python - 在 App Engine 中为 Web 请求实施速率限制或节流算法的有效方法？

Question

我正在寻找为 Web 应用程序实现移动时间窗口速率限制算法的有效方法。我正在寻找一种可扩展的算法。

到目前为止，我正在考虑使用分片计数器和内存缓存。

这里是伪语言的算法：

For each request:
1: get the number of requests in the last N minutes from memcache
2: if nothing found in the memcache (memcache flushed or first call?)
3:   get the number of requests in the last N minutes from ndb (expensive!)
4: if the number is to high
5:   block the request
6: increment the sharding counter
7: increment the memcache value (failsafe, if an error occurs here ignore it)
8: process the request

到目前为止，我发现的其他问题不适用于 App Engine 的上下文。

Answer 1

您可以完全在 memcache 中执行类似的操作，尽管它无法在随机键逐出或刷新中存活：

# Create a key based on time truncated to the minute.
key = 'X' + str(datetime.datetime.utcnow().replace(second=0, microsecond=0))
# Initialize the key and have it expire after a while.
if not memcache.add(key, 1, time=90):
    # If the key already exists, increment the value and save the result.
    count = memcache.incr(key)
    # Do something if it's greater than your per minute rate limit.
    if count > MAX_X_PER_MINUTE:
        raise Error