A native Scala client for interacting with Consul. There is currently one supported client, which uses http4s to make HTTP calls to Consul. Alternative implementations could be added with relative ease by providing an additional free interpreter for the
Add the following to your
libraryDependencies += "io.getnelson.helm" %% "http4s" % "x.y.z"
x.y.z is the desired Helm version. Check for the latest release Maven Central.
Consul operations are specified by the
ConsulOp algebra. Two examples are
import ConsulOp.ConsulOpF val setAlgebra: ConsulOpF[Unit] = ConsulOp.kvSet(key = "testKey", value = "testValue".getBytes) val getAlgebra: ConsulOpF[QueryResponse[List[KVGetResult]]] = ConsulOp.kvGet(key = "testKey", recurse = Some(false), datacenter = None, separator = None, index = None, maxWait = None)
These are however just descriptions of what operations the program might perform in the future, just creating these operations does not actually execute the operations. In order to perform the gets and sets, we need to use the http4s interpreter.
The http4s interpreter
First we create an interpreter, which requires an http4s client and a base url for consul:
import scala.concurrent.ExecutionContext import cats.effect.IO import helm.http4s._ import org.http4s.Uri.uri import org.http4s.client.blaze.BlazeClientBuilder val ec = ExecutionContext.global implicit val contextShift = IO.contextShift(ec) // It's better to run everything inside of resource.use() where possible, but this makes for a simpler example val client = BlazeClientBuilder[IO](ec).resource.allocated.unsafeRunSync()._1 val baseUrl = uri("http://127.0.0.1:8500") val interpreter = new Http4sConsulClient(baseUrl, client)
Now we can apply commands to our http4s client to get back IOs which actually interact with consul.
import helm._ import cats.effect.IO val set: IO[Unit] = helm.run(interpreter, setAlgebra) val get: IO[QueryResponse[List[KVGetResult]]] = helm.run(interpreter, getAlgebra) // actually execute the calls val setResult: Unit = set.unsafeRunSync() val getResult: QueryResponse[List[KVGetResult]] = get.unsafeRunSync()
Typically, the Helm algebra would be a part of a
Coproduct with other algebras in a larger program, so running the
IO immediately after
helm.run is not typical.
Contributions are welcome; particularly to expand the algebra with additional operations that are supported by Consul but not yet supported by Helm.