feat: receiver/prometheusremotewrite - Content-Type negotiation

Signed-off-by: Arthur Silva Sens <[email protected]>

.chloggen/prwreceiver-content-type.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: receiver/prometheusremotewrite
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Implement Content-Type negotiation for Prometheus Remote Write requests
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [35565]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: Warning - The HTTP Server still doesn't do anything. It's just a placeholder for now.
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api, user]

receiver/prometheusremotewritereceiver/receiver.go

@@ -8,12 +8,15 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"strings"
 	"time"
 
+	promConfig "github.com/prometheus/prometheus/config"
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/component/componentstatus"
 	"go.opentelemetry.io/collector/consumer"
 	"go.opentelemetry.io/collector/receiver"
+	"go.uber.org/zap/zapcore"
 )
 
 func newRemoteWriteReceiver(settings receiver.Settings, cfg *Config, nextConsumer consumer.Metrics) (receiver.Metrics, error) {
@@ -31,8 +34,8 @@ type prometheusRemoteWriteReceiver struct {
 	settings     receiver.Settings
 	nextConsumer consumer.Metrics
 
-	config *Config
-	server *http.Server
+	config  *Config
+	server  *http.Server
 }
 
 func (prw *prometheusRemoteWriteReceiver) Start(ctx context.Context, host component.Host) error {
@@ -64,6 +67,53 @@ func (prw *prometheusRemoteWriteReceiver) Shutdown(ctx context.Context) error {
 	return prw.server.Shutdown(ctx)
 }
 
-func (prw *prometheusRemoteWriteReceiver) handlePRW(_ http.ResponseWriter, _ *http.Request) {
-	fmt.Println("handleWrite called")
+func (prw *prometheusRemoteWriteReceiver) handlePRW(w http.ResponseWriter, req *http.Request) {
+	contentType := req.Header.Get("Content-Type")
+	if contentType == "" {
+		prw.settings.Logger.Warn("message received without Content-Type header, rejecting")
+		http.Error(w, "Content-Type header is required", http.StatusUnsupportedMediaType)
+		return
+	}
+
+	msgType, err := prw.parseProto(contentType)
+	if err != nil {
+		prw.settings.Logger.Warn("Error decoding remote-write request", zapcore.Field{Key: "error", Type: zapcore.ErrorType, Interface: err})
+		http.Error(w, err.Error(), http.StatusUnsupportedMediaType)
+		return
+	}
+	if msgType != promConfig.RemoteWriteProtoMsgV2 {
+		prw.settings.Logger.Warn("message received with unsupported proto version, rejecting")
+		http.Error(w, "Unsupported proto version", http.StatusUnsupportedMediaType)
+		return
+	}
+}
+
+// parseProto parses the content-type header and returns the version of the remote-write protocol.
+// We can't expect that senders of remote-write v1 will add the "proto=" parameter since it was not
+// a requirement in v1. So, if the parameter is not found, we assume v1.
+func (prw *prometheusRemoteWriteReceiver) parseProto(contentType string) (promConfig.RemoteWriteProtoMsg, error) {
+	contentType = strings.TrimSpace(contentType)
+
+	parts := strings.Split(contentType, ";")
+	if parts[0] != "application/x-protobuf" {
+		return "", fmt.Errorf("expected %q as the first (media) part, got %v content-type", "application/x-protobuf", contentType)
+	}
+
+	for _, part := range parts[1:] {
+		parameter := strings.Split(part, "=")
+		if len(parameter) != 2 {
+			return "", fmt.Errorf("as per https://www.rfc-editor.org/rfc/rfc9110#parameter expected parameters to be key-values, got %v in %v content-type", part, contentType)
+		}
+
+		if strings.TrimSpace(parameter[0]) == "proto" {
+			ret := promConfig.RemoteWriteProtoMsg(parameter[1])
+			if err := ret.Validate(); err != nil {
+				return "", fmt.Errorf("got %v content type; %w", contentType, err)
+			}
+			return ret, nil
+		}
+	}
+
+	// No "proto=" parameter found, assume v1.
+	return promConfig.RemoteWriteProtoMsgV1, nil
 }

receiver/prometheusremotewritereceiver/receiver_test.go

@@ -0,0 +1,77 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package prometheusremotewritereceiver // import "github.com/open-telemetry/opentelemetry-collector-contrib/receiver/prometheusremotewritereceiver"
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"testing"
+
+	promConfig "github.com/prometheus/prometheus/config"
+	"github.com/stretchr/testify/assert"
+	"go.opentelemetry.io/collector/component/componenttest"
+	"go.opentelemetry.io/collector/consumer/consumertest"
+	"go.opentelemetry.io/collector/receiver/receivertest"
+)
+
+func TestHandlePRWContentTypeNegotiation(t *testing.T) {
+	factory := NewFactory()
+	cfg := factory.CreateDefaultConfig()
+
+	prwReceiver, err := factory.CreateMetricsReceiver(context.Background(), receivertest.NewNopSettings(), cfg, consumertest.NewNop())
+	assert.NoError(t, err)
+	assert.NotNil(t, prwReceiver, "metrics receiver creation failed")
+
+	ctx, cancel := context.WithCancel(context.Background())
+	t.Cleanup(cancel)
+
+	assert.NoError(t, prwReceiver.Start(ctx, componenttest.NewNopHost()))
+	t.Cleanup(func() {
+		assert.NoError(t, prwReceiver.Shutdown(ctx), "Must not error shutting down")
+	})
+
+	for _, tc := range []struct {
+		name         string
+		contentType  string
+		extectedCode int
+	}{
+		{
+			name:         "no content type",
+			contentType:  "",
+			extectedCode: http.StatusUnsupportedMediaType,
+		},
+		{
+			name:         "unsupported content type",
+			contentType:  "application/json",
+			extectedCode: http.StatusUnsupportedMediaType,
+		},
+		{
+			name:         "x-protobuf/no proto parameter",
+			contentType:  "application/x-protobuf",
+			extectedCode: http.StatusUnsupportedMediaType,
+		},
+		{
+			name:         "x-protobuf/v1 proto parameter",
+			contentType:  fmt.Sprintf("application/x-protobuf;proto=%s", promConfig.RemoteWriteProtoMsgV1),
+			extectedCode: http.StatusUnsupportedMediaType,
+		},
+		{
+			name:         "x-protobuf/v2 proto parameter",
+			contentType:  fmt.Sprintf("application/x-protobuf;proto=%s", promConfig.RemoteWriteProtoMsgV2),
+			extectedCode: http.StatusOK,
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			req, err := http.NewRequest(http.MethodPost, "http://localhost:9090/api/v1/write", nil)
+			assert.NoError(t, err)
+
+			req.Header.Set("Content-Type", tc.contentType)
+			resp, err := http.DefaultClient.Do(req)
+			assert.NoError(t, err)
+
+			assert.Equal(t, tc.extectedCode, resp.StatusCode)
+		})
+	}
+}