text: // Copyright (c) 2020, Compiler Explorer Authors
  // All rights reserved.
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are met:
  //
  //     * Redistributions of source code must retain the above copyright notice,
  //       this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above copyright
  //       notice, this list of conditions and the following disclaimer in the
  //       documentation and/or other materials provided with the distribution.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  // ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
  // LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  // CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  // SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  // CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  // POSSIBILITY OF SUCH DAMAGE.
  
  import {executionAsyncId} from 'async_hooks';
  
  import {default as Queue} from 'p-queue';
  
  export class CompilationQueue {
      constructor(concurrency, timeout) {
          this._running = new Set();
          this._queue = new Queue({
              concurrency,
              timeout,
              throwOnTimeout: true,
          });
      }
  
      static fromProps(ceProps) {
          return new CompilationQueue(
              ceProps('maxConcurrentCompiles', 1),
              ceProps('compilationEnvTimeoutMs'));
      }
  
      enqueue(job) {
          const enqueueAsyncId = executionAsyncId();
          // If we're asked to enqueue a job when we're already in a async queued job context, just run it.
          // This prevents a deadlock.
          if (this._running.has(enqueueAsyncId))
              return job();
          return this._queue.add(() => {
              const jobAsyncId = executionAsyncId();
              if (this._running.has(jobAsyncId))
                  throw new Error('somehow we entered the context twice');
              try {
                  this._running.add(jobAsyncId);
                  return job();
              } finally {
                  this._running.delete(jobAsyncId);
              }
          });
      }
  
      status() {
          const pending = this._queue.pending;
          const size = this._queue.size;
          return {
              busy: pending > 0 || size > 0,
              pending,
              size,
          };
      }
  }
  