fix(sdk-trace-base): eager exporting for batch span processor

CHANGELOG.md

@@ -22,6 +22,7 @@ For experimental package changes, see the [experimental CHANGELOG](experimental/
     * `telemetry.sdk.name`
     * `telemetry.sdk.language`
     * `telemetry.sdk.version`
+* fix(sdk-trace-base): eager exporting for batch span processor [#3458](https://github.com/open-telemetry/opentelemetry-js/pull/3458) @seemk
 
 ### :books: (Refine Doc)
 

packages/opentelemetry-sdk-trace-base/src/export/BatchSpanProcessorBase.ts

@@ -43,6 +43,7 @@ export abstract class BatchSpanProcessorBase<T extends BufferConfig>
 
   private _finishedSpans: ReadableSpan[] = [];
   private _timer: NodeJS.Timeout | undefined;
+  private _nextExport: number = 0;
   private _shutdownOnce: BindOnceFuture<void>;
 
   constructor(private readonly _exporter: SpanExporter, config?: T) {
@@ -72,6 +73,8 @@ export abstract class BatchSpanProcessorBase<T extends BufferConfig>
       );
       this._maxExportBatchSize = this._maxQueueSize;
     }
+
+    this._resetTimer(this._scheduledDelayMillis);
   }
 
   forceFlush(): Promise<void> {
@@ -100,17 +103,11 @@ export abstract class BatchSpanProcessorBase<T extends BufferConfig>
     return this._shutdownOnce.call();
   }
 
-  private _shutdown() {
-    return Promise.resolve()
-      .then(() => {
-        return this.onShutdown();
-      })
-      .then(() => {
-        return this._flushAll();
-      })
-      .then(() => {
-        return this._exporter.shutdown();
-      });
+  private async _shutdown() {
+    this.onShutdown();
+    this._clearTimer();
+    await this._flushAll();
+    await this._exporter.shutdown();
   }
 
   /** Add a span in the buffer. */
@@ -120,42 +117,38 @@ export abstract class BatchSpanProcessorBase<T extends BufferConfig>
       return;
     }
     this._finishedSpans.push(span);
-    this._maybeStartTimer();
+    this._exportCompleteBatch();
   }
 
   /**
    * Send all spans to the exporter respecting the batch size limit
    * This function is used only on forceFlush or shutdown,
    * for all other cases _flush should be used
    * */
-  private _flushAll(): Promise<void> {
-    return new Promise((resolve, reject) => {
-      const promises = [];
-      // calculate number of batches
-      const count = Math.ceil(
-        this._finishedSpans.length / this._maxExportBatchSize
-      );
-      for (let i = 0, j = count; i < j; i++) {
-        promises.push(this._flushOneBatch());
-      }
-      Promise.all(promises)
-        .then(() => {
-          resolve();
-        })
-        .catch(reject);
-    });
+  private async _flushAll(): Promise<void> {
+    const promises = [];
+    // calculate number of batches
+    const count = Math.ceil(
+      this._finishedSpans.length / this._maxExportBatchSize
+    );
+    for (let i = 0, j = count; i < j; i++) {
+      promises.push(this._exportOneBatch());
+    }
+
+    await Promise.all(promises);
   }
 
-  private _flushOneBatch(): Promise<void> {
-    this._clearTimer();
+  private async _exportOneBatch(): Promise<void> {
     if (this._finishedSpans.length === 0) {
-      return Promise.resolve();
+      return;
     }
+
     return new Promise((resolve, reject) => {
       const timer = setTimeout(() => {
         // don't wait anymore for export, this way the next batch can start
         reject(new Error('Timeout'));
       }, this._exportTimeoutMillis);
+      unrefTimer(timer);
       // prevent downstream exporter calls from generating spans
       context.with(suppressTracing(context.active()), () => {
         // Reset the finished spans buffer here because the next invocations of the _flush method
@@ -179,20 +172,43 @@ export abstract class BatchSpanProcessorBase<T extends BufferConfig>
     });
   }
 
-  private _maybeStartTimer() {
-    if (this._timer !== undefined) return;
-    this._timer = setTimeout(() => {
-      this._flushOneBatch()
-        .then(() => {
-          if (this._finishedSpans.length > 0) {
-            this._clearTimer();
-            this._maybeStartTimer();
-          }
-        })
-        .catch(e => {
-          globalErrorHandler(e);
-        });
-    }, this._scheduledDelayMillis);
+  private async _tryExportOneBatch(): Promise<void> {
+    try {
+      await this._exportOneBatch();
+    } catch (e) {
+      globalErrorHandler(e);
+    }
+  }
+
+  private async _export() {
+    await this._tryExportOneBatch();
+
+    if (this._finishedSpans.length >= this._maxExportBatchSize) {
+      this._resetTimer(0);
+    } else {
+      this._resetTimer(this._scheduledDelayMillis);
+    }
+  }
+
+  private _exportCompleteBatch() {
+    if (this._finishedSpans.length < this._maxExportBatchSize) {
+      return;
+    }
+
+    if (this._nextExport === 0) {
+      return;
+    }
+
+    this._resetTimer(0);
+  }
+
+  private _resetTimer(timeout: number) {
+    this._nextExport = timeout;
+    this._clearTimer();
+
+    this._timer = setTimeout(async () => {
+      await this._export();
+    }, timeout);
     unrefTimer(this._timer);
   }
 

packages/opentelemetry-sdk-trace-base/test/common/export/BatchSpanProcessorBase.test.ts

@@ -174,7 +174,7 @@ describe('BatchSpanProcessorBase', () => {
       assert.strictEqual(spy.args.length, 0);
     });
 
-    it('should export the sampled spans with buffer size reached', done => {
+    it('should export the sampled spans with buffer size reached', async () => {
       const clock = sinon.useFakeTimers();
       const processor = new BatchSpanProcessor(exporter, defaultBufferConfig);
       for (let i = 0; i < defaultBufferConfig.maxExportBatchSize; i++) {
@@ -189,14 +189,11 @@ describe('BatchSpanProcessorBase', () => {
       processor.onStart(span, ROOT_CONTEXT);
       processor.onEnd(span);
 
-      setTimeout(async () => {
-        assert.strictEqual(exporter.getFinishedSpans().length, 5);
-        await processor.shutdown();
-        assert.strictEqual(exporter.getFinishedSpans().length, 0);
-        done();
-      }, defaultBufferConfig.scheduledDelayMillis + 1000);
-      clock.tick(defaultBufferConfig.scheduledDelayMillis + 1000);
+      clock.tick(0);
+      assert.strictEqual(exporter.getFinishedSpans().length, 5);
       clock.restore();
+      await processor.shutdown();
+      assert.strictEqual(exporter.getFinishedSpans().length, 0);
     });
 
     it('should force flush when timeout exceeded', done => {