Suggestions for Jenkins on multi-platform projects

Our team uses Jenkins as our Continuous Integration tool. I would like in this post to describe our usage, and suggest a few ideas that could improve this great tool.  But first let me explain what we are building...

What we build

The product that we are building is a Mathematical Programming engine. The most basic usage is that you feed it with the mathematical formulation of the business problem that you want to solve, and ask for the best possible solution to this problem.  The program then cranks up all the CPUs/cores it can find on your machine and returns with an answer after a few tens of a second, or a few hours (some problems are REALLY complicated).

The core of the engine is a library built from 500.000 lines of C code. In addition to this library, we have APIs in half a dozen other languages (C++, Java, Python, etc), and connectors for several third party applications.  No less than 14 platforms (including Windows, Linux on various CPU types, MacOs, AIX, HP-UX, etc.) are supported.

We are therefore very glad to use continuous builds: you really don't want to discover a possible compiler bug, or a non-determinism in the code on some exotic platform just before the release!

Our current setup

On our master branch (the one that receives most of the commits from the developers) we use two job families.

The first one builds the software in Debug mode and runs a fully comprehensive suite of tests. We have around 20 such jobs for all the platform/compiler/settings combinations we support. Run times vary widely: some of the jobs are done in 1h30, while others need almost 7 hours.

The second family (the 'distrib' jobs) builds the Release versions of the product. There is one job per platform. Each job builds all the components for this platform (e.g. on Windows32, we support both Visual Studio 2008 and 2010), packages them into some releasable form (could be a Zip, a TarZ or an installer) and tests the basic functionality of the software (e.g. the distributed samples). For those jobs, the run times vary even more: from 30 minutes to 10 hours, depending on the platform.

This setup has been in place for some time now. It works, and it's extremely useful!

Whishes

Although Jenkins is a great tool, it doesn't yet have all the features I'd like.  So here are a few ideas, just in case the developers would not have already enough...

Detect stale jobs

We sometimes have jobs that stop running (no new run is triggered, or no available nodes).  This is of course not intended, and it would be nice to be able to detect those easily.  I suppose that adding a 'Last build' column to the list view, that would display the time since the job entered its current state, would be nice.  Something like 'Ended 8.6 hr' or 'Queued 1.3 hr' or 'Started 12 min'...

Then I'd know that if the code changed 3 hours ago, I shouldn't see any number larger than 3 hours...

Detect hung jobs

We have many jobs running, typically 20 to 30 simultaneously. And some builds last for several hours.  It happens that tests hang, or are abnormally slow.  These situations should be detected as soon as possible for investigation.

Unfortunately, the 'Build History' list is not very helpful, for two reasons. It has too few jobs for us: with 50 builds, only the last 5 hours are covered, which is less than the duration of many of our builds. But then if this limit was increased, we'd probably need a list of 200 or so jobs, which would not be easy to handle.

I would thus suggest to allow filtering on the 'building' status.  When this flag would be set, the 'Build History' would only display the jobs that are currently being built.

A view 'by revision'

I often need to check if a given revision of the source has been built by a given job, or what is the latest revision that is good on a set of jobs.  For example, I may want to merge this revision to some 'stable' branch for other teams to use.

I think that a grid view with the following attributes would be very useful for this: each line is a commit id or SVN revision, each column is a job, each cell is blue, red or gray (or even empty if this revision has not yet been part of a run of the job, or the run is not finished yet).


Do you think these would be useful additions?

A Taste of C++11

Herb Sutter has an example of what C++11 feels like. Here it is, from the video:

string flip(string s) {
   reverse(s.begin(), s.end());
   return s;
}

int main() {
   vector<future<string>> v;
   
   v.push_back(async([] { return flip(   " ,olleH"); }));
   v.push_back(async([] { return flip(" egdelwonK"); }));
   v.push_back(async([] { return flip("\n!rebmahC"); }));

   for (auto& e : v) {
      cout << e.get();
   }
}

Concurrency, futures and lambda functions... Moved objects, automatic type deductions and new for loop syntax...

A whole new language, isn't it?

About 'Making Things Happen'

I just finished reading 'Making Things Happen: Mastering Project Management', by Scott Berkun.

Rather than trying to explain why this is a really great book (although it is, and you can find reviews here, here and there), I thought I'd rather just mention a few ideas/topics/quotes I noticed while reading.  If you want to know more about these items, you know where to go...

p 11 - PMs have to balance several pairs of forces: ego/no-ego, autocrat/delegator, tolarate ambiguity/pursue perfection, oral/written, acknowledge complexity/champion simplicity, impatient/patient, courage/fear, believer/skeptic.  Depending on the phase of the project, or the situation at hand, PMs must balance these forces differently

p 16 - "PMs have to understand the advantage of their perspective and choose to make use of it"

p 25 - A schedule has a forcing function: people tend to try and stick with it

About schedules: a simple way to build one is to ask people in the team to provide an indented list of one liner tasks with estimates no longer than 2 days

p 137 - Specifications are needed to build a plan, and help define tests:

- ensure the right thing gets build

- create milestones to focus the team

- enable reviews and feedback

They should be in VCS (markdown format?) to allow others to check what changed.  PM should make it clear with the team what the goals for the specs are (p 138)

p 143 - "Remember that good feedback comes more easily if you ask for it than if you wait for it."

p 144 - Ask the readers of the spec 'Do you have what you need to do your best work?'

p 145 - When writing a spec, put the questions about the specs itself at the end, or in another document.

p 183 - PM is tough: you have to invest in relationships with people, regardless of how much they're investing in you

p 185 - PM should discuss, wich each person, his role, the other person's role, and the common parts.  This sets expectations.

p 186 - "What can I do to help you do your best work?"

p 215 - When an urgent issue arises:

- Calm down

- Evaluate the problem

- Calm down again

- Get the right persons in a room (and often, you don't belong to this group -- Offer help, but don't get in the way)

p 221 - "The challenge [of managing projects] isn't sailing in calm, open waters with clear skies. Instead, the challenge is in knowing w to juggle, prioritize and respond to all the unexpected and difficult things that you're confronted with".

"Taking responsibility for something doesn't make it your fault: it means that you will be accountable for resolving the situation"

p 224 - Getting to Yes, by Roger Fisher -- Know you BATNA (Best Alternative To Negociated Agreement)

p 232 - It's much more expensive to recover from burnout than to slow the project down

p 232 - Feelings about feelings

If someone says something to you that makes you sad ("You smell funny"), next that happens is a feeling (anger) about this first feeling (sadness) and one usually only can express the former (the feeling about the feeling). Cf Virginia Satir

p 233 - Living, loving and learning, by Leo Buscaglia

p 233 - Beware the hero complex (the person creates bad situations to be able to solve them)

p 234 - 'Always' and 'never' are not valid answers to the question of when a process is necessary

p 235 - Beware codependance between bad management and heroes, where the former creates the bad situation that the other saves

p 236 - Exercises for bad situations

p 242 - "To be a good leader, you must learn how to find, build, earn, and grant trust to others - as well as learn how to cultivate trust in yourself"

p 253 - Criticizing others

p 254 - What to do after a mistake, what to learn from your mistakes

p 255 - Never reprimand in real time

p 257 - Self-Reliance, by Ralf Waldo Emerson

p 261 - PMs do ordered lists of stuff

p 265 - Saying no.  "If you're asked something, say no and point them to me"

p 354 - Project Management Clinic (closed now, but archives available) - http://www.scottberkun.com/forums/pmclinic

LaTeX-like Project Management

With project management role comes the need for a project scheduling tool.  The obvious choice would be Microsoft Project, but I thought I'd rather look for some free programs first.

I tried two that are very similar to MS-Project: OpenProj and GanttProject.  Both are open-source software.  Both have a GUI that's centered around a Gantt chart, and allow you to manipulate activities as in MS-Project.  But both also lack a very basic feature: resource leveling.  They don't have any intelligence whatsoever, and the user must check by himself that resources are not overloaded, and correct issues by adding spurious precedence or 'starts after' constraints.  I therefore don't really see how to actually use these tools for any serious work...

But then I discovered The TaskJuggler.  It's a command-line program written in Ruby that will read a text file and output HTML pages with various reports like a gantt chart or a resource allocation graph.  Installing the tool is as easy (once/if you have Ruby) as typing 'gem install taskjuggler'.

Using a text file as the input for all your project data has important benefits. The first one is that you can make use of your Source Management system to allow multiple people to collaborate on the file, while with a binary file (or even a text file that's completely rewritten by your tool when you save it) can't effectively permit sharing.  Another is that changes are much easier to track, as a change to a single part of the project will not touch the rest of the file.  So it's possible to revert individual changes...

This very much reminds me the difference between a word processing program, and LaTeX...


Here are some screenshots:

The Gantt chart

The resource allocation chart

And here is an example of a trivial project file. You'll find a much more complete example of a project file in the tutorial that is provided with the project.

project tiny "Example TJ3 Project"  2012-01-09 +12m {
  timezone "Europe/Paris"
}

resource Xavier "Xavier Nodet" {}

resource dev "Developers" {
  managers Xavier
  resource dev1 "Dev1" {}
  resource dev2 "Dev2" {}
}

task Tiny "Our Tiny Project" {
  responsible Xavier

  task t1 "Task 1" {
    
    task sub1 "Sub-task 1.1" {
      effort 30d
      allocate dev1
    }
    task sub2 "Sub-task 1.2" {
      effort 10d
      allocate dev1
    }
  }

  task t2 "Task 2" {
    effort 20d
    allocate dev2
    depends !t1.sub1
  }
  
  task deliveries "Milestones" {

    task start "Project start" {
      start ${projectstart}
    }
    
    task ega "EGA" {
      start 2012-11-01
      depends !!t1, !!t2
    }
  }
}

# Skipping the report generation part...

I only scratched the surface so far, but this seems very promising to me...

Results are not enough

Of course, results are a very important part of a manager's evaluation.  But that's not the end of the story...

Consider the manager of a great team of engineers. One can expect that the team will deliver good results. And this may be the case even if the manager is not so great... Conversely, let's consider the manager of a bad team: it may be the case that whatever the manager will do, the team will not deliver. In the long run, a great manager will manage to improve the results he gets from the team, but it may take quite some time. Evaluation of the managers only from the team's results is thus not enough, and may even be completely counter-productive...

So what's a good manager to do?

Of course, a manager must make plans. But that's not enough: as Tom Foster puts it, managers should build robust plans that take external factors not under their control into account. And they should be judged on the fact that they not only planned for success, but made it more likely to happen. Luck, or the lack of it, should not play a role. Kids learning chess often setup traps, only to discover that their opponent did you fall into it. They plan for the best, instead of planning for the worst. Explicitly supposing that things can go wrong is a good way to not depend on random external factors, and improve the likelihood of getting good results.

Getting results is not the mark of a good manager.  Consistently getting results is.

Partial working copies with Subversion

When working on large and/or multi-platform projects, it often happens that your Subversion working copy contains items that are useless: ports for other platforms, module that you don't need for your work, etc.

Recent Subversion versions allow to specify the maximum depth to use when updating a given target.  You can e.g. specify that you only want the files in a given directory, but not its sub-directories.  Or you want a given directory to be empty, or removed from the working copy entirely.

Let's consider you've checked out an entire working copy, with the following structure:

root
  dir1
    file1.1
    file1.2
    subdir1.1
    subdir1.2
    subdir1.3
    subdir1.4
  dir2
    file2.1
    subdir2.1
      file2.1.1
  dir3
    file3.1
    dir3.1

If you're not interested anymore in subdir2.1 and its content, you can issue the following commands:
> cd root/dir2
> svn update --set-depth exclude subdir2.1
Now dir2 only has file2.1, and an 'svn update' command that does not specify a '--set-depth' option will not bring back subdir2.1 or any of its content.

If you're only interested in the files inside dir1, but not the subdir1.*, you could do:
> cd root
> svn update --set-depth files dir1

This tells SVN to only get the files in dir1, but not its sub-directories

Similarly, you can use '--set-depth empty' to get an empty directory (this can be useful to ask for one of its sub-directories), '--set-depth immediates' to get the immediate sub-directories, and use '--set-depth infinity' to restore the default and get everything in a given directory.

On the reverse, if you have to checkout a working copy but you know you only need some parts of it, you can use the '--depth' option (not '--set-depth', go figure...) of the checkout command.  Then you create your paths in your working copy, step by step:

> svn checkout --depth empty [repository URL] root

> svn update --set-depth empty root/dir1

> svn update --set-depth infinity root/dir1/subdir1.2

> svn update --set-depth infinity root/dir3

Hope this helps!

New features in C++0x allow really impressive stuff...

Slack has a very interesting blog entry about Automatic memoization in C++0x...

Memoization is a pretty well-known optimization technique which consists in “remembering” (i.e.: caching) the results of previous calls to a function, so that repeated calls with the same parameters are resolved without repeating the original computation.

He starts with the short and simple Python function that returns a memoized function from any regular one, and then shows how C++0x features can be used to do the same!

Very impressive...