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Jaromir Hamala

Jaromir Hamala

Director of Engineering

Jaromir wrote his first line of code when he was seven years old. Since then, he has been interested in understanding how systems work ‘under the hood,’ and enjoys blogging about it. Jaromir’s areas of specialty include: performance and stability tuning of JVM, garbage collectors, data grids, application servers and architecture and design of applications. He enjoys pushing systems towards their limits, sharpening his skills by exploring HotSpot source code, contributing to open source projects and arguing about development over a pint of beer.

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LockSupport.parkNanos() Under the Hood and the Curious Case of Parking, Part II: Windows

Jaromir Hamala
by Jaromir Hamala

In the previous post we have seen how LockSupport.parkNanos() is implemented on Linux, what behavior to expect and how we can tune it. The post was well-received and a few people asked how parkNanos() behaves on Windows. I’ve used Linux as a daily driver for over a decade and I didn’t feel like exploring Windows. […]

LockSupport.parkNanos() Under the Hood and the Curious Case of Parking

Jaromir Hamala
by Jaromir Hamala

When a colleague of mine was running some experiments, he noticed `LockSupport.parkNanos()` would either return almost immediately or in roughly 50 microseconds steps. In other words: Calling `LockSupport.parkNanos(10000)` would not return after 10 microseconds, but roughly after 50 μs. `LockSupport.parkNanos(55000)` would not return after 55 μs, but roughly after 100 μs, etc. The 50 μs […]

Hazelcast Jet Tutorial: Building Custom JDBC Sinks

Jaromir Hamala
by Jaromir Hamala

Part I: Intro Hazelcast Jet supports writing into a number of 3rd party systems, including HDFS, Apache Kafka and others. But what if you want to write into your own system which is not supported by Jet out-of-the-box? Starting with the version 0.6 Jet offers a new simple-to-use API for building custom Sinks and this […]

Use Hazelcast Jet to stream data from an IMap to a Kafka topic

Jaromir Hamala
by Jaromir Hamala

Today I would like to show you how to use Hazelcast Jet to stream data from Hazelcast IMDG IMap to Apache Kafka. IMap is a distributed implementation of java.util.Map, it’s super-easy to use and it’s probably the most popular Hazelcast IMDG data structure. This post assumes you have an existing application which uses IMap inside […]

Hazelcast IMDG 3.9 Is Out!

Jaromir Hamala
by Jaromir Hamala

We just released Hazelcast IMDG 3.9. It’s a release packed with new features, improvements and optimizations. Let me introduce you to a few of them: User Code Deployment from Clients In Hazelcast IMDG 3.8, we introduced an option for automatic distribution of your domain classes across cluster members. This greatly simplifies the deployment process as […]

Hazelcast IMDG 3.9 EA is available

Jaromir Hamala
by Jaromir Hamala

Hello Hazelcasters! First off I would like to introduce myself – I started contributing to the project about 4 years ago, later on I joined as a performance engineer and in last 2 years I led the core engineering team. I am very excited to be stepping to the position of head of engineering at […]

The simplest way to integrate Kryo with Hazelcast

Jaromir Hamala
by Jaromir Hamala

Hazelcast offers a bunch of strategies to serialize your domain objects. You can start with simple Java Serialization and change the the strategy when it turns out to be performance bottleneck. It’s also simple to plug-in your own serialization. Kryo is a popular serialization library. It’s super-fast yet easy-to-use. It does not pollute your domain […]

Hazelcast on AWS – Kernel Bug

Jaromir Hamala
by Jaromir Hamala

The other day we discovered a bug in older Linux kernel versions and I thought you would like to know about it. Summary Use Linux kernel 3.19+ when running Hazelcast on AWS. TCP connections can get stuck with older kernel versions. They appear to be fine, but data are not flowing. This can result in […]

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