chore: adding interceptor for getting headers before each request

examples/tracer-web/examples/zipkin/index.js

@@ -4,7 +4,14 @@ import { ZipkinExporter } from '@opentelemetry/exporter-zipkin';
 
 const provider = new WebTracerProvider();
 provider.addSpanProcessor(new SimpleSpanProcessor(new ConsoleSpanExporter()));
-provider.addSpanProcessor(new SimpleSpanProcessor(new ZipkinExporter()));
+provider.addSpanProcessor(new SimpleSpanProcessor(new ZipkinExporter({
+  // testing interceptor
+  // getHeadersBeforeSend: ()=> {
+  //   return {
+  //     foo: 'bar',
+  //   }
+  // }
+})));
 
 provider.register();
 

packages/opentelemetry-exporter-zipkin/README.md

@@ -30,7 +30,13 @@ const options = {
     'my-header': 'header-value',
   },
   url: 'your-zipkin-url',
-  serviceName: 'your-application-name'
+  serviceName: 'your-application-name',
+  // optional interceptor
+  getHeadersBeforeSend: () => {
+    return {
+      'my-header': 'header-value',
+    }
+  }
 }
 const exporter = new ZipkinExporter(options);
 ```
@@ -46,6 +52,10 @@ You can use built-in `SimpleSpanProcessor` or `BatchSpanProcessor` or write your
 - [SimpleSpanProcessor](https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/trace/sdk.md#simple-processor): The implementation of `SpanProcessor` that passes ended span directly to the configured `SpanExporter`.
 - [BatchSpanProcessor](https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/trace/sdk.md#batching-processor): The implementation of the `SpanProcessor` that batches ended spans and pushes them to the configured `SpanExporter`. It is recommended to use this `SpanProcessor` for better performance and optimization.
 
+### Options
+- **getHeadersBeforeSend** - optional interceptor that allows adding new headers everytime time the exporter is going to send spans.
+This is optional and can be used if headers are changing over time. This is a sync callback.
+
 ## Viewing your traces
 
 Please visit the Zipkin UI endpoint <http://localhost:9411>

packages/opentelemetry-exporter-zipkin/src/platform/browser/util.ts

@@ -24,6 +24,9 @@ import * as zipkinTypes from '../../types';
 
 /**
  * Prepares send function that will send spans to the remote Zipkin service.
+ * @param urlStr - url to send spans
+ * @param headers - headers
+ * send
  */
 export function prepareSend(urlStr: string, headers?: Record<string, string>) {
   let xhrHeaders: Record<string, string>;

packages/opentelemetry-exporter-zipkin/src/platform/node/util.ts

@@ -23,6 +23,9 @@ import * as zipkinTypes from '../../types';
 
 /**
  * Prepares send function that will send spans to the remote Zipkin service.
+ * @param urlStr - url to send spans
+ * @param headers - headers
+ * send
  */
 export function prepareSend(urlStr: string, headers?: Record<string, string>) {
   const urlOpts = url.parse(urlStr);

packages/opentelemetry-exporter-zipkin/src/types.ts

@@ -20,12 +20,13 @@ import { ExportResult } from '@opentelemetry/core';
  * Exporter config
  */
 export interface ExporterConfig {
-  headers?: { [key: string]: string };
+  headers?: Record<string, string>;
   serviceName?: string;
   url?: string;
   // Optional mapping overrides for OpenTelemetry status code and description.
   statusCodeTagName?: string;
   statusDescriptionTagName?: string;
+  getHeadersBeforeSend?: () => Record<string, string> | undefined;
 }
 
 /**
@@ -184,3 +185,5 @@ export type SendFunction = (
   zipkinSpans: Span[],
   done: (result: ExportResult) => void
 ) => void;
+
+export type GetHeaders = () => Record<string, string> | undefined;

packages/opentelemetry-exporter-zipkin/src/utils.ts

@@ -0,0 +1,24 @@
+/*
+ * Copyright The OpenTelemetry 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
+ *
+ *      https://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.
+ */
+import { GetHeaders } from './types';
+
+export function prepareGetHeaders(
+  getHeadersBeforeSend: GetHeaders
+): () => Record<string, string> | undefined {
+  return function () {
+    return getHeadersBeforeSend();
+  };
+}

packages/opentelemetry-exporter-zipkin/src/zipkin.ts

@@ -25,6 +25,7 @@ import {
   statusDescriptionTagName,
 } from './transform';
 import { SERVICE_RESOURCE } from '@opentelemetry/resources';
+import { prepareGetHeaders } from './utils';
 
 /**
  * Zipkin Exporter
@@ -34,19 +35,27 @@ export class ZipkinExporter implements SpanExporter {
   private readonly DEFAULT_SERVICE_NAME = 'OpenTelemetry Service';
   private readonly _statusCodeTagName: string;
   private readonly _statusDescriptionTagName: string;
+  private _urlStr: string;
   private _send: zipkinTypes.SendFunction;
+  private _getHeaders: zipkinTypes.GetHeaders | undefined;
   private _serviceName?: string;
   private _isShutdown: boolean;
   private _sendingPromises: Promise<unknown>[] = [];
 
   constructor(config: zipkinTypes.ExporterConfig = {}) {
-    const urlStr = config.url || ZipkinExporter.DEFAULT_URL;
-    this._send = prepareSend(urlStr, config.headers);
+    this._urlStr = config.url || ZipkinExporter.DEFAULT_URL;
+    this._send = prepareSend(this._urlStr, config.headers);
     this._serviceName = config.serviceName;
     this._statusCodeTagName = config.statusCodeTagName || statusCodeTagName;
     this._statusDescriptionTagName =
       config.statusDescriptionTagName || statusDescriptionTagName;
     this._isShutdown = false;
+    if (typeof config.getHeadersBeforeSend === 'function') {
+      this._getHeaders = prepareGetHeaders(config.getHeadersBeforeSend);
+    } else {
+      // noop
+      this._beforeSend = function () {};
+    }
   }
 
   /**
@@ -96,6 +105,18 @@ export class ZipkinExporter implements SpanExporter {
     });
   }
 
+  /**
+   * if user defines getHeadersBeforeSend in config then this will be called
+   * everytime before send, otherwise it will be replaced with noop in
+   * constructor
+   * @default noop
+   */
+  private _beforeSend() {
+    if (this._getHeaders) {
+      this._send = prepareSend(this._urlStr, this._getHeaders());
+    }
+  }
+
   /**
    * Transform spans and sends to Zipkin service.
    */
@@ -116,6 +137,7 @@ export class ZipkinExporter implements SpanExporter {
         this._statusDescriptionTagName
       )
     );
+    this._beforeSend();
     return this._send(zipkinSpans, (result: ExportResult) => {
       if (done) {
         return done(result);

packages/opentelemetry-exporter-zipkin/test/browser/zipkin.test.ts

@@ -97,6 +97,40 @@ describe('Zipkin Exporter - web', () => {
       });
     });
   });
+  describe('when getHeadersBeforeSend is defined', () => {
+    let server: any;
+    beforeEach(() => {
+      server = sinon.fakeServer.create();
+      spySend.restore();
+    });
+
+    afterEach(() => {
+      server.restore();
+    });
+
+    it('should add headers from callback', done => {
+      zipkinExporter = new ZipkinExporter({
+        getHeadersBeforeSend: () => {
+          return {
+            foo1: 'bar1',
+            foo2: 'bar2',
+          };
+        },
+      });
+      zipkinExporter.export(spans, () => {});
+
+      setTimeout(() => {
+        const [{ requestHeaders }] = server.requests;
+
+        ensureHeadersContain(requestHeaders, {
+          foo1: 'bar1',
+          foo2: 'bar2',
+        });
+
+        done();
+      });
+    });
+  });
 
   describe('export with custom headers', () => {
     let server: any;

packages/opentelemetry-exporter-zipkin/test/common/zipkin.test.ts

@@ -0,0 +1,50 @@
+/*
+ * Copyright The OpenTelemetry 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
+ *
+ *      https://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.
+ */
+
+import * as assert from 'assert';
+import { ZipkinExporter } from '../../src';
+import * as sinon from 'sinon';
+import { mockedReadableSpan } from '../helper';
+
+describe('zipkin - header interceptor', () => {
+  describe('getHeadersBeforeSend', () => {
+    describe('when callback is defined', () => {
+      it('should call callback before sending', () => {
+        const getHeadersBeforeSend = sinon.spy();
+        const span = Object.assign({}, mockedReadableSpan);
+        const exporter = new ZipkinExporter({
+          getHeadersBeforeSend,
+        });
+        const oldFunction = exporter['_send'];
+        exporter.export([span], () => {});
+
+        assert.strictEqual(getHeadersBeforeSend.callCount, 1);
+        assert.notStrictEqual(exporter['_getHeaders'], undefined);
+        assert.notStrictEqual(oldFunction, exporter['_send']);
+      });
+    });
+    describe('when callback is NOT defined', () => {
+      it('should call callback before sending', () => {
+        const span = Object.assign({}, mockedReadableSpan);
+        const exporter = new ZipkinExporter();
+        const oldFunction = exporter['_send'];
+        assert.strictEqual(exporter['_getHeaders'], undefined);
+        exporter.export([span], () => {});
+        assert.strictEqual(oldFunction, exporter['_send']);
+      });
+    });
+  });
+});