Thursday, February 24, 2011

Review of AWS SDK for Android (SimpleDB)

So development of my Android app, PayNanny, continues and I'm at the point where I can make some observations about the AWS SDK for Android (Beta release). Note that of the 4 AWS services (S3, SimpleDB, SNS, and SQS), I'm only using the SimpleDB API. I won't bore you with how easy it is to make a free AWS account but believe me, it's easy.

First off, I'm so happy I don't have to write an HTTP library or any of the framework necessary for code on a mobile device to interact with a cloud database Isn't is awesome that this is all that's required to add an entry to a SimpleDB domain (similar to a table) is:

List attributes = new ArrayList(5);
attributes.add(new ReplaceableAttribute().withName("date").withValue(date));
// more lines of attributes.add

PutAttributesRequest request = new PutAttributesRequest("timelog", UUID.randomUUID().toString(), attributes);

AmazonSimpleDB mDB = new AmazonSimpleDBClient(credentials);

Everything's taken care of (well, except transaction handling as SimpleDB is NoSQL) and it keeps your code compact and easy to read. Most of my utilization of the AWS SDK follows in the same vein and I heavily reference the AmazonSimpleDBClient class. I kept the database structure very flat to use SimpleDB the way it's supposed to be used. For instance, I've combined some things which would usually be different fields in an RDBMS into 1 attribute. Once I get this value from the database, I parse it according to the schema I designed.

Like any database-centric app, you're going to loop around your search results often so you'll take your List, pull out each Item, and look at the Attributes like:

// itemList is a List
for(Item item : itemList) {
    List attributeList = item.getAttributes();
    String itemName = item.getName();

    // parse attribute list and sort the data
    for(Attribute a : attributeList) {

It can get a little monotonous and having a bunch of nested loops always makes me nervous but what are you going to do.

SimpleDB is typeless - everything gets stored as a string. I find this to be good and bad. I liked not being so limited in what I had to send to the database but it makes writing optimized queries more difficult. Instead of writing an RDBMS SQL statement saying "get me all data between the dates of 1/2/11 and 1/8/11", I had to code a SimpleDB statement saying "get me all data with the date 1/2/11 or 1/3/11 or 1/4/11 or 1/5/11 or 1/6/11 or 1/7/11 or 1/8/11". So in effect, SimpleDB is pushing a bunch of logic that would usually be handled by the database server into the application code. Mobile devices are pretty fast but I'd rather some server farm in Oregon or wherever do this work than my Droid. Zero padding and offsetting numbers allows for some of this RDBMS functionality but I didn't utilize that in my code.

One major feature lacking in the API is access to the AWS Identify and Access Management (IAM), which is a vital requirement for those who wish to deploy Android apps without giving away your keys. In the meantime, check out the awskeyserver project, which does a good job providing this funtionality via Google App Engine.

I haven't made up my mind about the NoSQL concept. While I won't have to deal with the data consistency issues inherent in this design, I appreciate that the strong consistency option is built into SelectRequests. I don't think NoSQL databases wouldn work for, say, financial applications that need to keep track of a transaction but I don't see why it wouldn't be fine for a social app that needs to scale. Whenever I write stuff like that, I'm reminded of Ted Dziuba's great anti-NoSQL piece which includes the words "You Are Not Google".

Overall, I'm satisfied with this API and the performance I'm getting (for free, mind you). Once my app goes Beta, I hope to have more insights.

Saturday, February 19, 2011

Native Client - where web apps and native apps meet

I was motivated by a web apps presentation by Seth Ladd, a Google Chrome developer advocate, to write a short white paper why my organization should be moving in this direction. But it's hard to get around the fact that native apps still beat the pants off of web apps in many functional areas. Until this week, I wasn't aware Google was working on Native Client, a way to run native compiled code directly in the browser. This certainly makes sense if Chrome is to become a major OS.

I don't think I'm brave enough to fool around with the developer release SDK right now - I'm busy working on my Android app - but once it goes beta it'll be worth a look.

Tuesday, February 8, 2011


PayNanny is a household employer payroll app I'm working on for Android devices. So far, the only functionality I've built consists of a way for the user to "log in" (identification only - no authentication yet), create/delete/edit employee names, and link or delink their account with another.

I've open sourced it on github.