# PonyExpress
## Securely extend a Phoenix PubSub over SSL
PonyExpress creates two-way authenticated SSL connections over the WAN which
are intended to unidirectionally extend a PubSub over the internet. PubSub
broadcasts are forwarded from Server to Client.
The use case is when you have a trusted pair of nodes (for example a backend
and a BFF) that could use live-updating pubsub propagation. These might be
located in distinct layer-2 networks, for example, a BFF in the cloud which
services an on-premises backend. Or you may be wanting security in-depth with
end-to-end encryption in your layer-2 network to mitigate damage from a
potential network intrusion event. For whatever reason either case, if full
erlang distribution is not right for you, this is a low-footprint way of
propagating those `Phoenix.PubSub` messages (without writing a full
`Phoenix.Channel` client).
On the server side:
```elixir
iex> Phoenix.PubSub.PG2.start_link(:source, [])
iex> PonyExpress.Daemon.start_link(
pubsub_server: SourcePubSub,
port: <port>,
tls_opts: [
cacertfile: <ca_certfile>
certfile: <certfile>
keyfile: <keyfile>
])
```
On the client side:
```elixir
iex> Phoenix.PubSub.PG2.start_link(:dest, [])
iex> PonyExpress.Client.start_link(
server: <server IP>,
port: port,
topic: "my_topic",
pubsub_server: DestPubSub,
tls_opts: [
cacertfile: <ca_certfile>
certfile: <certfile>
keyfile: <keyfile>
])
iex> Phoenix.PubSub.subscribe(:dest, "my_topic")
```
Then you can send a message on the server side:
```elixir
iex> Phoenix.PubSub.broadcast(:source, "my_topic", "my_message")
```
And it will appear on the client side:
```elixir
iex> flush()
"my_message"
:ok
```
Consult the documentation for more comprehensive OTP-compliant strategies for
using this library.
## Installation
If [available in Hex](https://hex.pm/docs/publish), the package can be installed
by adding `pony_express` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:pony_express, "~> 0.4.1"}
]
end
```
Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
be found at [https://hexdocs.pm/pony_express](https://hexdocs.pm/pony_express).
## Testing
PonyExpress creates a series of testing keys in `/tmp/.pony-express-test/<32-byte-slug>`.
These keys are deleted if the test suite is successful and left for examination
if the test suite is not.