Repository: VictoriaMetrics/VictoriaMetrics
Pull request #1660 (2021-09-28 12:52:49)

app/vmselect: return NaN instead of 0 for empty value sets
The change affects `count/stddev/stdvar_over_time` funcs and makes
them to return NaN instead of zero when there is no datapoints
in a time window.
This is needed for improving compatibility with Prometheus.


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```diff
@@            Coverage Diff             @@
##           master    #1660      +/-   ##
==========================================
- Coverage   60.81%   60.76%   -0.06%     
==========================================
  Files         234      234              
  Lines       38972    38968       -4     
==========================================
- Hits        23702    23677      -25     
- Misses      13706    13725      +19     
- Partials     1564     1566       +2     
```


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|---|---|---|
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| [app/vmalert/remotewrite/remotewrite.go](https://codecov.io/gh/VictoriaMetrics/VictoriaMetrics/pull/1660/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=VictoriaMetrics#diff-YXBwL3ZtYWxlcnQvcmVtb3Rld3JpdGUvcmVtb3Rld3JpdGUuZ28=) | `63.44% <0.00%> (-1.38%)` | :arrow_down: |
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------

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Patch:
diff --git a/README.md b/README.md
index 361883f47..1fb365097 100644
--- a/README.md
+++ b/README.md
@@ -265,6 +265,52 @@ VictoriaMetrics also supports [importing data in Prometheus exposition format](#
 See also [vmagent](https://docs.victoriametrics.com/vmagent.html), which can be used as drop-in replacement for Prometheus.
 
 
+## How to send data from DataDog agent
+
+VictoriaMetrics accepts data from [DataDog agent](https://docs.datadoghq.com/agent/) or [DogStatsD]() via ["submit metrics" API](https://docs.datadoghq.com/api/latest/metrics/#submit-metrics) at `/datadog/api/v1/series` path.
+
+Run DataDog agent with `DD_DD_URL=http://victoriametrics-host:8428/datadog` environment variable in order to write data to VictoriaMetrics at `victoriametrics-host` host. Another option is to set `dd_url` param at [DataDog agent configuration file](https://docs.datadoghq.com/agent/guide/agent-configuration-files/) to `http://victoriametrics-host:8428/datadog`.
+
+Example on how to send data to VictoriaMetrics via DataDog "submit metrics" API from command line:
+
+```bash
+echo '
+{
+  "series": [
+    {
+      "host": "test.example.com",
+      "interval": 20,
+      "metric": "system.load.1",
+      "points": [[
+        0,
+        0.5
+      ]],
+      "tags": [
+        "environment:test"
+      ],
+      "type": "rate"
+    }
+  ]
+}
+' | curl -X POST --data-binary @- http://localhost:8428/datadog/api/v1/series
+```
+
+The imported data can be read via [export API](https://docs.victoriametrics.com/#how-to-export-data-in-json-line-format):
+
+```bash
+curl http://localhost:8428/api/v1/export -d 'match[]=system.load.1'
+```
+
+This command should return the following output if everything is OK:
+
+```
+{"metric":{"__name__":"system.load.1","environment":"test","host":"test.example.com"},"values":[0.5],"timestamps":[1632833641000]}
+```
+
+Extra labels may be added to all the written time series by passing `extra_label=name=value` query args.
+For example, `/datadog/api/v1/series?extra_label=foo=bar` would add `{foo="bar"}` label to all the ingested metrics.
+
+
 ## How to send data from InfluxDB-compatible agents such as [Telegraf](https://www.influxdata.com/time-series-platform/telegraf/)
 
 Use `http://<victoriametric-addr>:8428` url instead of InfluxDB url in agents' configs.
@@ -790,6 +836,7 @@ The exported CSV data can be imported to VictoriaMetrics via [/api/v1/import/csv
 Time series data can be imported via any supported ingestion protocol:
 
 * [Prometheus remote_write API](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#remote_write). See [these docs](#prometheus-setup) for details.
+* DataDog `submit metrics` API. See [these docs](#how-to-send-data-from-datadog-agent) for details.
 * InfluxDB line protocol. See [these docs](#how-to-send-data-from-influxdb-compatible-agents-such-as-telegraf) for details.
 * Graphite plaintext protocol. See [these docs](#how-to-send-data-from-graphite-compatible-agents-such-as-statsd) for details.
 * OpenTSDB telnet put protocol. See [these docs](#sending-data-via-telnet-put-protocol) for details.
diff --git a/app/vmagent/README.md b/app/vmagent/README.md
index d630d6f34..feb9cb092 100644
--- a/app/vmagent/README.md
+++ b/app/vmagent/README.md
@@ -21,6 +21,7 @@ to `vmagent` such as the ability to push metrics instead of pulling them. We did
   See [Quick Start](#quick-start) for details.
 * Can add, remove and modify labels (aka tags) via Prometheus relabeling. Can filter data before sending it to remote storage. See [these docs](#relabeling) for details.
 * Accepts data via all ingestion protocols supported by VictoriaMetrics:
+  * DataDog "submit metrics" API. See [these docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-send-data-from-datadog-agent).
   * InfluxDB line protocol via `http://<vmagent>:8429/write`. See [these docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-send-data-from-influxdb-compatible-agents-such-as-telegraf).
   * Graphite plaintext protocol if `-graphiteListenAddr` command-line flag is set. See [these docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-send-data-from-graphite-compatible-agents-such-as-statsd).
   * OpenTSDB telnet and http protocols if `-opentsdbListenAddr` command-line flag is set. See [these docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-send-data-from-opentsdb-compatible-agents).
diff --git a/app/vmagent/datadog/request_handler.go b/app/vmagent/datadog/request_handler.go
new file mode 100644
index 000000000..7f98ec955
--- /dev/null
+++ b/app/vmagent/datadog/request_handler.go
@@ -0,0 +1,99 @@
+package datadog
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmagent/common"
+	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmagent/remotewrite"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/auth"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/prompbmarshal"
+	parserCommon "github.com/VictoriaMetrics/VictoriaMetrics/lib/protoparser/common"
+	parser "github.com/VictoriaMetrics/VictoriaMetrics/lib/protoparser/datadog"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/tenantmetrics"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/writeconcurrencylimiter"
+	"github.com/VictoriaMetrics/metrics"
+)
+
+var (
+	rowsInserted       = metrics.NewCounter(`vmagent_rows_inserted_total{type="datadog"}`)
+	rowsTenantInserted = tenantmetrics.NewCounterMap(`vmagent_tenant_inserted_rows_total{type="datadog"}`)
+	rowsPerInsert      = metrics.NewHistogram(`vmagent_rows_per_insert{type="datadog"}`)
+)
+
+// InsertHandlerForHTTP processes remote write for DataDog POST /api/v1/series request.
+//
+// See https://docs.datadoghq.com/api/latest/metrics/#submit-metrics
+func InsertHandlerForHTTP(at *auth.Token, req *http.Request) error {
+	extraLabels, err := parserCommon.GetExtraLabels(req)
+	if err != nil {
+		return err
+	}
+	return writeconcurrencylimiter.Do(func() error {
+		ce := req.Header.Get("Content-Encoding")
+		return parser.ParseStream(req.Body, ce, func(series []parser.Series) error {
+			return insertRows(at, series, extraLabels)
+		})
+	})
+}
+
+func insertRows(at *auth.Token, series []parser.Series, extraLabels []prompbmarshal.Label) error {
+	ctx := common.GetPushCtx()
+	defer common.PutPushCtx(ctx)
+
+	rowsTotal := 0
+	tssDst := ctx.WriteRequest.Timeseries[:0]
+	labels := ctx.Labels[:0]
+	samples := ctx.Samples[:0]
+	for i := range series {
+		ss := &series[i]
+		rowsTotal += len(ss.Points)
+		labelsLen := len(labels)
+		labels = append(labels, prompbmarshal.Label{
+			Name:  "__name__",
+			Value: ss.Metric,
+		})
+		labels = append(labels, prompbmarshal.Label{
+			Name:  "host",
+			Value: ss.Host,
+		})
+		for _, tag := range ss.Tags {
+			n := strings.IndexByte(tag, ':')
+			if n < 0 {
+				return fmt.Errorf("cannot find ':' in tag %q", tag)
+			}
+			name := tag[:n]
+			value := tag[n+1:]
+			if name == "host" {
+				name = "exported_host"
+			}
+			labels = append(labels, prompbmarshal.Label{
+				Name:  name,
+				Value: value,
+			})
+		}
+		labels = append(labels, extraLabels...)
+		samplesLen := len(samples)
+		for _, pt := range ss.Points {
+			samples = append(samples, prompbmarshal.Sample{
+				Timestamp: pt.Timestamp(),
+				Value:     pt.Value(),
+			})
+		}
+		tssDst = append(tssDst, prompbmarshal.TimeSeries{
+			Labels:  labels[labelsLen:],
+			Samples: samples[samplesLen:],
+		})
+	}
+	ctx.WriteRequest.Timeseries = tssDst
+	ctx.Labels = labels
+	ctx.Samples = samples
+	remotewrite.PushWithAuthToken(at, &ctx.WriteRequest)
+	rowsInserted.Add(rowsTotal)
+	if at != nil {
+		rowsTenantInserted.Get(at).Add(rowsTotal)
+	}
+	rowsPerInsert.Update(float64(rowsTotal))
+	return nil
+}
diff --git a/app/vmagent/main.go b/app/vmagent/main.go
index d7d81ac96..7b2e02ace 100644
--- a/app/vmagent/main.go
+++ b/app/vmagent/main.go
@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmagent/csvimport"
+	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmagent/datadog"
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmagent/graphite"
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmagent/influx"
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmagent/native"
@@ -224,6 +225,36 @@ func requestHandler(w http.ResponseWriter, r *http.Request) bool {
 		influxQueryRequests.Inc()
 		influxutils.WriteDatabaseNames(w)
 		return true
+	case "/datadog/api/v1/series":
+		datadogWriteRequests.Inc()
+		if err := datadog.InsertHandlerForHTTP(nil, r); err != nil {
+			datadogWriteErrors.Inc()
+			httpserver.Errorf(w, r, "%s", err)
+			return true
+		}
+		// See https://docs.datadoghq.com/api/latest/metrics/#submit-metrics
+		w.Header().Set("Content-Type", "application/json; charset=utf-8")
+		w.WriteHeader(202)
+		fmt.Fprintf(w, `{"status":"ok"}`)
+		return true
+	case "/datadog/api/v1/validate":
+		datadogValidateRequests.Inc()
+		// See https://docs.datadoghq.com/api/latest/authentication/#validate-api-key
+		w.Header().Set("Content-Type", "application/json; charset=utf-8")
+		fmt.Fprintf(w, `{"valid":true}`)
+		return true
+	case "/datadog/api/v1/check_run":
+		datadogCheckRunRequests.Inc()
+		// See https://docs.datadoghq.com/api/latest/service-checks/#submit-a-service-check
+		w.Header().Set("Content-Type", "application/json; charset=utf-8")
+		w.WriteHeader(202)
+		fmt.Fprintf(w, `{"status":"ok"}`)
+		return true
+	case "/datadog/intake/":
+		datadogIntakeRequests.Inc()
+		w.Header().Set("Content-Type", "application/json; charset=utf-8")
+		fmt.Fprintf(w, `{}`)
+		return true
 	case "/targets":
 		promscrapeTargetsRequests.Inc()
 		promscrape.WriteHumanReadableTargetsStatus(w, r)
@@ -330,6 +361,35 @@ func processMultitenantRequest(w http.ResponseWriter, r *http.Request, path stri
 		influxQueryRequests.Inc()
 		influxutils.WriteDatabaseNames(w)
 		return true
+	case "datadog/api/v1/series":
+		datadogWriteRequests.Inc()
+		if err := datadog.InsertHandlerForHTTP(at, r); err != nil {
+			datadogWriteErrors.Inc()
+			httpserver.Errorf(w, r, "%s", err)
+			return true
+		}
+		// See https://docs.datadoghq.com/api/latest/metrics/#submit-metrics
+		w.WriteHeader(202)
+		fmt.Fprintf(w, `{"status":"ok"}`)
+		return true
+	case "datadog/api/v1/validate":
+		datadogValidateRequests.Inc()
+		// See https://docs.datadoghq.com/api/latest/authentication/#validate-api-key
+		w.Header().Set("Content-Type", "application/json; charset=utf-8")
+		fmt.Fprintf(w, `{"valid":true}`)
+		return true
+	case "datadog/api/v1/check_run":
+		datadogCheckRunRequests.Inc()
+		// See https://docs.datadoghq.com/api/latest/service-checks/#submit-a-service-check
+		w.Header().Set("Content-Type", "application/json; charset=utf-8")
+		w.WriteHeader(202)
+		fmt.Fprintf(w, `{"status":"ok"}`)
+		return true
+	case "datadog/intake/":
+		datadogIntakeRequests.Inc()
+		w.Header().Set("Content-Type", "application/json; charset=utf-8")
+		fmt.Fprintf(w, `{}`)
+		return true
 	default:
 		httpserver.Errorf(w, r, "unsupported multitenant path suffix: %q", p.Suffix)
 		return true
@@ -352,10 +412,17 @@ var (
 	nativeimportRequests = metrics.NewCounter(`vmagent_http_requests_total{path="/api/v1/import/native", protocol="nativeimport"}`)
 	nativeimportErrors   = metrics.NewCounter(`vmagent_http_request_errors_total{path="/api/v1/import/native", protocol="nativeimport"}`)
 
-	influxWriteRequests = metrics.NewCounter(`vmagent_http_requests_total{path="/write", protocol="influx"}`)
-	influxWriteErrors   = metrics.NewCounter(`vmagent_http_request_errors_total{path="/write", protocol="influx"}`)
+	influxWriteRequests = metrics.NewCounter(`vmagent_http_requests_total{path="/influx/write", protocol="influx"}`)
+	influxWriteErrors   = metrics.NewCounter(`vmagent_http_request_errors_total{path="/influx/write", protocol="influx"}`)
+
+	influxQueryRequests = metrics.NewCounter(`vmagent_http_requests_total{path="/influx/query", protocol="influx"}`)
+
+	datadogWriteRequests = metrics.NewCounter(`vmagent_http_requests_total{path="/datadog/api/v1/series", protocol="datadog"}`)
+	datadogWriteErrors   = metrics.NewCounter(`vmagent_http_request_errors_total{path="/datadog/api/v1/series", protocol="datadog"}`)
 
-	influxQueryRequests = metrics.NewCounter(`vmagent_http_requests_total{path="/query", protocol="influx"}`)
+	datadogValidateRequests = metrics.NewCounter(`vmagent_http_requests_total{path="/datadog/api/v1/validate", protocol="datadog"}`)
+	datadogCheckRunRequests = metrics.NewCounter(`vmagent_http_requests_total{path="/datadog/api/v1/check_run", protocol="datadog"}`)
+	datadogIntakeRequests   = metrics.NewCounter(`vmagent_http_requests_total{path="/datadog/intake/", protocol="datadog"}`)
 
 	promscrapeTargetsRequests      = metrics.NewCounter(`vmagent_http_requests_total{path="/targets"}`)
 	promscrapeAPIV1TargetsRequests = metrics.NewCounter(`vmagent_http_requests_total{path="/api/v1/targets"}`)
diff --git a/app/vminsert/datadog/request_handler.go b/app/vminsert/datadog/request_handler.go
new file mode 100644
index 000000000..5ae809a7c
--- /dev/null
+++ b/app/vminsert/datadog/request_handler.go
@@ -0,0 +1,97 @@
+package datadog
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/VictoriaMetrics/VictoriaMetrics/app/vminsert/common"
+	"github.com/VictoriaMetrics/VictoriaMetrics/app/vminsert/relabel"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/prompbmarshal"
+	parserCommon "github.com/VictoriaMetrics/VictoriaMetrics/lib/protoparser/common"
+	parser "github.com/VictoriaMetrics/VictoriaMetrics/lib/protoparser/datadog"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/writeconcurrencylimiter"
+	"github.com/VictoriaMetrics/metrics"
+)
+
+var (
+	rowsInserted  = metrics.NewCounter(`vm_rows_inserted_total{type="datadog"}`)
+	rowsPerInsert = metrics.NewHistogram(`vm_rows_per_insert{type="datadog"}`)
+)
+
+// InsertHandlerForHTTP processes remote write for DataDog POST /api/v1/series request.
+//
+// See https://docs.datadoghq.com/api/latest/metrics/#submit-metrics
+func InsertHandlerForHTTP(req *http.Request) error {
+	extraLabels, err := parserCommon.GetExtraLabels(req)
+	if err != nil {
+		return err
+	}
+	return writeconcurrencylimiter.Do(func() error {
+		ce := req.Header.Get("Content-Encoding")
+		err := parser.ParseStream(req.Body, ce, func(series []parser.Series) error {
+			return insertRows(series, extraLabels)
+		})
+		if err != nil {
+			return fmt.Errorf("headers: %q; err: %w", req.Header, err)
+		}
+		return nil
+	})
+}
+
+func insertRows(series []parser.Series, extraLabels []prompbmarshal.Label) error {
+	ctx := common.GetInsertCtx()
+	defer common.PutInsertCtx(ctx)
+
+	rowsLen := 0
+	for i := range series {
+		rowsLen += len(series[i].Points)
+	}
+	ctx.Reset(rowsLen)
+	rowsTotal := 0
+	hasRelabeling := relabel.HasRelabeling()
+	for i := range series {
+		ss := &series[i]
+		rowsTotal += len(ss.Points)
+		ctx.Labels = ctx.Labels[:0]
+		ctx.AddLabel("", ss.Metric)
+		ctx.AddLabel("host", ss.Host)
+		for _, tag := range ss.Tags {
+			n := strings.IndexByte(tag, ':')
+			if n < 0 {
+				return fmt.Errorf("cannot find ':' in tag %q", tag)
+			}
+			name := tag[:n]
+			value := tag[n+1:]
+			if name == "host" {
+				name = "exported_host"
+			}
+			ctx.AddLabel(name, value)
+		}
+		for j := range extraLabels {
+			label := &extraLabels[j]
+			ctx.AddLabel(label.Name, label.Value)
+		}
+		if hasRelabeling {
+			ctx.ApplyRelabeling()
+		}
+		if len(ctx.Labels) == 0 {
+			// Skip metric without labels.
+			continue
+		}
+		ctx.SortLabelsIfNeeded()
+		var metricNameRaw []byte
+		var err error
+		for _, pt := range ss.Points {
+			timestamp := pt.Timestamp()
+			value := pt.Value()
+			metricNameRaw, err = ctx.WriteDataPointExt(metricNameRaw, ctx.Labels, timestamp, value)
+			if err != nil {
+				return err
+			}
+		}
+	}
+	rowsInserted.Add(rowsTotal)
+	rowsPerInsert.Update(float64(rowsTotal))
+	return ctx.FlushBufs()
+}
diff --git a/app/vminsert/main.go b/app/vminsert/main.go
index 88238fa06..dabe0ecea 100644
--- a/app/vminsert/main.go
+++ b/app/vminsert/main.go
@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vminsert/csvimport"
+	"github.com/VictoriaMetrics/VictoriaMetrics/app/vminsert/datadog"
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vminsert/graphite"
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vminsert/influx"
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vminsert/native"
@@ -155,6 +156,36 @@ func RequestHandler(w http.ResponseWriter, r *http.Request) bool {
 		influxQueryRequests.Inc()
 		influxutils.WriteDatabaseNames(w)
 		return true
+	case "/datadog/api/v1/series":
+		datadogWriteRequests.Inc()
+		if err := datadog.InsertHandlerForHTTP(r); err != nil {
+			datadogWriteErrors.Inc()
+			httpserver.Errorf(w, r, "%s", err)
+			return true
+		}
+		// See https://docs.datadoghq.com/api/latest/metrics/#submit-metrics
+		w.Header().Set("Content-Type", "application/json; charset=utf-8")
+		w.WriteHeader(202)
+		fmt.Fprintf(w, `{"status":"ok"}`)
+		return true
+	case "/datadog/api/v1/validate":
+		datadogValidateRequests.Inc()
+		// See https://docs.datadoghq.com/api/latest/authentication/#validate-api-key
+		w.Header().Set("Content-Type", "application/json; charset=utf-8")
+		fmt.Fprintf(w, `{"valid":true}`)
+		return true
+	case "/datadog/api/v1/check_run":
+		datadogCheckRunRequests.Inc()
+		// See https://docs.datadoghq.com/api/latest/service-checks/#submit-a-service-check
+		w.Header().Set("Content-Type", "application/json; charset=utf-8")
+		w.WriteHeader(202)
+		fmt.Fprintf(w, `{"status":"ok"}`)
+		return true
+	case "/datadog/intake/":
+		datadogIntakeRequests.Inc()
+		w.Header().Set("Content-Type", "application/json; charset=utf-8")
+		fmt.Fprintf(w, `{}`)
+		return true
 	case "/prometheus/targets", "/targets":
 		promscrapeTargetsRequests.Inc()
 		promscrape.WriteHumanReadableTargetsStatus(w, r)
@@ -204,10 +235,17 @@ var (
 	nativeimportRequests = metrics.NewCounter(`vm_http_requests_total{path="/api/v1/import/native", protocol="nativeimport"}`)
 	nativeimportErrors   = metrics.NewCounter(`vm_http_request_errors_total{path="/api/v1/import/native", protocol="nativeimport"}`)
 
-	influxWriteRequests = metrics.NewCounter(`vm_http_requests_total{path="/write", protocol="influx"}`)
-	influxWriteErrors   = metrics.NewCounter(`vm_http_request_errors_total{path="/write", protocol="influx"}`)
+	influxWriteRequests = metrics.NewCounter(`vm_http_requests_total{path="/influx/write", protocol="influx"}`)
+	influxWriteErrors   = metrics.NewCounter(`vm_http_request_errors_total{path="/influx/write", protocol="influx"}`)
+
+	influxQueryRequests = metrics.NewCounter(`vm_http_requests_total{path="/influx/query", protocol="influx"}`)
+
+	datadogWriteRequests = metrics.NewCounter(`vm_http_requests_total{path="/datadog/api/v1/series", protocol="datadog"}`)
+	datadogWriteErrors   = metrics.NewCounter(`vm_http_request_errors_total{path="/datadog/api/v1/series", protocol="datadog"}`)
 
-	influxQueryRequests = metrics.NewCounter(`vm_http_requests_total{path="/query", protocol="influx"}`)
+	datadogValidateRequests = metrics.NewCounter(`vm_http_requests_total{path="/datadog/api/v1/validate", protocol="datadog"}`)
+	datadogCheckRunRequests = metrics.NewCounter(`vm_http_requests_total{path="/datadog/api/v1/check_run", protocol="datadog"}`)
+	datadogIntakeRequests   = metrics.NewCounter(`vm_http_requests_total{path="/datadog/intake/", protocol="datadog"}`)
 
 	promscrapeTargetsRequests      = metrics.NewCounter(`vm_http_requests_total{path="/targets"}`)
 	promscrapeAPIV1TargetsRequests = metrics.NewCounter(`vm_http_requests_total{path="/api/v1/targets"}`)
diff --git a/app/vmselect/promql/rollup.go b/app/vmselect/promql/rollup.go
index b14cebaf6..6ad3bda67 100644
--- a/app/vmselect/promql/rollup.go
+++ b/app/vmselect/promql/rollup.go
@@ -1112,13 +1112,6 @@ func newRollupQuantile(args []interface{}) (rollupFunc, error) {
 		// There is no need in handling NaNs here, since they must be cleaned up
 		// before calling rollup funcs.
 		values := rfa.values
-		if len(values) == 0 {
-			return rfa.prevValue
-		}
-		if len(values) == 1 {
-			// Fast path - only a single value.
-			return values[0]
-		}
 		phi := phis[rfa.idx]
 		qv := quantile(phi, values)
 		return qv
@@ -1359,10 +1352,7 @@ func rollupCount(rfa *rollupFuncArg) float64 {
 	// before calling rollup funcs.
 	values := rfa.values
 	if len(values) == 0 {
-		if math.IsNaN(rfa.prevValue) {
-			return nan
-		}
-		return 0
+		return nan
 	}
 	return float64(len(values))
 }
@@ -1379,10 +1369,7 @@ func rollupStdvar(rfa *rollupFuncArg) float64 {
 	// before calling rollup funcs.
 	values := rfa.values
 	if len(values) == 0 {
-		if math.IsNaN(rfa.prevValue) {
-			return nan
-		}
-		return 0
+		return nan
 	}
 	if len(values) == 1 {
 		// Fast path.
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index bdfe3cfe3..ddf3e8403 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -6,12 +6,14 @@ sort: 15
 
 ## tip
 
+* FEATURE: add ability to accept metrics from [DataDog agent](https://docs.datadoghq.com/agent/) and [DogStatsD](https://docs.datadoghq.com/developers/dogstatsd/). See [these docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-send-data-from-datadog-agent). This option simplifies the migration path from DataDog to VictoriaMetrics. See also [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/206).
 * FEATURE: vmagent [enterprise](https://victoriametrics.com/enterprise.html): add support for data reading from [Apache Kafka](https://kafka.apache.org/).
 * FEATURE: calculate quantiles in the same way as Prometheus does in such functions as [quantile_over_time](https://docs.victoriametrics.com/MetricsQL.html#quantile_over_time) and [quantile](https://docs.victoriametrics.com/MetricsQL.html#quantile). Previously results from VictoriaMetrics could be slightly different than results from Prometheus. See [this](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1625) and [this](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1612) issues.
 * FEATURE: add `rollup_scrape_interval(m[d])` function to [MetricsQL](https://docs.victoriametrics.com/MetricsQL.html), which returns `min`, `max` and `avg` values for the interval between samples for `m` on the given lookbehind window `d`.
 * FEATURE: vmui: add ability to naturally scroll and zoom graphs. See [this pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/1634).
 
 * BUGFIX: align behavior of the queries `a or on (labels) b`, `a and on (labels) b` and `a unless on (labels) b` where `b` has multiple time series with the given `labels` to Prometheus behavior. See [this pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/1643).
+* BUGFIX: vmagent: fix `openstack_sd_config` service discovery when both `domain_name` and `project_id` config options are set. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1655).
 
 
 ## [v1.66.2](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.66.2)
diff --git a/docs/Cluster-VictoriaMetrics.md b/docs/Cluster-VictoriaMetrics.md
index ee295a768..f8cc57b16 100644
--- a/docs/Cluster-VictoriaMetrics.md
+++ b/docs/Cluster-VictoriaMetrics.md
@@ -191,12 +191,11 @@ It is recommended setting up alerts in [vmalert](https://docs.victoriametrics.co
   - `<accountID>` is an arbitrary 32-bit integer identifying namespace for data ingestion (aka tenant). It is possible to set it as `accountID:projectID`,
     where `projectID` is also arbitrary 32-bit integer. If `projectID` isn't set, then it equals to `0`.
   - `<suffix>` may have the following values:
-     - `prometheus` and `prometheus/api/v1/write` - for inserting data with [Prometheus remote write API](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#remote_write)
-     - `influx/write` and `influx/api/v2/write` - for inserting data with [InfluxDB line protocol](https://docs.influxdata.com/influxdb/v1.7/write_protocols/line_protocol_tutorial/).
-     - `opentsdb/api/put` - for accepting [OpenTSDB HTTP /api/put requests](http://opentsdb.net/docs/build/html/api_http/put.html).
-       This handler is disabled by default. It is exposed on a distinct TCP address set via `-opentsdbHTTPListenAddr` command-line flag.
-       See [these docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#sending-opentsdb-data-via-http-apiput-requests) for details.
-     - `prometheus/api/v1/import` - for importing data obtained via `api/v1/export` on `vmselect` (see below).
+     - `prometheus` and `prometheus/api/v1/write` - for inserting data with [Prometheus remote write API](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#remote_write).
+     - `datadog/api/v1/series` - for inserting data with [DataDog submit metrics API](https://docs.datadoghq.com/api/latest/metrics/#submit-metrics). See [these docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-send-data-from-datadog-agent) for details.
+     - `influx/write` and `influx/api/v2/write` - for inserting data with [InfluxDB line protocol](https://docs.influxdata.com/influxdb/v1.7/write_protocols/line_protocol_tutorial/). See [these docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-send-data-from-influxdb-compatible-agents-such-as-telegraf) for details.
+     - `opentsdb/api/put` - for accepting [OpenTSDB HTTP /api/put requests](http://opentsdb.net/docs/build/html/api_http/put.html). This handler is disabled by default. It is exposed on a distinct TCP address set via `-opentsdbHTTPListenAddr` command-line flag. See [these docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#sending-opentsdb-data-via-http-apiput-requests) for details.
+     - `prometheus/api/v1/import` - for importing data obtained via `api/v1/export` at `vmselect` (see below).
      - `prometheus/api/v1/import/native` - for importing data obtained via `api/v1/export/native` on `vmselect` (see below).
      - `prometheus/api/v1/import/csv` - for importing arbitrary CSV data. See [these docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-import-csv-data) for details.
      - `prometheus/api/v1/import/prometheus` - for importing data in [Prometheus text exposition format](https://github.com/prometheus/docs/blob/master/content/docs/instrumenting/exposition_formats.md#text-based-format) and in [OpenMetrics format](https://github.com/OpenObservability/OpenMetrics/blob/master/specification/OpenMetrics.md). See [these docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-import-data-in-prometheus-exposition-format) for details.
diff --git a/docs/README.md b/docs/README.md
index 361883f47..1fb365097 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -265,6 +265,52 @@ VictoriaMetrics also supports [importing data in Prometheus exposition format](#
 See also [vmagent](https://docs.victoriametrics.com/vmagent.html), which can be used as drop-in replacement for Prometheus.
 
 
+## How to send data from DataDog agent
+
+VictoriaMetrics accepts data from [DataDog agent](https://docs.datadoghq.com/agent/) or [DogStatsD]() via ["submit metrics" API](https://docs.datadoghq.com/api/latest/metrics/#submit-metrics) at `/datadog/api/v1/series` path.
+
+Run DataDog agent with `DD_DD_URL=http://victoriametrics-host:8428/datadog` environment variable in order to write data to VictoriaMetrics at `victoriametrics-host` host. Another option is to set `dd_url` param at [DataDog agent configuration file](https://docs.datadoghq.com/agent/guide/agent-configuration-files/) to `http://victoriametrics-host:8428/datadog`.
+
+Example on how to send data to VictoriaMetrics via DataDog "submit metrics" API from command line:
+
+```bash
+echo '
+{
+  "series": [
+    {
+      "host": "test.example.com",
+      "interval": 20,
+      "metric": "system.load.1",
+      "points": [[
+        0,
+        0.5
+      ]],
+      "tags": [
+        "environment:test"
+      ],
+      "type": "rate"
+    }
+  ]
+}
+' | curl -X POST --data-binary @- http://localhost:8428/datadog/api/v1/series
+```
+
+The imported data can be read via [export API](https://docs.victoriametrics.com/#how-to-export-data-in-json-line-format):
+
+```bash
+curl http://localhost:8428/api/v1/export -d 'match[]=system.load.1'
+```
+
+This command should return the following output if everything is OK:
+
+```
+{"metric":{"__name__":"system.load.1","environment":"test","host":"test.example.com"},"values":[0.5],"timestamps":[1632833641000]}
+```
+
+Extra labels may be added to all the written time series by passing `extra_label=name=value` query args.
+For example, `/datadog/api/v1/series?extra_label=foo=bar` would add `{foo="bar"}` label to all the ingested metrics.
+
+
 ## How to send data from InfluxDB-compatible agents such as [Telegraf](https://www.influxdata.com/time-series-platform/telegraf/)
 
 Use `http://<victoriametric-addr>:8428` url instead of InfluxDB url in agents' configs.
@@ -790,6 +836,7 @@ The exported CSV data can be imported to VictoriaMetrics via [/api/v1/import/csv
 Time series data can be imported via any supported ingestion protocol:
 
 * [Prometheus remote_write API](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#remote_write). See [these docs](#prometheus-setup) for details.
+* DataDog `submit metrics` API. See [these docs](#how-to-send-data-from-datadog-agent) for details.
 * InfluxDB line protocol. See [these docs](#how-to-send-data-from-influxdb-compatible-agents-such-as-telegraf) for details.
 * Graphite plaintext protocol. See [these docs](#how-to-send-data-from-graphite-compatible-agents-such-as-statsd) for details.
 * OpenTSDB telnet put protocol. See [these docs](#sending-data-via-telnet-put-protocol) for details.
diff --git a/docs/Single-server-VictoriaMetrics.md b/docs/Single-server-VictoriaMetrics.md
index 106c5ca66..eff296f7b 100644
--- a/docs/Single-server-VictoriaMetrics.md
+++ b/docs/Single-server-VictoriaMetrics.md
@@ -269,6 +269,52 @@ VictoriaMetrics also supports [importing data in Prometheus exposition format](#
 See also [vmagent](https://docs.victoriametrics.com/vmagent.html), which can be used as drop-in replacement for Prometheus.
 
 
+## How to send data from DataDog agent
+
+VictoriaMetrics accepts data from [DataDog agent](https://docs.datadoghq.com/agent/) or [DogStatsD]() via ["submit metrics" API](https://docs.datadoghq.com/api/latest/metrics/#submit-metrics) at `/datadog/api/v1/series` path.
+
+Run DataDog agent with `DD_DD_URL=http://victoriametrics-host:8428/datadog` environment variable in order to write data to VictoriaMetrics at `victoriametrics-host` host. Another option is to set `dd_url` param at [DataDog agent configuration file](https://docs.datadoghq.com/agent/guide/agent-configuration-files/) to `http://victoriametrics-host:8428/datadog`.
+
+Example on how to send data to VictoriaMetrics via DataDog "submit metrics" API from command line:
+
+```bash
+echo '
+{
+  "series": [
+    {
+      "host": "test.example.com",
+      "interval": 20,
+      "metric": "system.load.1",
+      "points": [[
+        0,
+        0.5
+      ]],
+      "tags": [
+        "environment:test"
+      ],
+      "type": "rate"
+    }
+  ]
+}
+' | curl -X POST --data-binary @- http://localhost:8428/datadog/api/v1/series
+```
+
+The imported data can be read via [export API](https://docs.victoriametrics.com/#how-to-export-data-in-json-line-format):
+
+```bash
+curl http://localhost:8428/api/v1/export -d 'match[]=system.load.1'
+```
+
+This command should return the following output if everything is OK:
+
+```
+{"metric":{"__name__":"system.load.1","environment":"test","host":"test.example.com"},"values":[0.5],"timestamps":[1632833641000]}
+```
+
+Extra labels may be added to all the written time series by passing `extra_label=name=value` query args.
+For example, `/datadog/api/v1/series?extra_label=foo=bar` would add `{foo="bar"}` label to all the ingested metrics.
+
+
 ## How to send data from InfluxDB-compatible agents such as [Telegraf](https://www.influxdata.com/time-series-platform/telegraf/)
 
 Use `http://<victoriametric-addr>:8428` url instead of InfluxDB url in agents' configs.
@@ -794,6 +840,7 @@ The exported CSV data can be imported to VictoriaMetrics via [/api/v1/import/csv
 Time series data can be imported via any supported ingestion protocol:
 
 * [Prometheus remote_write API](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#remote_write). See [these docs](#prometheus-setup) for details.
+* DataDog `submit metrics` API. See [these docs](#how-to-send-data-from-datadog-agent) for details.
 * InfluxDB line protocol. See [these docs](#how-to-send-data-from-influxdb-compatible-agents-such-as-telegraf) for details.
 * Graphite plaintext protocol. See [these docs](#how-to-send-data-from-graphite-compatible-agents-such-as-statsd) for details.
 * OpenTSDB telnet put protocol. See [these docs](#sending-data-via-telnet-put-protocol) for details.
diff --git a/docs/vmagent.md b/docs/vmagent.md
index 66b5398b3..3e1426fa7 100644
--- a/docs/vmagent.md
+++ b/docs/vmagent.md
@@ -25,6 +25,7 @@ to `vmagent` such as the ability to push metrics instead of pulling them. We did
   See [Quick Start](#quick-start) for details.
 * Can add, remove and modify labels (aka tags) via Prometheus relabeling. Can filter data before sending it to remote storage. See [these docs](#relabeling) for details.
 * Accepts data via all ingestion protocols supported by VictoriaMetrics:
+  * DataDog "submit metrics" API. See [these docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-send-data-from-datadog-agent).
   * InfluxDB line protocol via `http://<vmagent>:8429/write`. See [these docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-send-data-from-influxdb-compatible-agents-such-as-telegraf).
   * Graphite plaintext protocol if `-graphiteListenAddr` command-line flag is set. See [these docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-send-data-from-graphite-compatible-agents-such-as-statsd).
   * OpenTSDB telnet and http protocols if `-opentsdbListenAddr` command-line flag is set. See [these docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-send-data-from-opentsdb-compatible-agents).
diff --git a/lib/promscrape/discovery/openstack/auth.go b/lib/promscrape/discovery/openstack/auth.go
index 03e4f3016..3208677b6 100644
--- a/lib/promscrape/discovery/openstack/auth.go
+++ b/lib/promscrape/discovery/openstack/auth.go
@@ -232,10 +232,7 @@ func buildScope(sdc *SDConfig) (map[string]interface{}, error) {
 		// ProjectName provided: either DomainID or DomainName must also be supplied.
 		// ProjectID may not be supplied.
 		if len(sdc.DomainID) == 0 && len(sdc.DomainName) == 0 {
-			return nil, fmt.Errorf("both domain_id and domain_name present")
-		}
-		if len(sdc.ProjectID) > 0 {
-			return nil, fmt.Errorf("both domain_id and domain_name present")
+			return nil, fmt.Errorf("domain_id or domain_name must present")
 		}
 		if len(sdc.DomainID) > 0 {
 			return map[string]interface{}{
@@ -254,13 +251,6 @@ func buildScope(sdc *SDConfig) (map[string]interface{}, error) {
 			}, nil
 		}
 	} else if len(sdc.ProjectID) > 0 {
-		// ProjectID provided. ProjectName, DomainID, and DomainName may not be provided.
-		if len(sdc.DomainID) > 0 {
-			return nil, fmt.Errorf("both project_id and domain_id present")
-		}
-		if len(sdc.DomainName) > 0 {
-			return nil, fmt.Errorf("both project_id and domain_name present")
-		}
 		return map[string]interface{}{
 			"project": map[string]interface{}{
 				"id": &sdc.ProjectID,
diff --git a/lib/protoparser/common/gzip_reader.go b/lib/protoparser/common/compress_reader.go
similarity index 55%
rename from lib/protoparser/common/gzip_reader.go
rename to lib/protoparser/common/compress_reader.go
index 8830a8335..a44dda0e9 100644
--- a/lib/protoparser/common/gzip_reader.go
+++ b/lib/protoparser/common/compress_reader.go
@@ -5,6 +5,7 @@ import (
 	"sync"
 
 	"github.com/klauspost/compress/gzip"
+	"github.com/klauspost/compress/zlib"
 )
 
 // GetGzipReader returns new gzip reader from the pool.
@@ -29,3 +30,24 @@ func PutGzipReader(zr *gzip.Reader) {
 }
 
 var gzipReaderPool sync.Pool
+
+// GetZlibReader returns zlib reader.
+func GetZlibReader(r io.Reader) (io.ReadCloser, error) {
+	v := zlibReaderPool.Get()
+	if v == nil {
+		return zlib.NewReader(r)
+	}
+	zr := v.(io.ReadCloser)
+	if err := zr.(zlib.Resetter).Reset(r, nil); err != nil {
+		return nil, err
+	}
+	return zr, nil
+}
+
+// PutZlibReader returns back zlib reader obtained via GetZlibReader.
+func PutZlibReader(zr io.ReadCloser) {
+	_ = zr.Close()
+	zlibReaderPool.Put(zr)
+}
+
+var zlibReaderPool sync.Pool
diff --git a/lib/protoparser/datadog/parser.go b/lib/protoparser/datadog/parser.go
new file mode 100644
index 000000000..ad539f293
--- /dev/null
+++ b/lib/protoparser/datadog/parser.go
@@ -0,0 +1,73 @@
+package datadog
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fasttime"
+)
+
+// Request represents DataDog POST request to /api/v1/series
+//
+// See https://docs.datadoghq.com/api/latest/metrics/#submit-metrics
+type Request struct {
+	Series []Series `json:"series"`
+}
+
+func (req *Request) reset() {
+	req.Series = req.Series[:0]
+}
+
+// Unmarshal unmarshals DataDog /api/v1/series request body from b to req.
+//
+// See https://docs.datadoghq.com/api/latest/metrics/#submit-metrics
+//
+// b shouldn't be modified when req is in use.
+func (req *Request) Unmarshal(b []byte) error {
+	req.reset()
+	if err := json.Unmarshal(b, req); err != nil {
+		return fmt.Errorf("cannot unmarshal %q: %w", b, err)
+	}
+	// Set missing timestamps to the current time.
+	currentTimestamp := float64(fasttime.UnixTimestamp())
+	series := req.Series
+	for i := range series {
+		points := series[i].Points
+		for j := range points {
+			if points[j][0] <= 0 {
+				points[j][0] = currentTimestamp
+			}
+		}
+	}
+	return nil
+}
+
+// Series represents a series item from DataDog POST request to /api/v1/series
+//
+// See https://docs.datadoghq.com/api/latest/metrics/#submit-metrics
+type Series struct {
+	Host string `json:"host"`
+
+	// Do not decode Interval, since it isn't used by VictoriaMetrics
+	// Interval int64 `json:"interval"`
+
+	Metric string   `json:"metric"`
+	Points []Point  `json:"points"`
+	Tags   []string `json:"tags"`
+
+	// Do not decode Type, since it isn't used by VictoriaMetrics
+	// Type string `json:"type"`
+}
+
+// Point represents a point from DataDog POST request to /api/v1/series
+type Point [2]float64
+
+// Timestamp returns timestamp in milliseconds from the given pt.
+func (pt *Point) Timestamp() int64 {
+	return int64(pt[0] * 1000)
+}
+
+// Value returns value from the given pt.
+func (pt *Point) Value() float64 {
+	return pt[1]
+}
diff --git a/lib/protoparser/datadog/streamparser.go b/lib/protoparser/datadog/streamparser.go
new file mode 100644
index 000000000..ace0165b0
--- /dev/null
+++ b/lib/protoparser/datadog/streamparser.go
@@ -0,0 +1,138 @@
+package datadog
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"sync"
+
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/bytesutil"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/cgroup"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fasttime"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/flagutil"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/protoparser/common"
+	"github.com/VictoriaMetrics/metrics"
+)
+
+// The maximum request size is defined at https://docs.datadoghq.com/api/latest/metrics/#submit-metrics
+var maxInsertRequestSize = flagutil.NewBytes("datadog.maxInsertRequestSize", 64*1024*1024, "The maximum size in bytes of a single DataDog POST request to /api/v1/series")
+
+// ParseStream parses DataDog POST request for /api/v1/series from reader and calls callback for the parsed request.
+//
+// callback shouldn't hold series after returning.
+func ParseStream(r io.Reader, contentEncoding string, callback func(series []Series) error) error {
+	switch contentEncoding {
+	case "gzip":
+		zr, err := common.GetGzipReader(r)
+		if err != nil {
+			return fmt.Errorf("cannot read gzipped DataDog data: %w", err)
+		}
+		defer common.PutGzipReader(zr)
+		r = zr
+	case "deflate":
+		zlr, err := common.GetZlibReader(r)
+		if err != nil {
+			return fmt.Errorf("cannot read deflated DataDog data: %w", err)
+		}
+		defer common.PutZlibReader(zlr)
+		r = zlr
+	}
+	ctx := getPushCtx(r)
+	defer putPushCtx(ctx)
+	if err := ctx.Read(); err != nil {
+		return err
+	}
+	req := getRequest()
+	defer putRequest(req)
+	if err := req.Unmarshal(ctx.reqBuf.B); err != nil {
+		unmarshalErrors.Inc()
+		return fmt.Errorf("cannot unmarshal DataDog POST request with size %d bytes: %s", len(ctx.reqBuf.B), err)
+	}
+	rows := 0
+	series := req.Series
+	for i := range series {
+		rows += len(series[i].Points)
+	}
+	rowsRead.Add(rows)
+
+	if err := callback(series); err != nil {
+		return fmt.Errorf("error when processing imported data: %w", err)
+	}
+	return nil
+}
+
+type pushCtx struct {
+	br     *bufio.Reader
+	reqBuf bytesutil.ByteBuffer
+}
+
+func (ctx *pushCtx) reset() {
+	ctx.br.Reset(nil)
+	ctx.reqBuf.Reset()
+}
+
+func (ctx *pushCtx) Read() error {
+	readCalls.Inc()
+	lr := io.LimitReader(ctx.br, int64(maxInsertRequestSize.N)+1)
+	startTime := fasttime.UnixTimestamp()
+	reqLen, err := ctx.reqBuf.ReadFrom(lr)
+	if err != nil {
+		readErrors.Inc()
+		return fmt.Errorf("cannot read compressed request in %d seconds: %w", fasttime.UnixTimestamp()-startTime, err)
+	}
+	if reqLen > int64(maxInsertRequestSize.N) {
+		readErrors.Inc()
+		return fmt.Errorf("too big packed request; mustn't exceed `-maxInsertRequestSize=%d` bytes", maxInsertRequestSize.N)
+	}
+	return nil
+}
+
+var (
+	readCalls       = metrics.NewCounter(`vm_protoparser_read_calls_total{type="datadog"}`)
+	readErrors      = metrics.NewCounter(`vm_protoparser_read_errors_total{type="datadog"}`)
+	rowsRead        = metrics.NewCounter(`vm_protoparser_rows_read_total{type="datadog"}`)
+	unmarshalErrors = metrics.NewCounter(`vm_protoparser_unmarshal_errors_total{type="datadog"}`)
+)
+
+func getPushCtx(r io.Reader) *pushCtx {
+	select {
+	case ctx := <-pushCtxPoolCh:
+		ctx.br.Reset(r)
+		return ctx
+	default:
+		if v := pushCtxPool.Get(); v != nil {
+			ctx := v.(*pushCtx)
+			ctx.br.Reset(r)
+			return ctx
+		}
+		return &pushCtx{
+			br: bufio.NewReaderSize(r, 64*1024),
+		}
+	}
+}
+
+func putPushCtx(ctx *pushCtx) {
+	ctx.reset()
+	select {
+	case pushCtxPoolCh <- ctx:
+	default:
+		pushCtxPool.Put(ctx)
+	}
+}
+
+var pushCtxPool sync.Pool
+var pushCtxPoolCh = make(chan *pushCtx, cgroup.AvailableCPUs())
+
+func getRequest() *Request {
+	v := requestPool.Get()
+	if v == nil {
+		return &Request{}
+	}
+	return v.(*Request)
+}
+
+func putRequest(req *Request) {
+	requestPool.Put(req)
+}
+
+var requestPool sync.Pool


Test patch:
diff --git a/lib/protoparser/datadog/parser_test.go b/lib/protoparser/datadog/parser_test.go
new file mode 100644
index 000000000..4cacf9721
--- /dev/null
+++ b/lib/protoparser/datadog/parser_test.go
@@ -0,0 +1,66 @@
+package datadog
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestRequestUnmarshalFailure(t *testing.T) {
+	f := func(s string) {
+		t.Helper()
+		var req Request
+		if err := req.Unmarshal([]byte(s)); err == nil {
+			t.Fatalf("expecting non-nil error for Unmarshal(%q)", s)
+		}
+	}
+	f("")
+	f("foobar")
+	f(`{"series":123`)
+	f(`1234`)
+	f(`[]`)
+}
+
+func TestRequestUnmarshalSuccess(t *testing.T) {
+	f := func(s string, reqExpected *Request) {
+		t.Helper()
+		var req Request
+		if err := req.Unmarshal([]byte(s)); err != nil {
+			t.Fatalf("unexpected error in Unmarshal(%q): %s", s, err)
+		}
+		if !reflect.DeepEqual(&req, reqExpected) {
+			t.Fatalf("unexpected row;\ngot\n%+v\nwant\n%+v", &req, reqExpected)
+		}
+	}
+	f("{}", &Request{})
+	f(`
+{
+  "series": [
+    {
+      "host": "test.example.com",
+      "interval": 20,
+      "metric": "system.load.1",
+      "points": [[
+        1575317847,
+        0.5
+      ]],
+      "tags": [
+        "environment:test"
+      ],
+      "type": "rate"
+    }
+  ]
+}
+`, &Request{
+		Series: []Series{{
+			Host:   "test.example.com",
+			Metric: "system.load.1",
+			Points: []Point{{
+				1575317847,
+				0.5,
+			}},
+			Tags: []string{
+				"environment:test",
+			},
+		}},
+	})
+}
diff --git a/lib/protoparser/datadog/parser_timing_test.go b/lib/protoparser/datadog/parser_timing_test.go
new file mode 100644
index 000000000..f3c2b568a
--- /dev/null
+++ b/lib/protoparser/datadog/parser_timing_test.go
@@ -0,0 +1,39 @@
+package datadog
+
+import (
+	"fmt"
+	"testing"
+)
+
+func BenchmarkRequestUnmarshal(b *testing.B) {
+	reqBody := []byte(`{
+  "series": [
+    {
+      "host": "test.example.com",
+      "interval": 20,
+      "metric": "system.load.1",
+      "points": [
+        1575317847,
+        0.5
+      ],
+      "tags": [
+        "environment:test"
+      ],
+      "type": "rate"
+    }
+  ]
+}`)
+	b.SetBytes(int64(len(reqBody)))
+	b.ReportAllocs()
+	b.RunParallel(func(pb *testing.PB) {
+		var req Request
+		for pb.Next() {
+			if err := req.Unmarshal(reqBody); err != nil {
+				panic(fmt.Errorf("unexpected error: %w", err))
+			}
+			if len(req.Series) != 1 {
+				panic(fmt.Errorf("unexpected number of series unmarshaled: got %d; want 4", len(req.Series)))
+			}
+		}
+	})
+}