A while ago my colleague Olav Maassen asked a question on our company mailing list about the best book to read to learn OSx development. His question made me think not about the best book but about how I learned new programming languages in the past. Read more
2012 May
Cloudera Manager is a web based management application for your Apache Hadoop cluster. It makes the installation and configuration for your Hadoop cluster a whole lot easier and is free for a cluster up to 50 nodes. In particular I like the suggested configuration settings based on your cluster hardware.
All the configuration settings of Cloudera Manager are persisted in the configuration database, which can be manually exported through the admin interface. One of our clients wanted to export these settings programmatically for auditing and backup purposes.
Currently there isn’t an automated way to do that, besides backing up the entire database. Here is a little shell script that allows you to download the configuration automatically in text format.
For a deployment, Deployit calculates the step list based on your model. But what if you want to add an extra step? There are several ways to do this. This cookbook entry will explain a simple case: executing a remote shell command on a server.
Some of you may know that I like to add drawings to support my posts.
This time the drawing itself is the subject of the post and you can actually use it. So please take a look at it and put it to use as you see fit. If you like it (or hate it…) or if you want to share your experiences using it please leave a comment.
You can download it here (PDF):
Xebia Scrum Process Overview
Or copy it from here
Apache Hive is a data warehouse system built on top of Hadoop. Using SQL-like language you can query data stored in the Hadoop filesystem (HDFS). Those queries are then translated into Map Reduce jobs and executed on your cluster.
As an example we’ll analyze tweets from the Twitter Streaming logs and calculate the top 5 hashtags per day which are associated with positive sentiment signals (smileys).
You can imagine how this can be expand this to simple sentiment analysis on your (potential) customer feedback.
Lots of groups struggle with product features in the discovery phase of their products and services. Here is a relatively easy and quick exercise to make sense out of a mess of stories.
Read more
The problem
Your project has a nice test coverage, let’s say 85%. Your nightly build reports a wide range of metrics and they are all above your accepted levels. Your team consists of well-motivated people all willing to learn the latest frameworks and techniques. And you have adopted Scrum, Agile, Kanban or another recent/agile software process.
But lately you have noticed that simple new features take more and more time to implement. That despite of your test coverage, bugs have crept in your production code which can take days to solve. And that solving the highest prioritized issues is sometimes delayed because specific knowledge is located at a single person, who can only handle one task at a time.
What’s going on?
Automated testing and metrics are certainly useful, but they don’t catch everything. For instance, it is perfectly possible to have meaningless unit tests which cover 100% of your code.
You could write code with splendid metrics but which is impossible to understand by your colleagues, because method- or variable names are badly chosen.
Maybe you have written code while a colleague has already written something similar, thus missing an opportunity for reuse.
And last but not least, while there are many tools for measuring the quality of Java code, the choice of tools for non-Java code is much more limited; Think of JSF or JSP pages or new languages for which tools have not had enough time yet to develop.
Solution: Code reviews!
Code is not only written for computers, but also for humans. So why not let humans take their part in the code quality process?
Your colleague can see immediately if your code is difficult to understand or not. He can check coding standards in those areas where tools are still missing. And there’s more:
- He could spot bugs in your code
- You might have misinterpreted or missed a functional requirement
- Your colleague might know of a cool third party library you could have used
On top of that, by letting colleagues read each other’s code, knowledge of the code base will be spread thoughout the team.
And by discussing suggested improvements of the reviewed code, general coding knowledge is spread through the team as well.
Tips for how to do it
In my experience, there are a few things which work well when integrating code reviews into your software development process:
First, arrange a brain storm session for your whole team, and agree on a set of review criteria.
By agreeing as a team on a set of review criteria, you prevent discussions later on.
Think of such things as:
- descriptive variable- and method names
- meaningful unit tests
- conformance to gui standards
- non functional requirements such as performance or security
When assigning reviews, make sure they are assigned to a random colleague. After all you have agreed on a set of standards to review on, so a junior colleague might just as well review your code as a senior. And, different people have different points of view, so it’s good to have many different colleagues review your code.
Look for integration with your bug tracking tool. Code reviews become much easier if commits can be traced back from a bug report or feature request.
For instance, Jira has a nice integration with Crucible which enables you to assign reviews to teammembers straight from a Jira issue.
Alternatives
The major disadvantage of code reviews is that they take extra time. It is my personal opinion that this investment in time will pay itself back with interest.
However, if you find it impossible to convince your manager or colleagues to allocate the extra time, then doing selective reviews might be a good alternative; for instance, you could subscribe to each other’s commit e-mails and check those.
But, if time is not an issue, an alternative that goes a even bit further might be pair programming.
At Xebia, we like experimenting with new solutions that enable us to give a more satisfying answer to our customers. One of these questions is: are Agile and Scrum applicable to non-IT environments? And though we are known with project such as wikispeed, we wanted to prove it on ourselves. So we did. Read more
Sometimes you would want a shadow on a view.
Easiest and quickest way is to just add it on the view’s layer:
-(void)loadView {
CGRect frame = [[UIScreen mainScreen] applicationFrame];
self.view = [[UIView alloc] initWithFrame:frame];
self.view.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
self.view.backgroundColor = [UIColor blackColor];
UIView *glowView = [[UIView alloc] initWithFrame:CGRectMake(frame.size.width /2 -10, frame.size.height /2 -30, 20, 60)];
glowView.autoresizingMask = UIViewAutoresizingFlexibleBottomMargin |
UIViewAutoresizingFlexibleTopMargin |
UIViewAutoresizingFlexibleLeftMargin |
UIViewAutoresizingFlexibleRightMargin;
glowView.backgroundColor = [UIColor whiteColor];
[self.view addSubview:glowView];
//Setup the shadow on the view's CALayer.
CALayer *viewLayer = glowView.layer;
viewLayer.shadowOffset = CGSizeMake(0, 0);
viewLayer.shadowColor = [[UIColor yellowColor] CGColor];
viewLayer.shadowPath = [UIBezierPath bezierPathWithRect:glowView.bounds].CGPath;
viewLayer.shadowRadius = 10.0f;
viewLayer.shadowOpacity = 1.0f;
//Let's animate it while we're at it.
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"shadowOpacity"];
animation.duration = 0.5f;
animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
animation.fromValue = [NSNumber numberWithFloat:1.0];
animation.toValue = [NSNumber numberWithFloat:0.0];
animation.autoreverses = YES;
animation.repeatCount = HUGE_VALF;
[viewLayer addAnimation:animation forKey:@"shadowOpacity"];
}
I must admit, this is kind of basic stuff. But it seems a lot of people actually forget about the fact that all UIView subclasses are based on Core Animation CALayers.
See the source code https://github.com/xebia/ios-DemoForBlog and try the example, the interesting bits about this example are all contained within the fourth tab of the application, it’s the XSDFourthViewController in the code.
Spring just started, so in time for an attempt at predicting the future (it has just started to use a cliché). Together with a few colleagues we brainstormed about what we think is important. After that I created the post below. In short: software development processes, local and public clouds and security. Minor disclaimer: this is my own view.