Auto-refresh for Fever on AppFog

Today, I got asked something about my “Installing Fever on AppFog” tutorial. Fever has an inbuilt module to refresh your RSS feeds periodically but this module doesn’t work on all types of servers and it certainly doesn’t work on AppFog. Shaun, being the good guy that he is, lists out a way to set up a curl command with a cron job to refresh the feeds automatically. Unfortunately, AppFog doesn’t support crontab directly either. So, I got asked if there’s a solution for this. After a little bit of Googling and finding this solution on stackoverflow, I built up a working solution specific to Fever on Appfog. The detail follows –

Building a cron job on AppFog involves you to create an additional app that will poll the Fever Refresh API endpoint using a PHP curl command. The code that you must use is as follows –

<?php
    set_time_limit(0);
    while (true) {
        print "blahn";
        $ch = curl_init("http://fever.nitinkhanna.com/?refresh");
        curl_exec($ch);
        curl_close($ch);
        sleep(900);
    }
?>

After you copy this, follow the instructions given on the stackoverflow page I’ve referenced. In short, the steps are –
1. Copy the above code and put it in a file – index.php in a new folder on your computer. Replace the “fever.nitinkhanna.com/?refresh” with your own Refresh Endpoint. To find your Endpoint, open your Fever installation and to into Extras.
2. Run the “af push” command on the directory using your Terminal
3. Deploy from the current directory, give the app a name (I gave it FeverCron)
4. It detects the language to be PHP, but say No to that.
5. Select Standalone when it asks for Application Type
6. Select php when it asks run time.
7. When it asks for php start command, give “php index.php”
8. This is important – when it asks you to select the Infrastructure, select the same one as the one you select for your Fever installation. (I selected AWS US East for both)
9. Your app does not need a deployed URL
10. Select the default memory and instances and say No to binding or creating services to bind with the app
11. Say Yes to saving the configuration. After this, your app will be uploaded and started.

If you want to check your app’s functionality, there are two ways –
1. After every 15 minutes (900 seconds), your app will call the Fever Refresh endpoint, so your Fever installation will automatically refresh. This will show up in the Fever App
2. Alternatively, I’ve added a small debug code to print “blah” every time it runs. After a couple of runs of 15 minute intervals, call a command “af logs FeverCron”. This will show blah printed out a couple of times and will also show errors if there are any.

This has working for me all afternoon, without fail. Since Appfog is really good infrastructure, it doesn’t crash or overload because of such a refresh time.

Special thanks to Leonel on stackoverflow for his helpful answer to an important problem.