grpc-js-core: use Map for metadata store

In more recent versions of Node, Maps are more performant than
POJOs when used as maps. Switching to Maps also eliminates an
expensive delete operation, as well as uses of hasOwnProperty().

packages/grpc-js-core/src/metadata.ts

@@ -4,19 +4,21 @@ const LEGAL_KEY_REGEX = /^[0-9a-z_.-]+$/;
 const LEGAL_NON_BINARY_VALUE_REGEX = /^[ -~]*$/;
 
 export type MetadataValue = string|Buffer;
-
-export interface MetadataObject { [key: string]: MetadataValue[]; }
+export type MetadataObject = Map<string, MetadataValue[]>;
 
 function cloneMetadataObject(repr: MetadataObject): MetadataObject {
-  const result: MetadataObject = {};
-  forOwn(repr, (value, key) => {
-    result[key] = value.map(v => {
+  const result: MetadataObject = new Map<string, MetadataValue[]>();
+
+  repr.forEach((value, key) => {
+    const clonedValue: MetadataValue[] = value.map(v => {
       if (v instanceof Buffer) {
         return Buffer.from(v);
       } else {
         return v;
       }
     });
+
+    result.set(key, clonedValue);
   });
   return result;
 }
@@ -64,7 +66,7 @@ function validate(key: string, value?: MetadataValue): void {
  * A class for storing metadata. Keys are normalized to lowercase ASCII.
  */
 export class Metadata {
-  protected internalRepr: MetadataObject = {};
+  protected internalRepr: MetadataObject = new Map<string, MetadataValue[]>();
 
   /**
    * Sets the given value for the given key by replacing any other values
@@ -76,7 +78,7 @@ export class Metadata {
   set(key: string, value: MetadataValue): void {
     key = normalizeKey(key);
     validate(key, value);
-    this.internalRepr[key] = [value];
+    this.internalRepr.set(key, [value]);
   }
 
   /**
@@ -89,10 +91,13 @@ export class Metadata {
   add(key: string, value: MetadataValue): void {
     key = normalizeKey(key);
     validate(key, value);
-    if (!this.internalRepr[key]) {
-      this.internalRepr[key] = [value];
+
+    const existingValue: MetadataValue[]|undefined = this.internalRepr.get(key);
+
+    if (existingValue === undefined) {
+      this.internalRepr.set(key, [value]);
     } else {
-      this.internalRepr[key].push(value);
+      existingValue.push(value);
     }
   }
 
@@ -103,9 +108,7 @@ export class Metadata {
   remove(key: string): void {
     key = normalizeKey(key);
     validate(key);
-    if (Object.prototype.hasOwnProperty.call(this.internalRepr, key)) {
-      delete this.internalRepr[key];
-    }
+    this.internalRepr.delete(key);
   }
 
   /**
@@ -116,11 +119,7 @@ export class Metadata {
   get(key: string): MetadataValue[] {
     key = normalizeKey(key);
     validate(key);
-    if (Object.prototype.hasOwnProperty.call(this.internalRepr, key)) {
-      return this.internalRepr[key];
-    } else {
-      return [];
-    }
+    return this.internalRepr.get(key) || [];
   }
 
   /**
@@ -130,7 +129,8 @@ export class Metadata {
    */
   getMap(): {[key: string]: MetadataValue} {
     const result: {[key: string]: MetadataValue} = {};
-    forOwn(this.internalRepr, (values, key) => {
+
+    this.internalRepr.forEach((values, key) => {
       if (values.length > 0) {
         const v = values[0];
         result[key] = v instanceof Buffer ? v.slice() : v;
@@ -157,8 +157,11 @@ export class Metadata {
    * @param other A Metadata object.
    */
   merge(other: Metadata): void {
-    forOwn(other.internalRepr, (values, key) => {
-      this.internalRepr[key] = (this.internalRepr[key] || []).concat(values);
+    other.internalRepr.forEach((values, key) => {
+      const mergedValue: MetadataValue[] =
+          (this.internalRepr.get(key) || []).concat(values);
+
+      this.internalRepr.set(key, mergedValue);
     });
   }
 
@@ -168,7 +171,7 @@ export class Metadata {
   toHttp2Headers(): http2.OutgoingHttpHeaders {
     // NOTE: Node <8.9 formats http2 headers incorrectly.
     const result: http2.OutgoingHttpHeaders = {};
-    forOwn(this.internalRepr, (values, key) => {
+    this.internalRepr.forEach((values, key) => {
       // We assume that the user's interaction with this object is limited to
       // through its public API (i.e. keys and values are already validated).
       result[key] = values.map((value) => {

packages/grpc-js-core/test/test-metadata.ts

@@ -1,7 +1,7 @@
 import * as assert from 'assert';
 import * as http2 from 'http2';
 import {range} from 'lodash';
-import {Metadata} from '../src/metadata';
+import {Metadata, MetadataObject, MetadataValue} from '../src/metadata';
 
 class TestMetadata extends Metadata {
   getInternalRepresentation() {
@@ -277,21 +277,24 @@ describe('Metadata', () => {
       };
       const metadataFromHeaders = TestMetadata.fromHttp2Headers(headers);
       const internalRepr = metadataFromHeaders.getInternalRepresentation();
-      assert.deepEqual(internalRepr, {
-        key1: ['value1'],
-        key2: ['value2'],
-        key3: ['value3a', 'value3b'],
-        'key-bin': [
-          Buffer.from(range(0, 16)), Buffer.from(range(16, 32)),
-          Buffer.from(range(0, 32))
+      const expected: MetadataObject = new Map<string, MetadataValue[]>([
+        ['key1', ['value1']], ['key2', ['value2']],
+        ['key3', ['value3a', 'value3b']],
+        [
+          'key-bin',
+          [
+            Buffer.from(range(0, 16)), Buffer.from(range(16, 32)),
+            Buffer.from(range(0, 32))
+          ]
         ]
-      });
+      ]);
+      assert.deepEqual(internalRepr, expected);
     });
 
     it('creates an empty Metadata object from empty headers', () => {
       const metadataFromHeaders = TestMetadata.fromHttp2Headers({});
       const internalRepr = metadataFromHeaders.getInternalRepresentation();
-      assert.deepEqual(internalRepr, {});
+      assert.deepEqual(internalRepr, new Map<string, MetadataValue[]>());
     });
   });
 });