app/vmselect/prometheus: follow-up after 86dae56bd0

Return error if the provided latency_offset query arg cannot be parsed.
This should simplify debugging in production.

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3481

app/vmselect/prometheus/prometheus.go

@@ -831,7 +831,10 @@ func QueryHandler(qt *querytracer.Tracer, startTime time.Time, at *auth.Token, w
 		return nil
 	}
 
-	queryOffset := getLatencyOffsetMilliseconds(r)
+	queryOffset, err := getLatencyOffsetMilliseconds(r)
+	if err != nil {
+		return err
+	}
 	if !searchutils.GetBool(r, "nocache") && ct-start < queryOffset && start-ct < queryOffset {
 		// Adjust start time only if `nocache` arg isn't set.
 		// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/241
@@ -962,7 +965,10 @@ func queryRangeHandler(qt *querytracer.Tracer, startTime time.Time, at *auth.Tok
 		return err
 	}
 	if step < maxStepForPointsAdjustment.Milliseconds() {
-		queryOffset := getLatencyOffsetMilliseconds(r)
+		queryOffset, err := getLatencyOffsetMilliseconds(r)
+		if err != nil {
+			return err
+		}
 		if ct-queryOffset < end {
 			result = adjustLastPoints(result, ct-queryOffset, ct+step)
 		}
@@ -1102,16 +1108,12 @@ func getRoundDigits(r *http.Request) int {
 	return n
 }
 
-func getLatencyOffsetMilliseconds(r *http.Request) int64 {
+func getLatencyOffsetMilliseconds(r *http.Request) (int64, error) {
 	d := latencyOffset.Milliseconds()
 	if d <= 1000 {
 		d = 1000
 	}
-	lo, err := searchutils.GetDuration(r, "latency_offset", d)
+	return searchutils.GetDuration(r, "latency_offset", d)
-	if err != nil {
-		return d
-	}
-	return lo
 }
 
 // QueryStatsHandler returns query stats at `/api/v1/status/top_queries`

app/vmselect/prometheus/prometheus_test.go

@@ -5,7 +5,6 @@ import (
 	"net/http"
 	"reflect"
 	"testing"
-	"time"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmselect/netstorage"
 )
@@ -198,16 +197,35 @@ func TestAdjustLastPoints(t *testing.T) {
 	})
 }
 
-func TestGetLatencyOffsetMilliseconds(t *testing.T) {
+func TestGetLatencyOffsetMillisecondsSuccess(t *testing.T) {
-	f := func(got, exp int64) {
+	f := func(url string, expectedOffset int64) {
-		if got != exp {
+		t.Helper()
-			t.Fatalf("expected offset %d; got %d", exp, got)
+		r, err := http.NewRequest("GET", url, nil)
+		if err != nil {
+			t.Fatalf("unexpected error in NewRequest(%q): %s", url, err)
+		}
+		offset, err := getLatencyOffsetMilliseconds(r)
+		if err != nil {
+			t.Fatalf("unexpected error: %s", err)
+		}
+		if offset != expectedOffset {
+			t.Fatalf("unexpected offset got %d; want %d", offset, expectedOffset)
 		}
 	}
-
+	f("http://localhost", latencyOffset.Milliseconds())
-	r, _ := http.NewRequest(http.MethodGet, "http://localhost", nil)
+	f("http://localhost?latency_offset=1.234s", 1234)
-	f(getLatencyOffsetMilliseconds(r), latencyOffset.Milliseconds())
+}
-
+
-	r, _ = http.NewRequest(http.MethodGet, "http://localhost?latency_offset=10s", nil)
+func TestGetLatencyOffsetMillisecondsFailure(t *testing.T) {
-	f(getLatencyOffsetMilliseconds(r), 10*time.Second.Milliseconds())
+	f := func(url string) {
+		t.Helper()
+		r, err := http.NewRequest("GET", url, nil)
+		if err != nil {
+			t.Fatalf("unexpected error in NewRequest(%q): %s", url, err)
+		}
+		if _, err := getLatencyOffsetMilliseconds(r); err == nil {
+			t.Fatalf("expecting non-nil error")
+		}
+	}
+	f("http://localhost?latency_offset=foobar")
 }

docs/CHANGELOG.md

@@ -15,10 +15,11 @@ The following tip changes can be tested by building VictoriaMetrics components f
 
 ## tip
 
-* FEATURE: `vmselect`: support overriding of `-search.latencyOffset` value via URL param `latency_offset`. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3481).
+* FEATURE: support overriding of `-search.latencyOffset` value via URL param `latency_offset` when performing requests to [/api/v1/query](https://docs.victoriametrics.com/keyConcepts.html#instant-query) and [/api/v1/query_range](https://docs.victoriametrics.com/keyConcepts.html#range-query). See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3481).
- 
+
 * BUGFIX: allow specifying values bigger than 2GiB to the following command-line flag values on 32-bit architectures (`386` and `arm`): `-storage.minFreeDiskSpaceBytes` and `-remoteWrite.maxDiskUsagePerURL`. Previously values bigger than 2GiB were incorrectly truncated on these architectures.
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): stop dropping metric name by a mistake on the [/metric-relabel-debug](https://docs.victoriametrics.com/vmagent.html#relabel-debug) page.
+
 * BUGFIX: allow specifying values bigger than 2GiB to the following command-line flag values on 32-bit architectures (`386` and `arm`): `-storage.minFreeDiskSpaceBytes` and `-remoteWrite.maxDiskUsagePerURL`. Previously values bigger than 2GiB were incorrectly truncated on these architectures.
 
 ## [v1.85.1](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.85.1)