Clojurians Log v2

Hi! Using websocket-client to connect into websocket endpoint. This works just fine but I have a problem when target endpoint is not there when trying to make the connection

The connection creation just hangs forever, no errors or anything

I must be missing something

I think it is because websocket-client returns a deferred which I must first dereference to use it

And that dereferencing will hang until the connection is established, which it never manages to do since the target endpoint isn't available

So, is there a way to tell the websocket-client a connection timeout?

First, you can use (d/timeout _) to fail the deferred after timeout you need

OK, that was what I was more or less looking for I think

Second, there’s a ConnectionTimeout that fires when you cannot establish a TCP connection. The problem with Websocket protocol is that it requires one another round-trip to setup the stream: handshake request/response (see https://github.com/ztellman/aleph/pull/422 and https://github.com/netty/netty/issues/8841). If your server is “not there”, it fails. If your server unable to finish the handshake - it’s not managed by the Aleph for now (it would be after PR is merged tho’).

Right

Well in this case the target server is starting sometimes when I'm trying to establish connection

And it will get up eventually

(or if it doesn't then there's a bigger problem)

(-> (websocket-client ...)
    (d/timeout! 5e3 ::timeout)
    (d/chain' (fn [conn] (if-not (identical? ::timeout conn) conn (time/in 5e3 (websocket-client ...))))))

Out of my head, didn’t test it 🙂

hehe

TCP doesn’t have a solution for “server is starting” as a protocol, unfortunately 😉

Yeah I know

It is pretty obvious that I need to retry a bit later if it isn't just there

And do that for x times or give up

Correct

Hi! There is a lot of middleware for the HTTP client. Yet I don’t understand how to use them when sending HTTP calls. For example, when GET-ting a JSON file, how to finish with the body being parsed automatically? What option should I specify?

What I’ve tried:

@(http/get "<https://blockchain.info/latestblock>")

@(http/get "<https://blockchain.info/latestblock>" 
           {:middleware middleware/wrap-request})

Wrap-request is applied automatically

:as :json should work

let me try

what works! Does it mean, I can just pass the standard clj-http args?

Almost always :)

There’s a list of those things that are different

In README

when sending JSON body, with that work?

:form-params {:foo 42}
:content-type :json

Yep

Or :application/json

I don’t remember exactly

yes, it seems to be the full version (defmethod coerce-form-params :application/json

What about clj-http? Do they accept short version?

yes, the take just :content-type :json

Feel free to open an issue with “clj-http parity” tag :)

Or I’ll do that in the evening

but it’s not a problem, really. Instead, it would be nice to add more examples in readme because auto encode/decode JSON happens constantly

ok probably I’ll contribute

what is good about clj-http, you never remember all the options, but they’ve got rich base of examples, so you just copy and paste

Let me know if I can help with anything

The idea was that you can just copy example for clj-http and it works 😂

But, yeah... documentation is a weak point for now

And it requires constant attention

maybe I was confused with a docstring to aleph.http/request function which highlights only the basic args

but it’s clear now, thanks a lot!

My pleasure!