# Http Gateway protocol return

**URL:** <https://forum.dfinity.org/t/http-gateway-protocol-return/15535>\
**Category:** Developers\
**Tags:** candid\
**Created:** [September 20, 2022, 9:14am UTC](https://forum.dfinity.org/t/http-gateway-protocol-return/15535 "2022-09-20T09:14:40Z")\
**Posts on this page:** 9\
**Page:** 1

<div class="post-metadata">

**Author:** ![CarbonDev](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/carbondev/32/1826_2.png) [@CarbonDev](https://forum.dfinity.org/u/CarbonDev)\
**Post date:** [September 20, 2022, 9:14am UTC](https://forum.dfinity.org/t/http-gateway-protocol-return/15535/1 "2022-09-20T09:14:40Z")

</div>

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

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

```

the token is of the type:

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

```

The result looks like it should in the spec ([The Internet Computer Interface Specification | Internet Computer Home](https://internetcomputer.org/docs/current/references/ic-interface-spec#http-gateway-interface)) I think?

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

---

<div class="post-metadata">

**Author:** ![cryptoschindler](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/cryptoschindler/32/26_2.png) [@cryptoschindler](https://forum.dfinity.org/u/cryptoschindler)\
**Post date:** [September 20, 2022, 10:00am UTC](https://forum.dfinity.org/t/http-gateway-protocol-return/15535/2 "2022-09-20T10:00:15Z")

</div>

Those are the types we successfully use for streaming:

```auto
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;
  }
}

```

---

<div class="post-metadata">

**Author:** ![frederikrothenberger](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/frederikrothenberger/32/3826_2.png) [@frederikrothenberger](https://forum.dfinity.org/u/frederikrothenberger)\
**Post date:** [September 20, 2022, 10:17am UTC](https://forum.dfinity.org/t/http-gateway-protocol-return/15535/3 "2022-09-20T10:17:42Z")

</div>

Hi @CarbonDev

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

---

<div class="post-metadata">

**Author:** ![CarbonDev](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/carbondev/32/1826_2.png) [@CarbonDev](https://forum.dfinity.org/u/CarbonDev)\
**Post date:** [September 20, 2022, 10:38am UTC](https://forum.dfinity.org/t/http-gateway-protocol-return/15535/4 "2022-09-20T10:38:40Z")

</div>

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](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

```auto
(
  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

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

```

---

<div class="post-metadata">

**Author:** ![cryptoschindler](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/cryptoschindler/32/26_2.png) [@cryptoschindler](https://forum.dfinity.org/u/cryptoschindler)\
**Post date:** [September 20, 2022, 10:59am UTC](https://forum.dfinity.org/t/http-gateway-protocol-return/15535/5 "2022-09-20T10:59:27Z")

</div>

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

```auto
callback: shared () -> async ();

```

When you then specify callback you do the following

```auto
// 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;
          });

...

```

---

<div class="post-metadata">

**Author:** ![CarbonDev](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/carbondev/32/1826_2.png) [@CarbonDev](https://forum.dfinity.org/u/CarbonDev)\
**Post date:** [September 20, 2022, 11:03am UTC](https://forum.dfinity.org/t/http-gateway-protocol-return/15535/6 "2022-09-20T11:03:12Z")

</div>

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

```auto
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

---

<div class="post-metadata">

**Author:** ![frederikrothenberger](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/frederikrothenberger/32/3826_2.png) [@frederikrothenberger](https://forum.dfinity.org/u/frederikrothenberger)\
**Post date:** [September 20, 2022, 11:14am UTC](https://forum.dfinity.org/t/http-gateway-protocol-return/15535/7 "2022-09-20T11:14:00Z")

</div>

@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?

---

<div class="post-metadata">

**Author:** ![CarbonDev](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/carbondev/32/1826_2.png) [@CarbonDev](https://forum.dfinity.org/u/CarbonDev)\
**Post date:** [October 9, 2022, 4:54pm UTC](https://forum.dfinity.org/t/http-gateway-protocol-return/15535/8 "2022-10-09T16:54:59Z")

</div>

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

---

<div class="post-metadata">

**Author:** ![peterparker](https://avatars.discourse-cdn.com/v4/letter/p/b9bd4f/32.png) [@peterparker](https://forum.dfinity.org/u/peterparker)\
**Post date:** [October 9, 2022, 5:33pm UTC](https://forum.dfinity.org/t/http-gateway-protocol-return/15535/9 "2022-10-09T17:33:57Z")

</div>

I’ve got a sample repo [GitHub - peterpeterparker/icstreaming: https://forum.dfinity.org/t/http-request-streaming-callback-does-not-stream-chunks-anymore/11298](https://github.com/peterpeterparker/icstreaming) 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?