Hosting interactive code in the Cloud

Azure WebJobs SDK alpha 2 makes it very easy to host code in the cloud and run it interactively.  You can now invoke your SDK functions directly from the dashboard. Some great uses here:

1. Provide admin diagnostic commands for your live site.
2. Easily host code in azure for testing benchmarking code within a datacenter.
3. Sharing your functions so that others trusted folks can call them, without the hassle of writing an MVC front end. 
4. This provides a great live-site debugging tool since you can replay erroneous executions without perturbing the rest of the system.  (Couple that with other SDK debugging features like Who wrote this blob?)

For example, suppose you have a function Writer(). In this case, we’ll just do something silly (take a string and write it out multiple times), but you can imagine doing something more interesting like providing diagnostic functions on your live site (eg ,”GetLogs”, “ClearStaleData”, etc).

 using Microsoft.WindowsAzure.Jobs; // From nuget: Microsoft.WindowsAzure.Jobs.Host
using System.IO;

namespace Live
{
    class Program
    {
        static void Main(string[] args)
        {
            var host = new JobHost();

            host.RunAndBlock();
        }

        // Given a string, write it our 'multiple' times. ("A",3) ==> "AAA".
        public static void Writer(string content, int multiply, [BlobOutput("test/output.txt")] TextWriter output)
        {
            for (int i = 0; i < multiply; i++)
            {
                output.Write(content);
            }
        }
    }
}

Once you run the program to azure, if you go to the dashboard, you’ll see the function show up in the function list (it’s “published” when the JobHost ctor runs):

You can click on that function and see a history of executions and their status. :

You can click on the blue “run function”  to invoke the function directly from the dashboard! This lets you fill in the parameters. Notice that the parameters are parsed from strings. So ‘multiply’ is strongly-typed as an integer, and we parse it by invoking the Int.TryParse function.

And of course, the above page has a shareable password-protected permalink, (looks like: https://simplebatch.scm.azurewebsites.net/azurejobs/function/run?functionId=simplebatch3.Live.Live.Program.Writer ) so that you can share out the invocation ability with others.

You can hit run and the function will get invoked! The assumes that your webjob is running, and the invoke works by queuing a message that the JobHost.RunAndBlock() call will listen to.  (This means that your webjob needs to actually be running somewhere, although if it’s not, that dashboard will warn you about that too). Run will also take you to the “permalink” for the function instance execution, which is a shareable URL that provides information about the function execution. You can see that the output parameter was written to a blob “test/output.txt” and it wrote 9 bytes and the hyperlink will take you to the blobs contents. It also notes that the execution reason was “Ran form dashboard”.

You can also hit “replay function”  on an existing instance to replay the function. This will take you back to the invoke page and  a) pre-seed the parameters with values from the execution and b) record a “parent” link to the permalink back to the original instance of the execution so you can see what was replayed.