Clojurians Log v2

https://docs.oracle.com/javase/9/docs/api/java/lang/Process.html#pid--

nice

oontz oontz oontz

? ? ?

the sound of techno

In the #beginners channel? Perhaps more appropriate for #music or #off-topic ?

@mario.cordova.862 the first thing I would think about is to upgrade your JDK and garbage collector. Since you're still using concurrent mark and sweep (which has already been removed in recent JDK versions) it suggests you have something older - I suppose JDK 8?. JDK 11+ is perfectly fine to use these days and even if you cannot upgrade JDK I'd suggest you try G1 Gc (available in JDK 8 too. Also, are all the errors you mentioned happening about the time when the app gets unresponsive? For lightweight investigation I suggest using jcmd (much better in recent jDK versions) or similar tools to quickly inspect JVM (e.g. class histogram). You can also configure JVM to make a heap dump on OOM via -XX:+*HeapDumpOnOutOfMemoryError* (https://docs.oracle.com/javase/8/docs/technotes/guides/troubleshoot/clopts001.html) and examine it later e.g. via VisualVM (or Yourkit, Eclipse MAT, etc.)

Does anyone know how local variables are handled w.r.t. the GC in the case that clojures are maintained for a long time? What do I mean. I mean that if I have a function which has local variables whose values are HUGE data structures, and the function returns a clojure which DOES NOT reference those variables, is the GC able to deallocate them or is the entire stack-frame maintained. e.g., in this contrived example, the function returned only references p whose value is an integer, so m and q, can be deallocated. foo returns a function. Suppose that I hold onto that function, in an global variable. Is it my responsibility to deallocate m and q or will the GC do it for me?

(defn foo [f]
  (let [m (range 10000000)
        q (map inc m)
        p 12]
    (doseq [x q]
       (if (f q) (throw (ex-info ...))))
    (fn [g]
      (g p))))

A closure only retains values bound to its free variables. Both sequences are candidate for GC when foo returns.

Hello there. I'm trying to deploy a simple reagent app to heroku and I'm lost.

Following this guide doesn't work: https://devcenter.heroku.com/articles/using-node-js-with-clojure-and-clojurescript-applications

I get this Error: browser bootstrap used in incorrect target when I run heroku logs --tail

Wait, let me post more from the logs

2020-10-14T09:15:45.000000+00:00 app[api]: Build succeeded
2020-10-14T09:15:46.930655+00:00 heroku[web.1]: Starting process with command `node public/js/compiled/main.js`
2020-10-14T09:15:50.116752+00:00 app[web.1]: Setting JAVA_TOOL_OPTIONS defaults based on dyno size. Custom settings will override them.
2020-10-14T09:15:50.323232+00:00 app[web.1]: /app/public/js/compiled/main.js:1564
2020-10-14T09:15:50.323261+00:00 app[web.1]: throw new Error("browser bootstrap used in incorrect target");
2020-10-14T09:15:50.323262+00:00 app[web.1]: ^
2020-10-14T09:15:50.323263+00:00 app[web.1]: 
2020-10-14T09:15:50.323263+00:00 app[web.1]: Error: browser bootstrap used in incorrect target
2020-10-14T09:15:50.323264+00:00 app[web.1]: at Object.<anonymous> (/app/public/js/compiled/main.js:1564:11)
2020-10-14T09:15:50.323264+00:00 app[web.1]: at Object.<anonymous> (/app/public/js/compiled/main.js:1695:3)
2020-10-14T09:15:50.323264+00:00 app[web.1]: at Module._compile (internal/modules/cjs/loader.js:1015:30)
2020-10-14T09:15:50.323265+00:00 app[web.1]: at Object.Module._extensions..js (internal/modules/cjs/loader.js:1035:10)
2020-10-14T09:15:50.323265+00:00 app[web.1]: at Module.load (internal/modules/cjs/loader.js:879:32)
2020-10-14T09:15:50.323266+00:00 app[web.1]: at Function.Module._load (internal/modules/cjs/loader.js:724:14)
2020-10-14T09:15:50.323266+00:00 app[web.1]: at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)
2020-10-14T09:15:50.323266+00:00 app[web.1]: at internal/main/run_main_module.js:17:47
2020-10-14T09:15:50.376140+00:00 heroku[web.1]: Process exited with status 1
2020-10-14T09:15:50.412256+00:00 heroku[web.1]: State changed from starting to crashed
2020-10-14T09:15:51.886696+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=<http://evening-caverns-84275.herokuapp.com|evening-caverns-84275.herokuapp.com> request_id=b6bb93ae-1e8d-4b0f-ae8c-168effede9dc fwd="152.32.111.228" dyno= connect= service= status=503 bytes= protocol=https
2020-10-14T09:15:52.666612+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=<http://evening-caverns-84275.herokuapp.com|evening-caverns-84275.herokuapp.com> request_id=8031aa23-9a08-4d57-839f-0864b8b33081 fwd="152.32.111.228" dyno= connect= service= status=503 bytes= protocol=https

There's also an interesting version of fn* using :once true metadata for one-shot closures: https://stackoverflow.com/questions/23586710/what-is-fn-and-how-does-it-differ-from-fn

@leonoel, so closures contain only the values bound to free variables, not to the environment frames which contain those variables? If that's so, that's terrific.

Is this the sample app from the Heroku guide or your own reagent app?

Posting a link to the logs or adding them as a thread would be a preferred way to share, avoiding taking up lots of space in the main thread. Thanks

I essentially copied everything over

@signup867 You say a "simple Reagent" so I suppose you only target the front-end. If so you don't need NodeJS. The error seems your trying to run the Reagent/React compiled file with node which that cannot works. > 2020-10-14T09:15:46.930655+00:00 heroku[web.1]: Starting process with command node public/js/compiled/main.js If you tried this command on localhost, you'll get the same error. Node don't know about JS targeting the browser https://github.com/thheller/shadow-cljs/blob/b05b8f41afd45564ef7b9831a07201d09a5c4a07/src/main/shadow/boot/browser.js#L9

The sample reagent app deploys correctly, btw.

@signup867 The third part of the guide your mentionning talks about targeting NodeJS so you can run an CLJS app like this one https://github.com/PrestanceDesign/cljs-sample-express but not a Reagent one.

Ahh, hmm so does that mean I have to roll out my own server?

My only thought is how bootstrap is being pulled in. I use a CDN for CSS libraries. If using local libraries then check the path to them is correct when deployed on Heroku

No you have a bunch of options like Netlify, Github pages, Surge, even Netify if you want to stay with: https://create-react-app.dev/docs/deployment/

https://blog.heroku.com/deploying-react-with-zero-configuration

I think I remember having exchanged with you last month about Reagent on Netlify, right? > Ahh, hmm so does that mean I have to roll out my own server? Maybe i didn't fully understand your needs for Heroku, do you need a backend?

I don't think this behavior is documented anywhere but that's what the compiler actually does and it's very reasonable to rely on that IMO

Hey folks! I'm trying to monkey-patch a function in one of my deps. I've tried both (intern 'dep-ns dep-fn (defn ...... as well as:

(in-ns 'dep-ns)

(defn dep-fn ....

(in-ns 'my-ns)

clj
Clojure 1.10.1
user=> (require 'clojure.set)
nil
user=> (in-ns 'clojure.set)
#object[clojure.lang.Namespace 0x5a772895 "clojure.set"]
clojure.set=> (defn union [x y] (prn "i've changed this"))
#'clojure.set/union
clojure.set=> (in-ns 'user)
#object[clojure.lang.Namespace 0x1c12f3ee "user"]
user=> (clojure.set/union #{:a} #{:b})
"i've changed this"
nil
user=>

(ns my.ns
   (:require [clojure.set])
(in-ns 'clojure.set)
(defn union [x y] (prn "i've changed this"))
(in-ns 'my.ns)
(clojure.set/union #{:a} #{:b})

can you show the stack trace?

Yeah hang on

But when I move it into a function (e.g. wrap the above lines inside a function) and then evaluate that function at the REPL, it works

So it would seem that union is being called elsewhere after I redefine it, when the reader goes through?

Would that make sense?

what does the stack trace say?

it should tell you where its called with three args. and union has a much more rich signature than what we did just for example purposes

([] [s1] [s1 s2] [s1 s2 & sets])

Hi, clojure beginner here. i also use java and javascript at work.

i am on windows 7. i use lein.bat. but i read this new other tool, clj, which needs powershell. which one should i use? i am now learning the basics of clojure. i plan to create web apps and games in the future. the goal is to use clojure in the back end and clojurescript in the front end.

Sorry I have to run off but I appreciate the help and will let you know if I get to the bottom of it :)

spanish article https://medium.com/@jorgetovar621/clojure-101-619646e142a6

If you're stuck on Windows 7, you probably can't install a recent enough Powershell to be able to use the new Clojure CLI.

But ask in #clj-on-windows in case folks there know more about Windows 7 and Powershell than I do (very likely -- I'm a lot more familiar with Windows 10).

Hello everyone! Is there a more ‘elegant’ way to write this?

(defn remove-empty-key [m k]
  (if (empty? (k m))
    (dissoc m k)
    m))

(-> (get-from-db {:some :person})
	(remove-empty-key :kids))

I suppose the more elegant way would be not to add the key to the map in the first place if the value is empty.

It comes from DB. It returns things like:

{:name "Maria"
 :kids []}

But remove-empty-key is simple and straightforward, so I’d say that’s as elegant as anything else.

Hello everybody! I add one more Clojure implementation on the website http://www.todobackend.com/. This time using a more recent "trending" stack with Reitit and Next-jdbc. You can check the repo directly here: https://github.com/PrestanceDesign/todo-backend-clojure-reitit I think that can be useful. Cheers!

Thanks. Hmmm upgrade to Windows 10 with the new laptop will be next year. I guess lein.bat is sufficient for now to learn clojure basics.

A lot of the tutorials out there still use Leiningen as well as many of the books, so you should be fine with lein for learning. Windows is a bit of a second-class citizen in the Clojure world, so even with Windows 10, it's a lot easier to do everything using WSL2 which is how I work with Clojure: WSL2 with Ubuntu, Clojure CLI, use VcXsrv (Xlaunch) on Windows to support X11 apps, then run everything on WSL2, including my editor.