Erps is an OTP-compliant remote protocol service

The general purpose of Erps is to extend the GenServer primitives over public networks using two-way TLS authentication and encryption without using OTP standard distribution, for cases when:

1. Latency, reliability, or network toplogy properties make using the erlang distribution gossip protocol unfavorable or unreliable
2. You prefer to use erlang distributed clusters strictly contain members of a given type, and have an orthogonal channel for cluster-to-cluster communication.
3. You want to keep groups of Erlang nodes in isolation with a restricted protocol language to achieve security-in-depth and prevent privilege escalation across cluster boundaries.

Erps is an asymmetric protocol, which means there are distinct roles for client and server. An Erps client is a 'dumb proxy' for a remote GenServer, forwarding all of its call/2 and cast/2 requests to the Erps server.

Erps is also a persistent protocol. The clients are intended to connect in to the target server and indefinitely issue requests over this channel, (more like websockets) instead of instantiating a new connection per request, (like HTTP, JSON API, GRPC, or GraphQL).

To that end, the Erps Client and Daemon support self-healing connections by default.

Testability

To make working with your program easier in developer or staging environments, Erps can be configured to use TCP. In order to seamlessly switch between these transport modules, Erps uses the Transport library; both clients and servers may be launched with transport: Transport.Tcp to use this mode.

Security model

Erps currently presumes that once authenticated via TLS, both ends of the Erps connection are trusted, and provides only basic security measures to protect the server and the client.

Distribution and Worker pools

There are no provisions for supporting out-of-the-box 'smart' distribution defaults or smart worker pool defaults, but this is planned.

Multiverses

Erps supports Multiverses out of the box. To activate multiverses at compile- time, you will probably want to have the following in your test.exs:

config :erps, use_multiverses: true

In order to use multiverses with any given Daemon or Client, you must also pass forward_callers: true in the options of the Erps.Daemon.start/3, Erps.Daemon.start_link/3, Erps.Client.start/3, Erps.Client.start_link/3 functions.

Examples

Examples on how to set up basic clients and servers are provided in in the documentation for Erps.Client and Erps.Server. On the server side you must use an Erps.Daemon to serve as the entry-point for multiple connections which are individually managed by servers; A Server cannot listen on a port for an inbound connection by itself.