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openshift

Hosting and Developing the HTML5 Game Cobalt Calibur with MongoDB, Node.js and OpenShift

Aug 22 • Posted 2 years ago

This was originally posted on the OpenShift blog by Thomas Hunter.

So, you’re interested in getting the HTML5 Game Cobalt Calibur hosted for free? Look no further, Red Hat’s OpenShift can do that for you. Follow this guide and you’ll be up and running in no time. Cobalt Calibur is a multiplayer browser-based game which uses a bunch of HTML5 features to run on the frontend, and requires a Node.js and MongoDB server on the backend. Luckily OpenShift will satisfy these requirements for you.

The first thing you’ll want to do is create an OpenShift account. It’s quite easy and painless, I promise. Once you’re done getting it setup, be sure to click any email validation links and then log in to the website.

Once you’ve got your account setup, you’re going to want to create an SSH key for your computer (if you haven’t done so previously). To create your SSH key, you will want to open up a Terminal emulator and run some commands. These commands should work fine for both OS X and Linux computers. If you’ve already got an SSH key (which you should if you’re a GitHub user), you can skip these steps.

If you’re on a Mac, you’ll want to go to your list of applications and run Terminal. You can get to this app quickly by pressing Cmd+Space, typing in Terminal, and pressing enter.

Below is what your terminal window will end up looking like. You’ll want to type the command ssh-keygen -t rsa, and press enter. You will then be prompted a few questions; just leave everything blank and keep hitting enter.

$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/USERNAME/.ssh/id_rsa): <press enter>
Created directory '/home/USERNAME/.ssh'.
Enter passphrase (empty for no passphrase): <press enter>
Enter same passphrase again: <press enter>
Your identification has been saved in /home/USERNAME/.ssh/id_rsa.
Your public key has been saved in /home/USERNAME/.ssh/id_rsa.pub.

Congrats, you’ve now got an SSH public/private key. This is a file which can be used to prove to a remote computer that you are who you say you are. We need to give a copy of this file to OpenShift so that you can use git to push changes to your code to them.

To get a copy of your key file, you’ll want to copy the text from ~/.ssh/id_rsa.pub. You can run the command

cat ~/.ssh/id_rsa.pub which will display the contents of that file to your screen. Select the text and copy the output into your clipboard (everything from ssh-rsa to the username@hostname part):

$ cat ~/.ssh/id_rsa.pub 
ssh-rsa AAAAB3NzaC1yc2BLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAHBLAH== USERNAME@HOSTNAME

Once you’ve copied that text, on the OpenShift website, click My Account > Add a new key to visit the Add a Public Key page, and paste the contents of the output into the big text box. In the small text box above it you can name your key (such as Living Room Desktop or Developer MacBook). You’ll want to use a descriptive name, because if your key is ever compromised, you’ll want to know which one to disable.

Now, click the Create button. OpenShift is now aware of your SSH public key, and you can interact with the git server they provide without problems. Feel free to repeat this process from other machines you plan on working from.

If you get an error when you save the key, you might not have copied the whole thing. If so, you might need to open it in an editor. On a Mac try Open ~/.ssh/id_rsa.pub, and on Linux, you might try gedit ~/.ssh/id_rsa.pub.

Now it is time to create our OpenShift application. To do this, visit the Create Application page from the main OpenShift navigation. On this page, you will see a big list of all the types of applications supported by OpenShift. Scroll down until you see the Node.js option and select that.

On the next screen you will be prompted for some very basic information. Specifically, you will be asked to name your application. Since we are uploading the Cobalt Calibur engine, it makes sense to name it something like cobaltcalibur.

You will also be prompted to create a “namespace” for your account. This is basically a way to associate all of your app URLs with your account. This is so that multiple people can have the same apps named “cobaltcalibur” without stepping on each others toes. I already entered a namespace name before, so I didn’t need to this time.

After you click Create Application, OpenShift will work it’s cloud magic behind the scenes. During this time it is probably creating some DNS entries, copying some skeleton files, creating a git repository, the works. After the process is done, you will be taken to a new screen:

If you like, you can click the blue link to see the skeleton application OpenShift has created for you. It will be a pretty boring, static page which is displayed by a very simple Node.js app.

What you will want to do though is copy the commands in green and paste them into your terminal. This will pull the skeleton code from your applications git repository and make a local copy. There are some (probably) important files in here that we will want to keep.

If you see the same listing of files, then congratulations, you’ve checked out your application from OpenShift.

Now that you’ve got your application created and checked out, we want to add MongoDB support to the application. OpenShift calls these Cartridges.

To add MongoDB, first browse to the All Applications page, and then click the title of the application you created:

On this screen you can see the information for accessing your git repository again, but more importantly, there is a big Add Cartridge button.

Click that big blue button, and the next screen will prompt you for the type of cartridge to be added. Click the MongoDB option:

Once you do this, it will prompt you to make sure you want to add MongoDB. Click the Add Cartridge button again, and after some processing happens in the background it will be added to your application. You will want to copy all of the information you are provided with on this screen, notably the user, password, database, and connection URL which contains the IP address and port number for the database. We’ll give this information to the Cobalt Calibur game later on.

Now that we’ve got the MongoDB cartridge added to our application, we want to actually start the MongoDB server. To do this, you will first need to install the rhc command line utility. You’ll want to follow steps 1 and 2 on that page, you can ignore the other steps. The rhc utility gives you more control over your OpenShift applications that the website does, and is needed to start up the MongoDB server. Run the command rhc app cartridge start -a APPNAME -c mongodb-2.0 and this will start the server for you:

You are now ready to download the Cobalt Calibur source code, configure it to work with your OpenShift account, and upload it to the server. To do this, browse to the Cobalt Calibur GitHub page and simply download the ZIP file.

Extract it to the same folder that the Node.js application was checked out into. This will overwrite the index.html page, the server.js file, and the node_modules/ folder; that is all fine.

Now, it’s time to update the server.js file so that it is able to connect to your MongoDB daemon, as well as bind to the proper ip address and port number that OpenShift requires. You can open up server.js in whatever your favorite editor is. Here is what the old code looks like:

// Web Server Configuration
var server_port = 80; // most OS's will require sudo to listen on 80
var server_address = '127.0.0.1';

// MongoDB Configuration
var mongo_host = '127.0.0.1';
var mongo_port = 27017;
var mongo_req_auth = false; // Does your MongoDB require authentication?
var mongo_user = 'admin';
var mongo_pass = 'password';
var mongo_collection = 'terraformia';

And here is what you will want to change it to:

// Web Server Configuration
var server_port = process.env.OPENSHIFT_INTERNAL_PORT; // most OS's will require sudo to listen on 80
var server_address = process.env.OPENSHIFT_INTERNAL_IP;

// MongoDB Configuration
var mongo_host = 'MONGO IP ADDRESS';
var mongo_port = 27017;
var mongo_req_auth = true; // Does your MongoDB require authentication?
var mongo_user = 'admin';
var mongo_pass = 'MONGO PASSWORD';
var mongo_collection = 'MONGO DATABASE NAME';

Notice how OpenShift provides some environment variables for the web server port and ip address. It might also provide these same variables for the mongo connection, but I didn’t see this information.

The application is now configured properly. You’ll want to now add your files to git, commit the files into git, and push your changes to the server.

git add -A .
git commit -m "Adding Cobalt Calibur files"
git push

You’ll see a bunch of messages from all of the git hooks performing various actions, this is probably a good thing.

Now, if you browse to the URL for your game instance and refresh the page, it should load for you. If not, you might need to run the following command (I needed to for some reason):

rhc app restart -a game

Congratulations, you’ve now got your own personal instance of Cobalt Calibur running on OpenShift for free!

There is one big bug with OpenShift though, they don’t support websockets yet. My guess is that the different apps are hosted in a shared environment, and each application gets one port number to the outside world. Websockets require a bunch of random high ports for different clients, so this doesn’t really work with the shared host environment. Luckily, socket.io will fallback to using long-polling AJAX. The game doesn’t always run perfectly under these conditions, e.g. the monsters or corruption might no load. OpenShift is planning on adding this feature sooner or later, you can vote on it in the mean time.

Thomas Hunter is an evented Node.js hacker transitioning from the world of request/response PHP web development, building everything from hardware control software to traditional web apps. Follow him on Twitter at @tlhunter.

Getting going quickly with Python, MongoDB, and Spatial data on OpenShift: Part II

Aug 18 • Posted 2 years ago

This post originally appeared on the OpenShift blog

As a follow up to my last post about getting spatial going in MongoDB on OpenShift, today we are going to put a web service in front of it using Python. There are several goals for this article:

  • Learn a little bit about Flask - a Python web framework
  • Learn about how to connect to MongoDB from Python
  • Create a REST Style web service to use in our SoLoMo application

I hope by the end you can see how using a Platform as a Service can get you going with Python, MongoDB, and Spatial faster than you can say…“Awesome Sauce”. We have a lot of ground to cover so let’s dig right in.

Creating the Python application

Here is OpenShift the command line to create the Python app

rhc app create -t python-2.6 -a pythonws 

Using the flask quickstart from GitHub

We have already put together a flask quickstart in the openshift github space. To get the framework into your application all you have to do is (from the README.md):

cd pythonws git remote add upstream -m master git://github.com/openshift/openshift-mongo-flask-example.git git pull -s recursive -X theirs upstream master 

There we now have a flask app that we can modify source code.

If you want to just check out the source code I used in the app you can see it on Github and follow the README.md instructions to clone it into your OpenShift account

Adding MongoDB and importing data

Time to add MongoDB to our application:

 rhc app cartridge add -a pythonws -t mongodb-2.0 

The previous post in this series will cover how to import the data from a JSON file of the national parks into your mondodb database and prepare it for spatial queries. Please follows those instructions to import the data into the pythonws DB into a collection called parkpoints.

Quick digression to explain Flask

Before we get into our specific application I am going to take a moment to explain the Python framework for this demo. Flask basically allows you to map URL patterns to methods (it also does a lot more, like templating, but this is the only part we are using today). For example, in the mybottleapp.py file that is now in your project you can find the line: @route(‘/’) def index(): return ‘Hello World!

This says that when a request comes in for the base URL, the function named

index gets executed. In this case the function just returns the string “Hello World!” and returning has the effect of sending the string to the requestor. @route(‘/name/’) def nameindex(name=’Stranger’): return ‘Hello, %s!’ % name

We can also grab pieces of the requested URL and pass it into the function. By enclosing a part of the URL in a < >, it indicates that we want to access it within our function. Here you can see where if the url looks like:

http://www.mysite.com/name/steve

Then the response will be Hello, steve!

Or the URL could be http://www.mysite.com/name

Hello, Stranger!

We are going to define URL mappings for some basic REST like functionality to interact with our spatial MongoDB data store.

Modify the source code

The first function we are going to write will be to just simply return all the records in the database. In a more full featured app you would probably want to add pagination and other features to this query but we won’t be doing that today.@app.route(“/ws/parks”) def parks(): #setup the connection conn = pymongo.Connection(os.environ[‘OPENSHIFT_NOSQL_DB_URL’]) db = conn.parks

 #query the DB for all the parkpoints result = db.parkpoints.find() #Now turn the results into valid JSON return str(json.dumps({'results':list(result)},default=json_util.default)) 

I chose to put the web services under the url /ws/parks so that we could use other parts of the URL namespace for other functionality. You can now go to your application URL (http://pythonws-.rhcloud.com/ws/parks) and you should be able to see all the documents in the DB.

Using MongoDB in Python

In the code above we simply make a connection to the MongoDB instance for this application and then execute a query. The pymongo package provides all the functionality to interact with the MongoDB instance from our Python code. The pymongo commands are very similar to the MongoDB command line interaction except two word commands like db.collection.findOne are split with a _, such as db.collection.find_one. Please go to the pymongo site to read more about the documentation.

Notice we use the environment variables to specify the connection URL. While not hard coding database connection parameters is good practice in non-cloud apps, in our case you MUST use the environment variables. Since your app can be idled and then spun up or it could be autoscaled, the IP and ports are not always guaranteed. By using the environment variables we make our code portable.

We pass the result set (which comes back as a Python dictionary) into json.dump so we can return JSON straight to the client. Since pymongo is returning the results in UTF and we want just plain text, we need to pass the json_util.default from the bson library into the json.dump command.

This is probably the easiest experience I have ever had writing a web service. I love Flask, Pymongo, and Python for the simplicity of “Just Getting Stuff Done”.

Grab just one park

Next we will implement the code to get back a park given a parks uniqueID. For ID we will just use the ID generated by MongoDB on document insertion (_id). The ID looks like a long random sequence and that is what we will pass into the URL.

return a specific park given it’s mongo _id

@app.route(“/ws/parks/park/”) def onePark(parkId): #setup the connection conn = pymongo.Connection(os.environ[‘OPENSHIFT_NOSQL_DB_URL’]) db = conn.parks

 #query based on the objectid result = db.parkpoints.find({'_id': objectid.ObjectId(parkId)}) #turn the results into valid JSON return str(json.dumps({'results' : list(result)},default=json_util.default)) 

Here you have to use another class from the bson library - ObjectID. The actual ObjectID in MongoDB is an object and so we have to take the ID passed in on the url and create an Object from it. The ObjectID class allows us to create one of these objects to pass into the query. Other than that the code is the same as above.

This little snippet also shows an example of grabbing part of the URL and passing it to a function. I explained this concept above but here we can see it in practice.

Time for the spatial query

Here we do a query to find national parks near a lattitude longitude pair

find parks near a lat and long passed in as query parameters (near?lat=45.5&lon=-82)

@app.route(“/ws/parks/near”) def near(): #setup the connection conn = pymongo.Connection(os.environ[‘OPENSHIFT_NOSQL_DB_URL’]) db = conn.parks

 #get the request parameters lat = float(request.args.get('lat')) lon = float(request.args.get('lon')) #use the request parameters in the query result = db.parkpoints.find({"pos" : { "$near" : [lon,lat]}}) #turn the results into valid JSON return str(json.dumps({'results' : list(result)},default=json_util.default)) 

This piece of code shows how to get request parameters from the URL. We capture the lat and lon from the request url and then cast them to floats to use in our query. Remember, everything in a URL comes across as a string so it needs to be converted before being used in the query. In a production app you would need to make sure that you were actually passed strings that could be parsed as floating point numbers. But since this app is just for demo purposes I am not going to show that here.

Once we have the coordinates, we pass them in the the query just like we did from the command line MongoDB client. The results come back in distance order from the point passed into the query. Remember, the ordering of the coordinates passed into the query need to match the ordering of the coordinates in your MongoDB collection.

Finish it off with a Regex query with spatial goodness

The final piece of code we are going to write allows for a query based both on the name and the location of interest.

find parks with a certain name (using regex) near a lat long pair such as above

@app.route(“/ws/parks/name/near/”) def nameNear(name): #setup the connection conn = pymongo.Connection(os.environ[‘OPENSHIFT_NOSQL_DB_URL’]) db = conn.parks

 #get the request parameters lat = float(request.args.get('lat')) lon = float(request.args.get('lon')) #compile the regex we want to search for and make it case insensitive myregex = re.compile(name, re.I) #use the request parameters in the query along with the regex result = db.parkpoints.find({"Name" : myregex, "pos" : { "$near" : [lon,lat]}}) #turn the results into valid JSON return str(json.dumps({'results' : list(result)},default=json_util.default)) 

Just like the example above we parse out the lat and lon from the URL query parameters. In looking at my architecture I do think it might have been better to add the name as a query parameter as well, but this will still work for this article. We grab the name from the end of the URL path and then compile it into a standard Python regular expression (regex). I added the re.I to make the regex case-insenstive. I then use the regex to search against the Name field in the document collection and do a geo search against the pos field. Again, the results will come back in distance order from the point passed into the query.

Conclusion

And with that we have wrapped up our little web service code - simple and easy using Python and MongoDB. Again, there are some further changes required for going to production, such as request parameter checking, maybe better URL patterns, exception catching, and perhaps a checkin URL - but overall this should put you well on your way. There are examples of:

  • Using Flask to write some nice REST style services in Python
  • Various methods to get URL information so you can use it in your code
  • How to interact with your MongoDB in Python using PyMongo and BSON libraries
  • Getting spatial data out of your application

Give it all a try on OpenShift and drop me a line to show me what you built. I can’t wait to see all the interesting spatial apps built by shifters.

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