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GUNNAR MORLING


RANDOM MUSINGS ON ALL THINGS SOFTWARE ENGINEERING

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 * Blog
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GUNNAR MORLING


RANDOM MUSINGS ON ALL THINGS SOFTWARE ENGINEERING

 * 
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 * 

 * Blog
 * Projects
 * Conferences
 * Podcasts
 * About




RECENT POSTS

Jan 1, 2024

THE ONE BILLION ROW CHALLENGE

Update Jan 4: Wow, this thing really took off! 1BRC is discussed at a couple of
places on the internet, including Hacker News, lobste.rs, and Reddit. For folks
to show-case non-Java solutions, there is a "Show & Tell" now, check that one
out for 1BRC implementations in Rust, Go, C++, and others. Some interesting
related write-ups include 1BRC in SQL with DuckDB by Robin Moffatt and 1 billion
rows challenge in PostgreSQL and ClickHouse by Francesco Tisiot. Thanks a lot
for all the submissions, this is going way beyond what I’d have expected! I am
behind a bit with evalutions due to the sheer amount of entries, I will work
through them bit by bit. I have also made a few clarifications to the rules of
the challenge; please make sure to read them before submitting any entries.
Let’s kick off 2024 true coder style— I’m excited to announce the One Billion
Row Challenge (1BRC), running from Jan 1 until Jan 31. Your mission, should you
decide to accept it, is deceptively simple: write a Java program for retrieving
temperature measurement values from a text file and calculating the min, mean,
and max temperature per weather station. There’s just one caveat: the file has
1,000,000,000 rows!

Read More...

Dec 17, 2023

TRACKING JAVA NATIVE MEMORY WITH JDK FLIGHT RECORDER

Update Dec 18: This post is discussed on Hacker News 🍊 As regular readers of
this blog will now, JDK Flight Recorder (JFR) is one of my favorite tools of the
Java platform. This low-overhead event recording engine built into the JVM is
invaluable for observing the runtime characteristics of Java applications and
identifying any potential performance issues. JFR continues to become better and
better with every new release, with one recent addition being support for native
memory tracking (NMT).

Read More...

Nov 14, 2023

CAN DEBEZIUM LOSE EVENTS?

This question came up on the Data Engineering sub-reddit the other day: Can
Debezium lose any events? I.e. can there be a situation where a record in a
database get inserted, updated, or deleted, but Debezium fails to capture that
event from the transaction log and propagate it to downstream consumers?

Read More...

Feb 28, 2023

FINDING JAVA THREAD LEAKS WITH JDK FLIGHT RECORDER AND A BIT OF SQL

The other day at work, we had a situation where we suspected a thread leak in
one particular service, i.e. code which continuously starts new threads, without
taking care of ever stopping them again. Each thread requires a bit of memory
for its stack space, so starting an unbounded number of threads can be
considered as a form of memory leak, causing your application to run out of
memory eventually. In addition, the more threads there are, the more overhead
the operating system incurs for scheduling them, until the scheduler itself will
consume most of the available CPU resources. Thus it’s vital to detect and fix
this kind of problem early on.

Read More...

Jan 15, 2023

GETTING STARTED WITH JAVA DEVELOPMENT IN 2023 — AN OPINIONATED GUIDE

27 years of age, and alive and kicking — The Java platform regularly comes out
amongst the top contenders in rankings like the TIOBE index. In my opinion,
rightly so. The language is very actively maintained and constantly improved;
its underlying runtime, the Java Virtual Machine (JVM), is one of, if not the
most, advanced runtime environments for managed programming languages. There is
a massive eco-system of Java libraries which make it a great tool for a large
number of use cases, ranging from command-line and desktop applications, over
web apps and backend web services, to datastores and stream processing
platforms. With upcoming features like support for vectorized computations
(SIMD), light-weight virtual threads, improved integration with native code,
value objects and user-defined primitives, and others, Java is becoming an
excellent tool for solving a larger number of software development tasks than
ever before.

Read More...

Jan 5, 2023

OH... THIS IS PROD?!

I strongly believe that you should avoid connecting to production environments
from local developer machines as much as possible. But sometimes, e.g. in order
to analyse some specific kinds of failures, doing so can be inevitable. Now, if
this is the case, I really, really want to be sure that I’m aware of the
environment I am working in. I absolutely want to avoid a situation as in the
catchy title of this post, when for instance you realize that you just ran some
integration test against a production environment. In the context of working
with the AWS CLI tool this means I’d like to be aware of the currently active
profile by means of coloring my shell accordingly. Here’s how I’ve set this up
using iTerm2 and zsh.

Read More...

Jan 3, 2023

IS YOUR BLOCKING QUEUE... BLOCKING?

Java’s BlockingQueue hierarchy is widely used for coordinating work between
different producer and consumer threads. When set up with a maximum capacity
(i.e. a bounded queue), no more elements can be added by producers to the queue
once it is full, until a consumer has taken at least one element. For scenarios
where new work may arrive more quickly than it can be consumed, this applies
means of back-pressure, ensuring the application doesn’t run out of memory
eventually, while enqueuing more and more work items.

Read More...

Dec 18, 2022

MAVEN, WHAT ARE YOU WAITING FOR?!

As part of my new job at Decodable, I am also planning to contribute to the
Apache Flink project (as Decodable’s fully-managed stream processing platform is
based on Flink). Right now, I am in the process of familiarizing myself with the
Flink code base, and as such I am of course building the project from source,
too.

Read More...

Nov 30, 2022

THE INSATIABLE POSTGRES REPLICATION SLOT

While working on a demo for processing change events from Postgres with Apache
Flink, I noticed an interesting phenomenon: A Postgres database which I had set
up for that demo on Amazon RDS, ran out of disk space. The machine had a disk
size of 200 GiB which was fully used up in the course of less than two weeks.
Now a common cause for this kind of issue are replication slots which are not
advanced: in that case, Postgres will hold on to all WAL segments after the
latest log sequence number (LSN) which was confirmed for that slot. Indeed I had
set up a replication slot (via the Decodable CDC source connector for Postgres,
which is based on Debezium). I then had stopped that connector, causing the slot
to become inactive. The problem was though that I was really sure that there was
no traffic in that database whatsoever! What could cause a WAL growth of ~18
GB/day then?

Read More...

Nov 28, 2022

RUNNING A QUARKUS NATIVE APPLICATION ON RENDER

This is a quick run down of the steps required for running JVM applications,
built using Quarkus and GraalVM, on Render. Render is a cloud platform for
running websites and applications. Like most other comparable services such as
fly.io, it offers a decent free tier, which lets you try out the service without
any financial commitment. Unlike most other services, with Render, you don’t
need to provide a credit card in order to use the free tier. Which means there’s
no risk of surprise bills, as often is the case with pay-per-use models, where a
malicious actor could DDOS your service and drive up cost for consumed CPU
resources or egress bandwidth indefinitely.

Read More...

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