finagle / finch   0.34.1

Apache License 2.0 Website GitHub

Scala combinator library for building Finagle HTTP services

Scala versions: 2.13 2.12

Finch is a thin layer of purely functional basic blocks atop of Finagle for building composable HTTP APIs. Its mission is to provide the developers simple and robust HTTP primitives being as close as possible to the bare metal Finagle API.


Scala CI Coverage Status Gitter Maven Central

Standard Modules

Finch uses multi-project structure and contains of the following modules:

Additional Modules

Finch's Github organization has even more modules (these are, however, not published regularly; reach out if you need published artifacts):


Every Finch module is published at Maven Central. Use the following sbt snippet ...

libraryDependencies ++= Seq(
  "com.github.finagle" %% "[finch-module]" % "[version]"

Hello World!

This "Hello World!" example is built with just finch-core:

import cats.effect.{IO, IOApp}
import io.finch._

object Main extends IOApp.Simple with Endpoint.Module[IO] {
  override def run: IO[Unit] = {
    val api: Endpoint[IO, String] = get("hello") { Ok("Hello, World!") }

See examples sub-project for more complete examples.


Use finch.g8 template to quickly bootstrap a minimal Finch project:

  • sbt new finch/finch.g8
  • cd helloworld
  • sbt run
  • curl http://localhost:8081/hello


We use wrk to load test Finch+Circe against Finagle+Jackson to get some insight on how much overhead, an idiomatic Finch application written in a purely functional way, involves on top of Finagle/Jackson. The results are quite impressive (for a pre-1.0 version): Finch performs on 95% of Finagle's throughput.

Here is the first three runs of the benchmark on 2013 MB Pro (2.8 GHz Intel Core i7 w/ 16G RAM).

Benchmark Run 1 Run 2 Run 3
Finagle + Jackson 29014.68 req/s 36783.21 req/s 39924.42 req/s
Finch + Circe 28762.84 req/s 36876.30 req/s 37447.52 req/s

Finch is also load tested against a number of Scala HTTP frameworks and libraries as part of the TechEmpower benchmark. The most recent round showed that Finch performs really well there, scoring a second place across all the Scala libraries.



Related Projects


There are plenty of ways to contribute into Finch:

  • Give it a star
  • Join the Gitter room and leave a feedback or help with answering users' questions
  • Submit a PR (there is an issue label "easy" for newcomers)
  • Be cool and wear a Finch T-Shirt

The Finch project supports the Typelevel code of conduct and wants all of its channels (Gitter, GitHub, etc.) to be welcoming environments for everyone.

Finch is currently maintained by Vladimir Kostyukov, Travis Brown, Ryan Plessner, and Sergey Kolbasov. After the 1.0 release, all pull requests will require two sign-offs by a maintainer to be merged.


Licensed under the Apache License, Version 2.0 (the "License"); you may not use this software except in compliance with the License.

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.