限速Google Cloud Tasks

Question

我正在尝试将Google Cloud Tasks的速率限制为每秒不超过1个已处理任务。

我用以下方法创建了队列：

gcloud tasks queues create my-queue \
          --max-dispatches-per-second=1 \
          --max-concurrent-dispatches=1 \
          --max-attempts=2 \
          --min-backoff=60s

描述它给我：

name: projects/my-project/locations/us-central1/queues/my-queue
rateLimits:
  maxBurstSize: 10
  maxConcurrentDispatches: 1
  maxDispatchesPerSecond: 1.0
retryConfig:
  maxAttempts: 2
  maxBackoff: 3600s
  maxDoublings: 16
  minBackoff: 60s
state: RUNNING

创建了一堆任务之后，我可以在日志中看到许多任务在1秒的时间内被不希望地处理了：

2019-07-27 02:37:48 default[20190727t043306]  Received task with payload: {'id': 51}
2019-07-27 02:37:48 default[20190727t043306]  "POST /my_handler HTTP/1.1" 200
2019-07-27 02:37:49 default[20190727t043306]  Received task with payload: {'id': 52}
2019-07-27 02:37:49 default[20190727t043306]  "POST /my_handler HTTP/1.1" 200
2019-07-27 02:37:49 default[20190727t043306]  Received task with payload: {'id': 53}
2019-07-27 02:37:49 default[20190727t043306]  "POST /my_handler HTTP/1.1" 200
2019-07-27 02:37:49 default[20190727t043306]  Received task with payload: {'id': 54}
2019-07-27 02:37:49 default[20190727t043306]  "POST /my_handler HTTP/1.1" 200
2019-07-27 02:37:49 default[20190727t043306]  Received task with payload: {'id': 55}
2019-07-27 02:37:49 default[20190727t043306]  "POST /my_handler HTTP/1.1" 200
2019-07-27 02:37:49 default[20190727t043306]  Received task with payload: {'id': 56}
2019-07-27 02:37:49 default[20190727t043306]  "POST /my_handler HTTP/1.1" 200
2019-07-27 02:37:49 default[20190727t043306]  Received task with payload: {'id': 57}
2019-07-27 02:37:49 default[20190727t043306]  "POST /my_handler HTTP/1.1" 200
2019-07-27 02:37:49 default[20190727t043306]  Received task with payload: {'id': 58}

我如何适当地强制它在此1秒时间间隔内运行不超过1个任务？

更新30/06：

我已经用基本设置再次尝试过，同样的问题。

有关设置和过程的更多详细信息：

1. 源代码https://github.com/GoogleCloudPlatform/python-docs-samples/tree/master/appengine/flexible/tasks，无需修改
2. 部署app.yaml，而不是app.flexible.yaml
3. 多次触发任务：python create_app_engine_queue_task.py --project = $ PROJECT_ID --queue = $ QUEUE_ID --location = $ LOCATION_ID --payload = hello
4. 检查日志：已读取gcloud应用日志

这次他们花了一些时间开始处理，但是之后似乎它们或多或少地同时被处理了：

完整日志：

2019-07-30 00:22:37 default[20190730t021951]  [2019-07-30 00:22:37 +0000] [9] [INFO] Starting gunicorn 19.9.0
2019-07-30 00:22:37 default[20190730t021951]  [2019-07-30 00:22:37 +0000] [9] [INFO] Listening at: http://0.0.0.0:8081 (9)
2019-07-30 00:22:37 default[20190730t021951]  [2019-07-30 00:22:37 +0000] [9] [INFO] Using worker: threads
2019-07-30 00:22:37 default[20190730t021951]  [2019-07-30 00:22:37 +0000] [23] [INFO] Booting worker with pid: 23
2019-07-30 00:22:37 default[20190730t021951]  [2019-07-30 00:22:37 +0000] [26] [INFO] Booting worker with pid: 26
2019-07-30 00:27:41 default[20190730t021951]  "POST /example_task_handler HTTP/1.1" 200
2019-07-30 00:27:41 default[20190730t021951]  Received task with payload: hello
2019-07-30 00:27:41 default[20190730t021951]  "POST /example_task_handler HTTP/1.1" 200
2019-07-30 00:27:41 default[20190730t021951]  Received task with payload: hello
2019-07-30 00:27:41 default[20190730t021951]  "POST /example_task_handler HTTP/1.1" 200
2019-07-30 00:27:41 default[20190730t021951]  Received task with payload: hello
2019-07-30 00:37:41 default[20190730t021951]  "POST /example_task_handler HTTP/1.1" 200
2019-07-30 00:37:41 default[20190730t021951]  Received task with payload: hello
2019-07-30 00:37:41 default[20190730t021951]  "POST /example_task_handler HTTP/1.1" 200
2019-07-30 00:37:41 default[20190730t021951]  Received task with payload: hello
2019-07-30 00:37:41 default[20190730t021951]  "POST /example_task_handler HTTP/1.1" 200
2019-07-30 00:37:41 default[20190730t021951]  Received task with payload: hello
2019-07-30 00:37:41 default[20190730t021951]  "POST /example_task_handler HTTP/1.1" 200
2019-07-30 00:37:41 default[20190730t021951]  Received task with payload: hello
2019-07-30 00:37:41 default[20190730t021951]  "POST /example_task_handler HTTP/1.1" 200
2019-07-30 00:37:41 default[20190730t021951]  Received task with payload: hello
2019-07-30 00:37:41 default[20190730t021951]  "POST /example_task_handler HTTP/1.1" 200
2019-07-30 00:37:41 default[20190730t021951]  Received task with payload: hello
2019-07-30 00:37:41 default[20190730t021951]  "POST /example_task_handler HTTP/1.1" 200
2019-07-30 00:37:41 default[20190730t021951]  Received task with payload: hello
2019-07-30 00:37:41 default[20190730t021951]  "POST /example_task_handler HTTP/1.1" 200
2019-07-30 00:37:41 default[20190730t021951]  Received task with payload: hello
2019-07-30 00:37:41 default[20190730t021951]  "POST /example_task_handler HTTP/1.1" 200
2019-07-30 00:37:41 default[20190730t021951]  Received task with payload: hello
2019-07-30 00:37:41 default[20190730t021951]  "POST /example_task_handler HTTP/1.1" 200
2019-07-30 00:37:41 default[20190730t021951]  Received task with payload: hello
2019-07-30 00:37:42 default[20190730t021951]  "POST /example_task_handler HTTP/1.1" 200
2019-07-30 00:37:42 default[20190730t021951]  Received task with payload: hello
2019-07-30 00:37:43 default[20190730t021951]  "POST /example_task_handler HTTP/1.1" 200
2019-07-30 00:37:43 default[20190730t021951]  Received task with payload: hello

Answer 1

tl; dr可能正在按预期工作。您可以预期会出现最初的maxBurstSize任务突发，然后减速到maxDispatchesPerSecond。

这样做的原因是“令牌桶”算法：有一个桶可以容纳最多maxBurstSize令牌，并且最初其中有很多令牌。如果计划时间已到，并且存储桶中有令牌并且少于maxConcurrentDispatches飞行中的任务，则会调度任务，否则我们将等待这些条件得到满足。分派任务时，令牌将从存储桶中删除。当存储桶未满时，将以的速率添加令牌maxDispatchesPerSecond。因此，速率并不完全是任务分配的限制。只要存储桶中有令牌并且任务可以运行，就可以以任意速率发送任务。只有当任务必须等待令牌时，我们才必须减速到给定的速率。由于存储桶已满，因此可以进行初始爆破。

在Cloud Tasks API和控制台中，存储桶大小为只读（API称为max_burst_size）。但是使用较旧的queue.yaml配置，您可以控制存储桶大小以及其他参数，例如

queue:
- name: my-appengine-queue
  rate: 2/s
  bucket_size: 20
  max_concurrent_requests: 5

然后gcloud app deploy queue.yaml。但是，如果您这样做，请注意以下陷阱：https : //cloud.google.com/tasks/docs/queue-yaml#pitfalls

仅供参考，有一个问题尚待探讨，看看是否可以改进文档。