Sometimes there's an action required like calling the application layer or responding to a ping, and the thread discovering the action is not the thread that should do the work. We enqueue a runnable on this executor and it gets handled by one of the executor's threads.

### Locks

We have 3 different things that we synchronize on.

#### Http2Connection

   */
  @AndroidIncompatible
  public void testTaskThrowsError() throws Exception {
    class MyError extends Error {}
    CyclicBarrier barrier = new CyclicBarrier(2);
    // we need to make sure the error gets thrown on a different thread.
    ExecutorService service = newSingleThreadExecutor();
    try {
      SequentialExecutor executor = new SequentialExecutor(service);
      Runnable errorTask =
          new Runnable() {

        try {
            init(f);
        } catch (final Exception e) {
            logger.error("Error setting filter config", e);
        }
    }

    /**
     * Gets the filter configuration.
     * @return the filter configuration or null
     */
    public FilterConfig getFilterConfig() {
        return null;
    }

  }

  /**
   * Returns the length of the array.
   *
   * @return the length of the array
   */
  public final int length() {
    return longs.length();
  }

  /**
   * Gets the current value at position {@code i}.
   *
   * @param i the index
   * @return the current value
   */
  public final double get(int i) {
    return longBitsToDouble(longs.get(i));
  }

  /**

            this.url = url;
            this.depth = depth;
        }

        /**
         * Gets the URL of this crawl request.
         *
         * @return the URL to be crawled
         */
        public String getUrl() {
            return url;
        }

        /**
         * Gets the depth of this crawl request in the crawling hierarchy.
         *
         * @return the crawling depth

}

// Wrapper to restClient.CallWithMethod to handle network errors, in case of network error the connection is disconnected
// and a healthcheck routine gets invoked that would reconnect.
func (client *storageRESTClient) callGet(ctx context.Context, rpcMethod string, values url.Values, body io.Reader, length int64) (io.ReadCloser, error) {
	if values == nil {
		values = make(url.Values)

     *
     * @param runtime the job runtime to set
     */
    public void setJobRuntime(final LaJobRuntime runtime) {
        jobRuntimeLocal.set(runtime);
    }

    /**
     * Gets the job runtime for the current thread.
     *
     * @return the job runtime for the current thread
     */
    public LaJobRuntime getJobRuntime() {
        return jobRuntimeLocal.get();
    }

            } catch (final Exception e) {
                logger.error("Could not destroy a process correctly.", e);
            }
        }
        return -1;
    }

    /**
     * Gets the set of session IDs for all currently running processes.
     *
     * @return set of session IDs for running processes
     */
    public Set<String> getRunningSessionIdSet() {

            for (final String role : roles) {
                if (StringUtil.isNotEmpty(role)) {
                    roleSet.add(role);
                }
            }
        }
    }

    /**
     * Gets the current time in milliseconds.
     * @return The current time in milliseconds.
     */
    protected long getCurrentTime() {
        return ComponentUtil.getSystemHelper().getCurrentTimeAsLong();
    }

    // This is trickier than expected. We plan to put 15 values in each of these (WARMUP_MIN to
    // WARMUP_MAX), but the tests assume no values get evicted. Even with a maximumSize of 100, one
    // of the values gets evicted. With weak keys, we use identity equality, which means using
    // System.identityHashCode, which means the assignment of keys to segments is nondeterministic,