BlazeServerBuilder asking for extra parameter

Question

I'm trying to write a simple http server in scala with http4. But when I follow tutorials to create a BlazeServer builder, it will say that I need to supply a Timer[IO] (gives me the error Unspecified value parameters: timer: Timer[IO]), which I can't seem to find any information on why.

val server = BlazeServerBuilder[IO](global)

You are probably using a different version from the docs, make sure you use **http4s** `0.23` and **cats-effect** `3` — Luis Miguel Mejía Suárez, Feb 12 '22 at 21:12

score 0 · Accepted Answer · answered Mar 31 '22 at 13:00

As Luis said, probably worth using the scala seed for http4s quickstart by calling

$ sbt new http4s/http4s.g8 --branch 0.23

This will give you a good idea about how to put together the server and routes and config)

In regards to your question, if you are using Blaze, you can see that timer is one of the implicit parametera for apply, this is the signature (in 0.21.9)

  def apply[F[_]](executionContext: ExecutionContext)(implicit
      F: ConcurrentEffect[F],
      timer: Timer[F]): BlazeServerBuilder[F]

you can create an implicit timer like this, assuming you have an implicit execution context (in the code below, that is ec)

implicit val timer: Timer[IO] = IO.timer(ec)

BlazeServerBuilder asking for extra parameter

1 Answers1