refactor: unifying shutdown once with BindOnceFuture

packages/exporter-trace-otlp-grpc/tsconfig.json

@@ -11,6 +11,15 @@
   "references": [
     {
       "path": "../exporter-trace-otlp-http"
+    },
+    {
+      "path": "../opentelemetry-core"
+    },
+    {
+      "path": "../opentelemetry-resources"
+    },
+    {
+      "path": "../opentelemetry-sdk-trace-base"
     }
   ]
 }

packages/exporter-trace-otlp-http/src/OTLPExporterBase.ts

@@ -15,7 +15,7 @@
  */
 
 import { SpanAttributes, diag } from '@opentelemetry/api';
-import { ExportResult, ExportResultCode } from '@opentelemetry/core';
+import { ExportResult, ExportResultCode, BindOnceFuture } from '@opentelemetry/core';
 import {
   OTLPExporterError,
   OTLPExporterConfigBase,
@@ -34,9 +34,8 @@ export abstract class OTLPExporterBase<
   public readonly hostname: string | undefined;
   public readonly attributes?: SpanAttributes;
   protected _concurrencyLimit: number;
-  protected _isShutdown: boolean = false;
-  private _shuttingDownPromise: Promise<void> = Promise.resolve();
   protected _sendingPromises: Promise<unknown>[] = [];
+  protected _shutdownOnce: BindOnceFuture<void>;
 
   /**
    * @param config
@@ -50,6 +49,7 @@ export abstract class OTLPExporterBase<
     this.attributes = config.attributes;
 
     this.shutdown = this.shutdown.bind(this);
+    this._shutdownOnce = new BindOnceFuture(this._shutdown, this);
 
     this._concurrencyLimit =
       typeof config.concurrencyLimit === 'number'
@@ -66,7 +66,7 @@ export abstract class OTLPExporterBase<
    * @param resultCallback
    */
   export(items: ExportItem[], resultCallback: (result: ExportResult) => void): void {
-    if (this._isShutdown) {
+    if (this._shutdownOnce.isCalled) {
       resultCallback({
         code: ExportResultCode.FAILED,
         error: new Error('Exporter has been shutdown'),
@@ -106,28 +106,16 @@ export abstract class OTLPExporterBase<
    * Shutdown the exporter.
    */
   shutdown(): Promise<void> {
-    if (this._isShutdown) {
-      diag.debug('shutdown already started');
-      return this._shuttingDownPromise;
-    }
-    this._isShutdown = true;
+    return this._shutdownOnce.call();
+  }
+
+  private _shutdown(): Promise<void> {
     diag.debug('shutdown started');
-    this._shuttingDownPromise = new Promise((resolve, reject) => {
-      Promise.resolve()
-        .then(() => {
-          return this.onShutdown();
-        })
-        .then(() => {
-          return Promise.all(this._sendingPromises);
-        })
-        .then(() => {
-          resolve();
-        })
-        .catch(e => {
-          reject(e);
-        });
-    });
-    return this._shuttingDownPromise;
+    this.onShutdown();
+    return Promise.all(this._sendingPromises)
+      .then(() => {
+        /** ignore resolved values */
+      });
   }
 
   abstract onShutdown(): void;

packages/exporter-trace-otlp-http/src/platform/browser/OTLPExporterBrowserBase.ts

@@ -69,7 +69,7 @@ export abstract class OTLPExporterBrowserBase<
     onSuccess: () => void,
     onError: (error: otlpTypes.OTLPExporterError) => void
   ): void {
-    if (this._isShutdown) {
+    if (this._shutdownOnce.isCalled) {
       diag.debug('Shutdown already started. Cannot send objects');
       return;
     }

packages/exporter-trace-otlp-http/src/platform/node/OTLPExporterNodeBase.ts

@@ -56,16 +56,14 @@ export abstract class OTLPExporterNodeBase<
     this.compression = config.compression || CompressionAlgorithm.NONE;
   }
 
-  onInit(_config: OTLPExporterNodeConfigBase): void {
-    this._isShutdown = false;
-  }
+  onInit(_config: OTLPExporterNodeConfigBase): void {}
 
   send(
     objects: ExportItem[],
     onSuccess: () => void,
     onError: (error: otlpTypes.OTLPExporterError) => void
   ): void {
-    if (this._isShutdown) {
+    if (this._shutdownOnce.isCalled) {
       diag.debug('Shutdown already started. Cannot send objects');
       return;
     }

packages/exporter-trace-otlp-http/tsconfig.json

@@ -7,5 +7,16 @@
   "include": [
     "src/**/*.ts",
     "test/**/*.ts"
+  ],
+  "references": [
+    {
+      "path": "../opentelemetry-core"
+    },
+    {
+      "path": "../opentelemetry-resources"
+    },
+    {
+      "path": "../opentelemetry-sdk-trace-base"
+    }
   ]
 }

packages/exporter-trace-otlp-proto/tsconfig.json

@@ -11,6 +11,15 @@
   "references": [
     {
       "path": "../exporter-trace-otlp-http"
+    },
+    {
+      "path": "../opentelemetry-core"
+    },
+    {
+      "path": "../opentelemetry-resources"
+    },
+    {
+      "path": "../opentelemetry-sdk-trace-base"
     }
   ]
 }

packages/opentelemetry-core/src/index.ts

@@ -39,4 +39,5 @@ export * from './utils/merge';
 export * from './utils/sampling';
 export * from './utils/url';
 export * from './utils/wrap';
+export * from './utils/callback';
 export * from './version';

packages/opentelemetry-core/src/utils/callback.ts

@@ -0,0 +1,54 @@
+/*
+ * 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 { Deferred } from './promise';
+
+/**
+ * Bind the callback and only invoke the callback once regardless how many times `BindOnceFuture.call` is invoked.
+ */
+export class BindOnceFuture<
+  R,
+  This = unknown,
+  T extends (this: This, ...args: unknown[]) => R = () => R
+> {
+  private _isCalled = false;
+  private _deferred = new Deferred<R>();
+  constructor(private _callback: T, private _that: This) {}
+
+  get isCalled() {
+    return this._isCalled;
+  }
+
+  get promise() {
+    return this._deferred.promise;
+  }
+
+  call(...args: Parameters<T>): Promise<R> {
+    if (!this._isCalled) {
+      this._isCalled = true;
+      try {
+        Promise.resolve(this._callback.call(this._that, ...args))
+          .then(
+            val => this._deferred.resolve(val),
+            err => this._deferred.reject(err)
+          );
+      } catch (err) {
+        this._deferred.reject(err);
+      }
+    }
+    return this._deferred.promise;
+  }
+}

packages/opentelemetry-core/src/utils/promise.ts

@@ -0,0 +1,39 @@
+/*
+ * 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.
+ */
+
+export class Deferred<T> {
+  private _promise: Promise<T>;
+  private _resolve!: (val: T) => void;
+  private _reject!: (error: unknown) => void;
+  constructor() {
+    this._promise = new Promise((resolve, reject) => {
+      this._resolve = resolve;
+      this._reject = reject;
+    });
+  }
+
+  get promise() {
+    return this._promise;
+  }
+
+  resolve(val: T) {
+    this._resolve(val);
+  }
+
+  reject(err: unknown) {
+    this._reject(err);
+  }
+}

packages/opentelemetry-core/test/test-utils.ts

@@ -0,0 +1,30 @@
+/*
+ * 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';
+
+/**
+ * Node.js v8.x and browser compatible `assert.rejects`.
+ */
+export async function assertRejects(promise: any, expect: any) {
+  try {
+    await promise;
+  } catch (err) {
+    assert.throws(() => {
+      throw err;
+    }, expect);
+  }
+}

packages/opentelemetry-core/test/utils/callback.test.ts

@@ -0,0 +1,63 @@
+/*
+ * 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 * as sinon from 'sinon';
+import { BindOnceFuture } from '../../src';
+import { assertRejects } from '../test-utils';
+
+describe('callback', () => {
+  describe('BindOnceFuture', () => {
+    it('should call once', async () => {
+      const stub = sinon.stub();
+      const that = {};
+      const future = new BindOnceFuture(stub, that);
+
+      await Promise.all([
+        future.call(1),
+        future.call(2),
+      ]);
+      await future.call(3);
+      await future.promise;
+
+      assert.strictEqual(stub.callCount, 1);
+      assert.deepStrictEqual(stub.firstCall.args, [1]);
+      assert.deepStrictEqual(stub.firstCall.thisValue, that);
+
+      assert(future.isCalled);
+    });
+
+    it('should handle thrown errors', async () => {
+      const stub = sinon.stub();
+      stub.throws(new Error('foo'));
+      const future = new BindOnceFuture(stub, undefined);
+
+      await assertRejects(future.call(), /foo/);
+      await assertRejects(future.call(), /foo/);
+      await assertRejects(future.promise, /foo/);
+    });
+
+    it('should handle rejections', async () => {
+      const stub = sinon.stub();
+      stub.rejects(new Error('foo'));
+      const future = new BindOnceFuture(stub, undefined);
+
+      await assertRejects(future.call(), /foo/);
+      await assertRejects(future.call(), /foo/);
+      await assertRejects(future.promise, /foo/);
+    });
+  });
+});

packages/opentelemetry-core/test/utils/promise.test.ts

@@ -0,0 +1,41 @@
+/*
+ * 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 { Deferred } from '../../src/utils/promise';
+import { assertRejects } from '../test-utils';
+
+describe('promise', () => {
+  describe('Deferred', () => {
+    it('should resolve', async () => {
+      const deferred = new Deferred();
+      deferred.resolve(1);
+      deferred.resolve(2);
+      deferred.reject(new Error('foo'));
+
+      const ret = await deferred.promise;
+      assert.strictEqual(ret, 1);
+    });
+
+    it('should reject', async () => {
+      const deferred = new Deferred();
+      deferred.reject(new Error('foo'));
+      deferred.reject(new Error('bar'));
+
+      await assertRejects(deferred.promise, /foo/);
+    });
+  });
+});