OSX, Brew, Kubernetes helm and Azure

I think I typed enough keywords as blog title 😉

So it happened that I had to deal with kubernetes, helm and Azure. To discover that both client and server version of kubernetes helm MUST be the same.

$ helm install ./something -n somename-000 -f ./some-config.yaml
To sign in, use a web browser to open the page https://microsoft.com/devicelogin and enter the code XXXXXXX to authenticate.
Error: incompatible versions client[v2.14.1] server[v2.13.1]

The problem lies in the fact that I installed kubernetes-helm with brew on osx. Which is an amazing tool but not always keep in a easy accessible way older versions.

So the question now would be: how do I install the older version 2.13.1 so that I can work?

First, brew allows you to install from URL. Specially git URLs pointing to the raw ruby script.

With that we can point to a specific point in time on GH (hashcode) for the right formulae. First we have to find it out.

# clone the homebrew GH repo
$ git clone https://github.com/Homebrew/homebrew-core.git

# go through the logs (manually in this case) for the right commit id
$ git log master -- Formula/kubernetes-helm.rb
 commit c3a105c41a8f8be942bf97554466af236c2fac72
 Author: BrewTestBot homebrew-test-bot@lists.sfconservancy.org
 Date:   Fri Mar 22 02:21:09 2019 +0000
 kubernetes-helm: update 2.13.1 bottle.
 commit fd2c01c0cd6ba9a32c5a84b9b914debd077c7498
 Author: Igor Kapkov igasgeek@me.com
 Date:   Fri Mar 22 11:03:08 2019 +1100
 kubernetes-helm 2.13.1 Closes #38158. Signed-off-by: FX Coudert <fxcoudert@gmail.com># clone the homebrew GH repo

Now we have the commit we want: c3a105c41a8f8be942bf97554466af236c2fac72.

You can verify it by accessing https://raw.githubusercontent.com/Homebrew/homebrew-core/c3a105c41a8f8be942bf97554466af236c2fac72/Formula/kubernetes-helm.rb.

which now lead us to a set of commands

# will install the 2.13.1 version as currently brew moved to 2.14.1
$ brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/c3a105c41a8f8be942bf97554466af236c2fac72/Formula/kubernetes-helm.rb

# will switch to 2.13.1 and pin it so that future update of brew won't update the formulae
$ brew switch kubernetes-helm 2.13.1
$ brew pin kuberntes-helm

Artifact Size. A story of size enforcement.

So it looks like I’ve not been posting here for quite some time. Last post was in 2017…

The maven enforcer on the binary size can be a very useful tool as well as disruptive and close to useless. I think, in this world of cloud deployment and containers it’s getting again useful as you want a microservice to be as little as possible and be aware if it breaks a certain limit.

I said it: a microservice. What if you are working on a HUGE monolith comprised by 185 different OSGi bundles and God only knows how many other form of binary content are distributed in there?

In this last case, you may have a limit, with some margin and then the size is creeping closer and closer to the limit. Then you send your PR, which increase the size by just 2KB and BANG! Fails the check. WTF! You sure think… not my fault. Why on earth… regardless.

The point now is to find if there has been any commit which pushed the size considerably in the “recent past”. A task that done by hand can be tedious and error prone. So here’s another script. With a very imaginative name: artifact-size.sh.

What it does is fairly simple. it takes 3 mandatory parameters: repo, name and numer of commits. Repo is the path to a local git clone of the project, name is the relative path to the generated artifact (the jar) and number of commits is, well…, the number of commits you want to go back in time.

Don’t worry, if just invoke it without any parameter it will give you a help.

It will then take that number of commits, go back in time and start working forwards one commit a time packaging your project and collecting in target/ a CSV with the meaningful info like: commit hash, size and something more. You can then open this CSV file in open office (for example) and start playing with filters, putting it through a complex pipe of bash command or, why not, read it as it is.

If you’re lucky like me, you can find a single commit pushing considerably the size (20MB+) and therefore can work with the developer on what can be done (reverting?).

Potential future improvements? Here are some ideas and PR are always welcome

  • get a % of increase as argument and flag already any commit that goes beyond such threshold.
  • take the above % and work with bisect pinning down the first commit that bumped the size beyond such threshold.


docker mongodb and insufficient free space

If you’re running a mongodb instance inside a docker container you may end up after a while of starting and shutting down the containers with mongodb no longer starting and complaining with the error message

ERROR: Insufficient free space for journal files

Indeed if you run from within the failing container a df -h you may easily see that the space for the mongodb data is less than 3GB. In my case was /data/db inside the container itself as I don’t care to preserve the data.

Running a command like

docker ps --filter status=dead --filter status=exited -aq | xargs docker rm -v

clean-up all the cached docker filesystem which add up one on top of each other.

If you then run the docker container with the –rm flag it will automatically clean-up after exiting.

$ docker run -rm -it <image>



Bash: compute dates

Often I found myself in the need of computing some math on dates. For example what is 10 weeks from a given date? Rather than opening a calendar and start counting you can quickly open a bash shell.

Example: what’s 6th of June 2017 plus 10 weeks?

$ date -j -v '+10w' -f '%Y-%m-%d' '2017-06-06'
Tue 15 Aug 2017 10:00:20 BST

Maven release plugin and local changes

It may happen that you’re trying to fix some issues that affects the release of a maven project and therefore you apply some changes locally and then run

mvn release:prepare -DdryRun=true -Darguments=-DskipTests

Then you get an error message like

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-release-plugin:2.5.3:prepare (default-cli) on project jackrabbit-oak: Cannot prepare the release because you have local modifications :
[ERROR] [oak-api/src/main/java/org/apache/jackrabbit/oak/api/PropertyState.java:modified]
[ERROR] [oak-api/src/main/java/org/apache/jackrabbit/oak/api/jmx/CacheStatsMBean.java:modified]
[ERROR] [oak-api/src/main/java/org/apache/jackrabbit/oak/api/jmx/CheckpointMBean.java:modified]
[ERROR] [oak-api/src/main/java/org/apache/jackrabbit/oak/api/jmx/IndexStatsMBean.java:modified]
[ERROR] [oak-api/src/main/java/org/apache/jackrabbit/oak/api/jmx/RepositoryStatsMBean.java:modified]

Sure. release-plugin is giving you an extra check about any local changes that may not end in the release. However you don’t want to commit those changes to the SCM just yet; you want first to see if they works.

A “quick” workaround is on the command line in the (verbose) form of

mvn release:prepare -DdryRun=true -Darguments=-DskipTests -DcheckModificationExcludeList=oak-api/src/main/java/org/apache/jackrabbit/oak/api/*,oak-api/src/main/java/org/apache/jackrabbit/oak/api/jmx/*

You can as well specify something in the poms directly however I never had the need.



Firefox install unsigned add-ons

Since Firefox 43, it won’t allow you to install unsigned extensions.

While it’s a good thing, you can revert it in case with the following steps:

To disable signature checks, you will need to set the xpinstall.signatures.required preference to “false”.

  • type about:config into the URL bar in Firefox
  • in the Search box type xpinstall.signatures.required
  • double-click the preference, or right-click and selected “Toggle”, to set it to false.

It will eventually show your unsigned extension with a warning but it should work out fine.


OSX Restarting GDrive App

If you use Google Drive and the OSX app, and like me you often travel and change network connection (VPNs count as well), you may have noticed that it won’t connect anymore.

While I don’t know why exactly, it may be due to some security things in the app itself, I noticed that by restarting the app it connects successfully.

Having to do it more than once a day, here is a simple script that with a double-click will restart it.


The weight of a property name in AEM

Jackrabbit 2.x / CQ5

Back in Jackrabbit 2.x, and therefore in CQ/AEM 5.x, everything was indexed by default other than you stated otherwise.

This translated that every time you run a query, Lucene was there for you serving an indexed answer.

In this scenario it didn’t really matter what property name you used for you application or if you defined additional node types.

This had the advantage that everything was indexed and therefore an index was almost always there serving your query and you didn’t have to think about it.

On the other hand we all know that the bigger the index is, the slower it will be in serving you the result set, as it will simply have to analyse more data.

Jackrabbit Oak / AEM6

Nowadays Apache Jackrabbit Oak, aka Jackrabbit 3.x, is the foundation of AEM6.

Opposed to JR2, in Oak almost nothing is indexed by default. Which means that if you would take a vanilla Oak and run a query, you have very good chances you’re going to traverse the repository (depending on your query).

This has the advantage that you can create very dedicated indexes that will overall perform better as they will be as tailored as possible to your query.

The disadvantage are that you’ll have to define each index and that you’ll have to know how fine tune your queries for getting the most out of this approach.

Not going deeply into the configuration of each individual available index type I think the two main properties, you’ll end-up tuning for better performances are

  • propertyNames
  • declaringNodeTypes

the first one will define what property your index is going to index while the second will restrict the index to a specific node type. In other words the condition for a node to be included into an index are

$nodetype in ($declaringNodeTypes) AND $property = $propertyNames


  • indexes on more than one property are not supported (yet)
  • an index cannot serve conditions where you ask something like WHERE property IS NULL.

This take us to the very topic of this post: be careful on how you use your property or structure your queries.

Remember the rule: the smaller the index the more efficient the query.

Let’s see how important is a property and a node type with an example then.

If you have a custom application in which you want to extract nodes after a specific date, a way of doing so would be

SELECT * FROM [nt:base]
WHERE [jcr:lastModified] >= CAST('...' AS DATE)

this query is very bad. It can’t really makes use of any index.

Let’s say you create an index on jcr:lastModified. The index itself will be almost as big as the repository as by default in AEM (almost?) every node as mix:lastModified.

A better way would be

SELECT * FROM [nt:base]
WHERE [myLastModified] >= CAST('...' AS DATE)

this will allow you to define an index on the property mylastModified which you’ll know it will contain only your application data. But we can get even better.

Let’s assume you have a very sparse and large content structure so you can’t apply path filters and you don’t want on the other side to create tons of myLastModified for addressing different aspects of your information.

Let’s assume then, for sake of example, that you categorise your data into:

  • comments
  • news
  • articles.

What you could do is create three different node types:

  • my:comments
  • my:news
  • my:articles

now you can define three different, very dedicated indexes

  • declaringNodeTypes = my:comments AND propertyNames = myLastModified
  • declaringNodeTypes = my:news AND propertyNames = myLastModified
  • declaringNodeTypes = my:articles AND propertyNames = myLastModified

One eventual query will look like

SELECT * FROM [my:comments]
WHERE [myLastModified] >= CAST('...' AS DATE)

Actually in the example above, assuming your nodes comes with mix:lastModified, as soon as you create a custom node type you could have simply used the jcr:lastModified date as they will be (I expect) the same size. You can change the exercise above with any property name like: colours, size, tags, etc.


Install MySQL on OSX

If you need a local instance of a mysql database for experiments and don’t really care about security as it’s not any production system here’s a quick way to install a mysql database on your OSX (tested with 10.9+)

  1. Download the latest OSX native package installation from the
    download page. It should be a dmg
    file. http://dev.mysql.com/downloads/mysql/
  2. Install it as any other OSX application. It will create under
    /usr/local/mysql-x.y.z with a symlink to /usr/local/mysql the
    entire directory structure that will be needed by mysql. From now
    on I will refer as /usr/local/mysql directory.
  3. sudo rm -r /usr/local/mysql/data
  4. sudo mkdir /usr/local/mysql/data
  5. sudo chown -R <youruser> /usr/local/mysql/data
  6. /usr/local/mysql/scripts/mysql_install_db

If everything worked out fine you should be able to start it with

$ mysqld_safe &

to stop it

$ mysqladmin -u root shutdown

I’ve created a couple of aliases and exports in my ~/.profile to ease the tasks

 export PATH=$PATH:/usr/local/mysql/bin
 alias mysql-start="mysqld_safe &"
 alias mysql-stop="mysqladmin -u root shutdown"