Implemented merged context with link

.chloggen/merged_context.yaml

@@ -0,0 +1,25 @@
+# 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. otlpreceiver)
+component: exporterhelper
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Link batcher context to all batched request's span contexts.
+
+# One or more tracking issues or pull requests related to the change
+issues: []
+
+# (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:
+
+# 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: [user]

exporter/exporterhelper/internal/batcher/default_batcher.go

@@ -17,7 +17,7 @@ import (
 )
 
 type batch struct {
-	ctx  context.Context
+	ctx  mergedContext
 	req  request.Request
 	done multiDone
 }
@@ -86,7 +86,7 @@ func (qb *defaultBatcher) Consume(ctx context.Context, req request.Request, done
 			// Do not flush the last item and add it to the current batch.
 			reqList = reqList[:len(reqList)-1]
 			qb.currentBatch = &batch{
-				ctx:  ctx,
+				ctx:  NewMergedContext(ctx),
 				req:  lastReq,
 				done: multiDone{done},
 			}
@@ -120,9 +120,10 @@ func (qb *defaultBatcher) Consume(ctx context.Context, req request.Request, done
 	// - Last result may not have enough data to be flushed.
 
 	// Logic on how to deal with the current batch:
-	// TODO: Deal with merging Context.
 	qb.currentBatch.req = reqList[0]
 	qb.currentBatch.done = append(qb.currentBatch.done, done)
+	qb.currentBatch.ctx = qb.currentBatch.ctx.Merge(qb.currentBatch.ctx)
+
 	// Save the "currentBatch" if we need to flush it, because we want to execute flush without holding the lock, and
 	// cannot unlock and re-lock because we are not done processing all the responses.
 	var firstBatch *batch
@@ -141,7 +142,7 @@ func (qb *defaultBatcher) Consume(ctx context.Context, req request.Request, done
 			// Do not flush the last item and add it to the current batch.
 			reqList = reqList[:len(reqList)-1]
 			qb.currentBatch = &batch{
-				ctx:  ctx,
+				ctx:  NewMergedContext(ctx),
 				req:  lastReq,
 				done: multiDone{done},
 			}

exporter/exporterhelper/internal/batcher/merged_context.go

@@ -0,0 +1,63 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package batcher // import "go.opentelemetry.io/collector/exporter/internal/queue"
+import (
+	"context"
+	"time"
+
+	"go.opentelemetry.io/otel/trace"
+)
+
+// mergedContext links the underlying context to all incoming span contexts.
+type mergedContext struct {
+	deadline   time.Time
+	deadlineOk bool
+	ctx        context.Context
+}
+
+func NewMergedContext(ctx context.Context) mergedContext {
+	deadline, ok := ctx.Deadline()
+	return mergedContext{
+		deadline:   deadline,
+		deadlineOk: ok,
+		ctx:        ctx,
+	}
+}
+
+// Merge links the span from incoming context to the span from the first context.
+func (mc *mergedContext) Merge(other context.Context) mergedContext {
+	deadline, deadlineOk := mc.Deadline()
+	if otherDeadline, ok := other.Deadline(); ok {
+		deadlineOk = true
+		if deadline.Before(otherDeadline) {
+			deadline = otherDeadline
+		}
+	}
+
+	link := trace.LinkFromContext(other)
+	trace.SpanFromContext(mc.ctx).AddLink(link)
+	return mergedContext{
+		deadline:   deadline,
+		deadlineOk: deadlineOk,
+		ctx:        mc.ctx,
+	}
+}
+
+// Deadline returns the latest deadline of all context.
+func (mc mergedContext) Deadline() (time.Time, bool) {
+	return mc.deadline, mc.deadlineOk
+}
+
+func (mc mergedContext) Done() <-chan struct{} {
+	return nil
+}
+
+func (mc mergedContext) Err() error {
+	return nil
+}
+
+// Value delegates to the first context.
+func (mc mergedContext) Value(key any) any {
+	return mc.ctx.Value(key)
+}

exporter/exporterhelper/internal/batcher/merged_context_test.go

@@ -0,0 +1,68 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package batcher
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/collector/component/componenttest"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+	"go.opentelemetry.io/otel/trace"
+)
+
+func TestMergedContextDeadline(t *testing.T) {
+	now := time.Now()
+	ctx1 := context.Background()
+	mergedContext := NewMergedContext(ctx1)
+
+	deadline, ok := mergedContext.Deadline()
+	require.False(t, ok)
+
+	ctx2, cancel2 := context.WithDeadline(context.Background(), now.Add(200))
+	defer cancel2()
+	mergedContext = mergedContext.Merge(ctx2)
+
+	deadline, ok = mergedContext.Deadline()
+	require.True(t, ok)
+	require.Equal(t, now.Add(200), deadline)
+
+	ctx3, cancel3 := context.WithDeadline(context.Background(), now.Add(300))
+	defer cancel3()
+	ctx4, cancel4 := context.WithDeadline(context.Background(), now.Add(100))
+	defer cancel4()
+	mergedContext = mergedContext.Merge(ctx3)
+	mergedContext = mergedContext.Merge(ctx4)
+
+	deadline, ok = mergedContext.Deadline()
+	require.True(t, ok)
+	require.Equal(t, now.Add(300), deadline)
+}
+
+func TestMergedContextLink(t *testing.T) {
+	tracerProvider := componenttest.NewTelemetry().NewTelemetrySettings().TracerProvider
+	tracer := tracerProvider.Tracer("go.opentelemetry.io/collector/exporter/exporterhelper")
+
+	ctx1 := context.WithValue(context.Background(), "key", "value")
+	ctx2, span2 := tracer.Start(ctx1, "span2")
+	defer span2.End()
+
+	mergedContext := NewMergedContext(ctx2)
+	ctx3, span3 := tracer.Start(ctx1, "span3")
+	defer span3.End()
+	mergedContext = mergedContext.Merge(ctx3)
+	ctx4, span4 := tracer.Start(ctx1, "span3")
+	defer span4.End()
+	mergedContext = mergedContext.Merge(ctx4)
+
+	span2.AddEvent("This is an event.")
+
+	spanFromMergedContext := trace.SpanFromContext(mergedContext)
+	require.Equal(t, span2, spanFromMergedContext)
+
+	require.Equal(t, trace.SpanContextFromContext(ctx3), span2.(sdktrace.ReadOnlySpan).Links()[0].SpanContext)
+	require.Equal(t, trace.SpanContextFromContext(ctx4), span2.(sdktrace.ReadOnlySpan).Links()[1].SpanContext)
+}