My first core.async program ... all works outside of the web app but barfs
once I put the functions inside a web container. I hope somebody in the
group can point to my obvious mistake...
The idea is that the function 'respond-within-sla' will give back a result
or a come back later message after N milliseconds. It is passed a number of
ms, three functions and the arguments for the final function ... which is
the one that should operate within the SLA.
(defn respond-within-sla [expected-result-milliseconds respond-ok
respond-later data-fetcher & args]
(let [data-channel (timeout expected-result-milliseconds)]
(go (if-let [data (<!! data-channel)]
((async/close! data-channel)
(respond-ok data))
(respond-later)))
(go
(>! data-channel (apply data-fetcher args)))))
To keep the volume of code to parse to a minimum I have made a few toy
functions that demonstrate the failure...
; test funcs
(defn ok [data]
(prn (str "send HTTP 200 ... got data " data)))
(defn later []
(prn (str "send HTTP 202 ... request received, come back later")))
(defn fetcher [arg1 arg2 arg3]
(prn (str "fetching data with args " arg1 " " arg2 " " arg3))
"response-data")
(defn failer [& args]
(Thread/sleep 1000)
(str "never gets here " args))
; test funcs
(defn ok [data]
(prn (str "send HTTP 200 ... got data " data)))
(defn later []
(prn (str "send HTTP 202 ... request received, come back later")))
(defn fetcher [arg1 arg2 arg3]
(prn (str "fetching data with args " arg1 " " arg2 " " arg3))
"response-data")
(defn failer [& args]
(Thread/sleep 1000)
(str "never gets here " args))
(defn generate-response [brand country resource]
(let [sla (or (env :sla-milliseconds) 100)]
(respond-within-sla sla ok later fetcher brand country resource)))
(defn generate-fail [brand country resource]
(let [sla (or (env :sla-milliseconds) 100)]
(respond-within-sla sla ok later failer brand country resource)))
>From within the REPL it all works fine...
(generate-response "A" "B" "C")
=> #<ManyToManyChannel
clojure.core.async.impl.channels.ManyToManyChannel@4b7ae3f7>
"fetching data with args A B C"
"send HTTP 200 ... got data response-data"
(generate-fail "A" "B" "C")
=> #<ManyToManyChannel
clojure.core.async.impl.channels.ManyToManyChannel@4eb8b5a9>
"send HTTP 202 ... request received, come back later"
Here is the compojure route..
(defroutes app
(GET "/:brand/:country/*" [brand country *]
(generate-response brand country *))
(ANY "*" []
(route/not-found "You must use a REST style to specify
brand and country keys in the URL")))
If I now start it up 'lein run' and try to exercise the functions from the
web server...
$ curl -I http://localhost:5000/A/B/D.jpg
HTTP/1.1 500 Server Error
Date: Fri, 26 Sep 2014 23:02:03 GMT
Content-Length: 0
Connection: close
Server: Jetty(7.6.8.v20121106)
And on the server I see this:
$ lein run
Compiling redirector.web
2014-09-27 01:01:48.426:INFO:oejs.Server:jetty-7.6.8.v20121106
2014-09-27 01:01:48.458:INFO:oejs.AbstractConnector:Started
SelectChannelConnector@0.0.0.0:5000
2014-09-27 01:02:03.535:WARN:oejs.AbstractHttpConnection:/A/B/D.jpg
java.lang.IllegalArgumentException: No implementation of method: :render of
protocol: #'compojure.response/Renderable found for class:
clojure.core.async.impl.channels.ManyToManyChannel
at clojure.core$_cache_protocol_fn.invoke(core_deftype.clj:544)
at compojure.response$fn__213$G__208__220.invoke(response.clj:9)
at compojure.core$make_route$fn__332.invoke(core.clj:100)
at compojure.core$if_route$fn__320.invoke(core.clj:46)
at compojure.core$if_method$fn__313.invoke(core.clj:33)
at compojure.core$routing$fn__338.invoke(core.clj:113)
at clojure.core$some.invoke(core.clj:2515)
at compojure.core$routing.doInvoke(core.clj:113)
at clojure.lang.RestFn.applyTo(RestFn.java:139)
at clojure.core$apply.invoke(core.clj:626)
at compojure.core$routes$fn__342.invoke(core.clj:118)
at clojure.lang.Var.invoke(Var.java:379)
at
ring.middleware.keyword_params$wrap_keyword_params$fn__534.invoke(keyword_params.clj:35)
at
ring.middleware.nested_params$wrap_nested_params$fn__576.invoke(nested_params.clj:84)
at ring.middleware.params$wrap_params$fn__507.invoke(params.clj:64)
at
ring.middleware.multipart_params$wrap_multipart_params$fn__612.invoke(multipart_params.clj:118)
at ring.middleware.flash$wrap_flash$fn__1286.invoke(flash.clj:35)
at ring.middleware.session$wrap_session$fn__1273.invoke(session.clj:98)
at ring.adapter.jetty$proxy_handler$fn__1426.invoke(jetty.clj:18)
at
ring.adapter.jetty.proxy$org.eclipse.jetty.server.handler.AbstractHandler$ff19274a.handle(Unknown
Source)
at
org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116)
at org.eclipse.jetty.server.Server.handle(Server.java:363)
at
org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:483)
at
org.eclipse.jetty.server.AbstractHttpConnection.headerComplete(AbstractHttpConnection.java:920)
at
org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:982)
at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:635)
"fetching data with args A B D.jpg"
at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:235)
at
org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:82)
at
org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:628)
at
org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:52)
at
org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:608)
at
org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:543)
at java.lang.Thread.run(Thread.java:744)
"send HTTP 200 ... got data response-data"
FYI I have tested the functions prior to adding the core.async code and
they all work fine from within Jetty and on Heroku.
It seems like somehow I am getting the wrong thing put into my response.
I am guessing that I have configured something wrong so here is my
project.clj
(defproject redirector "1.0.0-SNAPSHOT"
:description "Clojure HTTP redirector"
:url "http://redirector.herokuapp.com";
:license {:name "Eclipse Public License v1.0"
:url "http://www.eclipse.org/legal/epl-v10.html"}
:dependencies [[org.clojure/clojure "1.6.0"]
[compojure "1.1.9"]
[ring/ring-jetty-adapter "1.2.2"]
[com.novemberain/monger "2.0.0"]
[com.taoensso/carmine "2.7.0"]
[environ "0.5.0"]
[org.clojure/core.async "0.1.346.0-17112a-alpha"]]
:min-lein-version "2.0.0"
:plugins [[environ/environ.lein "0.2.1"]]
:hooks [environ.leiningen.hooks]
:main "redirector.web"
:aot :all
:uberjar-name "redirector-standalone.jar"
:profiles {:production {:env {:production true}}})
Any ideas, help would be greatly appreciated.
Thanks
Ray
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