public static SafeXmlReaderWriter Get(IScopeProvider scopeProvider, SystemLock xmlLock, XmlDocument xml, Action <XmlDocument> refresh, Action <XmlDocument, bool> apply, bool writer)
{
var scopeContext = scopeProvider.Context;
// no real scope = just create a reader/writer instance
if (scopeContext == null)
{
// obtain exclusive access to xml and create reader/writer
var releaser = xmlLock.Lock();
return(new SafeXmlReaderWriter(releaser, xml, refresh, apply, writer, false));
}
// get or create an enlisted reader/writer
var rw = scopeContext.Enlist(EnlistKey,
() => // creator
{
// obtain exclusive access to xml and create reader/writer
var releaser = xmlLock.Lock();
return(new SafeXmlReaderWriter(releaser, xml, refresh, apply, writer, true));
},
(completed, item) => // action
{
item.DisposeForReal(completed);
}, EnlistPriority);
// ensure it's not already in-use - should never happen, just being super safe
if (rw._using)
{
throw new InvalidOperationException("panic: used.");
}
rw._using = true;
return(rw);
}
public Task <bool> AcquireLockAsync(int millisecondsTimeout)
{
// signal other instances that we want the lock, then wait on the lock,
// which may timeout, and this is accepted - see comments below
// signal, then wait for the lock, then make sure the event is
// reset (maybe there was noone listening..)
_signal.Set();
// if more than 1 instance reach that point, one will get the lock
// and the other one will timeout, which is accepted
//This can throw a TimeoutException - in which case should this be in a try/finally to ensure the signal is always reset.
try
{
_lockRelease = _systemLock.Lock(millisecondsTimeout);
return(Task.FromResult(true));
}
catch (TimeoutException ex)
{
_logger.Error <MainDomSemaphoreLock>(ex);
return(Task.FromResult(false));
}
finally
{
// we need to reset the event, because otherwise we would end up
// signaling ourselves and committing suicide immediately.
// only 1 instance can reach that point, but other instances may
// have started and be trying to get the lock - they will timeout,
// which is accepted
_signal.Reset();
}
}
public override void Run()
{
lock (_locko)
{
_logger.Debug <XmlStoreFilePersister>("Run now (sync).");
// not really needed but safer (it's only us invoking Run, but the method is public...)
_released = true;
}
using (_runLock.Lock())
{
_store.SaveXmlToFile();
}
}