On Kanban: Is there a need for Kanban Certification? My answer is Yes, there is.

David J. Anderson has posted this question in a couple of places. My answer in short is: Yes.

I would certify the theoretical understanding of the individual to act as a coach.

"Kanban Coaching Professional" can be a good title. As the title suggests the certification will support the fact that the professional can coach a team guiding them through continuous improvement, from following Deming's System of Profound Knowledge and the 14 Points for Management all the way up to your 5 steps in the recipe for success.

I personally like the idea of Project Coach better than Project Manager. And of course as any other certification, passing it does not mean that you are actually a seasoned coach but that is of course subject for a different discussion.

Maven and Jenkins for Continuous Delivery (release and deployment)

That is the agile lean goal, to deliver value at a constant pace with minimum manual intervention right?

I have written before about continuously releasing snapshots but in reality what you want to make sure is that once something is tested it can be deployed and that can only be achieved if what you have tested and verified is a release.

Here is how to use Maven and Jenkins to help the team with continuous releases of maven projects.

The proposal here is to use only 3 digits ( M.m.b meaning Major, minor and bug fixing ) for any release version number. We can continuously release increasing the minor version number keeping bug fixing number equal zero. Of course we want to leave the major version number unchangeable because most likely that would say something about the maturity of our platform. This is usually a version that has even commercial meaning so we better leave it as a configuration parameter which will be touched only rarely.

Maven

Developers work on a SNAPSHOT project. If the project has modules then you use Aggregation (or Multi-Module) How can we make sure such project and its modules are all released without human intervention? In other words how can use Maven to force a release version from a single command? The below command uses -DdryRun which you would remove in real life but it is handy to see what would the command do as we soon will learn:

mvn clean --batch-mode release:prepare -DdryRun=true -DautoVersionSubmodules=true -DreleaseVersion=2.3000.0 -DdevelopmentVersion=2.3001.0-SNAPSHOT

The above releases all releasable (meaning ending in -SNAPSHOT) modules tagging them with the same ${releaseVersion} and the root project as well. You can confirm that looking at all pom.xml.tag files that are locally generated for each project. It also (as expected) changes the version number for the projects so developers can continue working on new features for the provided ${developmentVersion}. You might wonder why I decided to increase by 1 the minor number for the next development SNAPSHOT version. The reason is I want to make sure the team understand the last number is reserved for patching an existing in production version. The next expected version will have the released minor version number plus one only if the CI server actually did no other release before as you soon will learn so most likely the next released version minor number will be higher than 3001 in reality.

You can try the above again and again with different combinations provided that you remove the tag, next, releaseBackup and release properties temporary files:

find ../ -name "pom.xml.*"|grep -v svn|xargs rm -f; \
find ../ -name "release.properties"|xargs rm -f

Jenkins

1. Check "This build is parametrized". Define a String parameter called "MAJOR_VERSION_NUMBER" with default value equal your current release major version number. In our case this is just "2". Later on when building manually from Jenkins the parameter is pre-completed but definitely changeable.
2. Configure the build to invoke maven with goals and options that apply to your specific case. Following our example:

   #!/bin/bash
   mvn clean --batch-mode release:prepare -DdryRun=true -DautoVersionSubmodules=true -DreleaseVersion=$MAJOR_VERSION_NUMBER.$BUILD_NUMBER.0 -DdevelopmentVersion=$MAJOR_VERSION_NUMBER.$(($BUILD_NUMBER+1)).0-SNAPSHOT
   

   The shebang here is important to make sure parameter expansion works. You can see how we add 1 as discussed before.
3. I started configuring the build to invoke maven with goals and options that apply to your specific case. In our case go to "Perform Maven Release" and fill the boxes as in:

   Release Version: $MAJOR_VERSION_NUMBER.$BUILD_NUMBER.0
   Development version: $MAJOR_VERSION_NUMBER.$(($BUILD_NUMBER+1)).0-SNAPSHOT
   Dry run only?: check it to run just this as a POC
   

   However at the time of this writing the parameter expansion won't work in the spot above. You will need to use the literal maven command instead.

bash: extract tokens from a string using parameter expansion for example domain or host from url

There is literally no developer or sysadmin which will not understand what $var is but parameter expansion in bash is more than just a simple variable. When it comes to parsing strings most developers are familiar with high level functions that allow to tokenize them. Bash parameter expansion can help with this task using substring removal. Double hash-mark and double percentage-mark are your friends.

Below is a solution for the typical problem related to parsing urls:

url="http://sample.com/path/to/res?p1=1&p2=2"
url_no_params=${url%%\?*}
echo $url_no_params 
params=${url##*\?}
echo $params
host_and_path=${url##*\/\/}
echo $host_and_path
host=${host_and_path%%\/*}
echo $host

The above will result in:

$url="http://sample.com/path/to/res?p1=1&p2=2"
$url_no_params=${url%%\?*}
$echo $url_no_params 
http://sample.com/path/to/res
$params=${url##*\?}
$echo $params
p1=1&p2=2
$host_and_path=${url##*\/\/}
$echo $host_and_path
sample.com/path/to/res?p1=1&p2=2
$host=${host_and_path%%\/*}
$echo $host
sample.com

Java, is the JVM responsible for: OS Unable to fork: Cannot allocate memory ?

CREDITS: I would like to thank my old friend and now again coworker Josu Feijoo for his help on getting to the conclusions below.

This error means that no more processes or threads can be open due to memory starvation. Most likely a hard reset will be needed so certainly it is not a nice problem to have.

Clearly its resolution depends on what you are running but most likely there are too many threads been run in your system so the first step for troubleshooting would be to get all threads and identify the culprit:

$ top -H -b -n 1 

After you identify the culprit (tomcat in our case) take a look at how threads are going up indicating a leak:

$ top -H -b -n 1 | grep tomcat -c

In Java the JVM memory requirements are the sum of maximum heap memory, the maximum "perm space" memory and the number of threads multiplied by the thread stack size:

Xmx + MaxPermSize + (Xss * number of threads)

That is the reason Virtual memory consumption is so important. I see a lot of miss-leading comments and posts on the web claiming that you should only worry about resident memory (top RES) and not much for virtual memory (top VIRT) and under those assumptions some engineers might think the below is simply OK. Note how this JVM is using 2.3GB physical memory but 18GB virtual memory:

$ ps -e -o rss,vsize,cmd | grep tomcat
2298588 18019720 /opt/jdk/bin/java -Xmx2048m -XX:MaxPermSize=512m

This should not be OK for most web applications. Unless on purpose you need to maintain a lot of threads you should be suspecting of thread leaking. At that point you need to use jstack, jvisualvm or any other tool that allows you to connect to the debug port of the JVM to further troubleshoot which is the responsible leaker in the Java code. Or perhaps you can quickly inspect your code for threads you open and simply do not stop. You might be using some library or middleware responsible for it like the Camel ProducerTemplate. Housekeeping is necessary, resources are not infinite and those of us ignoring that rule will pay with a resource starvation surprise. stack

Needless to say that if you really need to spawn so many threads then do not forget to run the JVM with enough memory that accounts also for the thread stack consumption.

Add network routes in MAC OSX

Here is a snippet that shows how to add routes to a network only available after a VPN connection has been established. Note the two commands used, one refers to the interface (the vpn interface ppp0) while the other refers to the gateway (192.168.50.100).

$ sudo route -n add -net 10.0.0.32  -interface ppp0
add net 10.0.0.32: gateway ppp0
$ telnet 10.0.0.32 3389
Trying 10.0.0.32...
Connected to 10.0.0.32.
Escape character is '^]'
$ sudo route -n delete  10.0.0.32
delete host 10.0.0.32
$ telnet 10.0.0.32 3389
Trying 10.0.0.32...
^C #timeout
$ sudo route -n add -net 10.0.0.32  -gateway 192.168.50.100
add net 10.0.0.32
$ telnet 10.0.0.32 3389
Trying 10.0.0.32...
Connected to 10.0.0.32.
Escape character is '^]'

Find which process owns the socket listener AKA open port

In one word, lsof. For example the below will list the process which holds port 8080 open:

lsof -i tcp:8088

This is a useful one which any Linux sysadmin should be aware of.

top and cron - Log all commands being run every minute

To troubleshoot what is going on in Unix and Linux systems your first step is usually top. You can run it in two modes: interactive and batch mode. In batch mode the output can be piped to any other command making it ideal to leave it croned in a server to later on analyze what is going on there:

*/1 * * * *  COLUMNS=512 top -b -n 1 >> /tmp/top.log

Option b stands for batch mode. Finally "n 1" means top to end after a single iteration/refresh.