StackExchange.Redis异步调用挂起 [英] StackExchange.Redis async call hangs

问题描述

试图找出为什么这个code挂起。我可以删除在测试底部的3行中的任何一种，它不会挂起，但所有3一起使挂起。任何帮助将大大AP preciated！

  [事实]
公共异步任务CanAddValues​​InParallel（）{
    VAR复用器= ConnectionMultiplexer.Connect（localhost的）;
    变种分贝= muxer.GetDatabase（）;    等待AddAsync（DB，测试，1）;
    等待db.KeyDeleteAsync（测试）;    Task.Run（（）=＆GT; AddAsync（DB，测试，1））。等待（）;
}公共异步任务＆LT;布尔＆GT; AddAsync（DB了IDatabase，串键，字符串值）{
    返回等待db.StringSetAsync（键，值，空，When.NotExists）;
}
 

解决方案

这听起来好像同步上下文僵局从混合等待和等待。这就是为什么你的从不这么做 - （转换成吉尔伯特和沙利文）的 好，几乎没有！ 的

如果有帮助，我的犯罪嫌疑人的，取消等待在等待子树将修复它 - 这应该是微不足道的，因为这棵树可以用一个简单的直通取代：

 公共任务＆LT;布尔＆GT; AddAsync（DB了IDatabase，串键，字符串值）{
    返回db.StringSetAsync（键，值，空，When.NotExists）;
}
 

这里最重要的一点是，SE.Redis绕过同步上下文内部（正常库code），所以它不应该有僵局。

但最终：混合等待和等待是不是一个好主意。除了死锁，这是在异步同步 - 一个反模式

。

Trying to figure out why this code hangs. I can remove any one of the 3 lines at the bottom of the test and it won't hang, but all 3 together makes it hang. Any help would be greatly appreciated!

[Fact]
public async Task CanAddValuesInParallel() {
    var muxer = ConnectionMultiplexer.Connect("localhost");
    var db = muxer.GetDatabase();

    await AddAsync(db, "test", "1");
    await db.KeyDeleteAsync("test");

    Task.Run(() => AddAsync(db, "test", "1")).Wait();
}

public async Task<bool> AddAsync(IDatabase db, string key, string value) {
    return await db.StringSetAsync(key, value, null, When.NotExists);
}

解决方案

It sounds to me like a sync-context deadlock from mixing Wait and await. Which is why you never do that - (switching into "Gilbert and Sullivan"): well, hardly ever!

If it helps, I suspect that removing the await in the Wait subtree will fix it - which should be trivial since that tree can be replaced with a trivial pass-thru:

public Task<bool> AddAsync(IDatabase db, string key, string value) {
    return db.StringSetAsync(key, value, null, When.NotExists);
}

The important point here is that SE.Redis bypasses sync-context internally (normal for library code), so it shouldn't have the deadlock.

But ultimately: mixing Wait and await is not a good idea. In addition to deadlocks, this is "sync over async" - an anti-pattern.

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