Open source means openness
Cowsay is a Linux tool drawing a cow with a bubble into your terminal.
To have more fun starting your bash you can add it into your bash configuration in Debian:
$ sudo apt-get install cowsay fortuneNext edit your ~/.bashrc file and add the following script at the end of this config file:
if [ -x /usr/games/cowsay -a -x /usr/games/fortune ]; then
fortune | cowsay
fi
That’s it.
I have had the problem that I can’t connect a new SoundCore speaker device to my notbook running Debian. The problem was that the Bluetooth device was detected, but when I tried to connect it immediatly disconnected.
After a long trail and error the solution was simple:
$ sudo apt-get install pulseaudio-module-bluetooth
$ killall pulseaudioConnected again – and it worked! Find background here.
When I started with the Application Server Glassfish years ago I used to configure the Server always directly in the domain.xml file. This is the file containing the configuration and all your customizations when you configure your Glassfish form the Web Admin Interface. The same is true for Payara Server which is more widespread in projects today. (The main different from Glassfish to Payara is, that Payara offers support where Glassfish is the reference implementation for Jakarta EE).
I’ve never gotten rid of my habit of configuring the server directly in the domain .xml, although there is a command-line tool called ‘asadmin‘ for doing the configuration. When you run you projects in Docker you even can copy the domain.xml into a Payara Docker image as you will do with your application. But these days I learned that this is a clumsy and impractical way to do this. The problem with tweaking the domain.xml directly is that you can miss some important XML tags or new coniguration details. So using the asadmin tool is more stable also over differnt versions of Payara.
To configure the Payara Sever directly in your Dockerfile can be done easily when you use so called Preboot and Postboot commands. This are asadmin commands which can be placed in separate files.
So simply create two files called post-boot-commands.asadmin and pre-boot-commands.asadmin and copy these files into your custom Payara Docker image using the COPY command in your Dockerfile:
FROM payara/server-full
# add configuration files
USER root
# Preconfigure Resources
COPY ./my-scripts/preboot-commands.asadmin $POSTBOOT_COMMANDS
COPY ./my-scripts/post-boot-commands.asadmin $POSTBOOT_COMMANDS
RUN chown payara $POSTBOOT_COMMANDS
## Copy additional deployments here
## e.g. Postgres Driver
COPY ./my-scripts/postgresql-42.2.5.jar /opt/payara/paasDomain/lib/
...
USER payara
The Preeboot and Postboot scripts can contain any asadmin command to configure your server. For example to configure a JDBC Database Pool for Postgres the command will look like this:
# Create the JDBC connection pool for Postgres:
create-jdbc-connection-pool --datasourceclassname=org.postgresql.ds.PGSimpleDataSource --restype=javax.sql.DataSource --property user=${ENV=POSTGRES_USER}:password=${ENV=POSTGRES_PASSWORD}:Url=${ENV=POSTGRES_CONNECTION} my-database
# Create the JDBC resource:
create-jdbc-resource --connectionpoolid my-database jdbc/my-databaseNow build your Docker image and start you server:
$ docker build -t my-payara .
$ docker run -p 8080:8080 my-payaraThe Payara server will automatically execute the PreBoot and PostBoot scripts during startup and creates the configuration. In case your command is wrong or misspelled you will see the error message in the log file directly in the log file.
That’s it. Now you have a stable configuration setup for a Payara Docker Image that you can easily adapt to the latest version of Payara by simply upgrading the payara version in your Dockerfile.
This is just a short collection of VSCode commands and tricks which I personally did not know after switching from Eclipse ID.
Most things in VSCode can be controlled via the Command Palette:
Press Ctrl + Shift + P
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)
In some situations it may be helpful to rebuild all Java projects in your workspace
Java: Clean Java Language Server Workspace
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-addThis 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:
$ codeThis 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`
fiFind details also here.
Within my Node.js / yarn project I run into a strange problem. Suddenly my lerna build tool did no longer build my app module.
I am using a monorepo with module/directory structure like this
├── .gitignore
├── lerna.json
├── open-bpmn-app
├── open-bpmn-glsp
├── open-bpmn-theia
├── package.json
└── yarn.lock
The module ‘open-bpmn-app’ was ignored. As it turns out newer nx versions of lerna parse the .gitignore file in the root folder. You have to make sure that the root folder of your workspace packages is not excluded via .gitignore. In my case I had the following instructions included:
**/*-app/**
!**/*-app/package.jsonBy removing these two lines the problem was solved!
Today I once again came across a configuration issue in traefik.io regarding an authentication problem. Traefik is a cloud native networking solution for container platforms. It can be used for example within Kubernetes and is a build in function of K3S – a lightweight Kubernetes solution.
In K3S Traefik is used for the ingress configuration. For example to route Web traffic from an Internet domain to a specific service within your cluster.
My problem was that I wanted to install a private Docker Registry within my K3S cluster. The Docker Registry comes without any security. This is fine within a cluster, but in case you connect from outside you don’t want that your private registry is open for everyone. With Traefik you can easily secure you service. I will explain how you can do this.
Continue reading “Traefik and Basic Authentication”JsonForms is a powerful and very flexible framework to build complex forms just from a JSON Schemata. A form can contain various different controls and controls can be separated into categories and layout sections. This makes JsonForrms a first-hand framework if you have to deal with dynamic forms in a JavaScript application.
JsonForms already provides different so called Renderer Sets to handle complex input widgets. But further more you can also create easily you own widget if you have special needs not supported by JsonForms out of the box.
Continue reading “JsonFroms – Custom Component for SelectItems”
I have had a funny talk with Adam Bien about Programming, Workflow Engines, Open Source and Cloud Computing
Today I want to write about why comments are so important in software development and how you can improve them. For me, the most disappointing thing about good source code is when it is insufficiently commented. And this happens with closed code in the same way as with Open Source code. In the worst case, and this is usually the most common, source code is not commented at all. Especially in open source projects, this is a disdain against the community reading your code. But even in internal software projects, I consider missing comments to be a bad behaviour towards your colleagues, which should be avoided.
Of course, we all know the funny answers in this context. “Good code doesn’t need any comments” or “Take a look into the source code if you don’t understand something.” Is it laziness or ignorance not to write comments? No, I believe that many developers simply do not know how to write good comments. For this reason, I would like to explain here a very simple rule how to really improve your source code through comments.
The biggest mistake you can make when writing comments is assuming you have to explain what you are doing. In this case, you write comments that explain the obvious.
/**
* Builder Class to build Events
*/
public class EventBuilder {
....
}As long as the name of a class or method is not absolutely meaningless, a name should explain the usage of a class or method. So please do not explain that a Builder Class builds an object or a getter method returns an object. Writing such a comment is a waste of time. By the way, the same applies to those who have to read this kind of useless comments.
A second example for bad comments is explaining how the code works.
/**
* Build the event and return it.
*/
public T build() {
....
return event;
}Of course, you shouldn’t assume that the users reading your code are complete idiots. You can assume that other developers can code just as well as you do. And explaining software patterns in the comment of a method or class is pointless.
So now we have seen what bad comments are. But what does a good comment look like?
There is a great book from Simon Sinek with the Title “Start with Why: How Great Leaders Inspire Everyone to Take Action“. The core message of this book is, that you always should start by explaining the ‘Why’. The ‘What’ and ‘How’ are usually explaining the things later in more detail. For software developing the ‘What’ and ‘How’ is in deed in the code and needs no comments in many cases.
So starting with the ‘Why’ can make source code comments much more useful – for yourself and for others. Starting with ‘Why’ makes you think about what you’re actually doing. So going back to my previous examples a comment may look like this:
/**
* When using Events in the client, the EventBuilder may help
* to construct them in the correct way more easily.
*/
public class EventBuilder {
....
}So instead of describing what the class is, answer the question why you have invented it. The same is true for methods. As explained before if I want to understand the ‘How’, than I can read the source code in detail. But why does the class or method exist? This is what a comment is for:
/**
* To display the summary of an invoice in the client,
* this method calculates the summary including all taxes.
*/
public float summarizeInvoice() {
....
return event;
}I don’t want to go into more details. It’s obvious that the better you explain why you have written a class or method, it helps others like yourself to understand your code. So when you start writing your next code, think about why you’re doing this and comment that into your class or method header. You’ll see – your colleagues and your community will love it and will much prefer using your code.
The last 3 days I tried to install kubernetes 1.25.4 on a Debian 11 (Bullseye) box without success. The problem was that the kubeadm init process always hangs with the message:
....
[wait-control-plane] Waiting for the kubelet to boot up the control plane as static Pods from directory "/etc/kubernetes/manifests". This can take up to 4m0s
I1121 08:17:12.320743 8096 round_trippers.go:466] curl -v -XGET -H "Accept: application/json, */*" -H "User-Agent: kubeadm/v1.25.4 (linux/amd64) kubernetes/fdc7750" 'https://x.x.y.y:6443/healthz?timeout=10s'
I1121 08:17:12.321047 8096 round_trippers.go:508] HTTP Trace: Dial to tcp:x.x.y.y:6443 failed: dial tcp x.x.y.y:6443: connect: connection refused
....Even as I tried several different tutorials and guidelines I failed to solve this issue. (See also here)
Kuberentes supports different Container Runtimes. containerd is only one of them. Maybe containerd and Debian 11 are not the best friends. I don’t know…
cri-o is an alterative lightweight Container Runtime for Kubernetes. After I switched from containerd to cri-o everything worked like a charm. So here is my short guideline how to install cri-o on a fresh Debian 11 box.
Note: If you have already installed containerd you need to remove it first!
As usual for kuberentes first make sure that you have enabled the necessary enable kernel modules and setup the iptables:
$ sudo modprobe overlay
$ sudo modprobe br_netfilter
$ sudo tee /etc/sysctl.d/kubernetes.conf<<EOF
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
net.ipv4.ip_forward = 1
EOF
$ sudo sysctl --system
Next you need to add the repositories maintained by opensuse.org:
$ sudo -i
$ OS=Debian_11
$ VERSION=1.23
$ echo "deb https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/$OS/ /" > /etc/apt/sources.list.d/devel:kubic:libcontainers:stable.list
echo "deb http://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable:/cri-o:/$VERSION/$OS/ /" > /etc/apt/sources.list.d/devel:kubic:libcontainers:stable:cri-o:$VERSION.list
$ curl -L https://download.opensuse.org/repositories/devel:kubic:libcontainers:stable:cri-o:$VERSION/$OS/Release.key | apt-key add -
$ curl -L https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/$OS/Release.key | apt-key add -Now you can start installing cri-o from the new repository:
$ sudo apt update
$ sudo apt-get install -y cri-o cri-o-runc
$ sudo apt-mark hold cri-o cri-o-runc
# Start and enable CRI-O
$ sudo systemctl daemon-reload
$ sudo systemctl enable crio --nowThat’s it. To verify if your cri-o runtime is up and running call:
$ sudo systemctl status crio
● crio.service - Container Runtime Interface for OCI (CRI-O)
Loaded: loaded (/lib/systemd/system/crio.service; enabled; vendor preset: enabled)
Active: active (running) since Mon 2022-11-21 15:14:44 UTC; 21min ago
Docs: https://github.com/cri-o/cri-o
Main PID: 2372 (crio)
Tasks: 12
Memory: 770.4M
CPU: 28.268s
CGroup: /system.slice/crio.service
└─2372 /usr/bin/crio
Nov 21 15:18:12 master-1 crio[2372]: time="2022-11-21 15:18:12.035184530Z" level=info msg="Created container 0878bbfc957e8a7fb069b83a9101c9386d0bee5ea14c10c81ea0379c14cd3240: kube>
Nov 21 15:18:12 master-1 crio[2372]: time="2022-11-21 15:18:12.038925952Z" level=info msg="Starting container: 0878bbfc957e8a7fb069b83a9101c9386d0bee5ea14c10c81ea0379c14cd3240" id>
Nov 21 15:18:12 master-1 crio[2372]: time="2022-11-21 15:18:12.049779604Z" level=info msg="Started container" PID=9385 containerID=0d50842810cb5a0632b137a16e1d29845f4dc3cb9e8e8fc3>
Nov 21 15:18:12 master-1 crio[2372]: time="2022-11-21 15:18:12.063878077Z" level=info msg="Started container" PID=9383 containerID=0878bbfc957e8a7fb069b83a9101c9386d0bee5ea14c10c8>
Nov 21 15:22:56 master-1 crio[2372]: time="2022-11-21 15:22:56.803994649Z" level=info msg="Checking image status: registry.k8s.io/pause:3.8" id=2521c53d-4b83-4b95-8501-363d83ac149>
Nov 21 15:22:56 master-1 crio[2372]: time="2022-11-21 15:22:56.804517064Z" level=info msg="Image status: &ImageStatusResponse{Image:&Image{Id:4873874c08efc72e9729683a83ffbb7502ee7>
Nov 21 15:27:56 master-1 crio[2372]: time="2022-11-21 15:27:56.810307321Z" level=info msg="Checking image status: registry.k8s.io/pause:3.8" id=4b38e75e-8e03-4007-8554-323eb6c404a>
Nov 21 15:27:56 master-1 crio[2372]: time="2022-11-21 15:27:56.810772581Z" level=info msg="Image status: &ImageStatusResponse{Image:&Image{Id:4873874c08efc72e9729683a83ffbb7502ee7>
Nov 21 15:32:56 master-1 crio[2372]: time="2022-11-21 15:32:56.814927245Z" level=info msg="Checking image status: registry.k8s.io/pause:3.8" id=ba81dd6e-491d-43ed-a114-5b69a980569>
Nov 21 15:32:56 master-1 crio[2372]: time="2022-11-21 15:32:56.815618456Z" level=info msg="Image status: &ImageStatusResponse{Image:&Image{Id:4873874c08efc72e9729683a83ffbb7502ee7Now you can start init your kubernetes cluster:
$ sudo kubeadm init --pod-network-cidr=10.244.0.0/16