In dotnet core how can I ensure only one copy of my application is running?

问题

In the past I have done something like this

private static bool AlreadyRunning()
{
    var processes = Process.GetProcesses();
    var currentProc = Process.GetCurrentProcess();
    logger.Info($"Current proccess: {currentProc.ProcessName}");
    foreach (var process in processes)
    {
        if (currentProc.ProcessName == process.ProcessName && currentProc.Id != process.Id)
        {
            logger.Info($"Another instance of this process is already running: {process.Id}");
            return true;
        }
    }
    return false;
}

Which has worked well. In the new dotnet core world everything has a process name of dotnet so I can only run one dotnet app at a time! Not quite what I want :D

Is there an ideal way of doing this in dotnet? I see mutex suggested but I am not sure I understand the possible downsides or error states running on other systems than a windows machine.

回答1:

.NET Core now supports global named mutex. From PR description, that added that functionality:

On systems that support thread process-shared robust recursive mutexes, they will be used

On other systems, file locks are used. File locks, unfortunately, don't have a timeout in the blocking wait call, and I didn't find any other sync object with a timed wait with the necessary properties, so polling is done for timed waits.

Also, there is a useful note in Named mutex not supported on Unix issue about mutex name, that should be used:

By default, names have session scope and sessions are more granular on Unix (each terminal gets its own session). Try adding a "Global" prefix to the name minus the quotes.

回答2:

In the end I used a mutex and it seeeeeems okay.

I grabbed the code from here What is a good pattern for using a Global Mutex in C#?

The version of core I am using does not seem to have some of the security settings stuff so I just deleted it. I am sure it will be fine. (new Mutex only takes 3 parameters)

    private static void Main(string[] args)
    {
        LogManager.Configuration = new XmlLoggingConfiguration("nlog.config");
        logger = LogManager.GetLogger("console");
        logger.Info("Trying to start");

        const string mutexId = @"Global\{{guid-guid-guid-guid-guid}}";

        bool createdNew;
        using (var mutex = new Mutex(false, mutexId, out createdNew))
        {
            var hasHandle = false;
            try
            {
                try
                {
                    hasHandle = mutex.WaitOne(5000, false);
                    if (!hasHandle)
                    {
                        logger.Error("Timeout waiting for exclusive access");
                        throw new TimeoutException("Timeout waiting for exclusive access");
                    }
                }
                catch (AbandonedMutexException)
                {
                    hasHandle = true;
                }

                // Perform your work here.
                PerformWorkHere();
            }
            finally
            {
                if (hasHandle)
                {
                    mutex.ReleaseMutex();
                }
            }
        }
    }

来源：https://stackoverflow.com/questions/46302756/in-dotnet-core-how-can-i-ensure-only-one-copy-of-my-application-is-running

标签

singleton

.net-core

console-application

mutex