elastic-apm-node/lib/instrumentation/run-context/BasicRunContextManager.js

The official Elastic APM agent for Node.js

/*
 * Copyright Elasticsearch B.V. and other contributors where applicable.
 * Licensed under the BSD 2-Clause License; you may not use this file except in
 * compliance with the BSD 2-Clause License.
 */

'use strict';

const { AbstractRunContextManager } = require('./AbstractRunContextManager');

// A basic manager for run context. It handles a stack of run contexts, but does
// no automatic tracking (via async_hooks or otherwise). Use one of the
// subclasses.
//
// (Adapted from https://github.com/open-telemetry/opentelemetry-js/blob/main/packages/opentelemetry-context-async-hooks/src/AsyncHooksContextManager.ts)
class BasicRunContextManager extends AbstractRunContextManager {
  constructor(log, runContextClass) {
    super(log, runContextClass);
    this._stack = []; // Top of stack is the current run context.
  }

  // A string representation useful for debug logging. For example,
  //    BasicRunContextManager(
  //      RC(Trans(685ead, manual), [Span(9dd31c, GET httpstat.us, ended)]),
  //      RC(Trans(685ead, manual)) )
  toString() {
    return `${this.constructor.name}( ${this._stack
      .map((rc) => rc.toString())
      .join(', ')} )`;
  }

  enable() {
    return this;
  }

  disable() {
    this._stack = [];
    return this;
  }

  // Reset state for re-use of this context manager by tests in the same process.
  testReset() {
    this.disable();
    this.enable();
  }

  active() {
    return this._stack[this._stack.length - 1] || this.root();
  }

  with(runContext, fn, thisArg, ...args) {
    this._enterRunContext(runContext);
    try {
      return fn.call(thisArg, ...args);
    } finally {
      this._exitRunContext();
    }
  }

  // This public method is needed to support the semantics of
  // apm.startTransaction() and apm.startSpan() that impact the current run
  // context.
  //
  // Otherwise, all run context changes are via `.with()` -- scoped to a
  // function call -- or via the "before" async hook -- scoped to an async task.
  supersedeRunContext(runContext) {
    this._exitRunContext();
    this._enterRunContext(runContext);
  }

  _enterRunContext(runContext) {
    this._stack.push(runContext);
  }

  _exitRunContext() {
    this._stack.pop();
  }
}

module.exports = {
  BasicRunContextManager,
};