# puniverse/quasar

Fibers, Channels and Actors for the JVM

Repository: https://github.com/puniverse/quasar
Canonical: https://ross.abutalabs.com/products/puniverse-quasar
Homepage: http://docs.paralleluniverse.co/quasar/
Language: Java
License: NOASSERTION
License Family: other
Topics: java, jvm, fibers, actors, concurrency
Last push: 2024-01-21T07:18:32+00:00

## Health v2 (maintenance only)
Score: 23/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 0, release rhythm 8, longevity 100
- inputs: {"age_days": 4907, "days_push": 955, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 4551, forks 560 (observed 2026-08-28T04:08:53.308738+00:00)

## What it is
Quasar is a JVM library providing lightweight threads (fibers), Go-like channels, and Erlang-like actors for Java and Kotlin, using bytecode instrumentation via a Java agent. It enables high-performance asynchronous and concurrent programming with an actor model, supervision, and clustering support.

## Use cases
- run millions of lightweight threads on the JVM
- build Erlang-style actor systems in Java or Kotlin
- use Go-like channels for communication between concurrent tasks
- write blocking-style asynchronous code without callback hell
- build fault-tolerant concurrent applications with supervisors and hot code swapping
- cluster actors across JVM nodes

## When to choose
- you need lightweight concurrency on older JVMs without virtual threads (pre-JDK 21)
- you want an Erlang/Akka-style actor model tightly integrated with fibers and channels
- you are maintaining an existing Quasar/Comsat/Pulsar codebase

## When to avoid
- you are on JDK 21+ where native virtual threads (Project Loom) are available
- you want a actively developed library with a large community
- you cannot add a -javaagent instrumentation flag to your JVM launch
- you need a general-purpose distributed data grid (use Galaxy or other IMDGs instead)

## Facets
- artifact type: library
- maturity: maintenance
- function: concurrency, message-queue, streaming
- domain: developer-tools, microservices
- platform: jvm, cross-platform
- tags: fibers, actors, channels, lightweight-threads, erlang-style, go-style-channels, kotlin, clojure, real-time

## Member repositories
- puniverse/quasar (main) score 23

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:08:53.308738+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-29T18:20:04.800854+00:00, confidence not recorded.
  - readme: https://github.com/puniverse/quasar (fetched 2026-08-28T04:08:53.308738+00:00, sha c13e4212a54b)
  - homepage: http://docs.paralleluniverse.co/quasar/ (fetched 2026-08-29T09:05:46.278006+00:00, sha a69211b8ee49)
  - site_page: http://paralleluniverse.co/about (fetched 2026-08-29T09:05:46.341795+00:00, sha ebd362527a52)
  - site_page: http://docs.paralleluniverse.co/galaxy (fetched 2026-08-29T09:05:46.349627+00:00, sha 43944ac3ba10)
  - site_page: http://docs.paralleluniverse.co (fetched 2026-08-29T09:05:46.308749+00:00, sha eb8bdc238c61)
- Data as of 2026-08-30T08:39:29.467469+00:00.