Often a programmer sits back and reflects on, “how can I get better at my job?” A number of months ago I found myself sitting with that same reflection. One of the many ideas that popped into my head was to put together focused material around a topic. Training material, a blog series or something else. I wasn’t sure just yet what it would be, but I knew that was one of the many things I wanted to do. Fast forward a few months.
Fellow Tier 3 coder Richard Seroter, who I’d known for some time via his blog “Richard Seroter’s Architecture Musings” and I had a conversation about what we do, respectively, to keep our skills honed in tech. He brought up he’d be putting together material for Pluralsight for a while now and enjoyed that. It struck me as something I’d like to do too, considering my past reflection, so he made an intro. The rest is history!
Pluralsight Author, Achievement Reached
For now, check out my Riak Fundamentals Course and some of the other great material that Pluralsight has available. They’ve just acquired TekPub, Peepcode and a number of other companies too, so when you subscribe you don’t just get all the Pluralsight material but also access to all the material at these excellent course creating companies! In the coming days and weeks I’ll have some reviews of other courses I enjoyed. As always, enjoy, subscribe to my blog, subscribe to Pluralsight and cheers!
The review slipped past me this week. A little food poisoning will do that to a person. But I’m kicking again.
A Quick Summary
The RSS/News Feed section of the app has been built and put into action. So if you pull the latest code and run the application, navigate into the news section you’ll get the Basho Blog feed. This definitely needs cleaned up a bit from the UI perspective but the main elements are there.
Next steps are…
One of the things the team is aiming to knock out next is to get some MVVM (Mode View ViewModel) architecture setup to build against versus what we’ve started with, which is just the basic skeleton of things thrown together. It works, but it’ll be nice to have some clean architecture behind the application to work with.
I’m aiming to put together a blog entry on troubleshooting the build server for Junction and also the how-to on setting up the RSS/News Feed Reader section of the app in the coming week also. Subscribe to keep up with the latest in Junction news and also all the other tidbits on the blog. Cheers!
It’s time for another Tuesday Bi-weekly Review! We’ve been making some progress and so far we’ve tackled a few elements of the project. The first big task was to get more information out there for the community & team working on the project. I’ve spent some time along with the contributors on github and via other means to make more information available to what the intent is and how people can contribute. So if you’re interested in helping with an entire domain space or merely a small element of the application, ping me and I’ll work with you to make it as easy as possible to contribute. With that, let’s jump into what’s what and what’s new. Cheers!
We Have a Build Server, More on This Soon, but for now…
I’ll have a post on how to setup Team City and quick tour of what is setup for the Junction Project. So stay tuned and I’ll have that and other news posted as it happens this coming week along with Team City & other tutorials related to the project itself. For a quick sneak peek feel free to take a look at the build server located at: http://teamcity.cascadiahacks.org/. Just login with “guest” and no password.
More Items Listed and Working on First Feature Commits and Comments For…
So every two weeks I intend to provide an update for the Junction Project. Who might have joined, what was worked on, where we are and generally any other bits of news related to the project. This is the first “Junction Two Weeks on Tuesday Review” so enjoy! 🙂
Issues, as stories and tasks were added to get started with the project. Here’s a first draft of the things we’re all working on. If you’d like to jump in, feel free to ping me and I’ll add you to the project, you can submit a PR (Pull Request) or talk to me about organizing a hackathon to help move the project forward.
Github Issues – Working Items
The easiest way to view these is to log into the Huboard Kanban Board and give a look see of what is in progress and who’s working on what. Currently I’ve outlined the big items that we’re working on and would love a fellow coder to jump in on. If you’re interested, ping me @adron or just jump into the issues list on Github (or view by milestone – i.e. functional area) and comment on the issue you want to dive into, I’ll add you so you can get started!
For the “Call the Doctor (Administration and Maintenance)” part of the application there are a number of questions to answer. How should we connect to Riak to ensure a secure SSH connection? Should we even use SSH? Is there another way to connect to the Riak Cluster for a secure way to administer the cluster?
One of the features that is often available in Riak Client software (including the CorrguatedIron .NET Client, the riak-js client and others) is the ability to send requests to the Riak Cluster through a round robin style approach. What this means is each IP, of each node within the Riak Cluster is entered into a config file for the client. The client then goes through that list to send off requests to read, write or delete data in the database.
The client being responsible and knowledgeable about the data tier of the application in an architecture is an immediate red flag! The concept around SoC (Separation of Concerns) dictates that
“SoC is a principle for separating a computer program into distinct sections, such that each section addresses a separate concern.“
Having the client provide a network tier layer to round robin communication with the database leaves us in a scenario that should be separated into individual concerns. Below is some basic guidance on eliminating this SoC issue.
Client ONLY sends and receives communication: The client, especially in the situation with a distributed system like Riak should only be dealing with sending and receiving information from the cluster or a facade that provides an interface for that cluster.
Another layer should deal with the network communication and division of nodes and node communication. Ideally, in the case or Riak, and most distributed systems this should be dealt with at the network device layer (router).
The network device (router) layer would ideally be able to have (through software likely) a way to automate the failure, inclusion or exclusion of nodes with the cluster system. If a node goes down, the network device should handle the immediate cessation of communication with that node from all clients, routing the communication accordingly to an active node.
The node itself needs to maintain a continual information state available to the network. Ideally the network state would identify any addition or removal of a node and if possible the immediate failure of a node. Of course it isn’t always possible to be informed of a failure, but the first line of defense should start within the cluster itself among the nodes.
Having the client handle all of these parts of the functional architecture leads to a number of problems, not merely that the guidance of the SoC concept is broken. With the client attempting to track and be aware of the individual nodes in the cluster, it sets the client with a huge responsibility.
Take for instance the riak-js client. If a node goes down the client will need to be aware of which node has gone down. For a few seconds (yes, you have to wait entire seconds at this level) the node will be gone and the client won’t know it is down. The client would just have to reasonably wait. When the communication times out, the client would then have to have the responsibility of marking that particular node as down. At this point the client must track which node it is in some type of data repository local to the client. The client must also set a time or some way to identify when the node comes back up. Several questions start to come up such as;
Does the client do an arbitrary test to determine when the node comes back up?
When the node comes back up is it considered alive or damaged?
How would the client manage the IP (or identifier) of the node that has gone down?
How long would the client store that the node is down?
The list of questions can get long pretty quick, thus the bad karma of not following a good practice around separating your concerns appropriately! One has to be careful, a god class might be right around the corner otherwise! That’s it for this quick journey into some distributed database usage guidelines. Until next, happy data sciencing. 😉
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