Unable to send headers in HTTPoison.get

sahilpaudel

My code snippet.

def make_request(path, params) do
    url = construct_url(path, params)
    headers = []

    case HTTPoison.get(url, headers) do
      {:ok, %HTTPoison.Response{status_code: 200, body: body}} -> 
        case Poison.decode(body) do
          {:ok, decoded} -> {:ok, decoded}
          {:error, error} ->{:error, error}
        end
      {:ok,  %HTTPoison.Response{status_code: status_code }} -> 
          {:error, status_code}
      {:error, error} -> {:error, error}
    end
  
  end

  defp construct_url(path, params) do
    path <> params
  end

the above code is working fine as expected however if I add

headers = [{“Accept-Encoding”,“gzip, deflate”}, {“Content-Type”, “application/json”}]

It gives error

{:error, {:invalid, <<31>>, 0}}

Anything I am doing it wrong here

9 comments

/phoenix #elixir-httpoison

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2020-08-05 09:29:05 UTC

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Jacek

I suppose this can be about compressing the data your receive. Can HTTPoison decompress it on its own? I had a quick look at documentation and didn’t find anything about that. Have you tested your code with the Content-Type header only?

Post #1

speeddragon

I think that issue could be about Poison.decode/1? Not sure if HTTPoison uncompresses the body. If not, you need to decompress it before you parse it, because ASCII 31 isn’t a valid string character. Not sure if this is the case.

The first 32 characters in the ASCII-table are unprintable control codes and are used to control peripherals such as printers.
https://www.ascii-code.com/

Post #2

jaydorsey

Long shot, but your 2nd snippet looks like it is using magic quotes? Is that what you’re using, or is that an artifact from something else?

Post #3

sahilpaudel

Yes, but It working with Content-Type header only.

Post #4

sahilpaudel

No, I am not using magic quotes just the code snippet is showing as magic quotes in this forum.

Post #5

sahilpaudel

Can you please help me more like how should I approach.

Post #6

Jacek

Then you can’t use simple Poison.decode(body) since Poison expects string whereas what you pass in is its compressed version. Try to decompress it first, sth like :zlib.gunzip(body), however first you should probably check if the response includes the following header: Content-Encoding: gzip

Post #7

sahilpaudel

okay, will try this out.

Content-Encoding: gzip is present

Thanks.

Post #8

sahilpaudel

Thanks @Jacek,

It worked, just pasting the code below for future reference if someone get stuck here.

def make_request(path, params) do
    url = construct_url(path, params)
    headers = [
      {"Accept-Encoding","gzip, deflate"},{"Content-Type", "application/json"}
    ]

    case HTTPoison.get(url, headers) do
      {:ok, %HTTPoison.Response{status_code: 200, headers: resp_headers, body: body}} -> 
      
        resp_headers
          |> check_if_gzipped
          |> unzip_body(body)
          |> decode_body

      {:ok,  %HTTPoison.Response{status_code: status_code }} -> 
          {:error, status_code}
      {:error, error} -> {:error, error}
    end
  end

  def check_if_gzipped(headers) do
    Enum.any?(headers, fn (kv) ->
      case kv do
        {"Content-Encoding", "gzip"} -> true
        {"content-encoding", "gzip"} -> true
        {"Content-Encoding", "x-gzip"} -> true
        _ -> false
      end
    end)
  end

  def decode_body(body) do
    case Poison.decode(body) do
      {:ok, decoded} -> {:ok, decoded}
      {:error, error} ->{:error, error}
    end
  end

  def unzip_body(true, body), do: :zlib.gunzip(body)

  def unzip_body(false, body), do: body

  defp construct_url(path, params) do
    path <> params
  end

Post #9

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