Creating Zipped Actions in OpenWhisk

As I continue my journey of learning serverless and OpenWhisk, today I’m going to talk about another way to deploy your code - zipped actions. So what do we mean by zipped actions?

Previously I demonstrated creating actions based on single files. So action Cat was based on the file cat.js. You can also create actions as a sequence of other actions. Zipped actions are basically JavaScript files packed up as a npm module. Why would you want to do this?

First - OpenWhisk provides a set of npm modules you can require in your code. And while that last is nice, you may want something not on that list. By creating your own package of code, you can include that in your action. Secondly, you may just want to split your code into multiple files. The procedure isn’t too terribly difficult.

Let’s assume a simple action:


function main() {
    return { message: "Hello World"}
}

First, I add a package.json to the folder. (It will make things easier if your code for this particular action is in it’s own folder.)


{
  "name": "something",
  "version": "1.0.0",
  "main": "main.js",
  "dependencies" : {
  }
}

The name doesn’t matter (although you’ll probably want to pick something that is sensible for your action), but main should point to the JS file of your action, the entry point to this action as a whole.

Next, modify your action to export the main function:


function main() {
    return { message: "Hello World"}
}

exports.main = main;

Now you’ll want to zip your files. Be very, very, very careful at this step. Do not zip the folder, but the files in the folder. I used Windows’ built in “Send to Compressed folder” feature on the folder itself, and that created a zip where the first entry was the folder. You want to zip the files, not the folder.

Finally, you send this to OpenWhisk like so:

wsk action create packageAction --kind nodejs:6 action.zip

After that, you can run it like any normal action. Note that unzipping your code means it will take a bit longer to run your action if it’s cold (a fancy way of saying, “hasn’t been run lately”), but if your sure your action’s going to be pretty active, then you should be fine.

Now let’s consider a real example. In the past, I’ve used a npm package called FeedParser as a way to parse RSS feeds in Node.js. I thought it would be cool to build an action that would let me specify a RSS URL and get a JSON parsing of the data returned. I began with my package.json:


{
  "name": "rsstojson",
  "version": "1.0.0",
  "main": "main.js",
  "dependencies" : {
    "feedparser" : "*",
    "request":"*"
  }
}

I then ran:

npm install

To get all those dependencies installed. Next, I wrote my action:


var FeedParser = require('feedparser');
var request = require('request');

function main(args) {

    return new Promise(function(resolve, reject) {

        var fp = new FeedParser();
        
        request.get(args.url).pipe(fp);

        var items = [];
        var meta;

        fp.on('readable', function() {
            var stream = this;
            var item;

            while(item = stream.read()) {
                if(!meta) meta = item.meta;
                delete item.meta;
                items.push(item);
            }
        });

        fp.on('end', function() {
            resolve({items:items, meta:meta});
        });

    });

}

exports.main = main;

All I do is take in a URL argument, suck it down via the Request package, and then pipe it over to FeedParser. I noticed that FeedParser would create a ‘meta’ object for every feed item. This meta object includes the metadata about the feed itself. I thought this was useful, but didn’t like it being duplicated on every feed item. So I take it out of the first item and delete it from every item added to the array of results. I can then return the list of RSS entries and the metadata as well.

And that’s it! The output is pretty verbose so I won’t share a screen shot, but I’ve included a video about this topic below.

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