How to get Hangfire job scheduler to stagger my 20 minute interval jobs

Question

I have a number of tasks that i need run every 20 minutes. I can achieve this in Hangfire using the cron expression RecurringJob.AddOrUpdate(() => /* my method */, "*/20 * * * *")

The problem with this is, all my tasks will end up running at exactly the same time eg 00:00, 00:20, 00:40, 01:00

Does anyone know of a way to stagger one's 20 minute interval tasks without implementing some sort of manual intervention?

I'd just like Hangfire to run the jobs every 20 minutes from the time I create them, nothing too special :)

Answer 1

I'd try this: First, modify your add or update to specify a job id:

RecurringJob.AddOrUpdate("some-id", () => /* my method */, "*/20 * * * *");

followed by

RecurringJob.Trigger("some-id");

To run a recurring job now, call the Trigger method.

UPDATE: How about a delayed job then instead of a recurring job? Your "my method" creates a new delayed job at the end (Recursion), set to run after 20 mins. You will still use the Trigger method for the first run.

Answer 2

One 'hacky' way of achieving this is to set a small number of workers .

app.UseHangfire(config =>
{
    config.UseServer(2);
});

// or
var server = new BackgroundJobServer(2);

Whether you look at this and say 'oh great!' or 'that is a terrible idea' will depend completely on your own usage of Hangfire. If you only run a few things an hour, or every 15 minutes and you find they're 'treading' on each other then this could be a simple solution.

A second way: You could make an async Task and run await Task.Delay(TimeSpan.FromSeconds(10)) to make a short delay. This quite likely could cause your app to shutdown more slowly because it would think you're still running tasks. So I only only using this in an emergency, or if you're ok with the consequences.

Hopefully Hangfire will support this in a more organized way at some point.