[exporter/datadog] Run source providers in parallel

.chloggen/mx-psi_parallel-source-resolution.yaml

@@ -0,0 +1,21 @@
+# Use this changelog template to create an entry for release notes.
+# If your change doesn't affect end users, such as a test fix or a tooling change,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+
+# 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: datadogexporter
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Source resolution logic now runs all source providers in parallel to improve start times."
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [24234]
+
+# (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: |
+  All source providers now run in all environments so you may see more spurious logs from downstream dependencies when using the Datadog exporter.

exporter/datadogexporter/internal/hostmetadata/provider/provider.go

@@ -22,15 +22,47 @@ type chainProvider struct {
 }
 
 func (p *chainProvider) Source(ctx context.Context) (source.Source, error) {
-	for _, source := range p.priorityList {
-		zapProvider := zap.String("provider", source)
+	// Auxiliary type for storing source provider replies
+	type reply struct {
+		src source.Source
+		err error
+	}
+
+	// Cancel all providers when exiting
+	ctx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	// Run all providers in parallel
+	replies := make([]chan reply, len(p.priorityList))
+	for i, source := range p.priorityList {
 		provider := p.providers[source]
-		src, err := provider.Source(ctx)
-		if err == nil {
-			p.logger.Info("Resolved source", zapProvider, zap.Any("source", src))
-			return src, nil
+		replies[i] = make(chan reply)
+
+		go func(i int, source string) {
+			zapProvider := zap.String("provider", source)
+			p.logger.Debug("Trying out source provider", zapProvider)
+
+			src, err := provider.Source(ctx)
+			if err != nil {
+				p.logger.Debug("Unavailable source provider", zapProvider, zap.Error(err))
+			}
+
+			replies[i] <- reply{src: src, err: err}
+		}(i, source)
+	}
+
+	// Check provider responses in order to ensure priority
+	for i, ch := range replies {
+		reply := <-ch
+		if reply.err != nil {
+			// Provider was unavailable, error was logged on goroutine
+			continue
 		}
-		p.logger.Debug("Unavailable source provider", zapProvider, zap.Error(err))
+
+		p.logger.Info("Resolved source",
+			zap.String("provider", p.priorityList[i]), zap.Any("source", reply.src),
+		)
+		return reply.src, nil
 	}
 
 	return source.Source{}, fmt.Errorf("no source provider was available")

exporter/datadogexporter/internal/hostmetadata/provider/provider_test.go

@@ -0,0 +1,132 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package provider // import "github.com/open-telemetry/opentelemetry-collector-contrib/exporter/datadogexporter/internal/hostmetadata/provider"
+
+import (
+	"context"
+	"errors"
+	"testing"
+	"time"
+
+	"github.com/DataDog/opentelemetry-mapping-go/pkg/otlp/attributes/source"
+	"github.com/stretchr/testify/assert"
+	"go.uber.org/zap/zaptest"
+)
+
+var _ source.Provider = (*HostProvider)(nil)
+
+type HostProvider string
+
+func (p HostProvider) Source(context.Context) (source.Source, error) {
+	return source.Source{Kind: source.HostnameKind, Identifier: string(p)}, nil
+}
+
+var _ source.Provider = (*ErrorSourceProvider)(nil)
+
+type ErrorSourceProvider string
+
+func (p ErrorSourceProvider) Source(context.Context) (source.Source, error) {
+	return source.Source{}, errors.New(string(p))
+}
+
+var _ source.Provider = (*delayedProvider)(nil)
+
+type delayedProvider struct {
+	provider source.Provider
+	delay    time.Duration
+}
+
+func (p *delayedProvider) Source(ctx context.Context) (source.Source, error) {
+	time.Sleep(p.delay)
+	return p.provider.Source(ctx)
+}
+
+func withDelay(provider source.Provider, delay time.Duration) source.Provider {
+	return &delayedProvider{provider, delay}
+}
+
+func TestChain(t *testing.T) {
+	tests := []struct {
+		name         string
+		providers    map[string]source.Provider
+		priorityList []string
+
+		buildErr string
+
+		hostname string
+		queryErr string
+	}{
+		{
+			name: "missing provider in priority list",
+			providers: map[string]source.Provider{
+				"p1": HostProvider("p1SourceName"),
+				"p2": ErrorSourceProvider("errP2"),
+			},
+			priorityList: []string{"p1", "p2", "p3"},
+
+			buildErr: "\"p3\" source is not available in providers",
+		},
+		{
+			name: "all providers fail",
+			providers: map[string]source.Provider{
+				"p1": ErrorSourceProvider("errP1"),
+				"p2": ErrorSourceProvider("errP2"),
+				"p3": HostProvider("p3SourceName"),
+			},
+			priorityList: []string{"p1", "p2"},
+
+			queryErr: "no source provider was available",
+		},
+		{
+			name: "no providers fail",
+			providers: map[string]source.Provider{
+				"p1": HostProvider("p1SourceName"),
+				"p2": HostProvider("p2SourceName"),
+				"p3": HostProvider("p3SourceName"),
+			},
+			priorityList: []string{"p1", "p2", "p3"},
+
+			hostname: "p1SourceName",
+		},
+		{
+			name: "some providers fail",
+			providers: map[string]source.Provider{
+				"p1": ErrorSourceProvider("p1Err"),
+				"p2": HostProvider("p2SourceName"),
+				"p3": ErrorSourceProvider("p3Err"),
+			},
+			priorityList: []string{"p1", "p2", "p3"},
+
+			hostname: "p2SourceName",
+		},
+		{
+			name: "p2 takes longer than p3",
+			providers: map[string]source.Provider{
+				"p1": ErrorSourceProvider("p1Err"),
+				"p2": withDelay(HostProvider("p2SourceName"), 50*time.Millisecond),
+				"p3": HostProvider("p3SourceName"),
+			},
+			priorityList: []string{"p1", "p2", "p3"},
+
+			hostname: "p2SourceName",
+		},
+	}
+
+	for _, testInstance := range tests {
+		t.Run(testInstance.name, func(t *testing.T) {
+			provider, err := Chain(zaptest.NewLogger(t), testInstance.providers, testInstance.priorityList)
+			if err != nil || testInstance.buildErr != "" {
+				assert.EqualError(t, err, testInstance.buildErr)
+				return
+			}
+
+			src, err := provider.Source(context.Background())
+			if err != nil || testInstance.queryErr != "" {
+				assert.EqualError(t, err, testInstance.queryErr)
+			} else {
+				assert.Equal(t, testInstance.hostname, src.Identifier)
+			}
+		})
+	}
+}