stats/opentelemetry: dynamically calculate compressed message size in tests (#9346)

Tests in `stats/opentelemetry` and `stats/opentelemetry/csm` asserted a
hardcoded compressed message size of `57` bytes for a 10,000-byte zero
payload with gzip compression.
In Go 1.27, standard library `compress/gzip` compression improvements
changed the output size of this payload from 57 bytes to 54 bytes,
causing metric and trace size assertions to fail when executed under
newer Go toolchains.

Added `GzipCompressedMessageSize` helper in to compute the expected
compressed byte length dynamically via `compress/gzip`. Updated metric
and trace assertions to use the same.

RELEASE NOTES: None

Author: eshitachandwani

stats/opentelemetry/csm/observability_test.go

@@ -131,6 +131,7 @@ func (s) TestCSMPluginOptionUnary(t *testing.T) {
 	}
 	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
 	defer cancel()
+	unaryCompressedSize := float64(itestutils.GzipCompressedMessageSize(t, &testpb.SimpleRequest{Payload: &testpb.Payload{Body: make([]byte, 10000)}}))
 	tests := []struct {
 		name string
 		// To test the different operations for Unary RPC's from the interceptor
@@ -147,7 +148,7 @@ func (s) TestCSMPluginOptionUnary(t *testing.T) {
 			},
 			opts: itestutils.MetricDataOptions{
 				CSMLabels:                  csmLabels,
-				UnaryCompressedMessageSize: float64(57),
+				UnaryCompressedMessageSize: unaryCompressedSize,
 			},
 		},
 		{
@@ -171,7 +172,7 @@ func (s) TestCSMPluginOptionUnary(t *testing.T) {
 			},
 			opts: itestutils.MetricDataOptions{
 				CSMLabels:                  csmLabels,
-				UnaryCompressedMessageSize: float64(57),
+				UnaryCompressedMessageSize: unaryCompressedSize,
 			},
 		},
 		{
@@ -185,7 +186,7 @@ func (s) TestCSMPluginOptionUnary(t *testing.T) {
 			},
 			opts: itestutils.MetricDataOptions{
 				CSMLabels:                  csmLabels,
-				UnaryCompressedMessageSize: float64(57),
+				UnaryCompressedMessageSize: unaryCompressedSize,
 			},
 		},
 		{
@@ -197,7 +198,7 @@ func (s) TestCSMPluginOptionUnary(t *testing.T) {
 			},
 			opts: itestutils.MetricDataOptions{
 				CSMLabels:                  csmLabels,
-				UnaryCompressedMessageSize: float64(57),
+				UnaryCompressedMessageSize: unaryCompressedSize,
 			},
 		},
 	}
@@ -299,6 +300,7 @@ func (s) TestCSMPluginOptionStreaming(t *testing.T) {
 	}
 	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
 	defer cancel()
+	streamingCompressedSize := float64(itestutils.GzipCompressedMessageSize(t, &testpb.StreamingOutputCallRequest{Payload: &testpb.Payload{Body: make([]byte, 10000)}}))
 	tests := []struct {
 		name string
 		// To test the different operations for Streaming RPC's from the
@@ -361,7 +363,7 @@ func (s) TestCSMPluginOptionStreaming(t *testing.T) {
 			},
 			opts: itestutils.MetricDataOptions{
 				CSMLabels:                      csmLabels,
-				StreamingCompressedMessageSize: float64(57),
+				StreamingCompressedMessageSize: streamingCompressedSize,
 			},
 		},
 	}
@@ -510,9 +512,13 @@ func (s) TestXDSLabels(t *testing.T) {
 		customLabelAttr,
 	}
 
-	unaryCompressedBytesSentRecv := int64(57) // Fixed 10000 bytes with gzip assumption.
+	unaryCompressedBytesSentRecv := int64(itestutils.GzipCompressedMessageSize(t, &testpb.SimpleRequest{
+		Payload: &testpb.Payload{
+			Body: make([]byte, 10000),
+		},
+	})) // Fixed 10000 bytes with gzip.
 	unaryBucketCounts := []uint64{0x0, 0x1, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}
-	unaryExtrema := metricdata.NewExtrema(int64(57))
+	unaryExtrema := metricdata.NewExtrema(unaryCompressedBytesSentRecv)
 	wantMetrics := []metricdata.Metrics{
 		{
 			Name:        "grpc.client.attempt.started",

stats/opentelemetry/e2e_test.go

@@ -443,9 +443,10 @@ func (s) TestAllMetricsOneFunction(t *testing.T) {
 		}
 	}
 
+	compressedSize := testutils.GzipCompressedMessageSize(t, &testpb.SimpleRequest{Payload: &testpb.Payload{Body: make([]byte, 10000)}})
 	wantMetrics := testutils.MetricData(testutils.MetricDataOptions{
 		Target:                     ss.Target,
-		UnaryCompressedMessageSize: float64(57),
+		UnaryCompressedMessageSize: float64(compressedSize),
 	})
 	gotMetrics = testutils.WaitForServerMetrics(ctx, t, reader, gotMetrics, wantMetrics)
 	testutils.CompareMetrics(t, gotMetrics, wantMetrics)
@@ -846,9 +847,10 @@ func (s) TestMetricsAndTracesOptionEnabled(t *testing.T) {
 		}
 	}
 
+	compressedSize := testutils.GzipCompressedMessageSize(t, &testpb.SimpleRequest{Payload: &testpb.Payload{Body: make([]byte, 10000)}})
 	wantMetrics := testutils.MetricData(testutils.MetricDataOptions{
 		Target:                     ss.Target,
-		UnaryCompressedMessageSize: float64(57),
+		UnaryCompressedMessageSize: float64(compressedSize),
 	})
 	gotMetrics = testutils.WaitForServerMetrics(ctx, t, reader, gotMetrics, wantMetrics)
 	testutils.CompareMetrics(t, gotMetrics, wantMetrics)
@@ -873,7 +875,7 @@ func (s) TestMetricsAndTracesOptionEnabled(t *testing.T) {
 						},
 						{
 							Key:   "message-size-compressed",
-							Value: attribute.IntValue(57),
+							Value: attribute.IntValue(compressedSize),
 						},
 					},
 				},
@@ -890,7 +892,7 @@ func (s) TestMetricsAndTracesOptionEnabled(t *testing.T) {
 						},
 						{
 							Key:   "message-size-compressed",
-							Value: attribute.IntValue(57),
+							Value: attribute.IntValue(compressedSize),
 						},
 					},
 				},
@@ -924,7 +926,7 @@ func (s) TestMetricsAndTracesOptionEnabled(t *testing.T) {
 						},
 						{
 							Key:   "message-size-compressed",
-							Value: attribute.IntValue(57),
+							Value: attribute.IntValue(compressedSize),
 						},
 					},
 				},
@@ -941,7 +943,7 @@ func (s) TestMetricsAndTracesOptionEnabled(t *testing.T) {
 						},
 						{
 							Key:   "message-size-compressed",
-							Value: attribute.IntValue(57),
+							Value: attribute.IntValue(compressedSize),
 						},
 					},
 				},

stats/opentelemetry/internal/testutils/testutils.go

@@ -18,6 +18,8 @@
 package testutils
 
 import (
+	"bytes"
+	"compress/gzip"
 	"context"
 	"fmt"
 	"slices"
@@ -28,6 +30,7 @@ import (
 	"go.opentelemetry.io/otel/sdk/metric"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata/metricdatatest"
+	"google.golang.org/protobuf/proto"
 )
 
 // Redefine default bounds here to avoid a cyclic dependency with top level
@@ -765,6 +768,25 @@ func MetricData(options MetricDataOptions) []metricdata.Metrics {
 	}
 }
 
+// GzipCompressedMessageSize returns the byte length of the proto message after
+// gzip compression.
+func GzipCompressedMessageSize(t *testing.T, m proto.Message) int {
+	t.Helper()
+	data, err := proto.Marshal(m)
+	if err != nil {
+		t.Fatalf("proto.Marshal failed: %v", err)
+	}
+	var buf bytes.Buffer
+	zw := gzip.NewWriter(&buf)
+	if _, err := zw.Write(data); err != nil {
+		t.Fatalf("gzip.Write failed: %v", err)
+	}
+	if err := zw.Close(); err != nil {
+		t.Fatalf("gzip.Close failed: %v", err)
+	}
+	return buf.Len()
+}
+
 // CompareMetrics asserts wantMetrics are what we expect. For duration metrics
 // makes sure the data point is within possible testing time (five seconds from
 // context timeout).