timer trigger - Should a triggered Webjob complete?

Question

I have created a very simple WebJob with a TimerTrigger, for example;

        static async Task Main()
        {
            var builder = new HostBuilder();
            builder.ConfigureWebJobs(b =>
            {
                b.AddAzureStorageCoreServices();                
                b.AddTimers();
            });

            builder.ConfigureLogging((context, b) =>
            {
                b.AddConsole();
            });

            var host = builder.Build();
            using (host)
            {
                await host.RunAsync();
            }
        }
    }

    public class Functions
    {
        public static void ProcessTimerMessage([TimerTrigger("*/30 * * * * *", RunOnStartup = true)] TimerInfo timerInfo, ILogger logger)
        {
            logger.LogInformation("I am here");
        }
    }

When I run this in Azure it never finishes. I was expecting this to complete on each run and then start again on the next trigger. Instead it never stops running:

Answer 1

The TimerTrigger for WebJobs runs as a singleton instance at startup and will run continuously, internally keeping track of the interval it runs at (based on the provide cron pattern). If any single invocation takes longer than the interval, then it will contiune processing the work it's doing and skip the overlapping invocation until the current work is complete.

You can read the details here: https://github.com/Azure/azure-webjobs-sdk-extensions/wiki/TimerTrigger