rmoff’s random ramblings

✨ Data Engineering, Kafka, and other random geekery 🤓

Travelling for Work, with Kids at Home

I began travelling for my job when my first child was three months old. But don’t mistake correlation for causation…it wasn’t the broken nights' sleep that forced me onto the road, but an excellent job opportunity that seemed worth the risk. Nearly eight years later and I’m in a different job but still with a bunch of travel involved. How much I travel has varied. It’s tended to average around 30%, but has peaked at way more than that.

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Kafka Connect Change Log Level and Write Log to File

By default Kafka Connect sends its output to stdout, so you’ll see it on the console, Docker logs, or wherever. Sometimes you might want to route it to file, and you can do this by reconfiguring log4j. You can also change the configuration to get more (or less) detail in the logs by changing the log level. Finding the log configuration file The configuration file is called connect-log4j.properties and usually found in etc/kafka/connect-log4j.

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Replacing UTF8 non-breaking-space with bash/sed on the Mac

A script I’d batch-run on my Markdown files had inserted a UTF-8 non-breaking-space between Markdown heading indicator and the text, which meant that # My title actually got rendered as that, instead of an H3 title.

Looking at the file contents, I could see it wasn’t just a space between the # and the text, but a non-breaking space.

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How KSQL handles case

KSQL is generally case-sensitive. Very sensitive, at times ;-)

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KSQL REST API cheatsheet

Full reference is here

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Confluent Schema Registry REST API cheatsheet

The Schema Registry support a REST API for finding out information about the schemas within it. Here’s a quick cheatsheat with REST calls that I often use.

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What to Do When Docker on the Mac Runs Out of Space

I use Docker and Docker Compose a lot. Like, every day. It’s a fantastic way to build repeatable demos and examples, that can be torn down and spun up in a repeatable way. But…what happens when the demo that was working is spun up and then tail spins down in a blaze of flames?

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Quick Thoughts on Not Writing a Crap Abstract

I’ve reviewed a bunch of abstracts in the last couple of days, here are some common suggestions I made: No need to include your company name in the abstract text. Chances are I’ve not heard of your company, and even if I have, what does it add to my comprehension of your abstract and what you’re going to talk about? Possible exception would be the "hot" tech companies where people will see a talk just because it’s Netflix etc

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Moving from Ghost to Hugo

Why? I’ve been blogging for quite a few years now, starting on Blogger, soon onto WordPress, and then to Ghost a couple of years ago. Blogger was fairly lame, WP yucky, but I really do like Ghost. It’s simple and powerful and was perfect for my needs. My needs being, an outlet for technical content that respected formatting, worked with a markup language (Markdown), and didn’t f**k things up in the way that WP often would in its WYSIWYG handling of content.

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Pull new version of multiple Docker images

Tiny little snippet this one. Given a list of images:

$ docker images|grep confluent
confluentinc/cp-enterprise-kafka                5.0.0               d0c5528d7f99        3 months ago        600MB
confluentinc/cp-kafka                           5.0.0               373a4e31e02e        3 months ago        558MB
confluentinc/cp-zookeeper                       5.0.0               3cab14034c43        3 months ago        558MB
confluentinc/cp-ksql-server                     5.0.0               691bc3c1991f        4 months ago        493MB
confluentinc/cp-ksql-cli                        5.0.0               e521f3e787d6        4 months ago        488MB
…

Now there’s a new version available, and you want to pull down all the latest ones for it:

docker images|grep "^confluentinc"|awk '{print $1}'|xargs -Ifoo docker pull foo:5.1.0

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Docker Tips and Tricks with Kafka Connect, ksqlDB, and Kafka

A few years ago a colleague of mine told me about this thing called Docker, and I must admit I dismissed it as a fad…how wrong was I. Docker, and Docker Compose, are one of my key tools of the trade. With them I can build self-contained environments for tutorials, demos, conference talks etc. Tear it down, run it again, without worrying that somewhere a local config changed and will break things.

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Streaming data from Oracle into Kafka

This is a short summary discussing what the options are for integrating Oracle RDBMS into Kafka, as of December 2018 (refreshed June 2020). For a more detailed background to why and how at a broader level for all databases (not just Oracle) see this blog and this talk. What techniques & tools are there? Franck Pachot has written up an excellent analysis of the options available here. As of June 2020, this is what the line-up looks like:

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Tools I Use: iPad Pro

I’ve written recently about how I create the diagrams in my blog posts and talks, and from discussions around that, a couple of people were interested more broadly in how I use my iPad Pro. So, on the basis that if two people are interested maybe others are (and if no-one else is, I have a copy-and-paste answer to give to those two people) here we go. Kit iPad Pro 10.

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So how DO you make those cool diagrams?

I write and speak lots about Kafka, and get a fair few questions from this. The most common question is actually nothing to do with Kafka, but instead: How do you make those cool diagrams? So here’s a short, and longer, answer! Update July 2019 I’ve moved away from Paper -> read more here tl;dr An iOS app called Paper, from a company called FiftyThree So, how DO you make those cool diagrams?

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Get mtr working on the Mac

Install Not sure why the brew doesn’t work as it used to, but here’s how to get it working: brew install mtr sudo ln /usr/local/Cellar/mtr/0.92/sbin/mtr /usr/local/bin/mtr sudo ln /usr/local/Cellar/mtr/0.92/sbin/mtr-packet /usr/local/bin/mtr-packet (If you don’t do the two symbolic links (ln) you’ll get mtr: command not found or mtr: Failure to start mtr-packet: Invalid argument) Run sudo mtr google.com

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Kafka Connect CLI tricks

I do lots of work with Kafka Connect, almost entirely in Distributed mode—even just with 1 node -> makes scaling out much easier when/if needed. Because I’m using Distributed mode, I use the Kafka Connect REST API to configure and manage it. Whilst others might use GUI REST tools like Postman etc, I tend to just use the commandline. Here are some useful snippets that I use all the time.

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ERROR: Invalid interpolation format for “command” option in service…

Doing some funky Docker Compose stuff, including:

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Flatten CDC records in KSQL

The problem - nested messages in Kafka

Data comes into Kafka in many shapes and sizes. Sometimes it’s from CDC tools, and may be nested like this:

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Exploring JMX with jmxterm

Check out the jmxterm repository
Download jmxterm from https://docs.cyclopsgroup.org/jmxterm

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Accessing Kafka Docker containers’ JMX from host

See also docs. To help future Googlers… with the Confluent docker images for Kafka, KSQL, Kafka Connect, etc, if you want to access JMX metrics from within, you just need to pass two environment variables: <x>_JMX_HOSTNAME and <x>_JMX_PORT, prefixed by a component name. <x>_JMX_HOSTNAME - the hostname/IP of the JMX host machine, as accessible from the JMX Client. This is used by the JMX client to connect back into JMX, so must be accessible from the host machine running the JMX client.

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Robin Moffatt

Robin Moffatt is a Principal DevEx Engineer at Decodable. He likes writing about himself in the third person, eating good breakfasts, and drinking good beer.