Implementing Backend Rate Limiting with a Python Decorator

When building web products, certain features must restrict how frequently a user can perform actions to prevent malicious attacks, and both frontend and backend need such controls to avoid bypassing frontend limits.

For example, a testing platform that rents real devices may need to limit how often a user can take screenshots.

To satisfy the many backend endpoints that require frequency control, a Python decorator is introduced, offering easy extensibility and low modification cost.

The decorator defaults to a 0.3‑second interval, assuming typical user actions occur slower than that.

Decorator implementation:

"""
    seconds单位是秒
    需要捕获异常exceptions.FunctionFrequency
"""
def runFrequencyLimit(seconds=0.3):
    def call_func(fn):
        cache = {}
        @wraps(fn)
        def wrapper(*params, **paramMap):
            if fn.__name__ in cache:
                last_time  = cache[fn.__name__]
                if time.time() - last_time > seconds:
                    ret = fn(*params, **paramMap)
                    cache[fn.__name__] = time.time()
                    return ret
                else:
                    raise exceptions.FunctionFrequency()
            else:
                ret = fn(*params, **paramMap)
                cache[fn.__name__] = time.time()
                return ret
        return wrapper
    return call_func

Usage simply involves adding the decorator to the target function:

@runFrequencyLimit()
def handle_snapshot(self, *params, **paramMap):
    try:
        # screenshot operation omitted
    except exceptions.FunctionFrequency:
        print "操作过于频繁，请休息一下再试^_^"