Windows Service just stops. No messages, no alerts, errors, warning - nothing - windows-services

Question

I have a Windows service that just silently stops on its own. Here is the relevant code:
OnStart() method:
protected override void OnStart(string[] args)
{
try
{
InitializeLogging();
// we don't DO command line arguments
if (args.Length > 0)
{
eventLog.WriteEntry("All command line arguments are ignored. You must edit the app.config file manually to make changes to what watchers are run.");
throw new ArgumentException("Command line arguments are ignored.");
}
ReadAppConfig();
RecalculateStartTimes();
InitializeWatchers();
}
catch (Exception e)
{
eventLog.WriteFormattedEntry("Error on Start: {0}", e.Message);
}
finally
{
eventLog.WriteEntry("Service start completed");
}
}
OnStop() method:
protected override void OnStop()
{
eventLog.WriteEntry("Service stopped.");
}
InitializeWatchers() method:
private void InitializeWatchers()
{
try
{
var watchers = _watcherSection.Watchers.ToList<WatcherElement>();
eventLog.WriteEntry(string.Format("Initializing {0} watchers.", watchers.Count()));
var obsWatchers = watchers.ToObservable();
obsWatchers.SelectMany(
watcher =>
Observable.Timer(watcher.StartTime, TimeSpan.FromHours(watcher.Interval))
.SelectMany(
Observable.FromAsync(
async () => new
{
watcher,
response = await CheckFolder(watcher.Path)
})))
.Subscribe(
onNext: x =>
{
eventLog.WriteFormattedEntry("\nWatcher: {0}, Time:{1}", x.watcher.Name, DateTimeOffset.Now);
if (x.response.Success)
eventLog.WriteFormattedEntry("| Success!\n| Value: '{0}'\n| Message: {0}", x.response.Value, x.response.Message);
else
eventLog.WriteFormattedEntry("| FAILURE!\n| Value: '{0}'\n| Message: {0}\n| Errors: '{0}'", x.response.Value, x.response.Message, x.response.Exceptions.First());
},
onError: e =>
{
var err = e;
var sb = new StringBuilder();
sb.AppendLine("The observer threw an error:")
.AppendFormatLine("| Message: {0}", e.Message);
while (e.InnerException != null)
{
sb.AppendFormatLine("| Inner: {0}", e.InnerException.Message);
e = e.InnerException;
}
sb.AppendLine();
eventLog.WriteEntry(sb.ToString());
throw err;
});
eventLog.WriteEntry("about to wait.");
obsWatchers.Wait();
eventLog.WriteEntry("passed the wait");
}
catch (Exception e)
{
eventLog.WriteFormattedEntry("Exception thrown in InitializeWatchers(WatchersSection): {0}", e.Message);
throw;
}
}
When I run this code, the service starts normally. The event log records three events:
Service & Logging started.
Initializing 1 watchers.
Service start completed.
... and it stops. I have to manually refresh the Services window, but it quits running. I don't get any errors, or any of the other eventLog entries.
The frustrating thing is that this code works perfectly as a Console app. I've changed all the eventLog.WriteEntry() to Console.WriteLine(), but other than that, the code is identical and performs as expected.
Any wisdom would be appreciated.

Answer 1

I suspect that the Service Control Manager is terminating your service because it did not return from OnStart within the timeout window (30 seconds, IIRC).
I have a blog post on managed service basics, which is based on a blog entry by the BCL team. Note that the MSDN docs are insufficient; you must know the information in the BCL team blog post to correctly write a managed service.

Answer 2

Instead of using obsWatchers.Wait() which blocks and causes the problems Stephen has said, just asynchronously subscribe.
Add this property to your class:
private SingleAssignmentDisposable _subscription = new SingleAssignmentDisposable();
Add this to your OnStop method:
_subscription.Dispose();
In your InitializeWatchers(), eliminate the nested call to Subscribe and replace obsWatchers.Wait() with a call to subscribe, like so:
private void InitializeWatchers()
{
try
{
var watchers = _watcherSection.Watchers.ToList<WatcherElement>();
eventLog.WriteEntry(string.Format("Initializing {0} watchers.", watchers.Count()));
var obsWatchers = watchers.ToObservable();
_subscription.Disposable = obsWatchers
.SelectMany(watcher => Observable
.Timer(watcher.StartTime, TimeSpan.FromHours(watcher.Interval))
.SelectMany(_ => Observable.FromAsync(async () => new
{
watcher,
response = await CheckFolder(watcher.Path)
})))
.Subscribe(
onNext: x =>
{
eventLog.WriteFormattedEntry("\nWatcher: {0}, Time:{1}", x.watcher.Name, DateTimeOffset.Now);
if (x.response.Success)
eventLog.WriteFormattedEntry("| Success!\n| Value: '{0}'\n| Message: {0}", x.response.Value, x.response.Message);
else
eventLog.WriteFormattedEntry("| FAILURE!\n| Value: '{0}'\n| Message: {0}\n| Errors: '{0}'", x.response.Value, x.response.Message, x.response.Exceptions.First());
},
onError: e =>
{
var err = e;
var sb = new StringBuilder();
sb.AppendLine("The observer threw an error:")
.AppendFormatLine("| Message: {0}", e.Message);
while (e.InnerException != null)
{
sb.AppendFormatLine("| Inner: {0}", e.InnerException.Message);
e = e.InnerException;
}
sb.AppendLine();
eventLog.WriteEntry(sb.ToString());
throw err;
});
eventLog.WriteEntry("passed the wait");
}
catch (Exception e)
{
eventLog.WriteFormattedEntry("Exception thrown in InitializeWatchers(WatchersSection): {0}", e.Message);
throw;
}
}