Satisfy the Stringer interface for Peer and Metadata

Effectively allowing to print context containing Peers properly

Also enabling logging of Metadata in an easier way

RELEASE NOTES:

 - peer/peer: implement the Stringer interface for pretty-printing Peers
 - metadata/metadata: implement the Stringer interface for pretty printing metadata

Signed-off-by: Yolan Romailler <anomalroil@users.noreply.github.com>

metadata/metadata.go

@@ -90,6 +90,22 @@ func Pairs(kv ...string) MD {
 	return md
 }
 
+// String implements the Stringer interface for pretty-printing a MD. Ordering of the values is non-deterministic as it ranges over a map.
+func (md MD) String() string {
+	var sb strings.Builder
+	fmt.Fprintf(&sb, "MD{")
+	needSep := false
+	for k, v := range md {
+		if needSep {
+			fmt.Fprintf(&sb, ", ")
+		}
+		fmt.Fprintf(&sb, "%s=[%s]", k, strings.Join(v, ", "))
+		needSep = true
+	}
+	fmt.Fprintf(&sb, "}")
+	return sb.String()
+}
+
 // Len returns the number of items in md.
 func (md MD) Len() int {
 	return len(md)

metadata/metadata_test.go

@@ -22,6 +22,7 @@ import (
 	"context"
 	"reflect"
 	"strconv"
+	"strings"
 	"testing"
 	"time"
 
@@ -338,6 +339,26 @@ func (s) TestAppendToOutgoingContext_FromKVSlice(t *testing.T) {
 	}
 }
 
+func TestStringerMD(t *testing.T) {
+	for _, test := range []struct {
+		md   MD
+		want []string
+	}{
+		{MD{}, []string{"MD{}"}},
+		{MD{"k1": []string{}}, []string{"MD{k1=[]}"}},
+		{MD{"k1": []string{"v1", "v2"}}, []string{"MD{k1=[v1, v2]}"}},
+		{MD{"k1": []string{"v1"}}, []string{"MD{k1=[v1]}"}},
+		{MD{"k1": []string{"v1", "v2"}, "k2": []string{}, "k3": []string{"1", "2", "3"}}, []string{"MD{", "k1=[v1, v2]", "k2=[]", "k3=[1, 2, 3]", "}"}},
+	} {
+		strMd := test.md.String()
+		for _, want := range test.want {
+			if !strings.Contains(strMd, want) {
+				t.Fatalf("Metadata string '%s' is missing '%s'", strMd, want)
+			}
+		}
+	}
+}
+
 // Old/slow approach to adding metadata to context
 func Benchmark_AddingMetadata_ContextManipulationApproach(b *testing.B) {
 	// TODO: Add in N=1-100 tests once Go1.6 support is removed.

peer/peer.go

@@ -22,6 +22,7 @@ package peer
 
 import (
 	"context"
+	"fmt"
 	"net"
 
 	"google.golang.org/grpc/credentials"
@@ -39,6 +40,26 @@ type Peer struct {
 	AuthInfo credentials.AuthInfo
 }
 
+// String ensures the Peer types implements the Stringer interface in order to
+// allow to print a context with a peerKey value effectively.
+func (p *Peer) String() string {
+	if p == nil {
+		return "Peer<nil>"
+	}
+	ret := "Peer{"
+	if p.Addr != nil {
+		ret += fmt.Sprintf("Addr: '%s'", p.Addr.String())
+	}
+	if p.AuthInfo != nil {
+		if len(ret) > 5 {
+			ret += ", "
+		}
+		ret += fmt.Sprintf("AuthInfo: '%s'", p.AuthInfo.AuthType())
+	}
+	ret += "}"
+	return ret
+}
+
 type peerKey struct{}
 
 // NewContext creates a new context with peer information attached.

peer/peer_test.go

@@ -0,0 +1,145 @@
+/*
+ *
+ * Copyright 2024 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package peer
+
+import (
+	"context"
+	"fmt"
+	"testing"
+
+	"google.golang.org/grpc/credentials"
+)
+
+// A struct that implements AuthInfo interface and implements CommonAuthInfo() method.
+type testAuthInfo struct {
+	credentials.CommonAuthInfo
+}
+
+func (ta testAuthInfo) AuthType() string {
+	return "testAuthInfo"
+}
+
+func TestPeerSecurityLevel(t *testing.T) {
+	testCases := []struct {
+		authLevel credentials.SecurityLevel
+		testLevel credentials.SecurityLevel
+		want      bool
+	}{
+		{
+			authLevel: credentials.PrivacyAndIntegrity,
+			testLevel: credentials.PrivacyAndIntegrity,
+			want:      true,
+		},
+		{
+			authLevel: credentials.IntegrityOnly,
+			testLevel: credentials.PrivacyAndIntegrity,
+			want:      false,
+		},
+		{
+			authLevel: credentials.IntegrityOnly,
+			testLevel: credentials.NoSecurity,
+			want:      true,
+		},
+		{
+			authLevel: credentials.InvalidSecurityLevel,
+			testLevel: credentials.IntegrityOnly,
+			want:      true,
+		},
+		{
+			authLevel: credentials.InvalidSecurityLevel,
+			testLevel: credentials.PrivacyAndIntegrity,
+			want:      true,
+		},
+	}
+	for _, tc := range testCases {
+		ctx := NewContext(context.Background(), &Peer{AuthInfo: testAuthInfo{credentials.CommonAuthInfo{SecurityLevel: tc.authLevel}}})
+		p, ok := FromContext(ctx)
+		if !ok {
+			t.Fatalf("Unable to get peer from context")
+		}
+		err := credentials.CheckSecurityLevel(p.AuthInfo, tc.testLevel)
+		if tc.want && (err != nil) {
+			t.Fatalf("CheckSeurityLevel(%s, %s) returned failure but want success", tc.authLevel.String(), tc.testLevel.String())
+		} else if !tc.want && (err == nil) {
+			t.Fatalf("CheckSeurityLevel(%s, %s) returned success but want failure", tc.authLevel.String(), tc.testLevel.String())
+		}
+	}
+}
+
+type addr struct {
+	ipAddress string
+}
+
+func (addr) Network() string   { return "" }
+func (a *addr) String() string { return a.ipAddress }
+
+func TestPeerStringer(t *testing.T) {
+	testCases := []struct {
+		addr      *addr
+		authLevel credentials.SecurityLevel
+		want      string
+	}{
+		{
+			addr:      &addr{"example.com:1234"},
+			authLevel: credentials.PrivacyAndIntegrity,
+			want:      "Peer{Addr: 'example.com:1234', AuthInfo: 'testAuthInfo'}",
+		},
+		{
+			addr:      &addr{"1.2.3.4:1234"},
+			authLevel: -1,
+			want:      "Peer{Addr: '1.2.3.4:1234'}",
+		},
+		{
+			authLevel: credentials.InvalidSecurityLevel,
+			want:      "Peer{AuthInfo: 'testAuthInfo'}",
+		},
+		{
+			authLevel: -1,
+			want:      "Peer{}",
+		},
+	}
+	for _, tc := range testCases {
+		ctx := NewContext(context.Background(), &Peer{Addr: tc.addr, AuthInfo: testAuthInfo{credentials.CommonAuthInfo{SecurityLevel: tc.authLevel}}})
+		p, ok := FromContext(ctx)
+		if tc.authLevel == -1 {
+			p.AuthInfo = nil
+		}
+		if tc.addr == nil {
+			p.Addr = nil
+		}
+		if !ok {
+			t.Fatalf("Unable to get peer from context")
+		}
+		if p.String() != tc.want {
+			t.Fatalf("Error using peer String(): expected %q, got %q", tc.want, p.String())
+		}
+	}
+	t.Run("test String on nil Peer", func(st *testing.T) {
+		var test *Peer
+		if test.String() != "Peer<nil>" {
+			st.Fatalf("Error using String on nil Peer. Expected 'Peer<nil>', got: '%s'", test.String())
+		}
+	})
+	t.Run("test Stringer on context", func(st *testing.T) {
+		ctx := NewContext(context.Background(), &Peer{Addr: &addr{"1.2.3.4:1234"}, AuthInfo: testAuthInfo{credentials.CommonAuthInfo{SecurityLevel: credentials.PrivacyAndIntegrity}}})
+		if fmt.Sprintf("%v", ctx) != "context.Background.WithValue(type peer.peerKey, val Peer{Addr: '1.2.3.4:1234', AuthInfo: 'testAuthInfo'})" {
+			st.Fatalf("Error printing context with embedded Peer. Got: %v", ctx)
+		}
+	})
+}