Inconsistent API requests

Hello! I have been using AJAX in the front end of my phoenix app to give flickerless updates when text is edited and rendered (see AJAX code below). The fields of data in the Ajax code are available in the reply to Phoenix in params, e.g., params["title"].

I would like to use the api server more generally and have been testing it with Postman. I do this by creating a key-value pair for the headers section, e.g., key=‘data’ value = {“title”: “TEST”, content: 'YADA YADA", …}. The info in the api server reply is in conn.req_headers, which is a list of key-value pairs as listed further down.

I can handle either case, but would like to formulate my requests and replies in a uniform manner – What do you advise?


        url: "/api/notes/" + note_id,
        type: "put",
        data: {
            title: title,
            username: username,
            user_id: user_id,
            token : token,
            content: content,
            tag_string: tag_string,
            identifier: identifier,
        headers: {
            "X-CSRF-TOKEN": csrf
        dataType: "json",
        success: function (data) {

          document.getElementById("rendered_text3a").innerHTML = data.rendered_text;




[{"cache-control", "no-cache"},
 {"postman-token", "cee52325-1811-43b0-bd9c-413068e6b9d6"}, {"user_id", "9"},
  "{\"username\":\"jxxcarlson\",\"content\":\"This *is* a test\",\"tag_string\":\"foo,bar\",\"title\":\"Magick\"}"},
 {"username", "jxxcarlson"}, {"content", "This *is* a test"},
 {"title", "Magick"}, {"id", "1114"},
 {"user-agent", "PostmanRuntime/3.0.11-hotfix.2"}, {"accept", "*/*"},
 {"host", "localhost:4001"}, {"accept-encoding", "gzip, deflate"},
 {"content-length", "0"}, {"connection", "keep-alive"}]

NOTE added I extract info from conn.req_headers using the code below. Surely there is a better way!

   {:ok, data} = Poison.Parser.parse conn2value(conn, "data")

    defp key2value(list, key) do
      pair =  Enum.filter(list, fn(pair) -> {k, v} = pair; k == key end)
      [{_,value}] = pair

    defp conn2value(conn, key) do
      key2value(conn.req_headers, key)

Well the Drab library for Elixir would let Elixir control the page for the same flickerless updates.

Absinthe for Elixir would let you use GraphQL instead of AJAX, which would be MUCH more uniform to use and faster to process as well.

Or for still doing it as you are I would transfer the data in a post body and read it back from the body, I’d not mess with headers.

But still, parsing json is still json, I’d go with GraphQL instead of json straight.

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Thanks! I will start off by investigating GraphQL

A quick short, GraphQL is a json-like query language developed by facebook, you send the query to the server and the server fulfills it and send back json in the exact format the client wants it in based on the query.

Absinthe is a wonderous Elixir library that manages all the horror of it for you, fully typed and correct and handled and you just respond with the specific data that Absinthe asks you and it munges it in to how the client wants. :slight_smile:

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re GraphQL – excellent! I hate my AJAX code. It is totally Rube Goldberg. I’ll check out Absinthe as well.

There is even an absinthe over phoenix sockets library out around somewhere too for even faster speed. There are a ton of javascript libraries to work with GraphQL too that make it almost stupid-simple to use. The Apollo front-end framework is practically built for GraphQL too (and there is a phoenix websocket thing for it as well).

Stupid simple is what I need:-)

I’ll take a look at these others as well – I haven’t used sockets yet, but speed is important in this instance – real time editing / rendering of math/science text.

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I’ve run into some trouble getting absinthe to work on my app. The error message in the logs is

[debug] ** (Phoenix.Router.NoRouteError) no route found for POST /graphql (LookupPhoenix.Router)
    (lookup_phoenix) web/router.ex:1: LookupPhoenix.Router.match_route/4
    (lookup_phoenix) web/router.ex:1: LookupPhoenix.Router.do_call/2
    (lookup_phoenix) lib/lookup_phoenix/endpoint.ex:1: LookupPhoenix.Endpoint.phoenix_pipeline/1
    (lookup_phoenix) lib/plug/debugger.ex:123: LookupPhoenix.Endpoint."call (overridable 3)"/2
    (lookup_phoenix) lib/lookup_phoenix/endpoint.ex:1:
    (plug) lib/plug/adapters/cowboy/handler.ex:15: Plug.Adapters.Cowboy.Handler.upgrade/4
    (cowboy) /Users/carlson/dev/elixir/ns_umbrella/deps/cowboy/src/cowboy_protocol.erl:442: :cowboy_protocol.execute/4

The request in graphiQL is POST http://localhost:4001/graphql and the error message there is

SyntaxError: Unexpected token < in JSON at position 0

In web/router.ex I have the code

  forward "/graphiql", Absinthe.Plug.GraphiQL,
      schema: NoteApi.Schema

and in phoenix.router.ex I have added the code

  defmodule NoteApi.Router do
      use NoteApi.Web, :router
      # ...
      forward "/graphql", Absinthe.Plug,
        schema: NoteApi.Schema
      # ...

What would you suggest?

Do you have this on github somewhere? The reason is that no route found for POST /graphql really implies that your forward "/graphql", Absinthe.Plug.... line is not in your main router (this is not an absinthe issue, purely routing setup, normal Phoenix stuff).

Let me fiddle with it a bit – if I fail, I will push my graphQL branch to GitHub

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Well, my experiment didn’t work – here is the github link:

The code is in the graphQL branch — look in apps/lookupPhoenix

the forward code is at


Hmm, I’m not seeing a forward "/graphql", Absinthe.Plug.... line in your router file at:

Without that there the route is not exposed at /graphql, just like any other controller. :slight_smile:

I’m seeing this at lines 26-31 – were you in the graphQL branch?

  pipeline :api do
    plug :accepts, ["json"]

  forward "/graphiql", Absinthe.Plug.GraphiQL,
      schema: NoteApi.Schema

I’m seeing that too, but that is the forward for Absinthe.Plug.GraphiQL, which is the introspection helper path, but I’m not seeing a forward for forward "/graphql", Absinthe.Plug, schema: NoteApi.Schema, which is the actual path that you are having graphql communicate over?

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Some progress – I now understand your point about the “other” forward. I inserted it, and if I press PLAY in GraphiQL with an empty query and http://localhost:4001/graphql in GraphiQL, I get a good error message:

  "errors": [
      "message": "No operations provided."

and I see activity in the server log. However, if I use the query

  notes {

by analogy with, then I get the error message
Variables are invalid JSON: Unexpected token n in JSON at position 4.

Uhh, you see that in the output? If you check the browser console what was the actual body that was received? I don’t really use GraphiQL much so I’m wondering if there is a bug with that…

Now where are the absinthe devs, I know there are here somewhere…

Oh @benwilson512, where are you? :slight_smile:

Oops, operator error once again – I had pasted the query into the lower “Query Variables” pane. When I put it where it should be – above – all is good.

Trust me to make all possible mistakes :slight_smile:

Thanks so much for your help!

Ahh whoo, I thought I was going crazy there for a second, I could not figure out what was wrong. ^.^;

No problem! I quite like GraphQL, and Absinthe makes it awesome in Elixir. I’ve even called in to it from the back-end of the app at times too (yay report generation!). ^.^

It is indeed awesome … there is an Elm version as well, so I will use it for both Phoenix and Elm. Yay!

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