class ActiveLimitFilter implements Filter, Filter.Listener {

    @Override
    public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
        URL url = invoker.getUrl();
        String methodName = invocation.getMethodName();
        int max = invoker.getUrl().getMethodParameter(methodName, ACTIVES_KEY, 0);
        final RpcStatus rpcStatus = RpcStatus.getStatus(invoker.getUrl(), invocation.getMethodName());
        if (!RpcStatus.beginCount(url, methodName, max)) {
            long timeout = invoker.getUrl().getMethodParameter(invocation.getMethodName(), TIMEOUT_KEY, 0);
            long start = System.currentTimeMillis();
            long remain = timeout;
            synchronized (rpcStatus) {
                while (!RpcStatus.beginCount(url, methodName, max)) {
                    try {
                        rpcStatus.wait(remain);
                    } catch (InterruptedException e) {
                        // ignore
                    }
                    long elapsed = System.currentTimeMillis() - start;
                    remain = timeout - elapsed;
                    if (remain <= 0) {
                        throw new RpcException(RpcException.LIMIT_EXCEEDED_EXCEPTION,
                                "Waiting concurrent invoke timeout in client-side for service:  " +
                                        invoker.getInterface().getName() + ", method: " + invocation.getMethodName() +
                                        ", elapsed: " + elapsed + ", timeout: " + timeout + ". concurrent invokes: " +
                                        rpcStatus.getActive() + ". max concurrent invoke limit: " + max);
                    }
                }
            }
        }

        invocation.put(ACTIVELIMIT_FILTER_START_TIME, System.currentTimeMillis());

        return invoker.invoke(invocation);
    }

}