Capture log params from context metadata (#1049)

* capture log params from context metadata

* refactor

* tidy

* fix lint error

* update const naming

* add tests

* add more test cases

* helper func

* fix

* address comments

backend/log.go

@@ -38,6 +38,11 @@ func withContextualLogAttributes(ctx context.Context, pCtx PluginContext) contex
 			args = append(args, "uname", pCtx.User.Name)
 		}
 	}
+
+	if ctxLogAttributes := log.ContextualAttributesFromIncomingContext(ctx); len(ctxLogAttributes) > 0 {
+		args = append(args, ctxLogAttributes...)
+	}
+
 	ctx = log.WithContextualAttributes(ctx, args)
 	return ctx
 }

backend/log/context_grpc.go

@@ -0,0 +1,55 @@
+package log
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"google.golang.org/grpc/metadata"
+)
+
+const (
+	logParamsCtxMetadataKey = "loggerParamsCtxMetadata"
+	logParamSeparator       = ":::"
+)
+
+// WithContextualAttributesForOutgoingContext will append the given key/value log parameters to the outgoing context.
+func WithContextualAttributesForOutgoingContext(ctx context.Context, logParams []any) context.Context {
+	if len(logParams) == 0 || len(logParams)%2 != 0 {
+		return ctx
+	}
+
+	for i := 0; i < len(logParams); i += 2 {
+		k := fmt.Sprintf("%v", logParams[i])
+		v := fmt.Sprintf("%v", logParams[i+1])
+		if k == "" || v == "" {
+			continue
+		}
+
+		ctx = metadata.AppendToOutgoingContext(ctx, logParamsCtxMetadataKey, logParam(k, v))
+	}
+
+	return ctx
+}
+
+// ContextualAttributesFromIncomingContext returns the contextual key/value log parameters from the given incoming context.
+func ContextualAttributesFromIncomingContext(ctx context.Context) []any {
+	logParams := metadata.ValueFromIncomingContext(ctx, logParamsCtxMetadataKey)
+	if len(logParams) == 0 {
+		return nil
+	}
+
+	var attrs []any
+	for _, param := range logParams {
+		kv := strings.Split(param, logParamSeparator)
+		if len(kv) != 2 || kv[0] == "" || kv[1] == "" {
+			continue
+		}
+		attrs = append(attrs, kv[0], kv[1])
+	}
+	return attrs
+}
+
+func logParam(k, v string) string {
+	return fmt.Sprintf("%s%s%s", k, logParamSeparator, v)
+}

backend/log/context_grpc_test.go

@@ -0,0 +1,117 @@
+package log
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc/metadata"
+)
+
+func TestWithContextualAttributesForOutgoingContext(t *testing.T) {
+	tcs := []struct {
+		name      string
+		logParams []any
+		expected  []string
+	}{
+		{
+			name:      "empty log params",
+			logParams: []any{},
+			expected:  []string{},
+		},
+		{
+			name:      "log params with odd number of elements",
+			logParams: []any{"key1", "value1", "key2"},
+			expected:  []string{},
+		},
+		{
+			name:      "log params with empty key",
+			logParams: []any{"", "value1"},
+			expected:  []string{},
+		},
+		{
+			name:      "log params with empty value",
+			logParams: []any{"key1", ""},
+			expected:  []string{},
+		},
+		{
+			name:      "log params with valid key and value",
+			logParams: []any{"key1", "value1"},
+			expected:  []string{logParam("key1", "value1")},
+		},
+		{
+			name:      "log params with multiple key value pairs",
+			logParams: []any{"key1", "value1", "key2", "value2"},
+			expected:  []string{logParam("key1", "value1"), logParam("key2", "value2")},
+		},
+	}
+
+	for _, tc := range tcs {
+		t.Run(tc.name, func(t *testing.T) {
+			ctx := WithContextualAttributesForOutgoingContext(context.Background(), tc.logParams)
+			md, ok := metadata.FromOutgoingContext(ctx)
+			if len(tc.expected) == 0 {
+				require.False(t, ok)
+				return
+			}
+
+			require.True(t, ok)
+			got := md.Get(logParamsCtxMetadataKey)
+			if len(got) != len(tc.expected) {
+				t.Fatalf("expected %v, got %v", tc.expected, got)
+			}
+			for i := range got {
+				if got[i] != tc.expected[i] {
+					t.Fatalf("expected %v, got %v", tc.expected, got)
+				}
+			}
+		})
+	}
+}
+
+func TestContextualAttributesFromIncomingContext(t *testing.T) {
+	tcs := []struct {
+		name     string
+		md       metadata.MD
+		expected []any
+	}{
+		{
+			name:     "empty metadata",
+			md:       metadata.MD{},
+			expected: nil,
+		},
+		{
+			name:     "metadata without log params",
+			md:       metadata.MD{"key1": []string{"value1"}},
+			expected: nil,
+		},
+		{
+			name:     "metadata with valid log params",
+			md:       metadata.MD{logParamsCtxMetadataKey: []string{logParam("key1", "value1"), logParam("key2", "value2")}},
+			expected: []any{"key1", "value1", "key2", "value2"},
+		},
+		{
+			name:     "metadata with missing key",
+			md:       metadata.MD{logParamsCtxMetadataKey: []string{logParam("", "value1"), logParam("key2", "value2")}},
+			expected: []any{"key2", "value2"},
+		},
+		{
+			name:     "metadata with missing value",
+			md:       metadata.MD{logParamsCtxMetadataKey: []string{logParam("key1", ""), logParam("key2", "value2")}},
+			expected: []any{"key2", "value2"},
+		},
+		{
+			name:     "metadata with invalid key + value",
+			md:       metadata.MD{logParamsCtxMetadataKey: []string{logParam("", ""), logParam("key2", "value2")}},
+			expected: []any{"key2", "value2"},
+		},
+	}
+
+	for _, tc := range tcs {
+		t.Run(tc.name, func(t *testing.T) {
+			ctx := metadata.NewIncomingContext(context.Background(), tc.md)
+			got := ContextualAttributesFromIncomingContext(ctx)
+			require.Equal(t, tc.expected, got)
+		})
+	}
+}