Multiverses suite to enable isolated HTTP communications over multiverse shards

how-to-use

How to Use

in-your-phoenix-endpoint

In your Phoenix endpoint:

defmodule MyAppWeb.Endpoint do
  #...

  if Mix.env() == :test do
    plug Multiverses.Plug
  end

  #...
end

Warning

If you anticipate needing to recompile the Endpoint module on the fly you will need a better way to store the build environment, as the Mix module may not be available to the running VM.

in-your-test-assuming-the-multiverses-req-adapter-is-used

In your test (assuming the Multiverses.Req adapter is used)

• declare that your test shards over the Http multiverses name domain.
• alias Multiverses.Req instead of using the Req module.

defmodule MyAppTest do

alias Multiverses.Req

@port #....

setup do

Multiverses.shard(Http)

end

test "some test" do

result = Req.get("localhost:#{@port}")
assert result = #...

end end

how-it-works

How it works

The adapters for the http clients inject the Multiverses.shard/1 id into the http header x-multiverse-id. This is then intercepted by the Multiverses.Plug module plug in your Endpoint, which then performs a lookup to obtain the :$callers for the request; this :$callers chain is then added to the request process dictionary for the duration of the http Plug pipeline.

Because this exchange installs :$callers a side effect is that other services that are :$callers aware, such as Mox or Ecto will be able to see their respective checkouts.

cluster-awareness

Cluster awareness

Multiverses.Http is tested to work over a BEAM cluster.

If you spin up a cluster as a part of your tests, you can issue an http request to a node that is not the node running ExUnit and the :$callers for the request will be remote pids (relative to the request handlers). Before proceeding with clustered tests, check to see if the modules that depend on this (e.g. Mox, Ecto) are able to correctly route their sandbox checkouts to the correct node in the cluster.

other-backends

Other backends

Currently there is support only for the Req client library. If support for other libraries is desired, please issue a PR. Compilation of library adapters will be gated on the :http_clients application environment variable, which is currently set to [Req].