CODEWITHSUNDEEP
elixirphoenix-framework
Alan
Alan

Reputation: 241

Filter API connections with Plug

I'm trying to filter connections to my API.

In my mix.exs I've added:

pipeline :some_validation do
  plug VerifyLogicPlug
end

### INSIDE MY SCOPE:

  pipe_through [:some_validation, :previous_pipeline]

My plug looks like this:

defmodule VerifyLogicPlug do

  import Plug.Conn

  def init(options), do: options

  def call(conn, _options) do
    if some_logic do
      respond_blocked(conn)
    else
      conn # Continue the normal execution of the pipeline
    end
  end

  defp respond_blocked(conn) do
    response = %{
      error: %{
        status: 401,
        code: "BLOCKED",
        title: "BLOCKED"
      }
    }

    conn
    |> put_resp_content_type("application/json")
    |> send_resp(status, Poison.encode!(response))
    halt(conn) # I've tried both with and without this line
  end
end

I get the desired response in the API:

{
    "error": {
        "title": "BLOCKED",
        "status": 401,
        "code": "BLOCKED"
    }
}

But in the server I get some errors, depending on whether I use halt(conn) or not. With halt(conn):

[error] #PID<0.1003.0> running MyProject.Endpoint terminated
Server: localhost:4000 (http)
Request: GET (...)
** (exit) an exception was raised:
    ** (Plug.Conn.NotSentError) a response was neither set nor sent from the connection

Without halt(conn):

[error] #PID<0.1404.0> running MyProject.Endpoint terminated
Server: localhost:4000 (http)
Request: GET (...)
** (exit) an exception was raised:
    ** (Plug.Conn.AlreadySentError) the response was already sent

What I want (I think) is to use halt(conn) but don't get the Plug.Conn.NotSentError, as a response is being sent. Any hints on what's missing?

Thanks!

Upvotes: 0

Views: 823

Answers (1)

carpamon
carpamon

Reputation: 6623

You are sending the response twice.

Change the respond_block (which I suggest to rename to block_request) to:

conn
|> put_resp_content_type("application/json")
|> send_resp(status, Poison.encode!(response))
|> halt()

Upvotes: 1

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