When I describe CI to technologists that haven't used the practice yet, I tend to focus on one of its major benefits: a decrease in the time between when a defect is introduced and when it is fixed. This benefit is a direct result of a CI server's ability to provide rapid feedback of build statuses. In my opinion, rapid feedback of build events is the central tenet of CI and one that causes many to describe a CI system as a continuous feedback mechanism.
When a build is broken, I want to know immediately so I can take the proper action to fix it -- whether that be a compilation error, test failure, or even an increase in overall complexity. The sooner I know, the more relevant the information and the better chance I have to fix the problem.
Feedback, however, is useless without action. In the case of CI, this action must be prompt because a broken build affects everyone; therefore, the feedback mechanism employed by a CI server must be timely. The beauty is that most, if not all, CI servers available today provide an e-mail feedback mechanism; however, there is a cornucopia of other mediums to choose from ranging from Really Simple Syndication (RSS) feeds to SMS text messages to X10 devices. And these various feedback mechanisms quickly facilitate jumpstarting the necessary people into action.
The ubiquitous nature of e-mail makes it a simple and useful means of feedback -- every CI server I'm familiar with provides some type of e-mail feedback mechanism. In fact, most CI servers provide the capability for configuring who receives which message, based on a desired build event. For instance, a technical lead may always receive an e-mail regardless of build status, but the project manager only receives an e-mail when the build fails. Additionally, the developer or developers who checked any code into a CM system (and thus triggered a CI build) always receive an e-mail indicating the build's status.
Listing 1 is an example of a CruiseControl main configuration file (config.xml), which is configured to send an e-mail, in HTML format, to the project's "build master" for both successful and failed builds:
Listing 1. Sending an e-mail with CruiseControl
<publishers> <htmlemail mailhost="localhost" defaultsuffix="localhost" username="bfranklin" password="G0Fly@Kite" returnname="Buildmaster" returnaddress="buildmaster@localhost" subjectprefix="[CC]" xsldir="webapps/cruisecontrol/xsl" css="webapps/cruisecontrol/css/cruisecontrol.css"> <always address="buildmaster@localhost"/> </htmlemail> <publishers>
You can use the
defaultsuffix attribute of CruiseControl's e-mail task to also send e-mails to the developer(s) who committed the most recent changes, as well.
Figure 1 shows an example of the e-mail a user will receive based on the configuration in Listing 1:
Figure 1. A sample build status e-mail a la CruiseControl
While e-mail is arguably the de facto standard feedback mechanism for projects that use CI, if team members are flooded with too many e-mails, they may begin to ignore them, which, of course, defeats the purpose of a feedback mechanism in the first place. I find it more productive to configure CI systems to send e-mails only to the developer or developers who applied the most recent change to a code base and to project leads who don't mind receiving a flood of build status e-mails every day.
RSS is both a passive and active form of feedback, which can make this feedback mechanism more appealing because of a reduction in the amount of e-mail messages you'd receive otherwise. An RSS feed is a generated XML file (which conforms to a standard) that is updated based on certain events. An RSS reader then picks up the change and creates a passive message indicating new content. So, if you'd rather not get bombarded with e-mail, try this approach instead.
Within a CI system, this RSS feed can be updated based on the latest build status. For instance, Figure 2 is an example of the CruiseControl RSS XML that, by default, is generated for any build event:
Figure 2. RSS XML from CruiseControl
Simply point your handy RSS reader to this feed and when a new build event occurs, and the RSS feed is updated, bingo, you'll be notified. Figure 3 shows the RSS feed as displayed in an RSS reader:
Figure 3. RSS indicates things went wrong!
What if you're away from your computer and the build fails? If you believe that keeping an integration build successful is one of the highest priorities on your project, you'll want to know the build status at any point in time. One way to constantly keep abreast of build statuses is through the Short Message Service (SMS), which are short text messages sent to mobile phones.
Fortunately, the same mechanism used to send e-mail can also be used to send SMS text messages. For example, Listing 2 shows an example of using the CruiseControl e-mail task to send an SMS message:
Listing 2. SMS sample code
<publishers> <email mailhost="localhost" returnaddress="buildmaster@localhost" returnname="Buildmaster" reportsuccess="fixes" subjectprefix="brewery" buildresultsurl=""> <failure address="email@example.com"/> </email> </publishers>
I have configured the e-mail task in Listing 2 in such a manner that I will receive text messages only when there is a build failure, which is an effective means to reducing SMS messages. Furthermore, the
reportsuccess="fixes" attribute of the
Figure 4 shows an example of the message sent from the CruiseControl server when a build fails:
Figure 4. Text message on your phone -- has your build failed?
Using SMS to send text messages can be an effective form of feedback for urgent build status messages. Generally, it is not recommended that you send text messages every time a build occurs (especially if you pay per message!). Remember, too much information can become "noise" that reduces the effectiveness of feedback, so choose wisely.
E-mails work well and SMS is great when you're away from the office, but what if you just want to glance at something to determine a build's status? Luckily, there is an entire cottage industry around programmable devices, dubbed X10 devices, which can provide a more passive form of feedback when hooked up to CI systems. With X10-enabled devices, you can control most any electrical device that can be enabled using special hardware that can be manipulated through the X10 protocol. This means that every day devices such as lights can be used to notify us of a build failure.
For instance, Listing 3 offers an example of the code required to plug an X10 device into CruiseControl's publisher mechanism.
This example demonstrates turning on a red warning light if the build fails. The light is connected to an X10 controller (several "X10 kits" are commercially available). CruiseControl includes the Java™ COMM API so that you can use CruiseControl's config.xml to communicate with the device and turn it on or off.
The X10 controller will connect to a communications port on your build machine; the
port attribute indicates the communications port you are using. The
deviceCode attributes refer to the letter and number you set on the X10 controller for the device. The
onWhenBroken attribute indicates that the device will turn on when the build fails (and off when successful). Finally, the
interfaceModel attribute refers to X10 computer interface. The default is
Listing 3. X10 configuration code for CruiseControl.
<publishers> <x10 port="COM1" houseCode="A" deviceCode="3" onWhenBroken="true" interfaceModel="CM17A"/> </publishers>
Now, when this publisher is utilized, a device, such as the one shown in Figure 5, will turn on when the build is broken:
Figure 5. an X10 red warning light
There are a variety of X10 devices -- LavaLamps, sirens, you name it -- that can really enliven a project's environment. Adding these devices to a room is bound to create excitement, along with a clear indication of a build's status.
If you'd rather receive feedback instantly, have a look at client monitors and instant messaging. A client monitor is an application that is always running in the background and periodically polls your build server for the latest build status. Of course, everyone knows what instant messaging is, and a host of popular platforms, from AIM to Yahoo to MSN, are available for this purpose.
CruiseControl.NET (a Continuous Integration server for the .NET platform) provides a monitoring mechanism called CCTray that works with both CruiseControl.NET and the traditional Java built CruiseControl and is run from the Windows taskbar (which means it works only on Windows machines). An example of CCTray in action is shown in Figure 6:
Figure 6. CCTray monitor from the Windows taskbar
You can use another client monitor called Nag on non-Windows machines and even on other CI servers, such as Apache Continuum.
You can use instant messages (or IMs) to notify project members of the status of the build too. Just like using a monitor, it's another way to receive feedback quickly because of IM's ubiquity among developers.
CI servers like Apache Continuum provide a simple way to send IMs regarding a build's status. For example, Figure 7 displays an example of a failed build message, from Continuum, which is sent to a Google Talk instant message client using Jabber. CruiseControl also provides a Jabber publisher to send messages.
Figure 7. An IM signifying a failed build
Monitors and IMs are some of the quickest ways to send build status feedback, and I'm familiar with project teams that exclusively use these mechanisms. As long as this is coupled with another way to inform project members when they are away from their desk (such as with e-mail or SMS), this can be a highly effective form of feedback.
As you can see thus far, there are many types of feedback mechanisms available for you to utilize in a CI environment. Many other feedback mechanisms, which I did not cover, are available, including the Ambient Orb, Web browser plug-ins, sounds, and widgets. Table 1 provides a summary of the feedback mechanisms I covered in this article, plus a few others I didn't:
Table 1. Continuous Feedback Mechanisms
|Provides build status at discrete points in time|
|RSS||Pushes alerts regarding build status to an RSS reader|
|SMS||Alerts you to build status with text messages sent to your cell phone|
|X10||Provides feedback through visual means; popular examples include lava lamps and red flashing lights|
|Ambient Orb||Provides another visual means of assessing build status; can be customized for alerts based on specific information|
|Sounds||Alerts to build status through sound; especially useful for co-located teams|
|Displays||Provides feedback through an LCD monitor|
|Widgets||Displays the build status on the user's desktop; Yahoo! and MAC OS X provide Widgets for this purpose, including CruiseControl Dashboard for Java|
|Monitor||Alerts you to the build status from the Windows taskbar|
|Instant Message||Allows for instantaneous notification|
|Browser plug-ins||Notifies you to build status through the browser; similar to CCTray, a Firefox plug-in for CruiseControl displays a greed or red icon for success or failure, respectively|
The most effective way to proactively generate action is to use multiple feedback mechanisms in concert. Choose the combination that's most appropriate for you.
Remember, the purpose of build feedback is to initiate rapid action so that teams can fix a broken build. Typically, you'll need a combination of these feedback mechanisms to elicit this action. For instance, you may provide e-mails for all build events, SMS for build failures (and follow-up fixes), and an X10 device for visual notification. As your team matures in using these devices, you'll want to change it up every so often to add variety and keep people interested in build statuses. Be creative and have fun with it -- it's amazing how adding a few feedback gimmicks can enliven the mood and generate interest in the information they are providing!
|CruiseControl configuration for e-mail and SMS||j-ap11146.zip||1800KB||HTTP|
- Automation for the people (Paul Duvall, developerWorks): Read the complete series.
- "Bubble, Bubble, Build's In Trouble": Mike Clark, author of Pragmatic Project Automation, demonstrates a detailed example of configuring an X10 device for CruiseControl.
- "Jabber" (Gerhard Poul, developerWorks, May 2002): Gerhard Poul shows how XML-based Jabber fits into today's e-business infrastructure, highlighting instant messaging in a whole new way.
- "eXtreme Feedback for Software Development" (Alberto Savoia, DeveloperTesting, April 2004): Other examples of Continuous Feedback Mechanisms -- or as the author describes them: eXtreme Feeback Devices.
- "Pragmatic Automation": Mike Clark, author of Pragmatic Project Automation, covers various feedback devices to monitor build status.
- "Continuous Integration" (Martin Fowler, martinfowler.com, May 2006): A description of the purpose and practices of Continuous Integration.
- "Configuring Continuum for CI" (Testearly.com): An article that describes the basic setup and configuration of Continuum.
- Ambient Orb Ant task example (Testearly.com): Examples on using the Ambient Orb Ant task.
- The Java technology zone: Hundreds of articles about every aspect of Java programming.
Get products and technologies
- CruiseControl: An open source server for Continuous Integration.
- 4-Pack Firecracker Automation System: Hardware to help configure
your build to interface with X10 devices.
- Nag: A Continuous Integration montior that works with multiple CI servers and platforms.
- Yahoo! Widgets: Search for CruiseControl widgets for feedback to your desktop.
- Ambient Orb Ant task: A freely available open source Ant task for changing Ambient Orb colors based on build status.
- Improve Your Code Quality discussion forum: Regular developerWorks contributor Andrew Glover brings his considerable expertise as a consultant focused on improving code quality to this moderated discussion forum.
Paul Duvall is the CTO of Stelligent Incorporated, which helps companies address software quality with effective developer testing strategies and Continuous Integration techniques that enable teams to monitor and improve code quality early and often. He is a contributing author to the UML™ 2 Toolkit and currently co-authoring Continuous Integration: Improving Software Quality and Reducing Risk (Addison-Wesley).