SimpleSpanProcessor.ts

/*
 * 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 { context, TraceFlags } from '@opentelemetry/api';
import {
  ExportResultCode,
  globalErrorHandler,
  suppressTracing,
  BindOnceFuture,
} from '@opentelemetry/core';
import { Span } from '../Span';
import { SpanProcessor } from '../SpanProcessor';
import { ReadableSpan } from './ReadableSpan';
import { SpanExporter } from './SpanExporter';

/**
 * An implementation of the {@link SpanProcessor} that converts the {@link Span}
 * to {@link ReadableSpan} and passes it to the configured exporter.
 *
 * Only spans that are sampled are converted.
 */
export class SimpleSpanProcessor implements SpanProcessor {
  private _shutdownOnce: BindOnceFuture<void>;

  constructor(private readonly _exporter: SpanExporter) {
    this._shutdownOnce = new BindOnceFuture(this._shutdown, this);
  }

  forceFlush(): Promise<void> {
    // do nothing as all spans are being exported without waiting
    return Promise.resolve();
  }

  // does nothing.
  onStart(_span: Span): void {}

  onEnd(span: ReadableSpan): void {
    if (this._shutdownOnce.isCalled) {
      return;
    }

    if ((span.spanContext().traceFlags & TraceFlags.SAMPLED) === 0) {
      return;
    }

    // prevent downstream exporter calls from generating spans
    context.with(suppressTracing(context.active()), () => {
      this._exporter.export([span], result => {
        if (result.code !== ExportResultCode.SUCCESS) {
          globalErrorHandler(
            result.error ??
              new Error(
                `SimpleSpanProcessor: span export failed (status ${result})`
              )
          );
        }
      });
    });
  }

  shutdown(): Promise<void> {
    return this._shutdownOnce.call();
  }

  private _shutdown(): Promise<void> {
    return this._exporter.shutdown();
  }
}