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ZookeeperNet太难用，写了个RetryHelper来进行配套使用

2024-07-11 07:13:19   208人阅读

普通的zk用法，如下写法：

zk.Exists("/aaa", true);zk.Create(...);

 

但是由于这些API会抛Zookeeper的Exception，比如ConnectionLossException, NoNodeException等，所以必须配合一堆try/catch的机制来catch错误，catch后再处理...

写起来很麻烦

 

因此写了个RetryHelper来封装上面这个try/catch行为，用起来也比较方便，如下：

RetryHelper helper=RetryHelper.Make();helper.CreateNodeStructure = () => { Console.WriteLine("CreateNodeStructure"); };helper.FixConnectionLossAction = () => { Console.WriteLine("FixConnectionLossAction");};helper.IfErrorThen = () => { Console.WriteLine("IfErrorThen"); };helper.Execute(() =>{     this.zk.GetChildren(...);});

 

上面的意思是如果在Execute中，如果报错了，则会看报错的是哪种类型，如果是ConnectionLoss则执行FixConnectionLossAction委托，如果是NoNode则执行建立节点的委托

也就是将最常见的2个zookeeper动作给结构化了：建立节点目录结构以及连接丢失时的重新连接动作 

 

RetryHelper代码：

public class RetryHelper    {        private int retryDelay = 500;        private long signal = 0;        public Action IfErrorThen;        public Action CreateNodeStructure;        public Action FixConnectionLossAction;        public static RetryHelper Make()        {            return new RetryHelper();        }        public void Execute(Action action)        {            while (true)            {                try                {                    action();                    break;                }                catch (ZooKeeperNet.KeeperException.NoNodeException ex)                {                    //create node structure                    Console.WriteLine("retry helper NoNodeException: " + ex.Message);                    if (CreateNodeStructure != null)                        RetryHelper.Make().Execute(CreateNodeStructure);                    continue;                }                catch (ZooKeeperNet.KeeperException.ConnectionLossException ex)                {                    Console.WriteLine("retry helper ConnectionLossException: " + ex.Message);                    long attempSignal = Interlocked.Read(ref signal);                    while (Interlocked.Read(ref signal) > 0)                        Thread.Sleep(retryDelay);                    if (attempSignal == 0)                    {                        Interlocked.Increment(ref signal);                        if (FixConnectionLossAction != null)                            RetryHelper.Make().Execute(FixConnectionLossAction);                        Interlocked.Decrement(ref signal);                    }                    continue;                }                catch (Exception ex)                {                    Console.WriteLine("retry helper catch: " + ex.Message);                    Thread.Sleep(retryDelay);                    if (IfErrorThen != null)                        IfErrorThen();                    continue;                }            }        }    }

 

仔细看上面代码的朋友肯定也注意到里面catch connectionloss exception的代码块中使用了Interlocked，这是因为：在多线程系统侠，如果zk连接丢失了，由于多个地方都在尝试zk操作，所以会导致并发性的进入catch loss connection exception代码处理块，如果此时不加判断的处理所有并发请求，则会出现连接多次到zk，严重影响性能；因此，这里的代码实际上意图是将多次连接请求合并为一次连接。此处特别感谢我同事的code review，哈哈。

下面是个测试并发消除的demo，为了让结果清晰，我把RetryHelper的catch中的Console.WriteLine注释了

static void Main(string[] args)        {            RetryHelper helper=RetryHelper.Make();            helper.CreateNodeStructure = () => { Console.WriteLine("CreateNodeStructure"); };            helper.FixConnectionLossAction = () =>             {                 Console.WriteLine(Thread.CurrentThread.ManagedThreadId+" FixConnectionLossAction BEGIN "+DateTime.Now.ToString());                Thread.Sleep(2000);                Console.WriteLine(Thread.CurrentThread.ManagedThreadId + " FixConnectionLossAction END " + DateTime.Now.ToString());            };            helper.IfErrorThen = () => { Console.WriteLine("IfErrorThen"); };            var tasks=new List<Task>();            for (int i = 0; i < 10; i++)            {                var task = new Task(() => {                    helper.Execute(() =>                    {                        throw new ZooKeeperNet.KeeperException.ConnectionLossException();                    });                });                tasks.Add(task);            }            tasks.ForEach(t=>t.Start());            Task.WaitAll(tasks.ToArray());            Console.ReadKey();        }

 

运行：

 

 

code download

 

 

 


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