vmalert: allow disabling of step param attached to instant queries (#4574)

vmalert: allow disabling of `step` param attached to instant queries

This might be useful for using vmalert with datasources that to not support this param,
unlike VictoriaMetrics.

See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4573

Signed-off-by: hagen1778 <roman@victoriametrics.com>

app/vmalert/README.md

@@ -920,6 +920,8 @@ The shortlist of configuration flags is the following:
      Optional path to bearer token file to use for -datasource.url.
   -datasource.disableKeepAlive
      Whether to disable long-lived connections to the datasource. If true, disables HTTP keep-alives and will only use the connection to the server for a single HTTP request.
+  -datasource.disableStepParam
+     Whether to disable adding 'step' param to the issued instant queries. This might be useful when using vmalert with datasources that do not support 'step' param for instant queries, like Google Managed Prometheus. It is not recommended to enable this flag if you use vmalert with VictoriaMetrics.
   -datasource.headers string
      Optional HTTP extraHeaders to send with each request to the corresponding -datasource.url. For example, -datasource.headers='My-Auth:foobar' would send 'My-Auth: foobar' HTTP header with every request to the corresponding -datasource.url. Multiple headers must be delimited by '^^': -datasource.headers='header1:value1^^header2:value2'
   -datasource.lookback duration

app/vmalert/datasource/vm_prom_api.go

@@ -12,6 +12,9 @@ import (
 var (
 	disablePathAppend = flag.Bool("remoteRead.disablePathAppend", false, "Whether to disable automatic appending of '/api/v1/query' path "+
 		"to the configured -datasource.url and -remoteRead.url")
+	disableStepParam = flag.Bool("datasource.disableStepParam", false, "Whether to disable adding 'step' param to the issued instant queries. "+
+		"This might be useful when using vmalert with datasources that do not support 'step' param for instant queries, like Google Managed Prometheus. "+
+		"It is not recommended to enable this flag if you use vmalert with VictoriaMetrics.")
 )
 
 type promResponse struct {
@@ -166,12 +169,12 @@ func (s *VMStorage) setPrometheusInstantReqParams(r *http.Request, query string,
 		timestamp = timestamp.Truncate(s.evaluationInterval)
 	}
 	q.Set("time", fmt.Sprintf("%d", timestamp.Unix()))
-	if s.evaluationInterval > 0 { // set step as evaluationInterval by default
+	if !*disableStepParam && s.evaluationInterval > 0 { // set step as evaluationInterval by default
 		// always convert to seconds to keep compatibility with older
 		// Prometheus versions. See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1943
 		q.Set("step", fmt.Sprintf("%ds", int(s.evaluationInterval.Seconds())))
 	}
-	if s.queryStep > 0 { // override step with user-specified value
+	if !*disableStepParam && s.queryStep > 0 { // override step with user-specified value
 		// always convert to seconds to keep compatibility with older
 		// Prometheus versions. See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1943
 		q.Set("step", fmt.Sprintf("%ds", int(s.queryStep.Seconds())))

docs/CHANGELOG.md

@@ -35,6 +35,7 @@ The following tip changes can be tested by building VictoriaMetrics components f
 * FEATURE: [vmalert](https://docs.victoriametrics.com/vmalert.html): update retry policy for pushing data to `-remoteWrite.url`. By default, vmalert will make multiple retry attempts with exponential delay. The total time spent during retry attempts shouldn't exceed `-remoteWrite.retryMaxTime` (default is 30s). When retry time is exceeded vmalert drops the data dedicated for `-remoteWrite.url`. Before, vmalert dropped data after 5 retry attempts with 1s delay between attempts (not configurable). See `-remoteWrite.retryMinInterval` and `-remoteWrite.retryMaxTime` cmd-line flags.
 * FEATURE: [vmalert](https://docs.victoriametrics.com/vmalert.html): expose `vmalert_remotewrite_send_duration_seconds_total` counter, which can be used for determining high saturation of every connection to remote storage with an alerting query `sum(rate(vmalert_remotewrite_send_duration_seconds_total[5m])) by(job, instance) > 0.9 * max(vmalert_remotewrite_concurrency) by(job, instance)`. This query triggers when a connection is saturated by more than 90%. This usually means that `-remoteWrite.concurrency` command-line flag must be increased in order to increase the number of concurrent writings into remote endpoint. See [this feature request](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4516).
 * FEATUTE: [vmalert](https://docs.victoriametrics.com/vmalert.html): display the error message received during unsuccessful config reload in vmalert's UI. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4076) for details.
+* FEATUTE: [vmalert](https://docs.victoriametrics.com/vmalert.html): allow disabling of `step` param attached to [instant queries](https://docs.victoriametrics.com/keyConcepts.html#instant-query). This might be useful for using vmalert with datasources that to not support this param, unlike VictoriaMetrics. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4573) for details.
 * FEATURE: [vmauth](https://docs.victoriametrics.com/vmauth.html): expose `vmauth_user_request_duration_seconds` and `vmauth_unauthorized_user_request_duration_seconds` summary metrics for measuring requests latency per user.
 * FEATURE: [vmbackup](https://docs.victoriametrics.com/vmbackup.html): show backup progress percentage in log during backup uploading. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4460).
 * FEATURE: [vmrestore](https://docs.victoriametrics.com/vmrestore.html): show restoring progress percentage in log during backup downloading. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4460).

docs/vmalert.md

@@ -931,6 +931,8 @@ The shortlist of configuration flags is the following:
      Optional path to bearer token file to use for -datasource.url.
   -datasource.disableKeepAlive
      Whether to disable long-lived connections to the datasource. If true, disables HTTP keep-alives and will only use the connection to the server for a single HTTP request.
+  -datasource.disableStepParam
+     Whether to disable adding 'step' param to the issued instant queries. This might be useful when using vmalert with datasources that do not support 'step' param for instant queries, like Google Managed Prometheus. It is not recommended to enable this flag if you use vmalert to query VictoriaMetrics.
   -datasource.headers string
      Optional HTTP extraHeaders to send with each request to the corresponding -datasource.url. For example, -datasource.headers='My-Auth:foobar' would send 'My-Auth: foobar' HTTP header with every request to the corresponding -datasource.url. Multiple headers must be delimited by '^^': -datasource.headers='header1:value1^^header2:value2'
   -datasource.lookback duration