https://github.com/cr-org/supernova
:milky_way: Apache Pulsar client for Haskell
https://github.com/cr-org/supernova
apache-pulsar haskell nix
Last synced: 21 days ago
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:milky_way: Apache Pulsar client for Haskell
- Host: GitHub
- URL: https://github.com/cr-org/supernova
- Owner: cr-org
- License: apache-2.0
- Created: 2020-08-11T21:50:54.000Z (over 5 years ago)
- Default Branch: master
- Last Pushed: 2020-10-23T14:09:02.000Z (about 5 years ago)
- Last Synced: 2025-01-31T12:51:22.698Z (10 months ago)
- Topics: apache-pulsar, haskell, nix
- Language: Haskell
- Homepage: http://hackage.haskell.org/package/supernova
- Size: 293 KB
- Stars: 38
- Watchers: 9
- Forks: 5
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
supernova
=========
[](https://github.com/cr-org/supernova/actions)
⚠️ **it is still very much under development 🚧 so use it at your own risk** ⚠️
A *supernova* is a powerful and luminous stellar explosion. This transient astronomical event occurs during the last evolutionary stages of a massive star or when a white dwarf is triggered into runaway nuclear fusion. The original object, called the progenitor, either collapses to a [neutron](https://github.com/cr-org/neutron) star or black hole, or is completely destroyed. The peak optical luminosity of a supernova can be comparable to that of an entire galaxy before fading over several weeks or months.
[](https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA22352)
### Quick Start
The example located in `test/Main.hs` showcases a consumer & producer running concurrently (needs the `async` library).
```haskell
main :: IO ()
main = runPulsar conn $ do
c <- newConsumer topic sub
p <- newProducer topic
liftIO $ program c p
conn :: PulsarConnection
conn = connect defaultConnectData
topic :: Topic
topic = defaultTopic "app"
sub :: Subscription
sub = Subscription Exclusive "test-sub"
program :: Consumer IO -> Producer IO -> IO ()
program Consumer {..} Producer {..} =
let c = fetch >>= \(Message i m) -> msgDecoder m >> ack i >> c
p = sleep 3 >> traverse_ send messages >> p
in concurrently_ c p
```
A `Message` contains a `MessageID` you need for `ack`ing and a payload defined as a lazy `ByteString`.
> Note that we wait a few seconds before publishing a message to make sure the consumer is already subscribed. Otherwise, it might miss some messages.
Run it with the following command:
```shell
cabal new-run supernova-tests
```
By default, it logs to the standard output in DEBUG level. You can change it by suppling `LogOptions` to the alternative function `runPulsar'`.
```haskell
runPulsar' :: LogOptions -> PulsarConnection -> Pulsar a -> IO ()
```
### Streaming
Since both consumers and producers operate on any `MonadIO m`, we could leverage some streaming libraries. Here's the same example using [streamly](https://hackage.haskell.org/package/streamly).
```haskell
import Streamly
import qualified Streamly.Prelude as S
program :: Consumer IO -> Producer IO -> IO ()
program Consumer {..} Producer {..} =
let c = fetch >>= \(Message i m) -> msgDecoder m >> ack i >> c
p = sleep 3 >> traverse_ send messages >> p
in S.drain . asyncly . maxThreads 10 $ S.yieldM c <> S.yieldM p
```
### Development
It is recommended to use [Cachix](https://app.cachix.org/cache/hpulsar) to reduce the compilation time.
```shell
nix-build
```
Or within a Nix shell (run `nix-shell` at the project's root).
```shell
cabal new-build
```
#### Generate Hackage tarball
```shell
cabal new-sdist
```
#### Upload documentation
```shell
cabal new-haddock --haddock-for-hackage --enable-doc
cabal upload -d dist-newstyle/supernova-0.0.2-docs.tar.gz --publish
```