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HTTP Resources

Cascade includes a powerful system for building REST servers on top of Spray and Akka.

This document contains a detailed discussion of how Cascade's HTTP support works. If you'd rather start building immediately, please see our getting started guide.

Public Facing Components

Cascade's primary building block for REST servers is a Resource. A resource is an actor that you write to handle an incoming HTTP request. When you define your routes, you create a new resource actor each time the route is called.

There are a few other pieces of a Cascade HTTP server that work with resources. They're listed below.

  • AbstractResourceActor - this is an Akka Actor that you extend when you write your resource.
  • ResourceDriver - this is an object that contains a serve function intended to be called inside a route to create the resource actor, run the HTTP state machine (mentioned above), and complete the response. serve itself returns a function that is compatible with spray-routing's complete function.
  • SprayActor - this is an actor that starts a Spray HTTP server. It registers your routes, adds some of its own utility routes (e.g. /stats and /status) and sets up some configuration parameters (e.g. the Spray backlog). Use this actor to start up your server.

Internals

The remainder of this document describes the internals HTTP components of Cascade.

HttpResourceActor

This is an internal Akka Actor that runs a request through a state machine for part of an HTTP request lifecycle.

For example, the state machine ensures that the Content-Type header on the request is acceptable and supported before it moves on to parsing the request. AbstractResourceActor extends HttpResourceActor, so your resource also extends HttpResourceActor transitively.

ResourceService

This is an internal trait that SprayActor (see above) mixes in. ResourceService automatically adds a /status and /stats endpoint to all SprayActor-based servers.

See below for details on the two endpoints

Status

/status returns current build information for the project. This includes the service name, dependencies, and Git branch and commit information. In order to get this information, make a GET request to /status with a x-service-status header in request (the value of the header doesn't matter.)

For example, after running your project locally:

curl -H "x-service-status:true" http://localhost:9090/status

That curl call returns json data that looks like the following:

{
  "status":"ok",
  "service-name":"your-service",
  "dependencies":["all dependencies"],
  "git-info": {
    "branch":"develop",
    "branch-is-clean":"true",
    "commit-sha":"some-sha",
    "commit-date":"Wed Apr 16 12:01:28 PDT 2014"
  }
}

Stats

/stats returns internal Spray monitoring information for the build. In order to get this information, make a GET request to /stats with a x-service-stats header in the request (the value of the header doesn't matter.)

For example, after running your project locally:

curl -H "x-service-stats:true" http://localhost:9090/stats

That curl call returns json data that looks like the following:

{
  "uptimeInSec":10,
  "totalRequests":3,
  "openRequests":1,
  "maxOpenRequests":1,
  "totalConnections":3,
  "openConnections":1,
  "maxOpenConnections":1,
  "requestTimeouts":0
}