.NET Conf Demo 2016

This is the demo I was using in the F# talk for DotnetConf.

It extends the ASP.NET Music Store application to include a project which sends album details to a Cassandra cluster using F#! The F# project which does this is under src/MusicStore.Cassandra.

I've modified the music store project to be fixed to .NET Core RC2.

Component Overview

• The MusicStore app, an ASP.NET Core web application which sends an HTTP Put to the AnalyticsAPI
• AnalyticsApi, an ASP.NET Web Api 2 project which calls the F# code
• MusicStore.Cassandra, the F# project which talks to a Cassandra cluster

Most of the interesting stuff is in MusicStore.Cassandra.

Prerequisites: Cassandra

You can communicate with Cassandra over TCP. As such, there is no requirement to install Cassandra in some particular way. The application needs two things:

• An IP Address
• An Open port

Beyond that, any custom configuration is up to you.

Cassandra on Docker on the local machine

Note: I set up Docker on OS X. Instructions for Windows and Linux may differ. I might add these later on.

This is mostly taken from Alena Hall's excellent post on getting F# talking to Cassandra on Docker.

I chose to have a Cassandra cluster run in a Docker VM on my local machine. Here's how you can do that:

1. Get Docker

2. Open a command line.

3. Pull Cassandra and create a new image using the latest Cassandra tag. I've chosen cassandra-1 as the name, but you can use whatever you like.

   $ docker pull cassandra
   $ docker run --name cassandra-1	 -d cassandra
   

4. (Optional) Log into the Cassandra instance and check the health of the node.

   $ docker exec -it cassandra-1 bash
   $ nodetool status
   

5. (Optional) Create a second node and check it health.

   $ docker run --name cassandra-2	 -d cassandra
   $ docker exec -it cassandra-2 bash
   $ nodetool status
   

   You can create as many nodes as you see fit.

6. Log into each Cassandra instance you created and install vim (or you favorite text editor).

   $ docker exec -it cassandra-1 bash
   $ apt-get update
   $ apt-get install vim
   

7. Open up the /etc/cassandra/cassandra.yaml config file

   $ vim /etc/cassandra/cassandra.yaml
   

8. The rest of this assumes you are using vim.

   • Search for cluster_name. /cluster_name: ---> you can name this whatever you want
   • Search for listen_address. /listen_address: ---> Just make sure you have IP addresses for each node.
   • Search for rpc_address. /rpc_address: ---> replace 0.0.0.0 with the result of :r ! hostname-I
   • (Optional) search for seeds. /seeds ---> Since this is a small cluster, you can use a CSV of the IP addresses of your nodes. Example with one node: 172.17.0.2.

   Save your changes! Note that you can open this file in new tabs in your terminal and broadcast your output to all tabs to automate the above for each node.

9. Cassandra will communicate over Docker Port 9042. Set the IP Port to a number you feel is appropriate. I chose 8881, just like in the blog post I've linked above.

And that's it!

Setting the IP Address and Port in the AnalyticsApi config file:

The Web.config file has the following lines:

<appSettings>
	<!-- Change this to your own IP Address and port -->
    <add key="ipaddress" value="192.168.99.100"/>
    <add key="port" value="8881"/>
</appSettings>

As the comment suggests, you'll have to change these values to the IP address and port which correspond to the Docker Port that Cassandra listen on.