[dtest] Add a method for Prom remote writes (#3065)

src/cmd/tools/dtest/docker/harness/query_api_test.go

@@ -73,7 +73,9 @@ func testInvalidQueryReturns400(t *testing.T, tests []urlTest) {
 	coord := singleDBNodeDockerResources.Coordinator()
 
 	for _, tt := range tests {
+		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
 			assert.NoError(t, coord.RunQuery(verifyResponse(400), tt.url), "for query '%v'", tt.url)
 		})
 	}

src/cmd/tools/dtest/docker/harness/resources/coordinator.go

@@ -30,10 +30,14 @@ import (
 	"time"
 
 	"github.com/m3db/m3/src/query/generated/proto/admin"
+	"github.com/m3db/m3/src/query/generated/proto/prompb"
+	xhttp "github.com/m3db/m3/src/x/net/http"
 
 	"github.com/gogo/protobuf/jsonpb"
 	"github.com/gogo/protobuf/proto"
+	"github.com/golang/snappy"
 	"github.com/ory/dockertest/v3"
+	"github.com/prometheus/common/model"
 	"go.uber.org/zap"
 )
 
@@ -66,6 +70,8 @@ type Coordinator interface {
 
 	// WriteCarbon writes a carbon metric datapoint at a given time.
 	WriteCarbon(port int, metric string, v float64, t time.Time) error
+	// WriteProm writes a prometheus metric.
+	WriteProm(name string, tags map[string]string, samples []prompb.Sample) error
 	// RunQuery runs the given query with a given verification function.
 	RunQuery(verifier ResponseVerifier, query string) error
 }
@@ -323,6 +329,65 @@ func (c *coordinator) WriteCarbon(
 	// return nil
 }
 
+func (c *coordinator) WriteProm(name string, tags map[string]string, samples []prompb.Sample) error {
+	if c.resource.closed {
+		return errClosed
+	}
+
+	var (
+		url       = c.resource.getURL(7201, "api/v1/prom/remote/write")
+		reqLabels = []prompb.Label{{Name: []byte(model.MetricNameLabel), Value: []byte(name)}}
+	)
+
+	for tag, value := range tags {
+		reqLabels = append(reqLabels, prompb.Label{
+			Name:  []byte(tag),
+			Value: []byte(value),
+		})
+	}
+	writeRequest := prompb.WriteRequest{
+		Timeseries: []prompb.TimeSeries{
+			{
+				Labels:  reqLabels,
+				Samples: samples,
+			},
+		},
+	}
+
+	logger := c.resource.logger.With(
+		zapMethod("createDatabase"), zap.String("url", url),
+		zap.String("request", writeRequest.String()))
+
+	body, err := proto.Marshal(&writeRequest)
+	if err != nil {
+		logger.Error("failed marshaling request message", zap.Error(err))
+		return err
+	}
+	data := bytes.NewBuffer(snappy.Encode(nil, body))
+
+	req, err := http.NewRequestWithContext(context.Background(), http.MethodPost, url, data)
+	if err != nil {
+		logger.Error("failed constructing request", zap.Error(err))
+		return err
+	}
+	req.Header.Add(xhttp.HeaderContentType, xhttp.ContentTypeProtobuf)
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		logger.Error("failed making a request", zap.Error(err))
+		return err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode < 200 || resp.StatusCode > 299 {
+		logger.Error("status code not 2xx",
+			zap.Int("status code", resp.StatusCode),
+			zap.String("status", resp.Status))
+		return fmt.Errorf("status code %d", resp.StatusCode)
+	}
+
+	return nil
+}
+
 func makePostRequest(logger *zap.Logger, url string, body proto.Message) (*http.Response, error) {
 	data := bytes.NewBuffer(nil)
 	if err := (&jsonpb.Marshaler{}).Marshal(data, body); err != nil {
@@ -338,7 +403,7 @@ func makePostRequest(logger *zap.Logger, url string, body proto.Message) (*http.
 		return nil, fmt.Errorf("failed to construct request: %w", err)
 	}
 
-	req.Header.Add("Content-Type", "application/json")
+	req.Header.Add(xhttp.HeaderContentType, xhttp.ContentTypeJSON)
 
 	return http.DefaultClient.Do(req)
 }