feat(plugin-http): add plugin hooks before processing req and res (#963)

packages/opentelemetry-plugin-http/README.md

@@ -52,6 +52,8 @@ Http plugin has few options available to choose from. You can set the following:
 | Options | Type | Description |
 | ------- | ---- | ----------- |
 | [`applyCustomAttributesOnSpan`](https://github.com/open-telemetry/opentelemetry-js/blob/master/packages/opentelemetry-plugin-http/src/types.ts#L52) | `HttpCustomAttributeFunction` | Function for adding custom attributes |
+| [`requestHook`](https://github.com/open-telemetry/opentelemetry-js/blob/master/packages/opentelemetry-plugin-http/src/types.ts#L60) | `HttpRequestCustomAttributeFunction` | Function for adding custom attributes before request is handled |
+| [`responseHook`](https://github.com/open-telemetry/opentelemetry-js/blob/master/packages/opentelemetry-plugin-http/src/types.ts#L67) | `HttpResponseCustomAttributeFunction` | Function for adding custom attributes before response is handled |
 | [`ignoreIncomingPaths`](https://github.com/open-telemetry/opentelemetry-js/blob/master/packages/opentelemetry-plugin-http/src/types.ts#L28) | `IgnoreMatcher[]` | Http plugin will not trace all incoming requests that match paths |
 | [`ignoreOutgoingUrls`](https://github.com/open-telemetry/opentelemetry-js/blob/master/packages/opentelemetry-plugin-http/src/types.ts#L28) | `IgnoreMatcher[]` | Http plugin will not trace all outgoing requests that match urls |
 | [`serverName`](https://github.com/open-telemetry/opentelemetry-js/blob/master/packages/opentelemetry-plugin-http/src/types.ts#L28) | `string` | The primary server name of the matched virtual host. |

packages/opentelemetry-plugin-http/src/http.ts

@@ -203,6 +203,9 @@ export class HttpPlugin extends BasePlugin<Http> {
       hostname,
     });
     span.setAttributes(attributes);
+    if (this._config.requestHook) {
+      this._callRequestHook(span, request);
+    }
 
     request.on(
       'response',
@@ -212,6 +215,9 @@ export class HttpPlugin extends BasePlugin<Http> {
           { hostname }
         );
         span.setAttributes(attributes);
+        if (this._config.responseHook) {
+          this._callResponseHook(span, response);
+        }
 
         this._tracer.bind(response);
         this._logger.debug('outgoingRequest on response()');
@@ -316,6 +322,13 @@ export class HttpPlugin extends BasePlugin<Http> {
           context.bind(request);
           context.bind(response);
 
+          if (plugin._config.requestHook) {
+            plugin._callRequestHook(span, request);
+          }
+          if (plugin._config.responseHook) {
+            plugin._callResponseHook(span, response);
+          }
+
           // Wraps end (inspired by:
           // https://github.com/GoogleCloudPlatform/cloud-trace-nodejs/blob/master/src/plugins/plugin-connect.ts#L75)
           const originalEnd = response.end;
@@ -465,6 +478,28 @@ export class HttpPlugin extends BasePlugin<Http> {
     this._spanNotEnded.delete(span);
   }
 
+  private _callResponseHook(
+    span: Span,
+    response: IncomingMessage | ServerResponse
+  ) {
+    this._safeExecute(
+      span,
+      () => this._config.responseHook!(span, response),
+      false
+    );
+  }
+
+  private _callRequestHook(
+    span: Span,
+    request: ClientRequest | IncomingMessage
+  ) {
+    this._safeExecute(
+      span,
+      () => this._config.requestHook!(span, request),
+      false
+    );
+  }
+
   private _safeExecute<
     T extends (...args: unknown[]) => ReturnType<T>,
     K extends boolean

packages/opentelemetry-plugin-http/src/types.ts

@@ -57,6 +57,14 @@ export interface HttpCustomAttributeFunction {
   ): void;
 }
 
+export interface HttpRequestCustomAttributeFunction {
+  (span: Span, request: ClientRequest | IncomingMessage): void;
+}
+
+export interface HttpResponseCustomAttributeFunction {
+  (span: Span, response: IncomingMessage | ServerResponse): void;
+}
+
 /**
  * Options available for the HTTP Plugin (see [documentation](https://github.com/open-telemetry/opentelemetry-js/tree/master/packages/opentelemetry-plugin-http#http-plugin-options))
  */
@@ -65,8 +73,12 @@ export interface HttpPluginConfig extends PluginConfig {
   ignoreIncomingPaths?: IgnoreMatcher[];
   /** Not trace all outgoing requests that match urls */
   ignoreOutgoingUrls?: IgnoreMatcher[];
-  /** Function for adding custom attributes */
+  /** Function for adding custom attributes after response is handled */
   applyCustomAttributesOnSpan?: HttpCustomAttributeFunction;
+  /** Function for adding custom attributes before request is handled */
+  requestHook?: HttpRequestCustomAttributeFunction;
+  /** Function for adding custom attributes before response is handled */
+  responseHook?: HttpResponseCustomAttributeFunction;
   /** The primary server name of the matched virtual host. */
   serverName?: string;
   /** Require parent to create span for outgoing requests */

packages/opentelemetry-plugin-http/test/functionals/http-enable.test.ts

@@ -40,6 +40,7 @@ import { DummyPropagation } from '../utils/DummyPropagation';
 import { httpRequest } from '../utils/httpRequest';
 import { ContextManager } from '@opentelemetry/context-base';
 import { AsyncHooksContextManager } from '@opentelemetry/context-async-hooks';
+import { ClientRequest, IncomingMessage, ServerResponse } from 'http';
 
 const applyCustomAttributesOnSpanErrorMessage =
   'bad applyCustomAttributesOnSpan function';
@@ -76,6 +77,20 @@ export const customAttributeFunction = (span: ISpan): void => {
   span.setAttribute('span kind', SpanKind.CLIENT);
 };
 
+export const requestHookFunction = (
+  span: ISpan,
+  request: ClientRequest | IncomingMessage
+): void => {
+  span.setAttribute('custom request hook attribute', 'request');
+};
+
+export const responseHookFunction = (
+  span: ISpan,
+  response: IncomingMessage | ServerResponse
+): void => {
+  span.setAttribute('custom response hook attribute', 'response');
+};
+
 describe('HttpPlugin', () => {
   let contextManager: ContextManager;
 
@@ -207,6 +222,8 @@ describe('HttpPlugin', () => {
             (url: string) => url.endsWith(`/ignored/function`),
           ],
           applyCustomAttributesOnSpan: customAttributeFunction,
+          requestHook: requestHookFunction,
+          responseHook: responseHookFunction,
           serverName,
         };
         plugin.enable(http, provider, provider.logger, config);
@@ -703,6 +720,40 @@ describe('HttpPlugin', () => {
         });
         req.end();
       });
+
+      it('custom attributes should show up on client and server spans', async () => {
+        await httpRequest.get(
+          `${protocol}://${hostname}:${serverPort}${pathname}`
+        );
+        const spans = memoryExporter.getFinishedSpans();
+        const [incomingSpan, outgoingSpan] = spans;
+
+        assert.strictEqual(
+          incomingSpan.attributes['custom request hook attribute'],
+          'request'
+        );
+        assert.strictEqual(
+          incomingSpan.attributes['custom response hook attribute'],
+          'response'
+        );
+        assert.strictEqual(
+          incomingSpan.attributes['span kind'],
+          SpanKind.CLIENT
+        );
+
+        assert.strictEqual(
+          outgoingSpan.attributes['custom request hook attribute'],
+          'request'
+        );
+        assert.strictEqual(
+          outgoingSpan.attributes['custom response hook attribute'],
+          'response'
+        );
+        assert.strictEqual(
+          outgoingSpan.attributes['span kind'],
+          SpanKind.CLIENT
+        );
+      });
     });
 
     describe('with require parent span', () => {