Http Gateway protocol return

Developers
1

Hi,

I’m having a problem with the Gateway protocol that I can’t figure out. I’m trying to use the response body streaming, but the streaming seems to fail somewhere after http_request_streaming_callback is called.

What happens:
My Canister sends a HttpResonse with a straeming strategy from the canister after its called
My http_request_streaming_callback function gets called only 1 time (I can see that from the logs) despite more tokens.
Then I get the HttpResponse in the client with only the part of the body which was in the original HttpResponse, so nothing from http_request_streaming_callback was added.

That both happens in the local replica and on the ic.

So my theory is that my StreamingCallbackHttpResponse is wrong somehow, but I can’t figure out how. When I query http_request_streaming_callback from dfx it returns

(
  record {
    token = opt record { key = "test.txt"; index = 2 : nat64 };
    body = blob "chunk2";
  },
)

the token is of the type:

type StreamingCallbackToken = record {
  key: text;
  index: nat64;
};

The result looks like it should in the spec (The Internet Computer Interface Specification | Internet Computer Home) I think?

I’m totally stuck, would be great if somebody could help me.

1 Like
2

Those are the types we successfully use for streaming:

import Assets "../CanisterAssets";
import Marketplace "../Marketplace";
import Sale "../Sale";
import Shuffle "../Shuffle";
import Tokens "../Tokens";

module {
  public type HeaderField = (Text, Text);
  public type HttpResponse = {
    status_code: Nat16;
    headers: [HeaderField];
    body: Blob;
    streaming_strategy: ?HttpStreamingStrategy;
  };
  public type HttpRequest = {
    method : Text;
    url : Text;
    headers : [HeaderField];
    body : Blob;
  };
  public type HttpStreamingCallbackToken =  {
    content_encoding: Text;
    index: Nat;
    key: Text;
    sha256: ?Blob;
  };

  public type HttpStreamingStrategy = {
    #Callback: {
        // start custom
        callback: shared () -> async ();
        // end custom
        token: HttpStreamingCallbackToken;
    };
  };

  public type HttpStreamingCallbackResponse = {
    body: Blob;
    token: ?HttpStreamingCallbackToken;
  };

  public type Dependencies = {
    _Assets : Assets.Factory;
    _Shuffle : Shuffle.Factory;
    _Tokens : Tokens.Factory;
    _Marketplace : Marketplace.Factory;
    _Sale : Sale.Factory;
  }
}
3

Hi @CarbonDev

Service worker dev here. You typings seem to be fine. Could you point me to a deployed canister that shows this behavior?

1 Like
4

Thanks for the quick response, this canister has the problem: 6cgjb-xaaaa-aaaag-aae6q-cai
For a request to https://6cgjb-xaaaa-aaaag-aae6q-cai.raw.ic0.app/test.txt it should stream back “hallochunk2chunk2”, but I only get “hallo”.

dfx canister --network=ic call 6cgjb-xaaaa-aaaag-aae6q-cai http_request '(record { method = "GET"; url = "/test.txt"; headers = vec {}; body = blob ""})'
returns

(
  record {
    body = blob "hallo";
    headers = vec {
      record { "Content-Length"; "5" };
      record { "Content-Type"; "text/raw" };
    };
    streaming_strategy = opt variant {
      Callback = record {
        token = record { key = "test.txt"; index = 1 : nat64 };
        callback = func "6cgjb-xaaaa-aaaag-aae6q-cai".http_request_streaming_callback;
      }
    };
    status_code = 200 : nat16;
  },
)

and
dfx canister --network=ic call 6cgjb-xaaaa-aaaag-aae6q-cai http_request_streaming_callback '(record { key = "test.txt"; index = 1})'

returns

(
  record {
    token = opt record { key = "test.txt"; index = 2 : nat64 };
    body = blob "chunk2";
  },
5

What does your HttpStreamingStrategy look like? I remember there was some weird bug for motoko asset canisters, don’t know if it has been fixed now but this lead to the weird callback type

callback: shared () -> async ();

When you then specify callback you do the following

// start custom
      let self: Principal = this;
      let canisterId: Text = Principal.toText(self);
      let canister = actor (canisterId) : actor { http_request_streaming_callback : shared () -> async () };
      // end custom

...

  streaming_strategy = ?#Callback({
            token = Option.unwrap(token);
            callback = canister.http_request_streaming_callback;
          });

...
6

I’m using rust with the Candid Func type for that

pub enum StreamingStrategy {
    Callback {
        callback: Func,
        token: StreamingCallbackToken,
    },
}

but I don’t think its a problem with the streaming strategy, because the callback gets called one time when I do a http request, it seems to fail somewhere after the first callback returns

1 Like
7

@CarbonDev: I see you are using the raw domain. Then unfortunately I cannot help you because this domain does not use the service worker (but icx-proxy instead).

@Daniel-Bloom: Any idea what’s wrong here?

1 Like
8

Hi, I still haven’t found a solution, could there be a bug in the gateway?

9

I’ve got a sample repo GitHub - peterpeterparker/icstreaming: https://forum.dfinity.org/t/http-request-streaming-callback-does-not-stream-chunks-anymore/11298 I used to test the streaming strategy with images on the local replica. Just upgraded it to dfx v0.11.2 and ran a test locally with a 3mb images and everything was alright - i.e. strategy delivered the image with mulitple chunks. So not a direct answer but, maybe by comparing the sample and your code you might notice something different?

1 Like