Move correlation context propagation to correlation package (#479)

Correlation context propagation shouldn't be a part of the trace
package - it is a different aspect of the propagation cross-cutting
concern.

This commit also adds a DefaultHTTPPropagator function for correlation
context propagation and makes the plugins use it.

Co-authored-by: Joshua MacDonald <jmacd@users.noreply.github.com>

api/correlation/correlation_context_propagator.go

@@ -0,0 +1,99 @@
+package correlation
+
+import (
+	"context"
+	"net/url"
+	"strings"
+
+	"go.opentelemetry.io/otel/api/core"
+	"go.opentelemetry.io/otel/api/key"
+	"go.opentelemetry.io/otel/api/propagation"
+)
+
+// CorrelationContextHeader is specified by W3C.
+//nolint:golint
+var CorrelationContextHeader = "Correlation-Context"
+
+// CorrelationContext propagates Key:Values in W3C CorrelationContext
+// format.
+// nolint:golint
+type CorrelationContext struct{}
+
+var _ propagation.HTTPPropagator = CorrelationContext{}
+
+// DefaultHTTPPropagator returns the default context correlation HTTP
+// propagator.
+func DefaultHTTPPropagator() propagation.HTTPPropagator {
+	return CorrelationContext{}
+}
+
+// Inject implements HTTPInjector.
+func (CorrelationContext) Inject(ctx context.Context, supplier propagation.HTTPSupplier) {
+	correlationCtx := FromContext(ctx)
+	firstIter := true
+	var headerValueBuilder strings.Builder
+	correlationCtx.Foreach(func(kv core.KeyValue) bool {
+		if !firstIter {
+			headerValueBuilder.WriteRune(',')
+		}
+		firstIter = false
+		headerValueBuilder.WriteString(url.QueryEscape(strings.TrimSpace((string)(kv.Key))))
+		headerValueBuilder.WriteRune('=')
+		headerValueBuilder.WriteString(url.QueryEscape(strings.TrimSpace(kv.Value.Emit())))
+		return true
+	})
+	if headerValueBuilder.Len() > 0 {
+		headerString := headerValueBuilder.String()
+		supplier.Set(CorrelationContextHeader, headerString)
+	}
+}
+
+// Extract implements HTTPExtractor.
+func (CorrelationContext) Extract(ctx context.Context, supplier propagation.HTTPSupplier) context.Context {
+	correlationContext := supplier.Get(CorrelationContextHeader)
+	if correlationContext == "" {
+		return WithMap(ctx, NewEmptyMap())
+	}
+
+	contextValues := strings.Split(correlationContext, ",")
+	keyValues := make([]core.KeyValue, 0, len(contextValues))
+	for _, contextValue := range contextValues {
+		valueAndProps := strings.Split(contextValue, ";")
+		if len(valueAndProps) < 1 {
+			continue
+		}
+		nameValue := strings.Split(valueAndProps[0], "=")
+		if len(nameValue) < 2 {
+			continue
+		}
+		name, err := url.QueryUnescape(nameValue[0])
+		if err != nil {
+			continue
+		}
+		trimmedName := strings.TrimSpace(name)
+		value, err := url.QueryUnescape(nameValue[1])
+		if err != nil {
+			continue
+		}
+		trimmedValue := strings.TrimSpace(value)
+
+		// TODO (skaris): properties defiend https://w3c.github.io/correlation-context/, are currently
+		// just put as part of the value.
+		var trimmedValueWithProps strings.Builder
+		trimmedValueWithProps.WriteString(trimmedValue)
+		for _, prop := range valueAndProps[1:] {
+			trimmedValueWithProps.WriteRune(';')
+			trimmedValueWithProps.WriteString(prop)
+		}
+
+		keyValues = append(keyValues, key.New(trimmedName).String(trimmedValueWithProps.String()))
+	}
+	return WithMap(ctx, NewMap(MapUpdate{
+		MultiKV: keyValues,
+	}))
+}
+
+// GetAllKeys implements HTTPPropagator.
+func (CorrelationContext) GetAllKeys() []string {
+	return []string{CorrelationContextHeader}
+}

api/correlation/correlation_context_propagator_test.go

@@ -0,0 +1,215 @@
+package correlation_test
+
+import (
+	"context"
+	"net/http"
+	"strings"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+
+	"go.opentelemetry.io/otel/api/core"
+	"go.opentelemetry.io/otel/api/correlation"
+	"go.opentelemetry.io/otel/api/key"
+	"go.opentelemetry.io/otel/api/propagation"
+)
+
+func TestExtractValidDistributedContextFromHTTPReq(t *testing.T) {
+	props := propagation.New(propagation.WithExtractors(correlation.CorrelationContext{}))
+	tests := []struct {
+		name    string
+		header  string
+		wantKVs []core.KeyValue
+	}{
+		{
+			name:   "valid w3cHeader",
+			header: "key1=val1,key2=val2",
+			wantKVs: []core.KeyValue{
+				key.New("key1").String("val1"),
+				key.New("key2").String("val2"),
+			},
+		},
+		{
+			name:   "valid w3cHeader with spaces",
+			header: "key1 =   val1,  key2 =val2   ",
+			wantKVs: []core.KeyValue{
+				key.New("key1").String("val1"),
+				key.New("key2").String("val2"),
+			},
+		},
+		{
+			name:   "valid w3cHeader with properties",
+			header: "key1=val1,key2=val2;prop=1",
+			wantKVs: []core.KeyValue{
+				key.New("key1").String("val1"),
+				key.New("key2").String("val2;prop=1"),
+			},
+		},
+		{
+			name:   "valid header with url-escaped comma",
+			header: "key1=val1,key2=val2%2Cval3",
+			wantKVs: []core.KeyValue{
+				key.New("key1").String("val1"),
+				key.New("key2").String("val2,val3"),
+			},
+		},
+		{
+			name:   "valid header with an invalid header",
+			header: "key1=val1,key2=val2,a,val3",
+			wantKVs: []core.KeyValue{
+				key.New("key1").String("val1"),
+				key.New("key2").String("val2"),
+			},
+		},
+		{
+			name:   "valid header with no value",
+			header: "key1=,key2=val2",
+			wantKVs: []core.KeyValue{
+				key.New("key1").String(""),
+				key.New("key2").String("val2"),
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			req, _ := http.NewRequest("GET", "http://example.com", nil)
+			req.Header.Set("Correlation-Context", tt.header)
+
+			ctx := context.Background()
+			ctx = propagation.ExtractHTTP(ctx, props, req.Header)
+			gotCorCtx := correlation.FromContext(ctx)
+			wantCorCtx := correlation.NewMap(correlation.MapUpdate{MultiKV: tt.wantKVs})
+			if gotCorCtx.Len() != wantCorCtx.Len() {
+				t.Errorf(
+					"Got and Want CorCtx are not the same size %d != %d",
+					gotCorCtx.Len(),
+					wantCorCtx.Len(),
+				)
+			}
+			totalDiff := ""
+			wantCorCtx.Foreach(func(kv core.KeyValue) bool {
+				val, _ := gotCorCtx.Value(kv.Key)
+				diff := cmp.Diff(kv, core.KeyValue{Key: kv.Key, Value: val}, cmp.AllowUnexported(core.Value{}))
+				if diff != "" {
+					totalDiff += diff + "\n"
+				}
+				return true
+			})
+			if totalDiff != "" {
+				t.Errorf("Extract Tracecontext: %s: -got +want %s", tt.name, totalDiff)
+			}
+		})
+	}
+}
+
+func TestExtractInvalidDistributedContextFromHTTPReq(t *testing.T) {
+	props := propagation.New(propagation.WithExtractors(correlation.CorrelationContext{}))
+	tests := []struct {
+		name   string
+		header string
+	}{
+		{
+			name:   "no key values",
+			header: "header1",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			req, _ := http.NewRequest("GET", "http://example.com", nil)
+			req.Header.Set("Correlation-Context", tt.header)
+
+			ctx := context.Background()
+			ctx = propagation.ExtractHTTP(ctx, props, req.Header)
+			gotCorCtx := correlation.FromContext(ctx)
+			if gotCorCtx.Len() != 0 {
+				t.Errorf("Got and Want CorCtx are not the same size %d != %d", gotCorCtx.Len(), 0)
+			}
+		})
+	}
+}
+
+func TestInjectCorrelationContextToHTTPReq(t *testing.T) {
+	propagator := correlation.CorrelationContext{}
+	props := propagation.New(propagation.WithInjectors(propagator))
+	tests := []struct {
+		name         string
+		kvs          []core.KeyValue
+		wantInHeader []string
+		wantedLen    int
+	}{
+		{
+			name: "two simple values",
+			kvs: []core.KeyValue{
+				key.New("key1").String("val1"),
+				key.New("key2").String("val2"),
+			},
+			wantInHeader: []string{"key1=val1", "key2=val2"},
+		},
+		{
+			name: "two values with escaped chars",
+			kvs: []core.KeyValue{
+				key.New("key1").String("val1,val2"),
+				key.New("key2").String("val3=4"),
+			},
+			wantInHeader: []string{"key1=val1%2Cval2", "key2=val3%3D4"},
+		},
+		{
+			name: "values of non-string types",
+			kvs: []core.KeyValue{
+				key.New("key1").Bool(true),
+				key.New("key2").Int(123),
+				key.New("key3").Int64(123),
+				key.New("key4").Int32(123),
+				key.New("key5").Uint(123),
+				key.New("key6").Uint32(123),
+				key.New("key7").Uint64(123),
+				key.New("key8").Float64(123.567),
+				key.New("key9").Float32(123.567),
+			},
+			wantInHeader: []string{
+				"key1=true",
+				"key2=123",
+				"key3=123",
+				"key4=123",
+				"key5=123",
+				"key6=123",
+				"key7=123",
+				"key8=123.567",
+				"key9=123.567",
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			req, _ := http.NewRequest("GET", "http://example.com", nil)
+			ctx := correlation.WithMap(context.Background(), correlation.NewMap(correlation.MapUpdate{MultiKV: tt.kvs}))
+			propagation.InjectHTTP(ctx, props, req.Header)
+
+			gotHeader := req.Header.Get("Correlation-Context")
+			wantedLen := len(strings.Join(tt.wantInHeader, ","))
+			if wantedLen != len(gotHeader) {
+				t.Errorf(
+					"%s: Inject Correlation-Context incorrect length %d != %d.", tt.name, tt.wantedLen, len(gotHeader),
+				)
+			}
+			for _, inHeader := range tt.wantInHeader {
+				if !strings.Contains(gotHeader, inHeader) {
+					t.Errorf(
+						"%s: Inject Correlation-Context missing part of header: %s in %s", tt.name, inHeader, gotHeader,
+					)
+				}
+			}
+		})
+	}
+}
+
+func TestTraceContextPropagator_GetAllKeys(t *testing.T) {
+	var propagator correlation.CorrelationContext
+	want := []string{"Correlation-Context"}
+	got := propagator.GetAllKeys()
+	if diff := cmp.Diff(got, want); diff != "" {
+		t.Errorf("GetAllKeys: -got +want %s", diff)
+	}
+}