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.

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Standard Modules

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

• finch-core - core classes/functions
• finch-generic - generic derivation for endpoints
• finch-argonaut - Argonaut + Finch
• finch-circe - Circe + Finch
• finch-iteratee - Iteratee + Finch
• finch-fs2 - FS2 + Finch
• finch-refined - Refined + Finch
• finch-test - the test support classes/functions

Additional Modules

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

• finch-jackson - Jackson + Finch
• finch-json4s - JSON4s + Finch
• finch-playjson - PlayJson + Finch
• finch-sprayjson - SprayJson + Finch
• finch-oauth2 - Finagle OAuth2 + Finch

Installation

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!") }
    Bootstrap[IO].serve[Text.Plain](api).listen(":8080").useForever
  }
}

See examples sub-project for more complete examples.

Quickstart

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

Performance

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).

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.

Documentation

• The main documentation is hosted at http://finagle.github.io/finch/
• The documentation source may be found in the docs/ folder
• The latest Scaladoc is available at http://finagle.github.io/finch/api/

Adopters

• PITS Global Data Recovery Services
• Despegar
• Earnest
• Globo.com
• Glopart
• Hotel Urbano
• Konfettin
• JusBrasil
• Sabre Labs
• Spright
• SoFi
• Qubit
• QuizUp
• Lookout
• Project September
• Merit
• D.A.Consortium
• Redbubble
• Zalando
• Rakuten
• Threat Stack
• RelinkLabs
• Submit a pull-request to include your company/project into the list

Related Projects

• Finch Template: A Redbubble approach to building services with Finch
• Finch Server: Finch’s integration into TwitterServer
• Finch Sangria: Finch’s GraphQL support
• Finch Demo: Community-maintained Finch user guide
• Finch Rich: Macro-based controllers for Finch
• Finch Quickstart: A skeleton Finch project
• Finch OAuth2: the OAuth2 support backed by the finagle-oauth2 library
• Finch Todo Backend: Finch implementation of todobackend

Contributing

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.

License

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.