Helm

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 ConsulOp algebra.

Getting Started

Add the following to your build.sbt:

libraryDependencies += "io.verizon.helm" %% "http4s" % "1.4.78-scalaz-7.1"

The Helm binaries are located on maven central, so no additional resolvers are needed.

Algebra

Consul operations are specified by the ConsulOp algebra. Two examples are get and set:

import helm._
import ConsulOp.ConsulOpF

val s: ConsulOpF[Unit] = : ConsulOp.kvSet("key", "value")

val g: ConsulOpF[Option[String]] = : ConsulOp.kvGet("key")

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 cats.effect.IO
import helm.http4s._
import org.http4s.Uri.uri
import org.http4s.client.blaze.Http1Client

val client = Http1Client[IO]().unsafeRunSync
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 cats.effect.IO

val s: IO[Unit] = helm.run(interpreter, ConsulOp.kvSet("testkey", "testvalue"))

val g: IO[Option[String]] = helm.run(interpreter, ConsulOp.kvGet("testkey"))

// actually execute the calls
s.unsafeRunSync
g.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.

Contributing

Contributions are welcome; particularly to expand the algebra with additional operations that are supported by Consul but not yet supported by Helm.