Mint adapter cannot upload more than 65535 bytes on HTTP/2

[jayjun]

• tesla 1.3.3
• mint 1.1.0

To reproduce,

client = Tesla.client([], Tesla.Adapter.Mint)
Tesla.post(client, "https://httpbin.org/post", String.duplicate("0", 65536))

returns :exceeds_window_size error.

%Mint.HTTPError{
  module: Mint.HTTP2,
  reason: {:exceeds_window_size, :connection, 65535}
}

Full error

{:error,
 %Mint.HTTP2{
   buffer: <<0, 0, 4, 8, 0, 0, 0, 0, 0, 127, 255, 0, 0>>,
   client_settings: %{
     enable_push: true,
     max_concurrent_streams: 100,
     max_frame_size: 16384
   },
   client_settings_queue: {[[]], []},
   decode_table: %Mint.HTTP2.HPACK.Table{
     entries: [],
     length: 0,
     max_table_size: 4096,
     size: 0
   },
   encode_table: %Mint.HTTP2.HPACK.Table{
     entries: [],
     length: 0,
     max_table_size: 4096,
     size: 0
   },
   headers_being_processed: nil,
   hostname: "httpbin.org",
   mode: :active,
   next_stream_id: 5,
   open_client_stream_count: 1,
   open_server_stream_count: 0,
   ping_queue: {[], []},
   port: 443,
   private: %{},
   ref_to_stream_id: %{#Reference<0.4203460067.3989045250.44202> => 3},
   scheme: "https",
   server_settings: %{
     enable_push: true,
     initial_window_size: 65536,
     max_concurrent_streams: 128,
     max_frame_size: 16777215,
     max_header_list_size: :infinity
   },
   socket: {:sslsocket, {:gen_tcp, #Port<0.2811>, :tls_connection, :undefined},
    [#PID<0.1699.0>, #PID<0.1698.0>]},
   state: :open,
   streams: %{
     3 => %{
       id: 3,
       received_first_headers?: false,
       ref: #Reference<0.4203460067.3989045250.44202>,
       state: :open,
       window_size: 65536
     }
   },
   transport: Mint.Core.Transport.SSL,
   window_size: 65535
 },
 %Mint.HTTPError{
   module: Mint.HTTP2,
   reason: {:exceeds_window_size, :connection, 65535}
 }}

That is because window_size: 65535 is set initially, according to standard, but is not updated when the server sends WINDOW_UPDATE frames.

Each time Tesla sends data using Mint.HTTP.stream_request_body, the window size is decremented by data’s size. When the window size gets low, the server sends WINDOW_UPDATE frames to increment the connection’s window size. Calling Mint.HTTP.stream to read responses will automatically do this.

https://github.com/teamon/tesla/blob/754d4a6ffe41ff508fc7fa460508a40e965b2960/lib/tesla/adapter/mint.ex#L178-L187

However, the adapter repeatedly calls Mint.HTTP.stream_request_body without calling Mint.HTTP.stream so the window size hits zero and Mint errors.

[teamon]

Hi @jayjun, thanks for reporting the issue. Would you be able to provide the fix as a PR?

[jayjun]

Unfortunately not at the moment because I don’t have the bandwidth to learn Tesla internals, Mint and HTTP/2 enough to do a good job.

[slapers]

If someone hits this error until this is solved, as a temporary solution you can force the connection to be http1 by adding some options for the adapter:

Tesla.post(client, url, content, [opts: [adapter: [protocols: [:http1]]]])

[sheharyarn]

Bumping this since this is a serious issue!

Thank you for all the work on Tesla!

[yordis]

@sheharyarn do you have some bandwidth to tackle the issue?

[sheharyarn]

@yordis I can definitely try, but would need someone to push me in the right direction. While I have a good amount of experience with Tesla in general, I don't have enough experience with Mint's internals.