Karl Brodowsky's IT-Blog

How to replace svn:keywords?

In the old days we used svn, cvs, rcs or other systems for source code management, that allowed enabling something like svn:keywords. This resulted in certain strings in the source code being replaced by strings containing some version information.

More often than we might think these were useful. The question „what version are we running?“ is often answered, but surprisingly often not correctly.

Now putting the version information into a comment or even better into a string that might even be logged or that might at least be extracted by using something like
strings xyz |egrep '\$Id.*\$'
allows to find out.

Now we are using git instead of svn, or at least we should be using git or plan our migration to git. There are other tools like Mercurial, that are probably just as good as git, but git is most common and every developer knows it or has to learn it anyway to stay in business.

Now git is not supporting these svn:keywords or at least not as easily, because it relies sha-checksums, which does not allow for changing file contents. There are some tricks like pre-checking and post-checkout scripts that might solve such issues, but this is kind of difficult to tame, due to the distributed characters of git including a local repo on each developers machine.

So it is better to accept that the time of this svn:keywords-stuff is over and look for something new. As an example we will consider the world of Java and JVM languages. Most use a Jenkins server to compile the software.

To create a release, even a temporary release or a release just for testing, the right way is to first label the head of the branch we are working on, then check out based on this label, compile that and upload it to the artifactory, if it is successful. Maybe rename the label or and another label. If not, maybe delete the label, depending on the processes.

Now the jar-files contain a META-INF-directory and a MANIFEST.MF. This should be the right place to put version information during such a build. More or less this can provide the same benefit as the svn:keywords, but it works with git and needs only be done in one place.

Details about how to do it will can be found out when needed.

I assume that the same approach can also be accomplished for other environments. We can even find ways that the software logs its version by changing a string in a source code file during the build process.

Happy New Year 2020

Un an nou fericit! — Onnellista uutta vuotta! — Feliĉan novan jaron! — Καλή Χρονια! — ¡Feliz año nuevo! — С новым годом! — FELIX SIT ANNUS NOVUS — Godt nytt år! — Щасливого нового року! — Frohes neues Jahr! — Felice anno nuovo! — Bonne année! — Gott nytt år! — Срећна нова година! — عام سعيد — Gullukkig niuw jaar! — Happy new year!

This is generated with a Java 13 program using Lambdas and secure random numbers:


import java.security.SecureRandom;

import java.util.List;

import java.util.stream.Stream;

import java.util.stream.Collectors;
public class HappyNewYearJava8 {
    private static final class Element implements Comparable<Element> {

        Element(Long sortKey, String text) {

            this.sortKey = sortKey;

            this.text = text;

        }
        private Long sortKey;

        private String text;
        public String getText() {

            return text;

        }
        public int compareTo(Element e) {

            return this.sortKey.compareTo(e.sortKey);

        }

    }
    public static void main(String[] args) {

        SecureRandom random = new SecureRandom();

        List<String> list = Stream.of("Frohes neues Jahr!",

                                      "Happy new year!",

                                      "Gott nytt år!",

                                      "¡Feliz año nuevo!",

                                      "Bonne année!",

                                      "FELIX SIT ANNUS NOVUS",

                                      "С новым годом!",

                                      "عام سعيد",

                                      "Felice anno nuovo!",

                                      "Godt nytt år!",

                                      "Gullukkig niuw jaar!",

                                      "Feliĉan novan jaron!",

                                      "Onnellista uutta vuotta!",

                                      "Срећна нова година!",

                                      "Un an nou fericit!",

                                      "Щасливого нового року!",

                                      "Καλή Χρονια!")

            .map(s->new Element(random.nextLong(), s))

            .sorted()

            .map(Element::getText)

            .collect(Collectors.toList());

System.out.println(String.join(" — ", list)); } }

Christmas 2019

Joyeux Noël! — ميلاد مجيد — Crăciun fericit! — God Jul! — God Jul! — Natale hilare! — С Рождеством! — З Рiздвом Христовим! — Prettige Kerstdagen! — Hyvää Joulua! — クリスマスおめでとう ; メリークリスマス — καλά Χριστούγεννα! — Buon Natale! — Срећан Божић! — Frohe Weihnachten! — ¡Feliz Navidad! — Feliĉan Kristnaskon! — Merry Christmas!

This time the greetings were generated with a C program:
#include <stdio.h> #include <stdint.h> #include <openssl/rand.h>


#define N 18

static const uint32_t n = N;

int main(int argc, char **argv) { char greetings[N][60] = { "С Рождеством!", "Hyvää Joulua!", "καλά Χριστούγεννα!", "Buon Natale!", "Prettige Kerstdagen!", "З Рiздвом Христовим!", "Merry Christmas!", "Срећан Божић!", "God Jul!", "¡Feliz Navidad!", "ميلاد مجيد", "クリスマスおめでとう ; メリークリスマス", "Natale hilare!", "Joyeux Noël!", "God Jul!", "Frohe Weihnachten!", "Crăciun fericit!", "Feliĉan Kristnaskon!" }; int32_t i, j; uint32_t x; uint32_t idx[N]; int rtc; uint64_t r = 0; for (i = n-1; i >= 0; i--) { idx[i] = i; } RAND_bytes((char *) &r, sizeof(r)); for (i = n-1; i > 0; i--) { j = r % i; r = r / i; x = idx[i]; idx[i] = idx[j]; idx[j] = x; } for (i = 0; i < n; i++) { if (i > 0) { printf(" — "); } printf("%s", greetings[idx[i]]); } printf("\n"); }

Ranges of Dates and Times

In Software we often deal with ranges of dates and times.

Let us look at it from the perspective of an end user.

When we say something like „from 2020-03-07 to 2019-03-10“ we mean the set of all timestamps $t$ such that

$\text{2019-03-07} \le d < \text{2019-03-11}$

or more accurately:

$\text{2019-03-07T00:00:00}+TZ \le d < \text{2019-03-11T00:00:00}+TZ$

Important is, that we mean to include the whole 24 hour day of 2019-03-10. Btw. please try to get used to the ISO-date even when writing normal human readable texts, it just makes sense…

Now when we are not talking about dates, but about times or instants of time, the interpretation is different.
When we say sonmething like „from 07:00 to 10:00“ or „from 2020-03-10T07:00:00+TZ to 2020-04-11T09:00:00+TZ“, we actually mean the set of all timestamps $t$ such that

$givenDate\text{T07:00:00}+TZ \le t < givenDate\text{T10:00:00}+TZ$

$\text{2020-03-10T07:00:00}+TZ \le t < \text{2020-04-11T09:00:00}+TZ,$

respectively. It is important that we have to add one in case of date only (accuracy to one day) and we do not in case of finer grained date/time information. The question if the upper bound is included or not is not so important in our everyday life, but it proves that commonly the most useful way is not to include the upper bound. If you prefer to have all options, it is a better idea to employ an interval library, i.e. to find one or to write one. But for most cases it is enough to exclude the upper limit. This guarantees disjoint adjacent intervals which is usually what we want. I have seen people write code that adds 23:59:59.999 to a date and compares with $\le$ instead of $<$ , but this is an ugly hack that needs a lot of boiler plate code and a lot of time to understand. Use the exclusive upper limit, because we have it.

Now the requirement is to add one day to the upper limit to get from the human readable form of date-only ranges to something computers can work with. It is a good thing to agree on where this transformation is made. And to do it in such a way that it even behaves correctly on those dates where daylight saving starts or ends, because adding one day might actually mean „23 hours“ or „25 hours“. If we need to be really very accurate, sometimes switch seconds need to be added.

Just another issue has come up here. Local time is much harder than UTC. We need to work with local time on all kinds of user interfaces for humans, with very few exceptions like for pilots, who actually work with UTC. But local date and time is ambiguous for one hour every year and at least a bit special to handle for these two days where daylight saving starts and ends. Convert dates to UTC and work with that internally. And convert them to local date on all kinds of user interfaces, where it makes sense, including documents that are printed or provided as PDFs, for example. When we work with dates without time, we need to add one day to the upper limit and then round it to the nearest $some-date\text{T00:00:00}+TZ$ for our timezone $TZ$ or know when to add 23, 24 or 25 hours, respectively, which we do not want to know, but we need to use modern time libraries like the java.time.XXX stuff in Java, for example.

Working with date and time is hard. It is important to avoid making it harder than it needs to be. Here some recommendations:

Try to use UTC for the internal use of the software as much as possible
Use local date or time or date and time in all kinds of user interfaces (with few exceptions)
add one day to the upper limit and round it to the nearest midnight of local time exactly once in the stack
exclude the upper limit in date ranges
Use ISO-date formats even in the user interfaces, if possible

Functional Scala London 2019

In December 2019 I attended the conference Functional Scala in London which was initiated and managed by John de Goes. See Skillsmatter about what happened to Scala Exchange. Of course a large part of the conference was related to ZIO, which seems to be a part of the eco system surrounding Scala with a lot of dynamic.

It was a single track conference with a lot of talks, so I have attended all of them:
Day 1 (2019-12-12)

KEYNOTE: XS — A Collections CLI [Paul Phillips] (Video)
Introduction to Interruption [Jakub Kozlowski] (Video)
Making Algorthms work with Functional Scala [Karl Brodowsky] (Video)
Solving the Scala Notebook Experience [Jeremy Smith & Jonathan Indig] (Video)
Mixing Scala & Kotlin [Alexey Soshin] (Video)
Prototyping the Future with Functional Scala [Mike Kotsur] (Video)
Test Effects: First Class [Adam Fraser] (Video)
Let’s Gossip! [Dejan Mijic & Przemyslaw Wierzbicki] (Video)
Ray Tracing with ZIO [Pierangelo Cecchetto] (Video)
Invertible Programs [Sergei Shabanau] (Video)
Hyper-pragmatic Pure FP Testing with DIStage-Testkit [Pavel Shirshov & Kai] (Video)
KEYNOTE: Unleash Your Fury [Jon Pretty] (Video)

Day 2 (2019-12-14)

Modern Data-Driven Applications with ZIO Streams [Itamar Ravid] (Video)
Functional Architecture [Piotr Golebiewski] (Video)
ZIO Chunk: A Fast, Pure Alternative to Arrays [Aleksandra A. Holubitska]
Caliban: Designing a Functional GraphQL Library [Pierre Ricadat] (Video)
Macros and Environmental Effects [Maxim Schuwalow] (Video)
Streaming Analytics with Scala and Spark [Bas Geerdink] (Video)
ZIO Actors [Mateusz Sokol] (Video)
Adventures in Type-safe Error Handling [Jacob Wang]
Composition using Arrows and Monoidal Categories [Oleg Nizhnik]
Practical Logic(al) Programming with Dotty [Lander Lopez]
Next-Level Type Safety: An Intro to Generalized Algebraic Data Types [Matthias Berndt]
KEYNOTE: The Many Faces of Modularity [Eric Torreborre]

See Agenda…

Maybe I will write more about some topics.

Talks will be on youtube in the near future.

Visit to reClojure in London 2019

On 2019-12-02 I visited the conference reClojure.

This was an admirable community effort to create a replacement for ScalaExchange, which simply did not happen because of the bankruptcy of Skillsmatter.

There was only one track, so the schedule is exactly what I visited.

I will just copy it below, because schedules from conference sites usually disappear after some time:

Building stuff with Clojure and 3D Printing. Clément Salaün.
How to design objects with Clojure, OpenSCAD and then 3D print them. This talk covers the motivations, basic concepts and features with a live demo.
Clojure Art. Karl Brodowsky.
Teaching or learning Clojure using images has been proven to be fun and beneficial! In this talk, learn how.
Growing Mobile Apps with ClojureScript and React Native. Daniel Neal.
Starting things is fun, but growing them can be a real challenge – and mobile apps are no different…
Live Coding a Mandelbrot Renderer. Peter Westmacott.
In this talk, Peter will demonstrate live coding of a fractal renderer, with the aim to show how complex beauty can emerge from simple mathematical rules and a little code.
Pizza Party Lunch (Thank You uSwitch!)
Short 10 minute talks. Various Speakers.
Unleash the power of the REPL. Dana Borinski.
Return to basics and dive into how to leverage the REPL to solve problems and debug more quickly – and with the added bonus of honing our Clojure skills!
Generating Generators. Andy Chambers.
Generating data for use in tests can be laborious and boring. However, using the database’s information schema you can alleviate that! Discover the ways to achieve this.
Living in a Box. Life in Containers with the JVM. Matthew Gilliard.
A focus on how containers and the JVM interact and what implications are there for Clojure Developers. Get the best results from the work gone into OpenJDK container support.
Closing Keynote – Code, meet data! Malcolm Sparks.
Computers have 3 jobs: Input, process, output. How have we made such a mess of something so fundamental? Observations, opportunities for Clojurists and hope for the future.

There is a youtube channel for reClojure, where we can now find recordings of the talks.

How to get rid of these HTML-entities in Files

It has been written here that HTML-entities (these ä etc) should be avoided with the exception of those that we need due to the HTML-syntax like <, >, & and maybe " and  . They were already mostly obsolete more than 20 years ago, but in those days we still did not automatically use UTF-8 or UTF-16, but often an 8-bit character encoding that could express only up to 256 characters, in reality around 200 due to control characters. At least these 200 could be used. That was enough for web pages in those days and texts in German, French, Russian, Greek, Hebrew, Arabic and many other language could well be written, as long as only one language or a few similar languages were used. For the rare occasions that required some characters that were not in this character set, it was an option to rely on these HTML-entities. Or for typing HTML-pages on an US-keyboard without any good tool support.

But now Unicode has been around for more than 25 years and more than 90% of the web pages use UTF-8.

Now some people think that these HTML-entities are kind of necessary or at least „safer“ and I see people still writing HTML-code with them in these days. Or tools by relatively well known companies, that produced such output not so long ago… It is a good thing to have some courage and to change something like this to readable and natural format. Or more generally to try out if a simpler or better solution works. Reasonable courage is good for this, too much of something good can go bad, as so often…

So, please teach your collegues not to use these ugly HTML-entities, where UTF-8-characters are the better option.

And here is a perl script that converts the HTML-entities with the exceptions mentioned above to UTF-8. In the project conversion-utils some more such scripts might be added. The script is a bit too long to be pasted inline in a code block, so it is better to find the current version on github.

Then you can do something like this:
git commit for file in *.html ; do echo $file mv $file ${file}~entities~ html2utf8 < ${file}~entities~ > $file echo /$file done git diff
to convert all files in a directory. I assume that you are using Linux or at least have bash like for example in cygwin.
There are other tools to do the same thing, I am sure. Just use anything that works for you to get away from this unreadable crap.

Devoxx UA and Devoxx BE 2019

In 2019 I visited Devoxx UA in Kiev and Devoxx BE in Antwerp.
Traveling was actually a little story by itself, so for now we can just assume that I magically was at the locations of DevoxxUA and DevoxxBE.

In Kiew I attended the following talks:

On Wednesday I attended the following talks in Antwerp:

On Thursday I attended the following talks in Antwerp:

On Friday I attended the following talks in Antwerp:

That’s it…
As always, a lot of these topics deserve an article in this blog. And a lot of video recordings from the conference are worth viewing.

Travelling to Devoxx UA and Devoxx BE 2019

Travelling to this years Devoxx conferences is worth its own short article, even though it is not very IT oriented material…

On the last weekend in October I brought a bicycle to a place near Frankfurt, let’s call it FrankfurtE. I took the train to Karlruhe and then back from FrankfurtE, but cycled from Karlsruhe to FrankfurtE.

On Wednesday evening 2019-11-30 I took a night train from Basel to Hannover and then a day train to some place in North-Rhine-Westphalia for private reasons, then in the evening a flight from Düsseldorf to Vienna and from there to Kiev. There was a problem with the plane, so we returned to Vienna. Austrian Airlines did a good job on rebooking, because they told us that they would find different alternative connections for all of us and send them to our phone, if possible. So there was no need to stand in a line for hours. Plus a decent hotel was booked which was next to the terminal. I had to translate all this information to Russian, because many of the passengers were only comfortable with Ukrainian and Russian languages and the guys in the airport only with German and English.

Then on the 2019-11-31 I flew back from Vienna to Frankfurt and then finally to Kiev, where I could visit the second half of the first day of Devoxx UA and the second day.

On Sunday 2019-11-03 I flew from Kiev to Frankfurt, picked my bicycle in FrankfurtE and took a train to Trier, where I stayed for the night.

On Monday 2019-11-04 I cycled to Marche-en-Famenne.

On Tuesday 2019-11-05 I cycled to Antwerp, where I participated Devoxx Belgium.

On Friday 2019-11-08 I cycled to Lanaken.

On Saturday 2019-11-09 to Bastogne.

And on Sunday 2019-11-10 to Luxemburg, from where I took the train home to Switzerland.

Just to give an idea, it is absolutely possible to use a bicycle as a means of transport on a business trip, but it has to make sense by not consuming more than one or two working days plus weekends, so it is basically necessary to go relatively long distances of 150 to 200 km on a full day and not spend more time than necessary on breaks. And most of the time it is the right choice to use the bigger highways, at least the biggest that are not forbidden to use, because beautiful quite scenic route usually are longer and would be too time consuming. It is not a vacation, but it remains a business trip. Then, on the other hand, this is not such a bad idea, because it really gives some time for thinking about some of the more interesting talks while cycling.

Company „Skillsmatter“ stops operations

The company Skillsmatter in London has been put „under administration“ and basically stopped its operations. The web site seems to suggest, that everything is still ok, but that is not the case and I have heard so from several sources. The owner Wendy Devolder writes on Twitter and on Linkedin. Or here are some more news from cbronline or from theregister. The adminstrator is Resolve. They had put a deadline on 2019-11-05 for potential buyers and nothing indicates that such a buyer could be found.

There are some hopes expressed, that either 10’000 people will donate 250 GPB each or that someone buys the company and keeps it afloat. Reasonably it is probably not going to happen.

Now it is hard to obtain further reliable information. Have the employees already been layed off? Have all conferences been cancelled, for example Clojure Exchange (ClojureX) and Scala Exchange (ScalaX)?

The websites mention nothing about it, but simply the fact that there is nothing mentioned indicates that the employees, who could update the site, are gone and that the conferences will probably not take place. Otherwise I would expect an update on the site mentioning that it is taking place in spite of the situation. In case of Clojure Exchange I have been informed by other participants that Clojure Exchange has been canceled and that there will probably be a „community conference“ instead. Being a speaker, I volunteered to perform my talk on this community conference instead.

In case of Scala Exchange there was a strange story. A keynote speaker, John de Goes, was „uninvited“ because of „inclusiveness“. As a result, he decided to create a competing conference, Functional Scala, at exactly the same time as Scala Exchange and also in London. Some speakers have reportedly decided to speak at Functional Scala instead of Scala Exchange and speakers were encouraged to do so. In the end this might come out as a good thing, because Functional Scala will probably take place and might be an option for those who have already booked their visit to Scala Exchange.

So what does all of this mean? If we are heading for bankruptcy of Skillsmatter and if the conferences (Clojure X for sure, Scala X probably) are canceled, we as speakers or simply visitors are entitled to refund for our ticket or our non refundable travel expenses as speakers to the extent that Skillsmatter would have covered them. But reasonably there will not be enough money left for this. A company can go bankrupt and still have funds that is hard to access, but in practice banks will help out if these funds can be documented. So in reality bankruptcy usually means that there are many debts and little money already. Now the salaries of the employees get the highest priority. When they have been paid, other open payments can be covered, according to the rules that apply in the country. Possibly the price for the ticket, that has already been paid, is simply lost. Possibly travel expenses are lost if they cannot be redirected to another event.

If you like to Donate 250 GBP and 10’000 people do so too, the company could continue. I do not think that this is going to happen.

I will keep you informed if I learn more about the issue that is interesting to potential conference visitors and speakers of events organized by skillsmatter.

Update 2019-11-12: I got in contact with the administrators. They did not want to confirm or deny that the conferences scheduled in December would take place. They just do not know, but it seems to be depending on finding a buyer. If a magical buyer appears and decides to reactivate the events, they might take place. Meanwhile all web pages of skillsmatter show a text that the company is „under administration“, so I guess each day it is getting less likely that there will be anything a buyer can reactivate. I know for sure that at least some employees have already been asked to leave.

Now the good news: The replacements for Scala Exchange and Clojure Exchange are already in place, meaning a conference about the same programming language at the same date and also in London. So if you have booked your hotel and your trip to London already, you might want to check them out:

reClojure Monday 2019-12-02 (only one day)
Functional Scala 2019-12-12/2019-12-13 (two days)

Update 2019-12-09:
Scala Exchange is not going to happen. See web page.
And since so much time has passed, it is becoming unlikely that a buyer turns up, so the company will be gone.

Update 2020-02-12:
The company found a buyer and will start working again. (see comment)

How to replace svn:keywords?

Happy New Year 2020

Christmas 2019

Ranges of Dates and Times

Links

Functional Scala London 2019

Links

Visit to reClojure in London 2019

How to get rid of these HTML-entities in Files

Devoxx UA and Devoxx BE 2019

Links

Travelling to Devoxx UA and Devoxx BE 2019

Company „Skillsmatter“ stops operations