I'm very interest in pedestal, I want to write a web server with core.async. is there any examples for pedestal with core.async? also, i'm curious about how to deal with jdbc with core.async.

thanks for any help.

Hi @doglooksgood, I’m glad to hear about your interest in Pedestal! I recommend reading through the Pedestal documentation, in particular the section on interceptor return values (http://pedestal.io/reference/interceptors#_interceptor_return_values). Unfortunately, I don’t have a sample project to point you to but I just created an issue (https://github.com/pedestal/pedestal-docs/issues/104) to track getting that done.

In a nutshell, Pedestal interceptors support going async. You just need to return a core.async channel which will yield an updated context

that's great, if I understand correct, pedestal can use core.async channel as a response. so basically i can use a go in handler and do everything I want?

I found on the document that I can return channel in interceptors

To be clear, you cannot return a channel as a response.

in other words

If you have a handler function, it can’t return a channel. But an interceptor can return a channel which will return a context map at some point

http://pedestal.io/reference/streaming#_using_a_core_async_channel_as_the_response this part looks confusing

Hm, I need to look into that because the following does not work

(defn home-page
  [request]
  (async/go
    (ring-resp/response "Hello World!")))

while this does

(def home-page
  (i/interceptor
   {:name ::home-page
    :enter (fn [ctx]
             (async/go
               (assoc ctx :response (ring-resp/response "Hello World!"))))}))

but I will follow up

ah

okay, I'll take a look

@doglooksgood I’m mistaken, when working with servlets you can return a channel as the response body

but not as the response

So this works

(defn home-page
  [request]
  (-> (async/go "Hello World!")
      ring-resp/response
      (ring-resp/content-type "text/html")))

But this behavior is specific to servlet interceptor chain providers

But I tend to use interceptors in these cases as opposed to handler functions

what does servlet means here?

use with some container like tomcat?

basically if you use jetty, tomcat or immutant to host your pedestal app

You don’t need to deploy your app as a war. You can start up a container to run it. Jetty is the popular choice and the default

(defn index [request]
  {:status 200
   :body (go "hello")})

(def routes
  (route/expand-routes
   #{["/index" :get index :route-name :index]}))

(def service-map
  (-> {::http/routes routes
       ::http/type :immutant
       ::http/port 8890}
      http/default-interceptors
      http/dev-interceptors
      http/create-server))

(mount/defstate server
  :start
  (http/start service-map)
  :stop
  (http/stop server))

(comment
  (mount/start #'server))

Hmm, change :immutant to :jetty

let me have a try

it should still fail

yes, I can't start when use jetty

very strange

That’s strange. I expect immutant to use the same servlet code as jetty in this case

hrm, it works for me though

@doglooksgood https://gist.github.com/ddeaguiar/9172555a94d75c749e4a059af6942918

async response with immutant

thanks!

np!

I'm afraid I can't find where is the key point?

async handler: https://gist.github.com/ddeaguiar/9172555a94d75c749e4a059af6942918#file-gistfile1-txt-L15-L19

app served by immutant https://gist.github.com/ddeaguiar/9172555a94d75c749e4a059af6942918#file-gistfile1-txt-L74

that works for me

thank you very much

👍

np!