Category: Allgemein

This is just a short collection of VSCode commands and tricks which I personally did not know after switching from Eclipse ID.

Open Command Palette

Most things in VSCode can be controlled via the Command Palette:

Press Ctrl + Shift + P

Tag and Push

To tag the new release and push the tag to Github open the command palette and use

Git: Create Tag
-> choose your projec
-> enter teh tag name

Next you can push your new local tag to github with the command

Git: Push (Follow Tags)

Clean Java Projects

In some situations it may be helpful to rebuild all Java projects in your workspace

Java: Clean Java Language Server Workspace

SSH Key – Github Pull hangs…

In case you run into a scenario that your build-in git pull command within VSCode hangs forever, this may be an issue related to the ssh-agent (find background here).

You can test if yoru ssh-agent is running (which is necessary for VSCode) by checking the following command in a terminal:

$ ssh-add -l
The agent has no identities.

The result here shows, that not SSH IDs are available and this causes the hang in VSCode.

To solve such a situation, you can open a Terminal and enter

$ eval `ssh-agent`
$ ssh-add

This will promt you for the password of your ssh private key and register the ssh-agent with the SSH id. Now you can start VSCode:

$ code

This way VSCode will inherit the environment variables it needs to get key services from ssh-agent, and therefore will not prompt for your passphrase so long as the ssh-agent process continues running.

To automate this you can add the following script into your ~/.bashrc or ~/.bash_profile file:

if [ -z "$SSH_AUTH_SOCK" ]; then
   # Check for a currently running instance of the agent
   RUNNING_AGENT="`ps -ax | grep 'ssh-agent -s' | grep -v grep | wc -l | tr -d '[:space:]'`"
   if [ "$RUNNING_AGENT" = "0" ]; then
        # Launch a new instance of the agent
        ssh-agent -s &> .ssh/ssh-agent
   fi
   eval `cat .ssh/ssh-agent`
fi

Find details also here.

I have had a funny talk with Adam Bien about Programming, Workflow Engines, Open Source and Cloud Computing

Follow Admin Bien`s Pod Cast

Eclipse is an IDE providing a lot of tools to develop software in various languages. Installing Eclipse is just download the latest version and unzipping it somewhere in your home folder.

But Eclipse comes with some non optimal default settings. So it’s better to fix these settings before you start coding.

Change the Memory Settings

First open the eclipse.ini file located in your install folder. You will find the following memory settings:

-Xms256m
-Xmx2048m

This settings are typical to low if you have 8G or more memory available in your notebook. So double both values first:

-Xms512m
-Xmx4g

Change the Workspace Settings

After your launched Eclipse you should change some other default settings in the preference dialog. Open Window -> Preferences and change the following defaults:

General -> Workspace: change the ‘Text file encoding’ to UTF-8

General -> Workspace : change ‘New Text file line delimiter’ to Unix

You all know the Single Page Layout of HTML pages. It means you have mainly only one page loaded. The page splits up the layout into different sections to get a clear and modern page design. There are a lot of web sites explaining this kind of modern web design and you can find hundreds of templates on different places like onepagelove.com. I also picked up such a design template to build a new site. As always the template is not perfect and you want to tweak it a little bit, to get your own individual style. After I looked into the CSS file and the layout setup, I was shocked. The CSS consisted of more then 2400 lines of code! And each HTML tag was applied with more than 5 style classes in average. For example a simple section within a 2-column layout looked something like this:

...
    <section class="bg-white dark:bg-gray-900">
        <div class="max-w-screen-xl px-4 pb-8 mx-auto lg:pb-16">                
        <h2 class="mb-4 text-3xl font-extrabold tracking-tight text-gray-900 dark:text-white">100% Open Source</h2>
            <div class="grid grid-cols-2 gap-8 text-gray-500 sm:gap-12 sm:grid-cols-3 lg:grid-cols-6 dark:text-gray-400">
            .....
         ....
....

So I asked my self: is this complexity needed? You may guess it – my answer is ‘no’. Now let me explain what is needed for a simple single page layout.

The Grid Layout

To design a good-looking website, you need to follow the principle of the golden ratio. This principle was discovered by Leonardo Da Vinci 500 years ago and is nothing new. To make it short: you split up your page into 12 columns and place the elements inside. For example to get an 2/3 ratio you place one block into columns 1-4 and the rest into 5-12.

Often this is archived with defining a lot col-classes for each ratio like this:

.col-1 {width: 8.33%;}
.col-2 {width: 16.66%;}
.col-3 {width: 25%;}
.col-4 {width: 33.33%;}
.col-5 {width: 41.66%;}
.col-6 {width: 50%;}
.col-7 {width: 58.33%;}
.col-8 {width: 66.66%;}
.col-9 {width: 75%;}
.col-10 {width: 83.33%;}
.col-11 {width: 91.66%;}
.col-12 {width: 100%;}

You my see this kind of css classes in many many layouts. But you don’t need this as you can use the grid design rule supported today by all modern browsers.

To use the grid layout you simply define your container class as a grid with 12 columns. The browser overtakes the column layout for you. See the following example:

<!DOCTYPE html>
<html lang="en">
<head>
<style>
.container {
  max-width: 1280px;
  border: 1px dashed;
  padding: 10px;
  margin-left: auto;
  margin-right: auto;

  display: grid;
  grid-template-columns: repeat(12, minmax(69px, 110px));
}
</style>
</head>
<body>
  <section class="container">
    <div style="grid-column-start: span 4; border: 1px solid green;">
      <p>The left column with some text...</p>
    </div>

    <div style="grid-column-start: span 8; border: 1px solid blue;">
      <p>The right column.....</p>
    </div>
  </section>
</body>
</html>

The important part here is the style class for the section defining a grid with 12 columns

  display: grid;
  grid-template-columns: repeat(12, minmax(64px, 110px));

If you inspect the page with your browsers developer tools, you can see that the section is divided into 12 parts like Leonardo Da Vinci would do it.

So this is quite simple. And I do not use any css classes for my column sections. It is quite enough if you set the grid-column-start directly in the style attribute.

<div style="grid-column-start: span 4;">
      ...
</div>

Get Responsive

Finally you may want to get more responsive. My first example has a minimal width of 768px as each column is defined with a minim width of 64px. In small displays this is not perfect. So lets define a responsive design to cancel out 12 column ration if the display is smaller then 768 px. This can be done with a @meia definition:

@media (max-width: 768px) {
  .container {
     grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  }
}

This code creates a flexible “auto-responsive” grid in which elements are always at least 280 pixels wide. But now, the grid automatically reduces the number of columns as soon as the width falls below 280 pixels.

So we simply changed from 12 columns to responsive design. Thant’s it.

In case you want to document a network diagram in a fast way without using a graphical tool, you can find the necessary ASCII characters on this wiki page . In this way you can draw boxes and connectors. See the following example.

                              Internet
---------------------------------------------------------------------------
 ❰PUBLIC-IP❱
      |
┌────────────┐     ┌────────────┐     ┌────────────┐     ┌────────────┐
│Master-Node │     │  Worker-1  │     │  Worker-2  │     │  Worker-3  │
└────────────┘     └────────────┘     └────────────┘     └────────────┘
      ├───────────────────┼─────────────────┼──────────────────┤
  ❰10.0.0.2❱         ❰10.0.0.3❱         ❰10.0.0.4❱         ❰10.0.0.4❱ 
---------------------------------------------------------------------------
                         Private Network 10.0.0.0/24

And here is another example:

     ╔═╧═╧═╧═╧═╧═╧══╗
     ║ Ardoino Nano ║
     ╚═╤═╤═╤═╤═╤═╤══╝
         │   │          ╭────────╮ 
         │   ╰──────────┤Sensor-2│   
         │              ╰────────╯
    ╭────┴───╮     
    │Sensor-1│     
    ╰────────╯    

Once you have developed a project under Java EE8 or Jakarta EE8, sooner or later you will get to the point where you need to migrate to Jakarta EE9. The most important part is to replace the old Java package names javax.* with jakarta.* . The renaming of the package names is needed for all EE packages but some other packages like javax.xml.* are still valid. So you need to be careful. But with a shell script this works well as you will see.

Change the Maven Dependency

Fist of all you should change the maven dependencies in your project:

Replace the maven java compiler plugin to source and target version 11 if not yet done

...
	<plugin>
		<groupId>org.apache.maven.plugins</groupId>
		<artifactId>maven-compiler-plugin</artifactId>
		<version>3.8.1</version>
		<configuration>
			<source>11</source>
			<target>11</target>
		</configuration>
	</plugin>
...

Next make sure you have the new jakarta EE9 dependency:

	<dependency>
	    <groupId>jakarta.platform</groupId>
	    <artifactId>jakarta.jakartaee-api</artifactId>
	    <version>9.0.0</version>
	    <scope>provided</scope>
	</dependency>

If you have removed the old JavaEE8 dependency and added the new Jakarta EE 9 dependency you should see a lot of compiler errors in your Java files because of the wrong import package names.

Replace javax.* with jakarta.*

You can run the following shell script against your java code. This script will replace the java package names automatically for all your java files. Just place the script into the root of your project and run the script from there. (The script is written for Linux OS but I guess you can adapt it to Windows Power Shell if needed):

#!/bin/bash

# this script can be used to replace deprecated javax. package names from a 
# Java EE8 project with the new jakarta. package names in Jakarta 9
# Initial version from rsoika, 2021

echo "replacing:"
echo "	javax.annotation.  -> jakarta.annotation."
echo "	javax.ejb.         -> jakarta.ejb."
echo "	javax.enterprise.  -> jakarta.enterprise."
echo "	javax.faces.       -> jakarta.faces."
echo "	javax.inject.      -> jakarta.inject."
echo "	javax.persistence. -> jakarta.persistence."
echo "	javax.ws.          -> jakarta.ws."
echo "Replacing now..."

###################
## REPLACE LOGIC ##
###################

# replace package names...
find * -name '*.java' | xargs perl -pi -e "s/javax.annotation./jakarta.annotation./g"
find * -name '*.java' | xargs perl -pi -e "s/javax.ejb./jakarta.ejb./g"
find * -name '*.java' | xargs perl -pi -e "s/javax.enterprise./jakarta.enterprise./g"
find * -name '*.java' | xargs perl -pi -e "s/javax.faces./jakarta.faces./g"
find * -name '*.java' | xargs perl -pi -e "s/javax.inject./jakarta.inject./g"
find * -name '*.java' | xargs perl -pi -e "s/javax.persistence./jakarta.persistence./g"
find * -name '*.java' | xargs perl -pi -e "s/javax.ws./jakarta.ws./g"

echo "DONE!"

That’s it! Now you should be able to compile and run your project with Jakarta EE9.

During testing Ceph & Kubernetes in combination with the ceph-csi plugin in run into a problem with some of my deployments. For some reason the deployment of a POD failed with the following event log:

Events:                                                                                                                                                                                                Type     Reason            Age                From                 Message      
---------------------------------------------------------------------------------------------
Warning  FailedScheduling  29s                default-scheduler        0/4 nodes are available: 4 persistentvolumeclaim "index" not found. 
Warning  FailedScheduling  25s (x3 over 29s)  default-scheduler        0/4 nodes are available: 4 pod has unbound immediate PersistentVolumeClaims. 
Normal   Scheduled         11s                default-scheduler        Successfully assigned office-demo-internal/documents-7c6c86466b-sqbmt to worker-3
Warning  FailedMount       3s (x5 over 11s)   kubelet, worker-3  MountVolume.SetUp failed for volume "demo-internal-index" : rpc error: code = Internal desc = mount failed: exit status 32
Mounting command: mount  
Mounting arguments: -t ext4 -o bind,_netdev /var/lib/kubelet/plugins/kubernetes.io/csi/pv/demo-internal-index/globalmount/demo-internal /var/lib/kubelet/pods/af2f33e0-06da-4429-9f75-908981cb85c3/volumes/kubernetes.io~csi/demo-internal-index/mount
Output: mount: /var/lib/kubelet/pods/af2f33e0-06da-4429-9f75-9034535485c3/volumes/kubernetes.io~csi/demo-internal-index/mount: special device /var/lib/kubelet/plugins/kubernetes.io/csi/pv/demo-internal-index/globalmount/demo-internal does not exist. 

The csi-plugin logs messages like:

 csi-rbdplugin Mounting command: mount                                                                                                                                                                 
 csi-rbdplugin Mounting arguments: -t ext4 -o bind,_netdev /var/lib/kubelet/plugins/kubernetes.io/csi/pv/demo-internal-index/globalmount/demo-internal-imixs /var/lib/kubelet/pods/af2f33e0-34535-4429- 
 9f75-908981cb85c3/volumes/kubernetes.io~csi/demo-internal-index/mount                                                                                                                                 
 csi-rbdplugin Output: mount: /var/lib/kubelet/pods/af2f33e0-06da-4429-35445-908981cb85c3/volumes/kubernetes.io~csi/demo-internal-index/mount: special device /var/lib/kubelet/plugins/kubernetes.io/cs 
 i/pv/demo-internal-index/globalmount/demo-internal does not exist.                                                                                                                              
 csi-rbdplugin E0613 15:56:55.814449   32379 utils.go:136] ID: 33 Req-ID: demo-internal-imixs GRPC error: rpc error: code = Internal desc = mount failed: exit status 32                               
 csi-rbdplugin Mounting command: mount                                                                                                                                                                 
 csi-rbdplugin Mounting arguments: -t ext4 -o bind,_netdev /var/lib/kubelet/plugins/kubernetes.io/csi/pv/demo-internal-index/globalmount/demo-internal /var/lib/kubelet/pods/af2f33e0-06da-5552- 
 9f75-908981cb85c3/volumes/kubernetes.io~csi/demo-internal-index/mount                                                                                                                                 
 csi-rbdplugin Output: mount: /var/lib/kubelet/pods/af2f33e0-06da-4429-9f75-908981cb85c3/volumes/kubernetes.io~csi/demo-internal-index/mount: special device /var/lib/kubelet/plugins/kubernetes.io/cs 
 i/pv/demo-internal-index/globalmount/demo-internal does not exist. 

After investigating many hours, I figured out that on the corresponding worker node there was something wrong with the corresponding PV directory

/var/lib/kubelet/plugins/kubernetes.io/csi/pv/demo-internal-index/

After deleting this directory on the worker node, everything works again. See also the discussion here.

In this Blog Post I will explain how you can integrate the LibreOffice Online Editor into your Web Application.

In my example I will use a very simple approach just to demonstrate how thinks are working. I will not show how you integrate the editor with a iFrame into your web application because I assume that if you plan to integrate LibreOffice Online into your own application you are familiar with all the web development stuff.

So let’s started….

Continue reading “LibreOffice Online – How to Integrate into your Web Application”

After I deployed several Java Docker containers on my self managed Kubernetes cluster I recognized that the containers consume much more memory as defined in the Kubernetes resource limits.

        ....
        resources:
          requests:
            memory: "512Mi"
          limits:
            memory: "1Gi"
        ....

The Containers run OpenJDK 11 so per default it should respect the container memory limits and not overrun them. Running the same container with plain docker on the same worker node the memory limits where resprected:

$ docker run -it --rm --name java-test -p 8080:8080 -e JAVA_OPTS='-XX:MaxRAMPercentage=75.0' -m=300M jboss/wildfly:20.0.1.Final

$ docker stats
CONTAINER ID        NAME          CPU %     MEM USAGE / LIMIT     MEM %     NET I/O       BLOCK I/O    PIDS
515e549bc01f        java-test     0.14%     219MiB / 300MiB       73.00%    906B / 0B     0B / 0B      43

But starting same container with kubectl the memory limits were ignored

$ kubectl run java-test --image=jboss/wildfly:20.0.1.Final --limits='memory=300M' --env="JAVA_OPTS='-XX:MaxRAMPercentage=75.0'" 

$ kubectl top pod java-wildfly-test
NAME                CPU(cores)   MEMORY(bytes)   
java-wildfly-test   1089m        441Mi 

After several days of research I finally found the root of this strange behaviour. In my environment kubelet and the Docker daemon used a different cgroupDriver!

How to Verify cgroupDriver

To verify if kubelet and docker are using the same cgroupDriver you can use the following commands:

$ sudo cat /var/lib/kubelet/config.yaml | grep cgroupDriver
cgroupDriver: systemd

$ sudo docker info | grep -i cgroup
Cgroup Driver: systemd

In this example both use systemd which is typical for Kubernetes since version 1.19.3

But if for example the kubelet shows no cgroupDriver entry you need to fix this.

How to Set cgroupDriver

To fix the cgroupDriver entry for kubelet just edit the file

/var/lib/kubelet/config.yaml

and search for the entry

cgroupDriver: systemd

If it is not set just add the entry into the config file.

Finally you need to restart kubelet

$ systemctl daemon-reload
$ systemctl restart kubelet

The Metrics Server

To get the correct metrics displayed with kubectl top you need to install the open source project metrics-server. This service provides a scalable, efficient source of container resource metrics like CPU, memory, disk and network. These are also referred to as the “Core” metrics. The Kubernetes Metrics Server is collecting and aggregating these core metrics in your cluster and is used by other Kubernetes add ons, such as the Horizontal Pod Autoscaler or the Kubernetes Dashboard.