I recently need to set up caching for a very slow API service I was working with.  However the app I was working with forced a query param of “timestamp” on all requests.  This effectively killed the cache because all api requests were flowing through a single endpoint, and only the query params differentiated the requests.  So here’s how to set up caching and strip out query params with nginx.

http {
    # Create a storage location for 
    # caching and call this location "my-app"
    proxy_cache_path /data/nginx/cache levels=1:2 
         max_size=100m inactive=60m;
    server {
        location /api/  {
            # Strip out query param "timestamp"
            if ($args ~ (.*)&timestamp=[^&]*(.*)) {
                set $args $1$2;

            # Use the "my-app" cache defined above
            proxy_cache my-app;

            # Only cache 200 responses and cache for 20mins
            proxy_cache_valid 200 20m;

            # Create a unique cache key
            # Proxy the request

Originally posed to Instructables

Picture of Fiber Optic Star Ceiling Panel with Day Time Stars

I wanted to create a star ceiling, but since we are currently renting, I didn’t want to drill into the actual ceiling. So here’s how to create a portable star ceiling you can take with you. The total cost of this project is around USD $100

Step 1: Purchase fiber optic driver and cable

Picture of Purchase fiber optic driver and cable

I purchased this 150 light set off of ebay for around $60. This one came with a remote control and 16 colors to choose from. In addition, it’s low profile driver will be perfect to fit in the frame.

Step 2: Purchase a poster board

Picture of Purchase a poster board

I wanted something that was going to be sturdy enough to drill holes through, hold all the cables behind it, and look stylish. I came across this at Target for around $25.

Step 3: Remove the cardboard poster backing

Picture of Remove the cardboard poster backing

I removed the plastic cover from the poster to leave just the cardboard frame.

Step 4: Paint it black

Picture of Paint it black

Next I grabbed some MATTE black spray paint and gave a good solid coating over the back of the poster board

Step 5: (Optional) Day time stars

Picture of (Optional) Day time stars

I didn’t want my star ceiling to look like a solid black tile during the daytime, so using some white GLOSS spray paint I added some daytime stars. To do this, simply press down very gently on the top nozzle of the spray paint, till it sputters. It should look like it spitting. Then quickly aim it at your black background. It should only take a few spits to create the desired look

Step 6: Place the backboard in the frame

Picture of Place the backboard in the frame

Step 7: Drill holes for starfeild

Picture of Drill holes for starfeild

I highly recommend you drill holes where the daytime stars appear. This is because they will already have a very nice distribution across the entire surface of the board. I tried to make my own pattern instead and in looks very contrived instead of natural looking.

Step 8: Light shining through

Picture of Light shining through

Make sure all of your holes are clean and you patch up any unsightly looking spots on the front.

Step 9: Set your fiber optic driver foundation

Picture of Set your fiber optic driver foundation

Place your fiber optic driver in a place off to the side of the frame. Then secure with zip ties.

Step 10: Place fiber optic lights through pre-drilled holes

Picture of Place fiber optic lights through pre-drilled holes

Grabbing groups of lights at a time, start running the cables through your holes. You’ll want to keep these group somewhat organized, so I used more zip-ties. The group simply helps you lay the cables flat as you prepare to mount to ceiling. Don’t worry about the cables peaking through the front, we’ll trim those back later.

Step 11: Glue it good

Picture of Glue it good

Once you’ve got all of your cables placed in the holes, you can start gluing to keep them in place. I used Elmers Clear Glue liberally on every singly hole.

Step 12: Allow 12 hours for glue to dry

Picture of Allow 12 hours for glue to dry

Step 13: Trim back the ends

Picture of Trim back the ends

After the glue has dried, you’ll have a lot of cables sticking through the front. I used fingernail clippers to trim these flush with the board.

Step 14: Mount it

Picture of Mount it

That’s pretty much it for building the star panel. Now you can mount the panel in way you light and enjoy your new star field!

I’ve been learning a lot of Reactive Extensions (Rx) lately, and in the spirit of learning I decided to share some 984368initial thoughts on the concepts and give a very light overview.  Rx is very deep, but hopefully this article gives you an initial understanding and examples to solidify the knowledge.

If you haven’t heard of Rx before, I highly recommend reading Erik Meijer’s blog post in which he describes an alternate way of thinking about events.  In short, he describes events (mouse clicks, keyboard events) as a stream of data.  Think of an array where you have a list of items but with the added element of time in between each item.  For example, as your mouse moves it creates a stream of coordinates. (The dots represent time passing)

mouseMoves = [….{x: 45, y: 45}…….{x: 45, y: 50}…..{x: 50, y: 50}…]

See, mouseMoves is just an array with time between the items.  This is what is known as an Observable.

Once we have an observable, we can do all kinds of things to the stream of data.  We can filter it for certain items, we can map over each data item and transform it to something else, we can merge it with another Observable to create a new data stream.   The documentation for the javascript implementation, gives you just a taste of what you can do.

A Practical Example – Mouse Moves

Let’s say that we want to add a listener to our page that detects whenever the mouse hovers over an image tag.  In addition, while we want to know whenever the mouse is hovering over the image, we also want to throttle the number events actually occurring.  The following Rx code accomplishes this in just a few lines of code.

Let’s take this line by line to see just what is happening.

After querying the page for a list of image tags, we create two new Observables by attaching them to the images DOM list.  These observables are now listening to all mouseover and mouseout events.

// Listen to the stream of mouseover events
var mouseOvers = Rx.Observable.fromEvent(images, 'mouseover');

// Listen to the stream of mouseout events
var mouseOuts = Rx.Observable.fromEvent(images, 'mouseout');

Now that we are listening to events, we want to filter these events to only return every 300ms (as opposed to very fast which it would do right now) and only while we are still hovered over an image.  Here’s how this code works. We loop over the list of mouseover events streaming in using ‘map’. For each event we occur, we create a new Observable that is delayed by 300ms.  And lastly, we filter that nested observable with the ‘takeUntil‘ operator so that we only return a valid event if the mouse has not left the image.  At this point, the event is then returned to the outer ‘map‘ result for the final operator, ‘switchLatest.’ Switch latest takes in a stream of events and returns only the most recent event. This operator is especially useful for ajax calls, where you may have made a few requests, but only care about the data from the most recent request made.  Likewise, this returns the most recent mouseover event that was valid.

// Create an Observable for all mouseOvers
var imageHover = mouseOvers.
    // For each (map) mouseOver event
    map(function(e) { 
        // Wrap the event with an another Observable, so we can throttle it
        return Rx.Observable.return(     
            // Wait to see if the mouseOver is still on this same boxart
            // Don't return anything if a mouseout occurred, this stops the observable from returning anything else
    // Return the last throttled event

Now that we’ve created our observable with its propers filers, we simply ‘forEach‘ or ‘subscribe’ over the stream as if it were an array.

// Subscribe to the img hovers
imageHover.subscribe(function(x) {
    console.log('Mouse over image with alt tag: ' + x.alt);

That’s it!  We can now listen for mouseover events on images like an array.

This is just scratching the surface of Rx and we haven’t even touched on how Observables automatically unsubscribe themselves from events or handle errors.  If you’d like to learn and play more with observables, I highly recommend giving Jafar Husain’s interactive tutorial a try.

I’ve participated in a lot of hackathons over the last few years and luckily even won a few. (TechCrunch twice, Facebook, Angelhack) Hackathons are a great way to try out a new idea and get immediate feedback from the community.  They’re social, challenging and always a blast.

But sometimes they can be extremely frustrating due to poor planning, crunched time and various other factors. Here are few lesson’s I’ve learned the hard way, but I write this in hopes of saving you some pain.  Here’s what TO DO, if you really want to “kill it” at your next hackathon.

Show Up With An Idea

I can’t even begin to tell you what a bad choice it is to show up with no idea of what you’ll be working on.  I’m going to be stressing this fact, on every bullet point, so here the first time.  Your time is extremely limited. You don’t have time to wander around trying to come up with an idea of what to build.  You should come prepared with at least a vague idea or two, of what you’ll be working on.  Now, I’m not saying you have to have it completely planned and mocked out, but come with a plan.

Also make sure that the problem you are trying to solve is actually a problem.  Ask a few friends if they would use it.  If you can’t find any takers, chances are the judges won’t either.

Sell The Idea, Not The Code

At the end of the day, you’re presenting an idea to the audience and your job is to sell it.  The code doesn’t have to be pretty or work flawlessly.  In fact, no one will most likely ever look at it again.  Focus on what problem your trying to solve and gear all of your effort towards demoing that. Visually.  Sell the crowd and judges on what makes your concept, not your code, amazing and disruptive.

The truest code ever written at a hackathon. Not pretty, but it will work.

Stick To What You Know

A lot of people use a hackathon as a time to try out a new frameworks and even programming languages.  If you goal is to learn, have at it. If you want any possibility of winning, stick to what you know.  Your time is limited and you can’t afford to spend 5 hours learning how to use a new 3rd party API, a new language, or anything else new.

Prepare For Bad WiFi

The wifi will be slow so prepare to work and demo locally.  This gives you the huge advantage of faster iteration cycles during development and a demo which is fast and smooth.  Why hinge your entire project on an uncontrollable external factor?

Deliver A Great Demo

Remember the demo is the ONLY thing any one sees at the end of the day.  Make sure the demo is clear and gets your idea across.  In addition, practice your presentation over and over, making sure you articulate the problem and how your project solves that problem.

With these time saving tips in mind, I wish you all the best in your hackathon endeavors and hope you have a blast at your next hackathon.

Been taking a look at ReactJS over the last few days, which is an interesting view library from the folks over at Facebook.  What I really like about it so far is the “componentization” of  objects on a page.  The general idea being,  any part of the page should be able to stand on its own.  Think widgets.  In theory this is a nice idea until components need to interact.  For example, a list of items with a search box that filters the results.  Component 1 is the search box, Component 2 is the list of items.  In the traditional MVC pattern, the controller would be responsible for handling this interaction.  In react, you would create a parent component which would handle the passing of state change to the list component.  It doesn’t really matter what the parent component is, just that its children are the list and the search box.

Considering the issues I have with the traditional MVC pattern for front end web apps, I’m interested in how this approach by ReactJS performs in the real world at scale.  Especially on very interactive web apps.  In past large web apps, I’ve used an event bus to facilitate the communication between components and thereby reduce tight coupling.  My initial concern is that there will be hooks and callbacks being passed through each component in ReactJS, making the code a challenge.

Time to dig in and see the real world results.

I recently read The Principles of Object-Oriented JavaScript by Nicholas Zakas and was enthralled by his patterns for prototypal inheritance of both instantiated and non-instantiated objects.   As I put each of these patterns to practice I noticed an interesting “discrepancy” between the the way each was linked to its parent.  I thought it was interesting enough for me to dig into, so it might make an interesting blog post.

Example 1: Instantiated Object Inheritance

In the example below, we create our parent class “Animal” which is created via the function method.  We attach a simple method to the prototype which retrieves the private “species” variable.

Then we create a “Dog” subclass by creating it via the function method, then linking the two classes with

Dog.prototype = Object.create(Animal.prototype);

This overrides the default Dog prototype with the Animal prototype, resulting in the correct prototype chain.  Here is a very abbreviated version of the prototype chain.

Screen Shot 2014-05-14 at 4.43.33 PM

Note the very important constructor attachment required after we override the prototype.

Dog.prototype.constructor = Dog;

Pretty common sequence to chain these two classes together.  Any changes made to Animal will get automatically chained to Dog.  Now let’s take a look at the non-instantiated example.

Example 2: Non-instantiated Object Inheritance

In this example we’ll use a IIFE (Immediately-invoked functional expression) to create our parent class, with our retrieval function as above.  This pattern is common for singleton type use cases.

Now notice how we chain the prototypes of the Animal and Dog classes, specifically what is passed to the Object.create() function.

var myDog = Object.create(animal);

No mention of a prototype!  Why not?  Why are we attaching the object itself instead of its prototype?

The reason is because of what Animal is in this second example.  In example 1, Animal was created via the function literal resulting in an object with a full prototype chain inherited from Function. In the second example, animal was created via the inline object declaration “{}” resulting in an object with a prototype of “null”. To put it shortly, an object only has a prototype property if it was created via function literal.

Screen Shot 2014-05-14 at 4.43.40 PM

So if you called the following code, you would get a big fat error because animal has no prototype property.

var myDog = Object.create(animal.prototype); //TypeError

So in example 2, the Animal object itself is what gets chained to myDog. MyDog  can now add its own methods without modifying the original Animal object.