app/vmselect/promql: add timezone_offset(tz) function

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1306

app/vmselect/promql/exec_test.go

@@ -132,6 +132,49 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run("timezone_offset(UTC)", func(t *testing.T) {
+		t.Parallel()
+		q := `timezone_offset("UTC")`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{0, 0, 0, 0, 0, 0},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
+	t.Run("timezone_offset(America/New_York)", func(t *testing.T) {
+		t.Parallel()
+		q := `timezone_offset("America/New_York")`
+		offset, err := getTimezoneOffset("America/New_York")
+		if err != nil {
+			t.Fatalf("cannot obtain timezone: %s", err)
+		}
+		off := float64(offset)
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{off, off, off, off, off, off},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
+	t.Run("timezone_offset(Local)", func(t *testing.T) {
+		t.Parallel()
+		q := `timezone_offset("Local")`
+		offset, err := getTimezoneOffset("Local")
+		if err != nil {
+			t.Fatalf("cannot obtain timezone: %s", err)
+		}
+		off := float64(offset)
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{off, off, off, off, off, off},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run("time()", func(t *testing.T) {
 		t.Parallel()
 		q := `time()`

app/vmselect/promql/transform.go

@@ -123,6 +123,7 @@ var transformFuncs = map[string]transformFunc{
 	"histogram_stddev":   transformHistogramStddev,
 	"sort_by_label":      newTransformFuncSortByLabel(false),
 	"sort_by_label_desc": newTransformFuncSortByLabel(true),
+	"timezone_offset":    transformTimezoneOffset,
 }
 
 func getTransformFunc(s string) transformFunc {
@@ -1906,6 +1907,32 @@ func transformPi(tfa *transformFuncArg) ([]*timeseries, error) {
 	return evalNumber(tfa.ec, math.Pi), nil
 }
 
+func transformTimezoneOffset(tfa *transformFuncArg) ([]*timeseries, error) {
+	args := tfa.args
+	if err := expectTransformArgsNum(args, 1); err != nil {
+		return nil, err
+	}
+	tzString, err := getString(args[0], 0)
+	if err != nil {
+		return nil, fmt.Errorf("cannot get timezone name: %w", err)
+	}
+	tzOffset, err := getTimezoneOffset(tzString)
+	if err != nil {
+		return nil, fmt.Errorf("cannot get timezone offset for %q: %w", tzString, err)
+	}
+	rv := evalNumber(tfa.ec, float64(tzOffset))
+	return rv, nil
+}
+
+func getTimezoneOffset(tzString string) (int, error) {
+	loc, err := time.LoadLocation(tzString)
+	if err != nil {
+		return 0, fmt.Errorf("cannot load timezone %q: %w", tzString, err)
+	}
+	_, tzOffset := time.Now().In(loc).Zone()
+	return tzOffset, nil
+}
+
 func transformTime(tfa *transformFuncArg) ([]*timeseries, error) {
 	if err := expectTransformArgsNum(tfa.args, 0); err != nil {
 		return nil, err

app/vmselect/promql/tzdata.go

@@ -0,0 +1,9 @@
+// +build go1.15
+
+package promql
+
+import (
+	// This is needed for embedding tzdata into binary, so `timezone_offset` could work in an app running on a scratch base Docker image.
+	// The "time/tzdata" package has been appeared starting from Go1.15 - see https://golang.org/doc/go1.15#time/tzdata
+	_ "time/tzdata"
+)

docs/CHANGELOG.md

@@ -14,6 +14,7 @@ sort: 15
 * FEATURE: add ability to filter `/api/v1/status/tsdb` output with arbitrary [time series selectors](https://prometheus.io/docs/prometheus/latest/querying/basics/#time-series-selectors) passed via `match[]` query args. See [these docs](https://docs.victoriametrics.com/#tsdb-stats) and [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1168) for details.
 * FEATURE: automatically detect memory and cpu limits for VictoriaMetrics components running under [cgroup v2](https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html) environments such as [HashiCorp Nomad](https://www.nomadproject.io/). See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1269).
 * FEATURE: vmauth: allow `-auth.config` reloading via `/-/reload` http endpoint. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1194).
+* FEATURE: add `timezone_offset(tz)` function. It returns offset in seconds for the given timezone `tz` relative to UTC. This can be useful when combining with datetime-related functions. For example, `day_of_week(time()+timezone_offset("America/Los_Angeles"))` would return weekdays for `America/Los_Angeles` time zone. Special `Local` time zone can be used for returning an offset for the time zone set on the host where VictoriaMetrics runs. See [MetricsQL docs](https://docs.victoriametrics.com/MetricsQL.html) for more details.
 
 * BUGFIX: vmagent: do not retry scraping targets, which don't support HTTP. This should reduce CPU load and network usage at `vmagent` and at scrape target. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1289).
 * BUGFIX: vmagent: fix possible race when refreshing `role: endpoints` and `role: endpointslices` scrape targets in `kubernetes_sd_config`. Prevoiusly `pod` objects could be updated after the related `endpoints` object update. This could lead to missing scrape targets. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1240).

docs/MetricsQL.md

@@ -156,3 +156,4 @@ This functionality can be tried at [an editable Grafana dashboard](http://play-g
   anomalies in time series comparing to historical samples.
 - `zscore(q) by (group)` - returns independent [z-score](https://en.wikipedia.org/wiki/Standard_score) values for every point in every `group` of `q`.
   Useful for detecting anomalies in the group of related time series.
+- `timezone_offset("tz")` - returns offset in seconds for the given timezone `tz` relative to UTC. This can be useful when combining with datetime-related functions. For example, `day_of_week(time()+timezone_offset("America/Los_Angeles"))` would return weekdays for `America/Los_Angeles` time zone. Special `Local` time zone can be used for returning an offset for the time zone set on the host where VictoriaMetrics runs.

go.mod

@@ -8,7 +8,7 @@ require (
 	// like https://github.com/valyala/fasthttp/commit/996610f021ff45fdc98c2ce7884d5fa4e7f9199b
 	github.com/VictoriaMetrics/fasthttp v1.0.15
 	github.com/VictoriaMetrics/metrics v1.17.2
-	github.com/VictoriaMetrics/metricsql v0.14.0
+	github.com/VictoriaMetrics/metricsql v0.15.0
 	github.com/VividCortex/ewma v1.2.0 // indirect
 	github.com/aws/aws-sdk-go v1.38.40
 	github.com/cespare/xxhash/v2 v2.1.1

go.sum

@@ -88,8 +88,8 @@ github.com/VictoriaMetrics/fasthttp v1.0.15/go.mod h1:s9o5H4T58Kt4CTrdyJp4RorBKC
 github.com/VictoriaMetrics/metrics v1.12.2/go.mod h1:Z1tSfPfngDn12bTfZSCqArT3OPY3u88J12hSoOhuiRE=
 github.com/VictoriaMetrics/metrics v1.17.2 h1:9zPJ7DPfxdJWshOGLPLpAtPL0ZZ9AeUyQC3fIqG6Lvo=
 github.com/VictoriaMetrics/metrics v1.17.2/go.mod h1:Z1tSfPfngDn12bTfZSCqArT3OPY3u88J12hSoOhuiRE=
-github.com/VictoriaMetrics/metricsql v0.14.0 h1:XGbpZJVskUPJFo2C7vG6ATxXBwkBFPe7EWZXB2HZt2U=
+github.com/VictoriaMetrics/metricsql v0.15.0 h1:7tveqhA0xLumXhokcmgxiUn90VlKqiVtYZQ3p6y9Fu4=
-github.com/VictoriaMetrics/metricsql v0.14.0/go.mod h1:ylO7YITho/Iw6P71oEaGyHbO94bGoGtzWfLGqFhMIg8=
+github.com/VictoriaMetrics/metricsql v0.15.0/go.mod h1:ylO7YITho/Iw6P71oEaGyHbO94bGoGtzWfLGqFhMIg8=
 github.com/VividCortex/ewma v1.1.1/go.mod h1:2Tkkvm3sRDVXaiyucHiACn4cqf7DpdyLvmxzcbUokwA=
 github.com/VividCortex/ewma v1.2.0 h1:f58SaIzcDXrSy3kWaHNvuJgJ3Nmz59Zji6XoJR/q1ow=
 github.com/VividCortex/ewma v1.2.0/go.mod h1:nz4BbCtbLyFDeC9SUHbtcT5644juEuWfUAUnGx7j5l4=

vendor/github.com/VictoriaMetrics/metricsql/transform.go

@@ -88,6 +88,7 @@ var transformFuncs = map[string]bool{
 	"histogram_stddev":   true,
 	"sort_by_label":      true,
 	"sort_by_label_desc": true,
+	"timezone_offset":    true,
 }
 
 // IsTransformFunc returns whether funcName is known transform function.

vendor/modules.txt

@@ -20,7 +20,7 @@ github.com/VictoriaMetrics/fasthttp/stackless
 # github.com/VictoriaMetrics/metrics v1.17.2
 ## explicit
 github.com/VictoriaMetrics/metrics
-# github.com/VictoriaMetrics/metricsql v0.14.0
+# github.com/VictoriaMetrics/metricsql v0.15.0
 ## explicit
 github.com/VictoriaMetrics/metricsql
 github.com/VictoriaMetrics/metricsql/binaryop