聊聊Elasticsearch的TimedRunnable

class TimedRunnable extends AbstractRunnable implements WrappedRunnable {
    private final Runnable original;
    private final long creationTimeNanos;
    private long startTimeNanos;
    private long finishTimeNanos = -1;
​
    TimedRunnable(final Runnable original) {
        this.original = original;
        this.creationTimeNanos = System.nanoTime();
    }
​
    @Override
    public void doRun() {
        try {
            startTimeNanos = System.nanoTime();
            original.run();
        } finally {
            finishTimeNanos = System.nanoTime();
        }
    }
​
    @Override
    public void onRejection(final Exception e) {
        if (original instanceof AbstractRunnable) {
            ((AbstractRunnable) original).onRejection(e);
        }
    }
​
    @Override
    public void onAfter() {
        if (original instanceof AbstractRunnable) {
            ((AbstractRunnable) original).onAfter();
        }
    }
​
    @Override
    public void onFailure(final Exception e) {
        if (original instanceof AbstractRunnable) {
            ((AbstractRunnable) original).onFailure(e);
        }
    }
​
    @Override
    public boolean isForceExecution() {
        return original instanceof AbstractRunnable && ((AbstractRunnable) original).isForceExecution();
    }
​
    /**
     * Return the time since this task was created until it finished running.
     * If the task is still running or has not yet been run, returns -1.
     */
    long getTotalNanos() {
        if (finishTimeNanos == -1) {
            // There must have been an exception thrown, the total time is unknown (-1)
            return -1;
        }
        return Math.max(finishTimeNanos - creationTimeNanos, 1);
    }
​
    /**
     * Return the time this task spent being run.
     * If the task is still running or has not yet been run, returns -1.
     */
    long getTotalExecutionNanos() {
        if (startTimeNanos == -1 || finishTimeNanos == -1) {
            // There must have been an exception thrown, the total time is unknown (-1)
            return -1;
        }
        return Math.max(finishTimeNanos - startTimeNanos, 1);
    }
​
    @Override
    public Runnable unwrap() {
        return original;
    }
​
}

public final class QueueResizingEsThreadPoolExecutor extends EsThreadPoolExecutor {
    //......
​
    protected void afterExecute(Runnable r, Throwable t) {
        super.afterExecute(r, t);
        // A task has been completed, it has left the building. We should now be able to get the
        // total time as a combination of the time in the queue and time spent running the task. We
        // only want runnables that did not throw errors though, because they could be fast-failures
        // that throw off our timings, so only check when t is null.
        assert super.unwrap(r) instanceof TimedRunnable : "expected only TimedRunnables in queue";
        final TimedRunnable timedRunnable = (TimedRunnable) super.unwrap(r);
        final long taskNanos = timedRunnable.getTotalNanos();
        final long totalNanos = totalTaskNanos.addAndGet(taskNanos);
​
        final long taskExecutionNanos = timedRunnable.getTotalExecutionNanos();
        assert taskExecutionNanos >= 0 : "expected task to always take longer than 0 nanoseconds, got: " + taskExecutionNanos;
        executionEWMA.addValue(taskExecutionNanos);
​
        if (taskCount.incrementAndGet() == this.tasksPerFrame) {
            final long endTimeNs = System.nanoTime();
            final long totalRuntime = endTimeNs - this.startNs;
            // Reset the start time for all tasks. At first glance this appears to need to be
            // volatile, since we are reading from a different thread when it is set, but it
            // is protected by the taskCount memory barrier.
            // See: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/atomic/package-summary.html
            startNs = endTimeNs;
​
            // Calculate the new desired queue size
            try {
                final double lambda = calculateLambda(tasksPerFrame, Math.max(totalNanos, 1L));
                final int desiredQueueSize = calculateL(lambda, targetedResponseTimeNanos);
                final int oldCapacity = workQueue.capacity();
​
                if (logger.isDebugEnabled()) {
                    final long avgTaskTime = totalNanos / tasksPerFrame;
                    logger.debug("[{}]: there were [{}] tasks in [{}], avg task time [{}], EWMA task execution [{}], " +
                                    "[{} tasks/s], optimal queue is [{}], current capacity [{}]",
                            getName(),
                            tasksPerFrame,
                            TimeValue.timeValueNanos(totalRuntime),
                            TimeValue.timeValueNanos(avgTaskTime),
                            TimeValue.timeValueNanos((long)executionEWMA.getAverage()),
                            String.format(Locale.ROOT, "%.2f", lambda * TimeValue.timeValueSeconds(1).nanos()),
                            desiredQueueSize,
                            oldCapacity);
                }
​
                // Adjust the queue size towards the desired capacity using an adjust of
                // QUEUE_ADJUSTMENT_AMOUNT (either up or down), keeping in mind the min and max
                // values the queue size can have.
                final int newCapacity =
                        workQueue.adjustCapacity(desiredQueueSize, QUEUE_ADJUSTMENT_AMOUNT, minQueueSize, maxQueueSize);
                if (oldCapacity != newCapacity && logger.isDebugEnabled()) {
                    logger.debug("adjusted [{}] queue size by [{}], old capacity: [{}], new capacity: [{}]", getName(),
                            newCapacity > oldCapacity ? QUEUE_ADJUSTMENT_AMOUNT : -QUEUE_ADJUSTMENT_AMOUNT,
                            oldCapacity, newCapacity);
                }
            } catch (ArithmeticException e) {
                // There was an integer overflow, so just log about it, rather than adjust the queue size
                logger.warn(() -> new ParameterizedMessage(
                                "failed to calculate optimal queue size for [{}] thread pool, " +
                                "total frame time [{}ns], tasks [{}], task execution time [{}ns]",
                                getName(), totalRuntime, tasksPerFrame, totalNanos),
                        e);
            } finally {
                // Finally, decrement the task count and time back to their starting values. We
                // do this at the end so there is no concurrent adjustments happening. We also
                // decrement them instead of resetting them back to zero, as resetting them back
                // to zero causes operations that came in during the adjustment to be uncounted
                int tasks = taskCount.addAndGet(-this.tasksPerFrame);
                assert tasks >= 0 : "tasks should never be negative, got: " + tasks;
​
                if (tasks >= this.tasksPerFrame) {
                    // Start over, because we can potentially reach a "never adjusting" state,
                    //
                    // consider the following:
                    // - If the frame window is 10, and there are 10 tasks, then an adjustment will begin. (taskCount == 10)
                    // - Prior to the adjustment being done, 15 more tasks come in, the taskCount is now 25
                    // - Adjustment happens and we decrement the tasks by 10, taskCount is now 15
                    // - Since taskCount will now be incremented forever, it will never be 10 again,
                    //   so there will be no further adjustments
                    logger.debug(
                            "[{}]: too many incoming tasks while queue size adjustment occurs, resetting measurements to 0", getName());
                    totalTaskNanos.getAndSet(1);
                    taskCount.getAndSet(0);
                    startNs = System.nanoTime();
                } else {
                    // Do a regular adjustment
                    totalTaskNanos.addAndGet(-totalNanos);
                }
            }
        }
    }
​
    //......
}