Tag Archives: CI

Reviving CI test failures in local machine

The problem

These days, most serious software developments include a Continuous Integration server which runs tests. A problem appears when tests fail in the server but they do not fail locally. There can be differences in the used operating system, virtual machine, configuration, etc. Let’s take as an example the Jenkins server of Pharo. We use such server to not only build and test the Pharo images but also the VMs. There are 3 slaves (one for each: Windows, Linux and MacOSX) and tests are run in all of them. Still, it is common to have tests that we cannot reproduce locally. Why?

  • Random failures: tests that fail randomly. Of course, we would prefer not having these tests but sometimes we do.
  • Tests that fail because as a side effect of other tests.
  • The OS of the server or even its configuration/infrastructure is different.
  • The used virtual machine can be different (for example, Jenkins uses the VM it builds to test the other jobs).

What do we have now?

So, we have a failure in the server that we cannot reproduce locally. How can we understand what happened? So far, the only thing we have is a piece of a text-based stack trace. For example, let’s take this test failure:

Error Message
Assertion failed

As you can see, this is not that helpful and you may still don’t know what  has happened. Something really useful would be to at least know what where the values of the instance variables involved in that stack… Here is where Camillo Bruni had a nice idea 🙂

Fuelizing test failures

In Pharo, the stack of the running system is reified also from the language side and we can access them! (we can even modify them). We have instances of MethodContext which hold an instVar ‘sender’ that refers to the next sender in the stack (another MethodContext or nil if it is the last). Apart from ‘sender’, a context also includes the receiver, the method that caused its activation, the arguments and the temporal variables. The Fuel serializer can serialize any type of object including MethodContext. If we can serialize a MethodContext (and closures and methods), we can serialize a stack, right? And what does this mean? Well, it means that we can serialize a debugger with its current state. I have already shown several times (at ESUG Innovation Technology Award and at PharoConf) how we can use Fuel to serialize a debugger (from image X) in the middle of its execution and materialize it in image Y and continue debugging.

Pharo provides ‘exception’ objects and, at the end, test failures are exceptions (TestFailure). We can always ask its “signaler context” to an exception, in other words, the MethodContext that signals it. Once we have that MethodContext, we have all the stack (because that object has a sender and the sender context has a sender and ….). So, how do we serialize that?

context := testFailure signalerContext.
FLSerializer newFull
 serialize: context
 toFileNamed: 'context.fuel'.

So that piece of code will serialize all the stack of contexts including all the transitive closure: receiver, arguments, temporal variables, etc.

Reviving test failures

So we have serialized our test failure on a file. Now we want to revive them in our local machine. The first obvious thing is to materialize the original stack from the file. But then, what do we do with the stack? How can we do something useful with it? Well, Pharo allows us to open a debugger for a particular stack 🙂 . This means we can just open a debugger with the stack of the test failure! To do that:

| aContext |
aContext := FLMaterializer materializeFromFileNamed: 'context.fuel'.
 openContext: aContext
 label: 'This is the new debugger!'
 contents: nil

And that opens our nice debugger. Much better than a text-based stack trace, isn’t it?

Caveats when serializing a stack

When you serialize the whole stack, you may find some problems:
  1. The object graph that you serialize and, therefore, the resulting stream size can be really large depending on what the contexts have. Sometimes a context end up in the UI so you end up serializing lots of morphs, colors, forms, etc. If everything is fine, the file should be a couple hundred or thousands KB. If the file  size is in MB…then you may be serializing too much.
  2. Not only the graph is too big, but it also incorporates objects that CHANGE while being serialized (mostly when these are objects from the UI). This will cause Fuel to throw an error saying the graph has changed during serialization.
  3. If 2) happens, then depending where you trigger the fuel serialization, you may end up in a loop. For example, say you want to serialize each error with Fuel. So you change  SmalltalkImage>>logError:inContext:  to write the context with Fuel. Now, if 2) happens and Fuel throws an error, you will try to log that again causing again the serialization… infinitive loop.
  4. Apart from the previous points, there are still more problems. You can read the title “Limitation and known problems” in this post.
So… some workarounds are (still, not sure if they will help in all cases):
  • Deep copy the context before serializing it.
  • If you want to serialize particular contexts (for example, particular domain exceptions), then you may know WHERE to hook to make some instVars transient and, therefore, avoid serializing things you don’t want and that may cause 2).
  • Serialize a PART of the stack.

Jenkins integration

Thanks to Camillo and to Sean P. DeNigris, now Jenkins serializes (for some jobs) each test failure into a file (here you can see how to set up your own Jenkins for Pharo). For example, we have the job “pharo-2.0-tests”. If you select the OS and then a particular build number, you will have an artifact called “Pharo-2.0-AfterRunningTests.zip”. For example, this one: https://ci.lille.inria.fr/pharo/view/Pharo%202.0/job/pharo-2.0-tests/Architecture=32,OS=mac/lastSuccessfulBuild/artifact/Pharo-2.0-AfterRunningTests.zip. This zip contains all the .fuel files of all the test failures. Each file is named ClassXXX-testYYY.fuel.

To workaround the problem mentioned in the previous paragraphs (“Caveats when serializing a stack”), we just serialize a part of the stack: from the context that signals the failure up to the test method. Example:

"Start context slice"
> testMyFeatureBla
> ...
> ...
> assert: foo equals: bar
"end context slice"
  Exception signal

The idea is to serialize the least number of stack-frames possible while still giving decent debug feedback. To do that, our Jenkins code (HDTestReport>>serializeError: error of: aTestCase) is:

serializeError: error of: aTestCase
 "We got an error from a test, let's serialize it so we can properly debug it later on..."
 | context testCaseMethodContext |

 context := error signalerContext.
 testCaseMethodContext := context findContextSuchThat: [ :ctx|
 ctx receiver == aTestCase and: [ ctx methodSelector == #performTest ]].
 context := context copyTo: testCaseMethodContext.

 FLSerializer newFull
 " use the sender context, generally the current context is not interesting"
 serialize: context sender
 toFileNamed: aTestCase class name asString,'-', aTestCase selector, '.fuel'.
 ] on: Error do: [:err| "simply continue..." ]
During serialization the graph can somehow reach classes of the Jenkins code (like HDTestReport). If you materialize in an image where such class is not present, you will have a Fuel error. For this purpose in the same Pharo-2.0-AfterRunningTests.zip besides having the .fuel files, we also have a Pharo-2.0-AfterRunningTests.image which, as it names says, was saved after having run all tests (meaning it has the Jenkins code installed). This means we can directly use that image to materialize and it will work. The other option is to take another image and install the following before materializing:
Gofer new
 url: 'http://ss3.gemstone.com/ss/CISupport';
 package: 'HudsonBuildTools20';
This is temporal because soon Jenkins support code will be directly integrated in Pharo.
Anyway, I recommend using the same version of image that was used during serialization. So I think that using directly Pharo-2.0-AfterRunningTests.image is more reliable.


It is clear that there are several caveats. However, I do believe this is yet another step in CI and development. It is just one more tool you have at hand when something is failing in the server and you cannot reproduce it locally. It the worst case, it won’t help but it won’t hurt either. If you have luck, you may find out the cause 🙂 It is incredible all the things you can do when the stack is reified and visible from the language while also being serializable. For me, asking for a text-based stack trace in Smalltalk is like going to a cabaret and ask for a hug. We have so much power that we should take advantage of it. At the end, using a debugger is way better. Anyway, I do not recommend to remove the stack trace information, just adding also the Fuel possibility.

Installing Jenkins CI and configuring Pharo build scripts

A lot has been talked and discussed about CI in the last months. So I would like to share the experience I have gained while trying to do it myself locally in my Mac OS box.

CI introduction and Pharo integration

I guess most of you are aware of what Continuous Integration and CI server are. Basically are tools that help us to automatically build systems, run tests, make final binaries, run code critics, etc. One of the most popular ones is Jenkins (previously known as Hudson). We would like to have that for Smalltalk, but the problem is that most of them are targeted for a specific language, for example, for Java.

Fortunately for us, thanks to Yanni Chiu and Lukas Renggli, we have two things: 1) HudsonBuildTools: an integration between Jenkins and Pharo Smalltalk. 2) A builder.

HudsonBuildTools: You can check the package HudsonBuildTools in http://source.lukas-renggli.ch/hudson. Basically, the package is an adaptor between what Java expects and what Smalltalk generates. So from the Smalltalks results of running tests, this package generates the .xml files (probably the JUnit results) that Jenkins expects.  Not only for tests but also for Lint rules, test coverage, etc.

Builder: this is a set of bash files that help us all the process of building Pharo images from command line. Of course, we can then use this builder from Jenkins. The builder takes care of, for example, executing the VM and passing by argument the Smalltalk script to load what you want to load in the image. It also has some cache to improve its performance and some hooks to execute code after or before each build. It makes the integration with Jenkins extremely easy because at the end all you have to do is to create a myLoadScriptFile.st in the folder /scripts and that’s all.

Installing Jenkins

This should be easy. You just go to the jenkins website and you download the latest version for Mac OS. In my case it was here. After executing the .pkg you should have Jenkins installed in /Applications/Jenkins/. If you enter there, you will see only one file: jenkins.war. Where is Jenkins really then?  Well, that’s Jenkins “binary” (search in Google for more details about what a Java .war is). How do you start then Jenkins?  Well, it should be as easy as executing from a command line:

java -jar /Applications/Jenkins/jenkins.war

But of course, in my machine it didn’t start and throw an error saying the port 8009 was already in use…After googling a little bit, I found that I could change the port of the AJP13 protocol. I finally ended up changing both ports AJP13 and HTTP port (because default is 8080 and can be in conflict with some other stuff I have running). For more details about it read this link. So finally I had to start Jenkins like this:

java -jar /Applications/Jenkins/jenkins.war --ajp13Port=8010 --httpPort=7777

With that, I could successfully start Jenkins and I could browse its UI in: http://localhost:7777/.

Installing the builder

Nick Ager did a great post about Jenkins and Smalltalk. And the builder’s README is pretty clear. You should read both. I wont repeat all what they have already explained. I will just mention the problems I had and what I did to solve them.

1) The first problem I found is that build.sh expects that for Mac OSX:  PHARO_VM=”$VM_PATH/MacOS/Squeak VM Opt”. And VM_PATH=”$BASE_PATH/oneclick/Contents” (notice that “uname -s” MAC OSX will answer “Darwin”).  So… I needed to correctly set PHARO_VM to my VM. Hence,  after the “case “$(uname -s)” in” and before “# build configuration” I added the line:


So that way I am using that particular VM.

2) The second problem is that from Jenkins we will call the builder, so all those .sh has to be found in $PATH. What I did is to create the following startJenkins.sh:



export PATH="$PATH:/Users/mariano/PhD/Jenkins/builder"

java -jar $WARFILE --ajp13Port=8010 --httpPort=7777 > $LOGFILE 2>&1 &

java -jar /Applications/Jenkins/jenkins.war --ajp13Port=8010 --httpPort=7777

Notice that this is a simple script that I use *locally*. If you are running Jenkins in a server, you may probably want to use nohup or something like that.

Configuring Jenkins and the builder

More about the builder, tests and Jenkins

There were some things which were not easy or were not working out of the box. Hence, I will share them wth you.  Just to clarify if it is not already clear. If you want that Jenkins run tests, then you need not only a .st that loads the test, but also the “buildtools” script, which downloads the HudsonBuildTools. So if you create a job and you want to run tests for it you have to put something like:

build.sh -i Pharo-1.3 -o seaside3 -s seaside3
build.sh -i seaside3 -o seaside3-tests -s buildtools -s seaside3-tests

As you can imagine, for each script you pass with “-s” you need a corresponding .st in /scripts. We are putting two lines (commands) to the “execution shell”. The first takes the Pharo-1.3 image as input, loads seaside with the seaside3.st and then saves the image as seaside3.image. The second line, takes that seaside3.image as input, loads HudsonBuildTools (using buildtools.st), and then loads seaside3 tests and run them. We can see that seaside-tests.st is something like:

HDTestReport runPackages: ((WADevelopment allPackages
    select: [ :each | each name includesSubString: '-Tests-' ])
    collect: [ :each | each name ]).
HDLintReport runPackages: ((WADevelopment allPackages
    reject: [ :each | each name includesSubString: '-Tests-' ])
    collect: [ :each | each name ]).

In this case of Seaside3, the tests are not loaded by seaside-tests.st since they are loaded in seaside3.st. But you can split this in your projects and only load tests in the second image.

Notice that you only need the “buildtools” it if you want to run tests, lint, test coverage, etc. If you just want to build images, then “buildtools” parameter is not needed. You can read the README file for more details.

Non-Interactive UIManager

In my case, I was building an image which opens a Transcript and for some reason it also asks for the author name (it is fixed now). Anyway, one of the problems I found is that since the builder is running the image headless, we should use a non-interactive UIManager. To do that I need to evaluate:  “UIManager default nonInteractiveManager”. What I did is to add such line in /scripts/before.st. That way, all my scripts will include it by default.

Needed plugins

As explained in the README, for both, tests and lint, you need a special Jenkins plugin. To install them you can go from the web interface to “manage Jenkins” -> “manage plugins” or directly go to http://localhost:7777/pluginManager/. Then go to the tab “Available” and install those you need. Then restart Jenkins.

Creating Jenkins users

To create Jenkins users, you have to first enable security. Here you have a nice explanation of all the requires steps to be able to create users for Jenkins.

Test Coverage

If you want to run the test coverage you have to use the latest (VM.r2508 for example) CogVM from Eliot Miranda. TestCoverage uses a hook of the VM which is not working correctly in previous versions of the VM.


All in all between 1 and 2 hours, I was able to have my Jenkins running locally and building my own images. I am not a bash expert and I haven’t installed Jenkins before, so you should be able to do it fast also. If you were thinking that configuring Jenkins to build and test your images was something complicated and only for “gurus” then you should re-think it and give it a try. In my experience it was really straightforward. Of course, to have a real/secure Jenkins running you may need to spend some time giving correct permissions to files, users, etc, etc, etc.