Wednesday, August 13, 2008

Pushing the Boundaries of Testing and Continuous Integration

At Agile2008, I had the opportunity to present an experience report with two colleague's Raghav and Fabrizio about bringing robustness and performance testing into your development cycle and continuous build. Below is the video, along with the slides. Enjoy.

The submission can also be read here.

Pushing the Boundaries of Testing and Continuous Integration from Robbie Clutton on Vimeo

Sunday, August 03, 2008

Enterprise Agile vs Start Up Agile

Discussions in the office typically bring interesting conversation, and as I head to Agile2008 (I sit on the flight whilst writing this), I wanted to ask what's the difference between enterprise agile and start up agile, and how does that difference affect not just the maintainability of the products build, but also the innovation of the respective engineering group?

There is always the classic trade off between feature delivery and quality, but is it really the case that startups are generally exempt from these quality metrics? If this is the case, what other practices can be put in place instead of code metrics?

One of my memorably quotes from high school was my physics teacher, Mr Shave. He said to the class 'you can never prove anything, you can only disprove something'. This applies here with quality metrics. Code coverage, convention and duplication don't prove quality in code, even intergration testing or robustness and performance testing do not prove anything, they only dis-prove that your system doesn't fail under certain conditions. However, all of these steps do increase confidence in a product, and that is an integral part of any product development (confidence that is).

You can still not do any of this and be agile right? These practices are generally incoraged, but agile is about customer engagement and acceptance and if you're customer knows what they're getting and they accept your stories then it's OK right? What is enterprise agile anyway? Do enterprise developers build a product, deliver it into an in-life team and then move on? Does that require higher confidence as you're handing over? Is a start up developer likely to support that product in-life and as such be more likely to stick around, fix issues and add functionality?

GMail Log4J Appender

Application logging is vital for diagnostics on a server product, but there can be so much, how can you tell what to watch or follow? Through tools like Log4J, you can have separate logs for different levels (typically debug, info, error and fatal). In Log4J, these are called log appenders, they can be anything from console or file based, or custom log appenders. One of the custom appenders I've been playing with recently is email logging. Our team has some excellent scripts written by Senor DB which scan log files for patterns and send email reports based on it's findings. I wanted to see if I could add application logging directly into the application. I wanted an email based appender and here's how I got that.

Now, there is an SMTPAppender in the Log4J package, but I wanted to use GMail, and the Log4J appender doesn't quite set up properly for GMail. I used Spring implementation of JavaMail for sending emails and extended the SMTPAppender in the log4J package. The method you'll be most interested in overriding is 'append', this gets called when your log is called into action depending on the settings in your log4j configuration.

public GmailAppender() {
notifier = new JavaMailSenderImpl();
Properties props = new Properties();
props.setProperty("mail.smtp.auth", "true");
props.setProperty("mail.smtp.starttls.enable", "true");

try {
InetAddress addr = InetAddress.getLocalHost();
hostname = addr.getHostName();
} catch (UnknownHostException e) {


For brevity, I've used the constructor to build the notifier (JavaMailSenderImpl from Spring) with desired properties, you can just as easily use properties in the log4j config, and I'll do just that for the host name (which for me means which IP address the application is running on). You can see above we've set the STMP host for Gmail with the port, email address and password for the email to be sent from. The little extra bit of magic is the properties 'mail.smtp.auth' and 'mail.smpt.starttls.enable'. The last is to get the default machine name.
public void append(LoggingEvent event) {

SimpleMailMessage message = new SimpleMailMessage();
StringBuilder builder = new StringBuilder();
String[] stackTrace = event.getThrowableInformation().getThrowableStrRep();
for(int i = 0; i < stackTrace.length; i++)
builder.append(stackTrace[i] + "\n");
message.setSubject(event.getLevel().toString() + " on host " + hostname);
} catch (MailException ex){

Using the SimpleMailMessage (again from Spring), we add the text, the address and subject. The parts to grasp here are the layout and the stack trace. The layout is derived from your configuration, this is where you'd typically set the log message/heading including timestamp, thread name and other supporting information. Passing the event to the 'getLayout().format(event)' method returns this nicely formatted string. Then to get the stack trace we grab the array (each element being a line in the stack trace) from the event throwable information method. Someone thought that a method name indicating that your getting a string should pass back that array instead of adding new line characters, so we have to fix that before setting the text as the message body. Finally, we construct a useful subject containing the log level and host/IP address.

log4j.appender.mail.layout.ConversionPattern=%d{ISO8601} [%t] %-5p [%C{1}.%M() %L] - %m%n

I've mentioned the configuration a few times, and here is the basic one comprising the full path to the class, the threshold (meaning the lowest level to log at, I don't want an email for every debug log entry after all). There's the pattern I mentioned before, this pattern includes the date, threadname, level name, class, method and line number, then the message and a new line. Finally there's the host name. Each instance of my application has a different name to identify it, typically something development, staging, production. To enable that property in the class, simply add a Spring like named setter:

public void setHostname(String hostname){
this.hostname = hostname;

Properties like this can be set if you want to have the username/password of your GMail account configurable or anything else for that matter, just don't forget to set it on the JavaMailSenderImpl object before sending the email in the append method.