I would like to retry HTTPS requests with HTTP requests if there is a `ConnectException`. Is the cod...

# ktor

[Thomas]

I would like to retry HTTPS requests with HTTP requests if there is a ConnectException. Is the code below correct or is there a better way to do this?

client.install("HttpsToHttp") {
    requestPipeline.intercept(HttpRequestPipeline.Before) {
        val requestBuilder = this.context
        try {
            proceedWith(it)
        } catch (exception: ConnectException) {
            if (requestBuilder.url.protocol == URLProtocol.HTTPS) {
                requestBuilder.url.protocol = URLProtocol.HTTP
                proceedWith(requestPipeline.execute(requestBuilder, it)) // not sure if this is correct
            } else {
                throw exception
            }
        }
    }
}

[e5l]

Hi @Thomas, sorry for the delay. It doesn't look right for me. Probably you can grab idea from the HttpRedirect feature: https://github.com/ktorio/ktor/blob/b66e3072865de0bff9e6514a5d19cfc404985156/ktor-client/ktor-client-core/common/src/io/ktor/client/features/HttpRedirect.kt#L86

[Thomas]

Hi @e5l, thanks for the link. I tried to create a HttpSend interceptor like below, but the code does not appear to be reached. I think the ssl exception is thrown earlier.

clientConfig.install("HttpsToHttp") {
    feature(HttpSend)!!.intercept { origin, context ->
        // the code below is not even reached.
        try {
            execute(context)
        } catch (throwable: Throwable) {
            TODO()
        }
    }
}

[e5l]

could you share the stacktrace?

[Thomas]

Here is the exception. Looks like it is thrown here: https://github.com/ktorio/ktor/blob/b66e3072865de0bff9e6514a5d19cfc404985156/ktor-client/ktor-client-core/common/src/io/ktor/client/features/HttpSend.kt#L79
So that means it does not reach the interceptors a few lines lower in HttpSend.

Untitled

[e5l]

But it should. Could you try to catch the exception in the receivePipeline ? You can find it in client.receivePipeline

[Thomas]

Do you mean like this?

clientConfig.install("HttpsToHttp") {
    receivePipeline.intercept(HttpReceivePipeline.Before) {
        TODO()
    }
}

The TODO() is not reached here either, the ssl exception is still thrown like before

[e5l]

nope, I mean intercept both independently

[e5l]

receivePipeline.intercept(HttpReceivePipeline.Before) {
        try {
            proceedWith(it)
        } catch(cause: Throwable) {
        }
    }
}

[Thomas]

If I add your code then I can still not catch the exception. I don’t understand what you mean by intercepting both independently. Do you mean I need to intercept HttpSend like before and add the code in your comment using the receivePipeline as well?

[e5l]

Exactly

[Thomas]

So like this?

[Thomas]

None of them catches the ssl exception in the catch block where I added the TODO

[Thomas]

The ssl exception is thrown here (see stack trace in comments above) so how could it ever reach the interceptors that are called a few lines lower?

[e5l]

Trying to figure it out.

[e5l]

It turns out that you can catch the exception in sendPipeline Before phase

[e5l]

sendPipeline.intercept(HttpReceivePipeline.Before) {
        try {
            proceedWith(it)
        } catch(cause: Throwable) {
        }
    }
}

[Thomas]

@e5l that is great! I can confirm it catches the exception. Do you know how to retry the request (after modifying it) in the catch block?

[Thomas]

I don’t think it is possible to call proceedWith a second time. Is there a way to retry the request?

[e5l]

Nope, but you can store the flag outside sendPipeline interceptor and check it in send feature interceptor

[Thomas]

I tried the following but it throws an IllegalStateException with error message check failed.

[Thomas]

Untitled.kt

Untitled.kt

[Thomas]

Untitled

Untitled

[Thomas]

Hi @e5l, do you know why the above fails with IllegalStateException?