sdk/metric: Record measurements when context is done

CHANGELOG.md

@@ -20,6 +20,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ### Changed
 
+- Record synchronous measurements when the passed context is canceled instead of dropping in `go.opentelemetry.io/otel/sdk/metric`.
+  If you do not want to make measurment in such scenario then you need to handle it yourself.
+  You can do it e.g. by adding `if ctx.Err() != nil` condition before making the measurement.
+  However, we believe that you rather not want it as the telemetry may be necessary to diagnose a cancellation-related problem. (#4671)
 - Improve `go.opentelemetry.io/otel/trace.TraceState`'s performance. (#4722)
 - Improve `go.opentelemetry.io/otel/propagation.TraceContext`'s performance. (#4721)
 - Improve `go.opentelemetry.io/otel/baggage` performance. (#4743)

CONTRIBUTING.md

@@ -591,6 +591,20 @@ this.
 
 [^3]: https://github.com/open-telemetry/opentelemetry-go/issues/3548
 
+### Honoring context cancellation
+
+The implementation of OpenTelemetry API that is responsible for telemetry recording
+(starting a span, making a synchronous metric measurement, emitting a log)
+must not honor the cancelation of the passed context.
+Among other things, the telemetry may be necessary to diagnose a
+cancellation-related problem.
+The context can be used to pass request-scoped values
+such as Trace ID and Span ID.
+
+For other use cases
+(exporting telemetry, force flushing telemetry, shutting down a signal provider)
+the context cancelation should be honored.
+
 ## Approvers and Maintainers
 
 ### Approvers

sdk/metric/instrument.go

@@ -205,9 +205,6 @@ func (i *int64Inst) Record(ctx context.Context, val int64, opts ...metric.Record
 }
 
 func (i *int64Inst) aggregate(ctx context.Context, val int64, s attribute.Set) { // nolint:revive  // okay to shadow pkg with method.
-	if err := ctx.Err(); err != nil {
-		return
-	}
 	for _, in := range i.measures {
 		in(ctx, val, s)
 	}
@@ -238,9 +235,6 @@ func (i *float64Inst) Record(ctx context.Context, val float64, opts ...metric.Re
 }
 
 func (i *float64Inst) aggregate(ctx context.Context, val float64, s attribute.Set) {
-	if err := ctx.Err(); err != nil {
-		return
-	}
 	for _, in := range i.measures {
 		in(ctx, val, s)
 	}

sdk/metric/meter_test.go

@@ -168,6 +168,10 @@ func TestCallbackUnregisterConcurrency(t *testing.T) {
 
 // Instruments should produce correct ResourceMetrics.
 func TestMeterCreatesInstruments(t *testing.T) {
+	// The synchronous measurement methods must ignore the context cancelation.
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
 	attrs := attribute.NewSet(attribute.String("name", "alice"))
 	opt := metric.WithAttributeSet(attrs)
 	testCases := []struct {
@@ -340,7 +344,7 @@ func TestMeterCreatesInstruments(t *testing.T) {
 				ctr, err := m.Int64Counter("sint")
 				assert.NoError(t, err)
 
-				ctr.Add(context.Background(), 3)
+				ctr.Add(ctx, 3)
 			},
 			want: metricdata.Metrics{
 				Name: "sint",
@@ -359,7 +363,7 @@ func TestMeterCreatesInstruments(t *testing.T) {
 				ctr, err := m.Int64UpDownCounter("sint")
 				assert.NoError(t, err)
 
-				ctr.Add(context.Background(), 11)
+				ctr.Add(ctx, 11)
 			},
 			want: metricdata.Metrics{
 				Name: "sint",
@@ -378,7 +382,7 @@ func TestMeterCreatesInstruments(t *testing.T) {
 				gauge, err := m.Int64Histogram("histogram")
 				assert.NoError(t, err)
 
-				gauge.Record(context.Background(), 7)
+				gauge.Record(ctx, 7)
 			},
 			want: metricdata.Metrics{
 				Name: "histogram",
@@ -404,7 +408,7 @@ func TestMeterCreatesInstruments(t *testing.T) {
 				ctr, err := m.Float64Counter("sfloat")
 				assert.NoError(t, err)
 
-				ctr.Add(context.Background(), 3)
+				ctr.Add(ctx, 3)
 			},
 			want: metricdata.Metrics{
 				Name: "sfloat",
@@ -423,7 +427,7 @@ func TestMeterCreatesInstruments(t *testing.T) {
 				ctr, err := m.Float64UpDownCounter("sfloat")
 				assert.NoError(t, err)
 
-				ctr.Add(context.Background(), 11)
+				ctr.Add(ctx, 11)
 			},
 			want: metricdata.Metrics{
 				Name: "sfloat",
@@ -442,7 +446,7 @@ func TestMeterCreatesInstruments(t *testing.T) {
 				gauge, err := m.Float64Histogram("histogram")
 				assert.NoError(t, err)
 
-				gauge.Record(context.Background(), 7)
+				gauge.Record(ctx, 7)
 			},
 			want: metricdata.Metrics{
 				Name: "histogram",

sdk/trace/trace_test.go

@@ -1133,6 +1133,18 @@ func TestNilSpanEnd(t *testing.T) {
 	span.End()
 }
 
+func TestSpanWithCanceledContext(t *testing.T) {
+	te := NewTestExporter()
+	tp := NewTracerProvider(WithSyncer(te))
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	_, span := tp.Tracer(t.Name()).Start(ctx, "span")
+	span.End()
+
+	assert.Equal(t, 1, te.Len(), "span recording must ignore context cancelation")
+}
+
 func TestNonRecordingSpanDoesNotTrackRuntimeTracerTask(t *testing.T) {
 	tp := NewTracerProvider(WithSampler(NeverSample()))
 	tr := tp.Tracer("TestNonRecordingSpanDoesNotTrackRuntimeTracerTask")