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.

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?

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

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.

Doing some funky Docker Compose stuff, including:

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:

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

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.

(SO answer repost) You can use kafkacat to send messages to Kafka that include line breaks. To do this, use its -D operator to specify a custom message delimiter (in this example /): kafkacat -b kafka:29092 \ -t test_topic_01 \ -D/ \ -P <<EOF this is a string message with a line break/this is another message with two line breaks! EOF Note that the delimiter must be a single byte - multi-byte chars will end up getting included in the resulting message See issue #140

KSQL provides the ability to create windowed aggregations. For example, count the number of messages in a 1 minute window, grouped by a particular column: CREATE TABLE RATINGS_BY_CLUB_STATUS AS \ SELECT CLUB_STATUS, COUNT(*) AS RATING_COUNT \ FROM RATINGS_WITH_CUSTOMER_DATA \ WINDOW TUMBLING (SIZE 1 MINUTES) \ GROUP BY CLUB_STATUS; How KSQL, and Kafka Streams, stores the window timestamp associated with an aggregate, has recently changed. See #1497 for details. Whereas previously the Kafka message timestamp (accessible through the KSQL ROWTIME system column) stored the start of the window for which the aggregate had been calculated, this changed in July 2018 to instead be the timestamp of the latest message to update that aggregate value.