November 2022 – Shekhar Gulati

TIL #3: Using xbar to build ArgoCD deployment monitor

This week I was going over the latest edition(Volume 27) of Thoughtworks Technology Radar and found the addition of xbar in their Tools section. xbar lets you put output from any script/program in your macOS menu bar. I first wrote about it in October 2021 when I showed how you can use it show WordPress page views analytics in your macOS menu bar.

From the Thoughtworks Radar entry on xbar

On remote teams, we sorely lack having a dedicated build monitor in the room; unfortunately, newer continuous integration (CI) tools lack support for the old CCTray format. The result is that broken builds aren’t always picked up as quickly as we’d like. To solve this problem, many of our teams have started using xbar for build monitoring. With xbar, one can execute a script to poll build status, displaying it on the menu bar.

TIL #2: Kafka poison pill message and CommitFailedException

Yesterday I was working with a team that was facing issue with their Kafka related code. The Kafka consumer was failing with the exception

[] ERROR [2022-11-22 08:32:52,853] com.abc.MyKakfaConsumer: Exception while processing events
! java.lang.NullPointerException: Cannot invoke "org.apache.kafka.common.header.Header.value()" because the return value of "org.apache.kafka.common.header.Headers.lastHeader(String)" is null
! at com.abc.MyKakfaConsumer.run(MyKakfaConsumer.java:83)
! at java.base/java.lang.Thread.run(Thread.java:833)

The consumer code looked like as shown below.

TIL #1 : Using liquibase validCheckSum to solve a deployment issue

Taking inspiration from Simon Willison[1] I will start posting TIL (Today I learned) posts on something new/interesting I learn while building software. Today, I was working with a colleague on a problem where in our database migration script was working in the dev environment but failing in the staging environment. The customer platform team has mandated that we can’t access database directly and the only way to fix things is via liquibase scripts. In this post I will not discuss if I agree with them or not. That’s a rant for another day.

In our staging environment we were getting following exception

changelog-main.xml::2::author1 was: 8:a67c8ccae76190339d0fe7211ffa8d98 but is now: 8:d76c3d3a528a73a083836cb6fd6e5654
changelog-main.xml::3::author2 was: 8:0f90fb0771052231b1ax45c1x8bdffax but is now: 8:a25ca918b2eb27a2b453d6e3bf56ff77

If you have worked with Liquibase or any other similar database migration tool you will understand that this happens when developer has changed an existing changeset. This causes checksum to change for an existing changset. So, when next time liquibase tries to apply changset it gives validation error and fails.

Developer should never change an existing changeset and this is one thing we make sure we don’t miss during our code reviews.

Building a simple JSON processor using Java 17 and GraalVM

This week I finally decided to play with GraalVM to build a simple command-line JSON processor based on JsonPath. I find jq syntax too complex for my taste so I decided to build JSON processor based on JsonPath. Since, I wanted to release this as a native executable GraalVM seemed like a good soluton.

GraalVM is a relatively new JVM and JDK implementation built using Java itself. It supports additional programming languages and execution modes, like ahead-of-time compilation of Java applications for fast startup and low memory footprint.