Februari 2023

Currently, I'm involved in developing the RASPIKIDS course, which will be an online, hands-on course in Dutch language utilizing Raspberry Pi 3B+ and Docker. For additional details, please visit RASPIKIDS.

February 2020


See blog BAWJ.

December 2019


Last week I managed to establish an SSH connection between two containers. This week I could finish Chapter 12, Create the Container, more or less. The next step is to test a channel connection between two containers.

November 2019


Almost ready to link to We have to change the CNAME record at the provider from to

We also started with writing the course material for the online training BAWJ.

October 2019


Why not build a website with Documenter.jl? We did it today. When you go to AppliGate, you enter our new site. In the meantime, we got more experience with Julia. E.g., we resized Rob's picture with Images.jl. It was straightforward.

julia> using Images

julia> img = load("rob.png")

julia> img2 = imresize(img, ratio=0.5)

julia> save("rob2.png", img2)

September 2019


Reading Think Julia I discovered the package Serialization. While playing with it, I realized that it could solve my CQRS and Event Sourcing problem. With the method serialize, you can create a text representation of an object, that you can store. With deserialize, you do the reverse. Serialize writes to an IOStream, and deserialize reads from it. An IOStream can be an IOBuffer or a file. It makes Event Sourcing easier.

I also looked at channels. You can use channels to communicate between processes. For the time being, I will use inter CPU-core communication. Later on, I extend it to remote nodes. I only have to expand the methods of createSubscriber and createPublisher.


Last week I was busy implementing the database methods. I realized that the domain objects I wanted to keep must have an identification code. So Subscriber, Publisher, and Message got an id. To create the id, I used the hash function with a name and time as a parameter. It had consequences for the documentation. In the example code, I used the tag 'jldoctest,' so Documenter could test the example code during the generation of the manual. Because the ids keep changing, I had to give up. Too bad, because I found that a strong point of Documenter.jl. I replaced the test tag 'jldoctest' with the language tag 'julia.' Maybe there is something to do against continually changing values.

Infected by the CQRS thought, I decided to add changed domain objects to the database instead of modifying an existing record.