Can't seem to make URL request from ElapsedEventHandler

[SlurrerOfSpeech]

I've spent 10+ hours on trying to solve this and can't get it to work!

In short, I have a method

        private async void LoadAndSavePage(object source, ElapsedEventArgs e)
        {
             // ... 
        }

which is being called every 1 second when the Windows Service that contains it is running. I've confirmed that it is indeed being called; I can verify with

        private async void LoadAndSavePage(object source, ElapsedEventArgs e)
        {
            EventLog.WriteEntry("I got called!");
        }

However, as soon as I try to get a web page, for example

        private async void LoadAndSavePage(object source, ElapsedEventArgs e)
        {
            string html = new WebClient().DownloadString("[PLAIN]http://physicsforums.com");[/PLAIN] 
            EventLog.WriteEntry(html);
        }

it doesn't work. The function gets called as scheduled but it never gets to the point where it writes to the event log. Something about introducing a web request messes it up. I'm guessing maybe some type of permissions issue?

I've tried with several libraries including .NET's WebClient and HtmlAgilityPack's HtmlWeb, I've tried with different URLs, etc.

I know it doesn't have to do with the event having a maximum resolution time, for I've also tried

        private async void LoadAndSavePage(object source, ElapsedEventArgs e)
        {
            EventLog.WriteEntry("before sleep");
            Thread.Sleep(1500);
            EventLog.WriteEntry("after sleep");
        }

and confirmed that the whole thing runs.

 

[SlurrerOfSpeech]

Which one of these account types should my service be running under? https://msdn.microsoft.com/en-us/library/system.serviceprocess.serviceaccount(v=vs.110).aspx

I'm guessing NetworkService?

 

[Mark44]

However, as soon as I try to get a web page, for example

        private async void LoadAndSavePage(object source, ElapsedEventArgs e)
        {
            string html = new WebClient().DownloadString("[PLAIN]http://physicsforums.com");[/PLAIN] 
            EventLog.WriteEntry(html);
        }

it doesn't work.

The function gets called as scheduled but it never gets to the point where it writes to the event log. Something about introducing a web request messes it up. I'm guessing maybe some type of permissions issue?

That would be my guess, but that's just a guess. In your following post, you suggest running the service as a NetworkService. I would give that a shot.