelete,
 				"/api/v1/provisioning/templates/{name}",
-				srv.RouteDeleteTemplate,
+				api.Hooks.Wrap(srv.RouteDeleteTemplate),
 				m,
 			),
 		)
@@ -252,7 +252,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/v1/provisioning/alert-rules/{UID}",
-				srv.RouteGetAlertRule,
+				api.Hooks.Wrap(srv.RouteGetAlertRule),
 				m,
 			),
 		)
@@ -262,7 +262,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/v1/provisioning/alert-rules/{UID}/export",
-				srv.RouteGetAlertRuleExport,
+				api.Hooks.Wrap(srv.RouteGetAlertRuleExport),
 				m,
 			),
 		)
@@ -272,7 +272,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/v1/provisioning/folder/{FolderUID}/rule-groups/{Group}",
-				srv.RouteGetAlertRuleGroup,
+				api.Hooks.Wrap(srv.RouteGetAlertRuleGroup),
 				m,
 			),
 		)
@@ -282,7 +282,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/v1/provisioning/folder/{FolderUID}/rule-groups/{Group}/export",
-				srv.RouteGetAlertRuleGroupExport,
+				api.Hooks.Wrap(srv.RouteGetAlertRuleGroupExport),
 				m,
 			),
 		)
@@ -292,7 +292,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/v1/provisioning/alert-rules",
-				srv.RouteGetAlertRules,
+				api.Hooks.Wrap(srv.RouteGetAlertRules),
 				m,
 			),
 		)
@@ -302,7 +302,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/v1/provisioning/alert-rules/export",
-				srv.RouteGetAlertRulesExport,
+				api.Hooks.Wrap(srv.RouteGetAlertRulesExport),
 				m,
 			),
 		)
@@ -312,7 +312,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/v1/provisioning/contact-points",
-				srv.RouteGetContactpoints,
+				api.Hooks.Wrap(srv.RouteGetContactpoints),
 				m,
 			),
 		)
@@ -322,7 +322,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/v1/provisioning/mute-timings/{name}",
-				srv.RouteGetMuteTiming,
+				api.Hooks.Wrap(srv.RouteGetMuteTiming),
 				m,
 			),
 		)
@@ -332,7 +332,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/v1/provisioning/mute-timings",
-				srv.RouteGetMuteTimings,
+				api.Hooks.Wrap(srv.RouteGetMuteTimings),
 				m,
 			),
 		)
@@ -342,7 +342,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/v1/provisioning/policies",
-				srv.RouteGetPolicyTree,
+				api.Hooks.Wrap(srv.RouteGetPolicyTree),
 				m,
 			),
 		)
@@ -352,7 +352,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/v1/provisioning/templates/{name}",
-				srv.RouteGetTemplate,
+				api.Hooks.Wrap(srv.RouteGetTemplate),
 				m,
 			),
 		)
@@ -362,7 +362,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/v1/provisioning/templates",
-				srv.RouteGetTemplates,
+				api.Hooks.Wrap(srv.RouteGetTemplates),
 				m,
 			),
 		)
@@ -372,7 +372,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/v1/provisioning/alert-rules",
-				srv.RoutePostAlertRule,
+				api.Hooks.Wrap(srv.RoutePostAlertRule),
 				m,
 			),
 		)
@@ -382,7 +382,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/v1/provisioning/contact-points",
-				srv.RoutePostContactpoints,
+				api.Hooks.Wrap(srv.RoutePostContactpoints),
 				m,
 			),
 		)
@@ -392,7 +392,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/v1/provisioning/mute-timings",
-				srv.RoutePostMuteTiming,
+				api.Hooks.Wrap(srv.RoutePostMuteTiming),
 				m,
 			),
 		)
@@ -402,7 +402,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodPut,
 				"/api/v1/provisioning/alert-rules/{UID}",
-				srv.RoutePutAlertRule,
+				api.Hooks.Wrap(srv.RoutePutAlertRule),
 				m,
 			),
 		)
@@ -412,7 +412,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodPut,
 				"/api/v1/provisioning/folder/{FolderUID}/rule-groups/{Group}",
-				srv.RoutePutAlertRuleGroup,
+				api.Hooks.Wrap(srv.RoutePutAlertRuleGroup),
 				m,
 			),
 		)
@@ -422,7 +422,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodPut,
 				"/api/v1/provisioning/contact-points/{UID}",
-				srv.RoutePutContactpoint,
+				api.Hooks.Wrap(srv.RoutePutContactpoint),
 				m,
 			),
 		)
@@ -432,7 +432,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodPut,
 				"/api/v1/provisioning/mute-timings/{name}",
-				srv.RoutePutMuteTiming,
+				api.Hooks.Wrap(srv.RoutePutMuteTiming),
 				m,
 			),
 		)
@@ -442,7 +442,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodPut,
 				"/api/v1/provisioning/policies",
-				srv.RoutePutPolicyTree,
+				api.Hooks.Wrap(srv.RoutePutPolicyTree),
 				m,
 			),
 		)
@@ -452,7 +452,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodPut,
 				"/api/v1/provisioning/templates/{name}",
-				srv.RoutePutTemplate,
+				api.Hooks.Wrap(srv.RoutePutTemplate),
 				m,
 			),
 		)
@@ -462,7 +462,7 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 			metrics.Instrument(
 				http.MethodDelete,
 				"/api/v1/provisioning/policies",
-				srv.RouteResetPolicyTree,
+				api.Hooks.Wrap(srv.RouteResetPolicyTree),
 				m,
 			),
 		)

pkg/services/ngalert/api/generated_base_api_ruler.go

@@ -119,7 +119,7 @@ func (api *API) RegisterRulerApiEndpoints(srv RulerApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodDelete,
 				"/api/ruler/grafana/api/v1/rules/{Namespace}/{Groupname}",
-				srv.RouteDeleteGrafanaRuleGroupConfig,
+				api.Hooks.Wrap(srv.RouteDeleteGrafanaRuleGroupConfig),
 				m,
 			),
 		)
@@ -129,7 +129,7 @@ func (api *API) RegisterRulerApiEndpoints(srv RulerApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodDelete,
 				"/api/ruler/grafana/api/v1/rules/{Namespace}",
-				srv.RouteDeleteNamespaceGrafanaRulesConfig,
+				api.Hooks.Wrap(srv.RouteDeleteNamespaceGrafanaRulesConfig),
 				m,
 			),
 		)
@@ -139,7 +139,7 @@ func (api *API) RegisterRulerApiEndpoints(srv RulerApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodDelete,
 				"/api/ruler/{DatasourceUID}/api/v1/rules/{Namespace}",
-				srv.RouteDeleteNamespaceRulesConfig,
+				api.Hooks.Wrap(srv.RouteDeleteNamespaceRulesConfig),
 				m,
 			),
 		)
@@ -149,7 +149,7 @@ func (api *API) RegisterRulerApiEndpoints(srv RulerApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodDelete,
 				"/api/ruler/{DatasourceUID}/api/v1/rules/{Namespace}/{Groupname}",
-				srv.RouteDeleteRuleGroupConfig,
+				api.Hooks.Wrap(srv.RouteDeleteRuleGroupConfig),
 				m,
 			),
 		)
@@ -159,7 +159,7 @@ func (api *API) RegisterRulerApiEndpoints(srv RulerApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/ruler/grafana/api/v1/rules/{Namespace}/{Groupname}",
-				srv.RouteGetGrafanaRuleGroupConfig,
+				api.Hooks.Wrap(srv.RouteGetGrafanaRuleGroupConfig),
 				m,
 			),
 		)
@@ -169,7 +169,7 @@ func (api *API) RegisterRulerApiEndpoints(srv RulerApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/ruler/grafana/api/v1/rules",
-				srv.RouteGetGrafanaRulesConfig,
+				api.Hooks.Wrap(srv.RouteGetGrafanaRulesConfig),
 				m,
 			),
 		)
@@ -179,7 +179,7 @@ func (api *API) RegisterRulerApiEndpoints(srv RulerApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/ruler/grafana/api/v1/rules/{Namespace}",
-				srv.RouteGetNamespaceGrafanaRulesConfig,
+				api.Hooks.Wrap(srv.RouteGetNamespaceGrafanaRulesConfig),
 				m,
 			),
 		)
@@ -189,7 +189,7 @@ func (api *API) RegisterRulerApiEndpoints(srv RulerApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/ruler/{DatasourceUID}/api/v1/rules/{Namespace}",
-				srv.RouteGetNamespaceRulesConfig,
+				api.Hooks.Wrap(srv.RouteGetNamespaceRulesConfig),
 				m,
 			),
 		)
@@ -199,7 +199,7 @@ func (api *API) RegisterRulerApiEndpoints(srv RulerApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/ruler/{DatasourceUID}/api/v1/rules/{Namespace}/{Groupname}",
-				srv.RouteGetRulegGroupConfig,
+				api.Hooks.Wrap(srv.RouteGetRulegGroupConfig),
 				m,
 			),
 		)
@@ -209,7 +209,7 @@ func (api *API) RegisterRulerApiEndpoints(srv RulerApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodGet,
 				"/api/ruler/{DatasourceUID}/api/v1/rules",
-				srv.RouteGetRulesConfig,
+				api.Hooks.Wrap(srv.RouteGetRulesConfig),
 				m,
 			),
 		)
@@ -219,7 +219,7 @@ func (api *API) RegisterRulerApiEndpoints(srv RulerApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/ruler/grafana/api/v1/rules/{Namespace}",
-				srv.RoutePostNameGrafanaRulesConfig,
+				api.Hooks.Wrap(srv.RoutePostNameGrafanaRulesConfig),
 				m,
 			),
 		)
@@ -229,7 +229,7 @@ func (api *API) RegisterRulerApiEndpoints(srv RulerApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/ruler/{DatasourceUID}/api/v1/rules/{Namespace}",
-				srv.RoutePostNameRulesConfig,
+				api.Hooks.Wrap(srv.RoutePostNameRulesConfig),
 				m,
 			),
 		)

pkg/services/ngalert/api/generated_base_api_testing.go

@@ -68,7 +68,7 @@ func (api *API) RegisterTestingApiEndpoints(srv TestingApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/v1/rule/backtest",
-				srv.BacktestConfig,
+				api.Hooks.Wrap(srv.BacktestConfig),
 				m,
 			),
 		)
@@ -78,7 +78,7 @@ func (api *API) RegisterTestingApiEndpoints(srv TestingApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/v1/eval",
-				srv.RouteEvalQueries,
+				api.Hooks.Wrap(srv.RouteEvalQueries),
 				m,
 			),
 		)
@@ -88,7 +88,7 @@ func (api *API) RegisterTestingApiEndpoints(srv TestingApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/v1/rule/test/{DatasourceUID}",
-				srv.RouteTestRuleConfig,
+				api.Hooks.Wrap(srv.RouteTestRuleConfig),
 				m,
 			),
 		)
@@ -98,7 +98,7 @@ func (api *API) RegisterTestingApiEndpoints(srv TestingApi, m *metrics.API) {
 			metrics.Instrument(
 				http.MethodPost,
 				"/api/v1/rule/test/grafana",
-				srv.RouteTestRuleGrafanaConfig,
+				api.Hooks.Wrap(srv.RouteTestRuleGrafanaConfig),
 				m,
 			),
 		)

pkg/services/ngalert/api/hooks.go

@@ -0,0 +1,43 @@
+package api
+
+import (
+	"github.com/grafana/grafana/pkg/api/response"
+	"github.com/grafana/grafana/pkg/infra/log"
+	contextmodel "github.com/grafana/grafana/pkg/services/contexthandler/model"
+)
+
+type RequestHandlerFunc func(*contextmodel.ReqContext) response.Response
+
+type Hooks struct {
+	logger log.Logger
+	hooks  map[string]RequestHandlerFunc
+}
+
+// NewHooks creates an empty set of request handler hooks. Hooks can be used
+// to replace handlers for specific paths.
+func NewHooks(logger log.Logger) *Hooks {
+	return &Hooks{
+		logger: logger,
+		hooks:  make(map[string]RequestHandlerFunc),
+	}
+}
+
+// Add creates a new request hook for a path, causing requests to the path to
+// be handled by the hook function, and not the original handler.
+func (h *Hooks) Set(path string, hook RequestHandlerFunc) {
+	h.logger.Info("setting hook override for the specified route", "path", path)
+	h.hooks[path] = hook
+}
+
+// Wrap returns a new handler which will intercept paths with hooks configured,
+// and invoke the hooked in handler instead. If no hook is configured for a path,
+// then the given handler is invoked.
+func (h *Hooks) Wrap(next RequestHandlerFunc) RequestHandlerFunc {
+	return func(req *contextmodel.ReqContext) response.Response {
+		if hook, ok := h.hooks[req.Context.Req.URL.Path]; ok {
+			h.logger.Debug("hook defined - invoking new handler", "path", req.Context.Req.URL.Path)
+			return hook(req)
+		}
+		return next(req)
+	}
+}

pkg/services/ngalert/api/tooling/swagger-codegen/templates/controller-api.mustache

@@ -40,7 +40,7 @@ func (api *API) Register{{classname}}Endpoints(srv {{classname}}, m *metrics.API
 		metrics.Instrument(
 			http.Method{{httpMethod}},
 			"{{{path}}}",
-			srv.{{nickname}},
+			api.Hooks.Wrap(srv.{{nickname}}),
 			m,
 		),
   ){{/operation}}{{/operations}}

pkg/services/ngalert/ngalert.go

@@ -127,6 +127,7 @@ type AlertNG struct {
 	stateManager        *state.Manager
 	folderService       folder.Service
 	dashboardService    dashboards.DashboardService
+	api                 *api.API
 
 	// Alerting notification services
 	MultiOrgAlertmanager *notifier.MultiOrgAlertmanager
@@ -246,7 +247,7 @@ func (ng *AlertNG) init() error {
 		int64(ng.Cfg.UnifiedAlerting.DefaultRuleEvaluationInterval.Seconds()),
 		int64(ng.Cfg.UnifiedAlerting.BaseInterval.Seconds()), ng.Log)
 
-	api := api.API{
+	ng.api = &api.API{
 		Cfg:                  ng.Cfg,
 		DatasourceCache:      ng.DataSourceCache,
 		DatasourceService:    ng.DataSourceService,
@@ -271,8 +272,9 @@ func (ng *AlertNG) init() error {
 		FeatureManager:       ng.FeatureToggles,
 		AppUrl:               appUrl,
 		Historian:            history,
+		Hooks:                api.NewHooks(ng.Log),
 	}
-	api.RegisterAPIEndpoints(ng.Metrics.GetAPIMetrics())
+	ng.api.RegisterAPIEndpoints(ng.Metrics.GetAPIMetrics())
 
 	defaultLimits, err := readQuotaConfig(ng.Cfg)
 	if err != nil {
@@ -282,7 +284,7 @@ func (ng *AlertNG) init() error {
 	if err := ng.QuotaService.RegisterQuotaReporter(&quota.NewUsageReporter{
 		TargetSrv:     models.QuotaTargetSrv,
 		DefaultLimits: defaultLimits,
-		Reporter:      api.Usage,
+		Reporter:      ng.api.Usage,
 	}); err != nil {
 		return err
 	}
@@ -349,6 +351,12 @@ func (ng *AlertNG) IsDisabled() bool {
 	return !ng.Cfg.UnifiedAlerting.IsEnabled()
 }
 
+// GetHooks returns a facility for replacing handlers for paths. The handler hook for a path
+// is invoked after all other middleware is invoked (authentication, instrumentation).
+func (ng *AlertNG) GetHooks() *api.Hooks {
+	return ng.api.Hooks
+}
+
 func readQuotaConfig(cfg *setting.Cfg) (*quota.Map, error) {
 	limits := &quota.Map{}