unlogged-sdk VS Graal

Hello HN! Parth, and Shardul here. We have been building unlogged.io for the last 21 months. We started as a time travel debugger and pivoted to record and replay with assertions, mocking, and code coverage. You can save the replays in the form of a JSON and commit them to your git.

Both Parth and I come from an e-commerce/payments background where production bugs meant heavy financial losses. Big billion days/Black Friday sales meant months of code freezes with low productivity. Before committing the code, we wanted to replay production traffic and know the breaking changes right away, like in sub-second. Kind of like unit+integration tests on steroids.

So, we built an SDK that adds probes to the code in compile time. The SDK logs code execution, in detail.

Git: https://github.com/unloggedio/unlogged-sdk

We also built an IDE plugin that keeps monitoring code changes, hot reloads these changes, replays the relevant methods, and alerts on failing replays. It also lets developers call Java methods directly, mock downstream methods in run time, highlight code coverage in real-time, and show performance numbers for methods with inlay hints. (right above each method)

Git: https://github.com/unloggedio/intellij-java-plugin

We are excited to launch the first version of our product that replays with assertions + mocking + code coverage reports right inside the IDE.

Link to our IntelliJ plugin: https://plugins.jetbrains.com/plugin/18529-unlogged/

Record and Replay Demo: https://www.youtube.com/watch?v=muCyE-doEB0

Define Assertions on Replay: https://www.youtube.com/watch?v=YKsi1p634-M

Track Code Coverage: https://www.youtube.com/watch?v=NMmp954kfaU

Generate JUnit Test Cases: https://www.youtube.com/watch?v=rTUmg5b1Z_Q

Mocking when replaying: https://www.youtube.com/watch?v=O_aqU1u-Kmw

Documentation: http://read.unlogged.io/

Roadmap:

1. Create a production logger

Link to the source code: https://github.com/unloggedio/unlogged-sdk

will fix the link on the plugin page, thanks for noticing it.

Contrary to what vocal Kotlin advocates might believe, Kotlin only matters on Android, and that is thanks to Google pushing it no matter what.

https://spectrum.ieee.org/the-top-programming-languages-2023

https://snyk.io/reports/jvm-ecosystem-report-2021/

And even so, they had to conceed Android and Kotlin on their own, without the Java ecosystem aren't really much useful, thus ART is now updatable via Play Store, and currently supports OpenJDK 17 LTS on Android 12 and later devices.

As for your question regarding numbers, mostly Java 74.6%, C++ 13.7%, on the OpenJDK, other JVM implementations differ, e.g. GraalVM is mostly Java 91.8%, C 3.6%.

https://github.com/openjdk/jdk

https://github.com/oracle/graal

Two examples from many others, https://en.wikipedia.org/wiki/List_of_Java_virtual_machines

Pkl was built using the GraalVM Truffle framework. So it supports runtime compilation using Futurama Projections. We have been working with Apple on this for a while, and I am quite happy that we can finally read the sources!

https://github.com/oracle/graal/tree/master/truffle

Disclaimer: graalvm dev here.

That's pretty interesting. It's not as aggressive as Bee sounds, but the Espresso JVM is somewhat similar in concept. It's a full blown JVM written in Java with all the mod cons, which can either be compiled ahead of time down to memory-efficient native code giving something similar to a JVM written in C++, or run itself as a Java application on top of another JVM. In the latter mode it obviously doesn't achieve top-tier performance, but the advantage is you can easily hack on it using all the regular Java tools, including hotswapping using the debugger.

When run like this, the bytecode interpreter, runtime system and JIT compiler are all regular Java that can be debugged, edited, explored in the IDE, recompiled quickly and so on. Only the GC is provided by the host system. If you compile it to native code, the GC is also written in Java (with some special conventions to allow for convenient direct memory access).

What's most interesting is that Espresso isn't a direct translation of what a classical C++ VM would look like. It's built on the Truffle framework, so the code is extremely high level compared to traditional VM code. Details like how exactly transitions between the interpreter/compiled code happen, how you communicate pointer maps to the GC and so on are all abstracted away. You don't even have to invoke the JIT compiler manually, that's done for you too. The only code Espresso really needs is that which defines the semantics of the Java bytecode language and associated tools like the JDWP debugger protocol.

https://github.com/oracle/graal/tree/master/espresso

This design makes it easy to experiment with new VM features that would be too difficult or expensive to implement otherwise. For example it implements full hotswap capability that lets you arbitrarily redefine code and data on the fly. Espresso can also fully self-host recursively without limit, meaning you can achieve something like what's described in the paper by running Espresso on top of Espresso.

I'm also using GraalVM if that's of any help.

Quarkus is one of Java frameworks for microservices development and cloud-native deployment. It is developed as container-first stack and working with GraalVM and HotSpot virtual machines (VM).

Apologies, I didn't mean to imply DCEVM went poof, just that I was sad it didn't make it into OpenJDK so one need not do JDK silliness between the production one and the "debugging one" since my experience is that's an absolutely stellar way to produce Heisenbugs

And I'll be straight: Graal scares me 'cause Oracle but I just checked and it looks to the casual observer that it's straight-up GPLv2 now so maybe my fears need revisiting: https://github.com/oracle/graal/blob/vm-23.1.0/LICENSE

> to be compiled to a single executable is a strength that Java does not have

I think this is very outdated claim: https://www.graalvm.org/

https://github.com/oracle/graal/issues/7182