UIGC is a middleware for Akka that provides actor garbage collection (actor GC). When you implement an Akka actor with UIGC, the middleware will automatically detect when the actor is safe to terminate and stop it for you. Say goodbye to memory leaks and buggy memory management code!
UIGC is currently a research prototype. We are actively looking for contributors of all skill levels to help bring it out of the research lab and into the real world! See Contributing for details.
UIGC consists of two parts:
- A unified API for implementing Akka actors with automatic memory management.
- A collection of GC engines that UIGC uses to detect when actors are garbage. UIGC currently supports two GC engines, described below.
This is the default GC engine, based on Dan Plyukhin's PhD thesis. CRGC has many good properties:
- No message delivery requirements: CRGC can be used in Akka Cluster because it does not require that messages are delivered in any particular order.
- Fault-tolerance: CRGC continues to collect garbage, even if messages are dropped or systems are unexpectedly downed.
- Fault-recovery: If a system is downed and it had references to actors, those actors can still be garbage collected.
That last point means you don't have to worry about garbage collection, even when things go wrong!
An implementation of Pony's MAC algorithm. To collect acyclic garbage, MAC uses weighted reference counting (WRC). To collect cyclic garbage (e.g. when two garbage actors have references to each other) actors send messages to a centralized cycle detector. Currently, the UIGC implementation of MAC only collects acyclic garbage.
This engine requires causal message delivery, which Akka only supports within a single JVM. Consequently, MAC cannot be used with Akka Cluster.
UIGC requires a forked version of Akka, which exposes some of Akka's internals to the garbage collector. Eventually, we plan for UIGC to build against the official Akka binaries. See the Github issue that tracks our progress towards this goal.
- Clone this fork of Akka.
- In the Akka build directory, run
sbt publishLocal. When the command is finished, search the output for a string like2.8.0-M3+18-6fadd9a8+20230727-1556-SNAPSHOT. Copy the string. Let's call itYOUR_AKKA_VERSION. - In the CRGC build directory, open
build.sbtand setakkaVersiontoYOUR_AKKA_VERSION. It should now read:val akkaVersion = <YOUR_AKKA_VERSION>. - In the CRGC build directory, run
sbt publishLocal.
Or you can run the scripts/build-linux-mac.sh script on Linux, macOS, or in the Bash environment on Windows. If the above instructions don't work for you, or if you can think of an easier install process, please raise a Github issue!
For a guide to using UIGC, see GUIDE.md.
Working on UIGC is a great way to get involved in research and open source software! Start by following the Installation guide. Then check out the issues page to find a starter project. Once you find a project, leave a comment to let us know you're working on it.
Please note that this software is released under the Hippocratic License, v3.0; see LICENSE.md for details. If this license is too restrictive for your organization, feel free to discuss by raising an issue or starting a discussion on Github. Please remember to be polite and thoughtful!