SNUnit: Scala Native HTTP server based on NGINX Unit
import snunit._
object HelloWorldExample {
def main(args: Array[String]): Unit = {
val server = SyncServerBuilder()
.withRequestHandler(req =>
req.send(
statusCode = StatusCode.OK,
content = s"Hello world!\n",
headers = Seq("Content-Type" -> "text/plain")
)
)
.build()
server.listen()
}
}
SNUnit is a Scala Native library to write HTTP server applications on top of NGINX Unit. It allows you to write both synchronous and asynchronous web servers with automatic restart on crashes, automatic load balancing of multiple processes, great performance and all the nice NGINX Unit features.
Running your app
Once built your SNUnit binary, you need to deploy it to the unitd
server.
You need to run unitd
in a terminal with:
unitd --no-daemon --log /dev/stdout --control unix:control.sock
This will run unitd
with a UNIX socket file named control.sock in your current directory.
Then, you need to create a json file with your configuration:
{
"listeners": {
"*:8081": {
"pass": "applications/myapp"
}
},
"applications": {
"myapp": {
"type": "external",
"executable": "snunit/binary/path"
}
}
}
Where executable
is the binary path which can be absolute or relative
to the unitd
working directory.
This configuration passes all requests sent to the port 8081
to the application myapp
.
To know more about configuring NGINX Unit, refer to its documentation.
To deploy the setting you can use curl:
curl -X PUT --unix-socket control.sock -d @config.json localhost/config
If everything went right, you should see this response:
{
"success": "Reconfiguration done."
}
In case of problems, you will get a 4xx response like this:
{
"error": "Invalid configuration.",
"detail": "Required parameter \"executable\" is missing."
}
Further informations can be found in unitd
logs in the running terminal.
Sync and async support
SNUnit has two different server implementations.
With SyncServerBuilder
you need to call .listen()
to start listening.
It is a blocking operation so your process is stuck on listening and can't do
anything else while listening.
Moreover, all the request handlers need to respond directly and can't be implemented
using Future
s or any other asyncronous mechanism since no Future
will run, being
the process stuck on the listen()
Unit event loop.
With AsyncServerBuilder
the server is automatically scheduled to run either on the
scala-native-loop event loop
(based on the libuv library) or epollcat event
loop, based on epoll/kqueue.
This allows you to complete requests asyncronously using whatever mechanism you prefer.
A process can accept multiple requests concurrently, allowing great parallelism.
Add either snunit-async-loop
or snunit-async-epollcat
to decide what implementation
you want to use.
Tapir support
SNUnit offers interpreters for Tapir server endpoints.
You can write all your application using Tapir and the convert your Tapir endpoints
with logic into a SNUnit Handler
.
Currently two interpreters are available: