Clojurians Log v2

yup, I wrote a macro with logging.

If you want to see what a variant of default options would be for logging:

(! 1574)-> clojure -M:rebel:test:dev/repl
Downloading: com/bhauman/rebel-readline/maven-metadata.xml from clojars
Selected port 61666 for the Socket REPL...
Starting Rebel Readline as the REPL...
[Rebel readline] Type :repl/help for online help info
dev=> (require '[next.jdbc :as jdbc] :reload-all)
nil
dev=> (def db-spec {:dbtype "h2:mem" :dbname "example"})
#'dev/db-spec
dev=> (def ds (jdbc/get-datasource db-spec))
#'dev/ds
dev=> (def lds (jdbc/with-logging ds println))
#'dev/lds
dev=> (jdbc/execute-one! lds ["create table foo (name varchar(32))"])
execute-one! [create table foo (name varchar(32))]
#:next.jdbc{:update-count 0}
dev=> (require '[next.jdbc.sql :as sql])
nil
dev=> (sql/insert! lds :foo {:name "Sean"})
execute-one! [INSERT INTO foo (name) VALUES (?) Sean]
nil
dev=> (sql/insert! lds :foo {:name "Piyer"})
execute-one! [INSERT INTO foo (name) VALUES (?) Piyer]
nil
dev=> (sql/find-by-keys lds :foo {:name "Piyer"})
execute! [SELECT * FROM foo WHERE name = ? Piyer]
[#:FOO{:NAME "Piyer"}]
dev=> 

That’s available on develop as an experiment, if you want to try it out via :git/url.

Why can’t you get-in a list within a map? (get-in account [:parties 0 :id]) where account is

{:id "164684366"
 :origin "neuromancer"
 :balance 1000, 
 :parties (list {:firstName "party-fn-60390295" :lastName "party-ln-60390295" :id 99})}

(get-in
 {:id      "164684366"
  :origin  "neuromancer"
  :balance 1000,
  :parties (vector {:firstName "party-fn-60390295" :lastName "party-ln-60390295" :id 99})}
 [:parties 0 :id])

From a design perspective, the reason why it doesn’t work with list is because lists do not have an efficient lookup by index (that’s just my guess).

As a general rule, I try to stick to vectors everywhere, unless lists are specifically needed (i.e. you need to append to the front efficiently, but that’s rare).

gotchya, been meaning to look into when to use vectors vs lists

;if you really need a list
(let [lookup-f (comp :id #(nth % 0) :parties)]
 (lookup-f
  {:id      "164684366"
   :origin  "neuromancer"
   :balance 1000,
   :parties (list {:firstName "party-fn-60390295" :lastName "party-ln-60390295" :id 99})}))
;=> 99

^^ If you really need to use a list.

I’ll probably change to vector, but I appreciate reading your code

But watch out, nth is an O(n) operation on a list.

For short lists, likely more than fine.

What’s considered short?

Haha, good question 🙂

Whatever doesn’t make people complain that things are taking too long 😝

My gut feeling is that I would be comfortable up to 1000 items.

And again, depends if that code is on a “hot path”.

Are you calling it once an hour, or thousands of times per second?

For now, once in a while, so nothing bad. But I’ll keep that in mind using lists from now on, and the length of the list will never be more than like 5 so I’d be good either way probably

It is considered a code smell, but I’m of the opinion that rules can be broken, if you know what you’re doing.

For lists of 5, you should never run into a problem IMO.

Btw one last improvement to that code:

;if you really need a list
(let [lookup-f (comp :id #(nth % 0 nil) :parties)]
 (lookup-f
  {:id      "164684366"
   :origin  "neuromancer"
   :balance 1000,
   :parties (list {:firstName "party-fn-60390295" :lastName "party-ln-60390295" :id 99})}))
;=> 99

(so it doesn’t throw an “Index out of bounds exception” if it can’t find the desired index) added a “not found” argument in the nth call

@titanroark This page has good background information on why you might want vector vs list etc https://clojure.org/reference/data_structures#Collections

Do s/fdef specs get written out in the same file as the concrete function or is it usually kept in a test file in the test directory of a project?

I put them in the same file right above the function

And because of the registry system in specs, the definition you create can be referred to with its associated atom? That's basically my understanding right now.

nice! does that log via log4j2 or simple stdout?

@munichlinux You supply the logging function(s) so it can do whatever you want.

(I’ve updated it a bit since the post above — see my note in #sql)

@rosenjcb Not sure what you mean by “atom” there — s/fdef specs are referenced by a fully-qualified symbol which is the name of the function they apply to (`s/def` specs are referenced by a fully-qualified keyword).

❤️

@seancorfield yup "atom" was the wrong term.

How do I add a ~/.lein/profiles.clj file?

you can literally just create the file

but most people consider it a bad idea (it introduces local failures that won't be reflected on other's setups)

I mostly just want to add stuff like https://github.com/venantius/ultra/ for better error messages

So I just create an empty profiles.clj file and add {:user {:plugins [[venantius/ultra "0.6.0"]]}} to it and it will work?

that's how it works yes

Awesome, thank you. I appreciate the feedback on local failures not being reflected on other’s setups, but at least for now I’m not working on a team and I still have a lot of learning to do before I do something like upload a library so I’m not super worried about that

i think as long as you're only using libraries like ultra (that don't modify a given program's execution, only what's printed to your console), you should be fine

it comes up a lot when a beginner dips their feet into clojure, adds some weird tooling config in profiles.clj, goes away for a bit, then come back to learning clojure and show up here with weird errors, having forgotten they even set up profiles.clj

@nbtheduke I've seen really weird errors caused by the kind of "magic" di tricks those libs use

oh word? that's annoying

I guess it's not super frequent, but it stands out in memory by how confusing it was

yeah, good at least to be aware

Interesting. I’ll make note of remembering what’s in my profiles.clj file.

or just remember to remove / move it if you hit weird errors

So I basically want to use Specter on just about every project. Since that modifies code, you would suggest not doing that in my profiles.clj and just manually putting it in my project.clj each time?

right, code you use for application logic does not belong in profiles.clj if you ever intend others to interact with that code in any way

and even if you are the only one using the code, it adds a weird failure point - change profiles.clj and now projects stop working

the best thing about a project manifest like lein's project.clj is that it works as a declarative standalone configuration which unambiguously points to versioned resources, using user level config tends to interfere with that

Okay, that makes sense to me. Thanks!

can someone point me to resources about concurrency optimizations in java (and/or clj)? along the lines of writing a new executor to minimize time wasted on threads waiting on io and maximize throughput

any suggested reading on working with both java interop and native form error handling, errors as data, and best practices for composing while considering error handling?

maximizing throughput is usually highly workload dependent, so it's hard to offer suggestions without knowing what the use case is. A good starting point might be the Fork/join framework, https://docs.oracle.com/javase/tutorial/essential/concurrency/forkjoin.html

does anyone know if there's a way to extract more info from that Parse object somehow? does it contain any? Instaparse and I tried looking at the docs but maybe I'm not so good at reading https://gist.github.com/Sose/9a68caa42bd0e25fe70e9d353b3503fe

the usage.txt file shows how I'm trying to use it

ahh apparently I can print it atleast.. but if I wanted to show something in my cljs web interface?

strjust gives me "[object Object]"

This is an interesting topic. First I think we need to decide what you mean by error. E.g 1. The system can't responsible continue. 2. There is a business case that's unaccounted for and we need to alert a human. Moving to a different topic, if a java lib is throwing unrecoverable execptions, then I assume we're discussing how to log that information. What else is there to do? Recovery? That seems rather specific to what's being done. Finally, I would assume composing error handling is similar to composing other functions. E.g a ring middle ware function might have a case where the db is down so it can't retrieve the file, at this point it's up to you too decided. What status code, etc..

also I need to figure out how to allow arg names in commands while inside a function def but not outside them :thinking-face:

or just let users introduce variables

What started as a fun project to practice Clojure & Clojurescript is turning into mainly a challenge in interpreting a custom programming language... I wish I had some kind of education in implementing languages 😄

@djonih sounds very intriguing... there is an #instaparse channel if you have specific questions and want to summon the masters... Do you have a clear idea of the desired result and what it looks like?

Losing my marbles 😄

@sova I just want to know how to get more data, any data, from the Parse object that I get when the parse is invalid. I noticed I can (print it)in the repl to see an error message but how to get that message out of it otherwise?

Great question. Let me do some snooping. In the intermediate time, are you familiar with the excellent online version of instaparse? http://instaparse-live.matt.is/

That spits out errors automatically as you change the input. There is probably the source code for that somewhere

ah, yeah that's what I want basically..

@djonih https://github.com/mhuebert/instaparse-live/blob/master/src/app/compute.cljs#L52

https://github.com/mhuebert/instaparse-live I guess this is it? I think I'll be able to find it

Yeah I did some digging, I think what you want is in app/compute.cljs with "insta/get-failure"

anyway, it's around there somewhere ^.^ @djonih

happy hacking

Ahh, (pr-str)is what I want I guess

better than docs is working code to examine

thank you so much for helping!

Oh yeah, there are some small caveats with clojurescript. pr-str for example.

i don't know if there is a good list anywhere, that would be helpful.

(of cljs caveats)

In most all cases i've encountered, it would be #2 - i'm looking to capture either an unchecked java exception or a business case error for user reporting. I'm most interested in function composing. Do i pass error conditions around as a map with one or more keys, check for that key in peer functions, etc

ah also found out about (cljs.pprint/pprint) ... can actually see the object and its keys and values that way

or I guess I should've tried (keys result) too but I completely forgot about that function and I didn't realize I could do that on a weird object thing