Archive for the ‘code’ Category

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Using weather data in Scratch

Friday, March 31st, 2023

In this post, I want to share an example of Scratch projects that use live weather data.

At the Raspberry Pi Clubs Conference last week, I talked about the idea of Scratch projects that use live data: projects that do something different every time you run them, based on when or where they are run.

I love this idea. It’s something I’ve talked about many times – like when I tried bringing NASA data into Scratch, or when I built Scratch extensions for different web APIs, such as Wikipedia, Twitter, and Spotify.

I think doing this brings a new perspective to Scratch. Live data can bring projects to life.

So I thought I’d share another example: this time, weather data from Open Meteo.

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How to make your own Scratch extension

Thursday, March 23rd, 2023

A workshop I prepared for the Raspberry Pi Clubs Conference about how to create your own custom Scratch blocks.

This workshop is a step-by-step guide for how to create a Scratch extension.

I created it for educators and coding group volunteers, who would like to customize Scratch for their students by giving them new and unique blocks to create with. In particular, I wanted to make this accessible to people who perhaps don’t necessarily think of themselves as developers and wouldn’t otherwise know how to clone the Scratch Team repos and start hacking it.

I’ve wrapped all the complicated bits in scripts that set everything up, and prepared an online Scratch extension development environment – so everything can be done in a web browser without having to install or configure anything on your own computer.

I’ve included step-by-step instructions for building different types of Scratch extensions, including Scratch blocks based on web APIs, and Scratch blocks based on JavaScript modules from npm.


workshop video on YouTube

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Using client quotas with IBM Event Streams

Sunday, February 26th, 2023

In this post, I want to highlight a feature that I often see under-used in IBM Event Streams, and show how you can easily give it a try.

Kafka can enforce quotas to limit the impact that client applications can have on your cluster. To quote the Kafka documentation:

It is possible for producers and consumers to produce/consume very high volumes of data or generate requests at a very high rate and thus monopolize broker resources, cause network saturation and generally DOS other clients and the brokers themselves.

Having quotas protects against these issues and is all the more important in large multi-tenant clusters where a small set of badly behaved clients can degrade user experience for the well behaved ones.

In fact, when running Kafka as a service this even makes it possible to enforce API limits according to an agreed upon contract.

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Running IBM Event Streams on a laptop (sort of)

Friday, December 23rd, 2022

How to run a tiny local Kafka cluster using IBM Event Streams images

For local development on Kafka projects, I always run the public open source builds of ZooKeeper and Kafka as Java processes directly on my laptop (similar to steps described in the Apache Kafka Quickstart).

But for a project this week, I needed to verify something with the distribution of Kafka that comes with IBM Event Streams.

I used a simple Docker Compose setup for this. I’ll use this post to share how I did it.

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Xbox LIVE events for Kafka

Monday, December 19th, 2022

I’ve made a Kafka Connect source connector for sending “real-time” events from Xbox LIVE to Kafka topics.

Quick primer if you’re not a gamer or don’t know what I’m talking about!
The Xbox platform comes with a social aspect: details about games you play and the achievements you earn playing them, are shared with your friends on the Xbox LIVE service. That is the source of data I’m using here.

Create an API key for your Xbox LIVE account, and run the Connector with it, and it will start producing two streams of events to your Kafka cluster:


Screenshot from Event Streams, but as a Kafka Connect connector, you could use any flavour of Kafka, including Apache Kafka.

ACHIEVEMENTS
Events when one of your friends earns an achievement.

PRESENCE
Events when your friends start playing a game, or go online/offline.

Details about the attributes of each of these events can be found in the Connector README, but here are a few screenshots to give you an idea.

An example message on the ACHIEVEMENTS topic.

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Spotify extension for Scratch

Saturday, December 17th, 2022

In this post, I want to share a new Scratch extension that I made this week, explain what it does, and suggest a few ideas for the sorts of ways that it could be used.

Overview

The extension makes some of the data from the Spotify Audio Features API available as blocks in Scratch.

It means you can get numeric values representing different characteristics of songs, directly into a Scratch project.

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Setting up the Event Streams UI for developer-only use

Friday, December 9th, 2022

A quick tip for how to give a developer access to the IBM Event Streams UI only for the Kafka topics used by their application, and not everything else.

Imagine I’m a Kafka cluster admin. I’m running a cluster with a variety of topics on it.

Only viewing their own topics

One of my developers is responsible for the flight tracking app, and wants to use the Event Streams UI. But I don’t want them to be able to access the other sensitive topics for other applications.

I can create them their own login for the UI, that only lets them see their own topics.

The permissions I want to give them are:

- operation: Read
  resource:
    name: FLIGHT.
    patternType: prefix
    type: topic

(Remember, managing my Kafka cluster through Kubernetes resources is a good fit with a CI/CD workflow.)

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Setting up trusted SSL for IBM Event Streams

Thursday, October 27th, 2022

A quick how-to for setting up Event Streams with trusted certificates when running a development project.

Problem

You’re working on a project using IBM Event Streams. It’s just a development project, so you’re not using an SSL certificate signed by your real, trusted, corporate signer.

Everything works, but…

You get errors like these every time you access the web tooling – which you have to click through.

And you get errors like these from your Kafka client applications – which you have to configure with a custom truststore to avoid (although, if you do need to do that, I have a guide to help!)

[2021-06-27 23:19:06,048] ERROR [Consumer clientId=consumer-dalegrp-1, groupId=dalegrp] Connection to node -1 (dale-kafka-saslscram-bootstrap-strimzi.apps.eem-test-fest-6.cp.fyre.ibm.com/9.46.199.58:443) failed authentication due to: SSL handshake failed (org.apache.kafka.clients.NetworkClient)
[2021-06-27 23:19:06,049] WARN [Consumer clientId=consumer-dalegrp-1, groupId=dalegrp] Bootstrap broker dale-kafka-saslscram-bootstrap-strimzi.apps.eem-test-fest-6.cp.fyre.ibm.com:443 (id: -1 rack: null) disconnected (org.apache.kafka.clients.NetworkClient)
[2021-06-27 23:19:06,069] ERROR Error processing message, terminating consumer process:  (kafka.tools.ConsoleConsumer$)
org.apache.kafka.common.errors.SslAuthenticationException: SSL handshake failed
Caused by: javax.net.ssl.SSLHandshakeException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
	at java.base/sun.security.ssl.Alert.createSSLException(Alert.java:131)
	at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:326)
	at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:269)
	at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:264)
	at java.base/sun.security.ssl.CertificateMessage$T13CertificateConsumer.checkServerCerts(CertificateMessage.java:1339)
	at java.base/sun.security.ssl.CertificateMessage$T13CertificateConsumer.onConsumeCertificate(CertificateMessage.java:1214)
	at java.base/sun.security.ssl.CertificateMessage$T13CertificateConsumer.consume(CertificateMessage.java:1157)
	at java.base/sun.security.ssl.SSLHandshake.consume(SSLHandshake.java:392)
	at java.base/sun.security.ssl.HandshakeContext.dispatch(HandshakeContext.java:444)
	at java.base/sun.security.ssl.SSLEngineImpl$DelegatedTask$DelegatedAction.run(SSLEngineImpl.java:1074)
	at java.base/sun.security.ssl.SSLEngineImpl$DelegatedTask$DelegatedAction.run(SSLEngineImpl.java:1061)
	at java.base/java.security.AccessController.doPrivileged(AccessController.java:770)
	at java.base/sun.security.ssl.SSLEngineImpl$DelegatedTask.run(SSLEngineImpl.java:1008)

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