如何在debian 8上设置rails sunspot solr production？(How can I set up rails sunspot solr production on debian 8?)

 如果您的目标是保护otherClass.executeCritical(con, arg)调用，那么您将需要锁定otherClass实例的粒度。 如果目标是在给定时间只有一个线程使用“主连接”，这似乎是你非常想要的东西，那么你需要锁定粒度在TCPMasterConnection的实例。 在后一种情况下，您的代码将如下所示： 
 
    public Object criticalFunction(int arg) {
        synchronized(con) {
          return otherClass.executeCritical(con, arg);
        }
    }
 
 现在，如果你在otherClass和con （TCPMasterConnection）中都有多线程不安全的代码，你可能想要一个更大粒度的锁。 在这种情况下，一个简单的事情可能是锁定在类级别，如其他答案中所述。 

If your goal is to protect the otherClass.executeCritical(con, arg) invocation, then you'll want to lock at the granularity of the otherClass instance. If the goal is to have only one thread using the "master connection" at a given time, which seems like it would be something you very much want, then you need the locking granularity to be at the instance of TCPMasterConnection. In the latter case, your code would look like this:
 
    public Object criticalFunction(int arg) {
        synchronized(con) {
          return otherClass.executeCritical(con, arg);
        }
    }
 
Now if you have multithread-unsafe code in both otherClass and con (of TCPMasterConnection), you'll maybe want a lock with larger granularity. In that case, an easy thing might be to lock at the class level as described in other answers.