Every time you call a function you allocate a new frame to the stack and might run into StackOverflowError but loop-recur mechanism uses tail call optimization which creates only one frame during the whole recursion

Use your memory profile dev tools to capture a memory profile and see where the RAM is being used

I am pretty sure you can avoid nesting thread in this case

(->> decision
     :updated_at
     tco/from-string
     (tf/unparse (tf/formatters :date)))

It does work

I think I am going to go with this way instead

personally I find it most readable

Yea I agree. Plus if the format of date changes then I have to remember to come inside this function and change the regex. Whereas in this case it should handle most changes.

deps.edn doesn't even build - in this case do you mean constructing separate classpaths or a separate build tool?

I would assume you'd have one deps file for the client process, and another for the server

This is kind of what I was getting at, I'm very new to all this so I'm trying to get the 'hello world' of setups with ansible and deps.edn, but struggling to figure it all out you know?

deps.edn is a tool for constructing a classpath, so I assume it would be useful for the ansible build for that specific usage. Often when packaging people want to set up a persistent cache of external artifacts on CI, and point the dep resolution to that cache

can I ask, what is a classpath?

in the jvm, the classpath is the list of locations used for finding resources, code, or class files

okay, and deps.edn is a way of saying 'here's a package, heres a list of files it brings to the table so use these

and stuff like that?

what deps.edn (or lein, or boot) do is take a list of dependencies, resolve their tree of transitive deps, download all the ones you don't have already to a cache, then point your java classpath to all those artifacts

I get it

thank you

it's not unusual in my experience for a clojure program in production to have ~20 explicit deps that are used directly, and hundreds of deps total once they are transitively resolved

in a running clojure program you can see your starting classpath with

> (System/getProperty "java.class.path")

Yeah my haskell programs had lots of dependencies

the reason I'm a little confused is because I've never done server/client applications in any language so I'm learning the theory and the practice slowly

right - so in theory your server and client could be 100% independent codebases and share nothing but an implicit agreement to use the same resource paths on some protocol

in practice, with clojure, one advantage is we can share the same data functions and configs between front end and back end code, to simplify that distributed interaction

(of course you can do this in any language if the server and client use the same runtime environment, but with clj / cljs we can do this with java backend and javascript browser client)

I don't mind having a server and client folder to seperate the codebases, but it would be nice to keep it all under the same project I guess?

at least until the client gets too big it should split off

are they server and client both jvm clojure? is it clj / cljs?

Yes

well, I haven't made anything yet. Right now I have a hello world reagent app

those were two different options

oh, clj / cljs OK

The client will be cljs

and the server clj I presume

The goal today is to just have some data on the server, just a string, and simply get it sent to the client to be displayed. Then stage two would be storing that in a database and learning how to get info out the db to the server, then serve it to the client

I don't want to do much, I just want the basic knack down and go from there

in my experience this structure was good: src/clj/foo/bar - everything under this path is server code, src/cljs/foo/bar - everything under this path is client src/cljc/foo/bar - everything under this path is code used by both client and server (custom data logic that both ends want, in particular)

for example a data validator would go in src/cljc so that client and server would implicitly agree on data format

with deps.edn I'd use one deps file to build deps for the jvm process that compiles the cljs to js, and another to build the deps for the server process

with leiningen it's easier to put all of this in one project file

I'd probably write server / client to make it easier for me but I take your point

Where would the location of these edn files go?

there's a strong convention to using clj / cljs / cljc as directory names

ooh okay

consider that you could also end up with java / js dirs

I did some work on braid.chat and server/client is how they were

that's fair, but breaking it up by file suffix simplifies things in the case where cljc can be loaded by both cljs and clj

I was wondering about this article: https://semaphoreci.com/community/tutorials/how-to-set-up-a-clojure-environment-with-ansible

It talks about setting up two roles, java and lein. how exactly do the two differ other than one is using a REPL and the other is just the program?

Or will they mostly do the ssame things? (I'm just thinking, how I'm going to do this when I'm not using leiningen so)

lein is a build tool - it constructs a class path, runs dev tasks, builds artifacts, etc.

java is the vm that actually runs clj code (even lein uses java to carry out the task you ask it for)

so in your case, you are trying to replace lein with deps.edn

you'll need to find some replacement for the lein uberjar task (which constructs an artifact to deploy), but otherwise deps.edn can construct a classpath and run a repl

okay thats great, so while the building the artifact isn't something I can do, I can still replace lein (I know I can do a repl so hopefully I can hook this into that?)

well lein is doing multiple roles, and the premise of deps.edn was to specialize away from that - so you've replaced some lein usecases but not all the lein usecases in that blogpost

okay gotcha

oh wait - that blog post is doing a bad thing - using lein to run a server process :/

which is good news for you because deps.edn is actually OK for running a server, lein isn;t :D

ahaha woohoo 😛

I assumed they would be using lein to build an uberjar - that's the sensible way to do ops with lein, but they are instead using the build tool to run the process in prod

it's the equivalent of shipping source + Makefile to your server, then running gcc before startup :P

im still trying to get my head around roles.. so, a role can do tasks, and sometimes you can have a common role to do common tasks. But in this post, the lein role just installs leiningen.. I don't really see where the magic happens

it isn't used to run leiningen?

its tough because this tutorial is working with code thats already written

---
# config/roles/lein/tasks/main.yml
# Install leiningen

- name: Copy lein script
  copy: src=lein dest=/usr/bin/lein owner=root group=root mode=755

They store a copy in the configuration and just copy it over, so I'm not really sure where in this post it starts the server? Like that's what I'm looking for at least

by the way thank you for talking about this with me I should have asked rather than bombard you with questions like I have 😞

nothing here looks specific to that codebase though: no matter how you code your app, you will end up running -main in some namespace to start a service

oh, I accidentally answered your question above: the convention is for program entry points to be named -main, so that is what starts the service

you can pass an argument to clojure.main to start the -main in a specific ns instead of a repl, and this is how one runs a clojure service if they aren't crazy like whoever put together this blogpost

there's a few reasons not to use lein to run on a server: lack of concrete redeployable artifact, useless parent process that starts up only to create your classpath, the wrong jvm settings for running a server

using deps.edn is luckily better behaved (but I'd still recommend making an uberjar or similar that allows recreating a specific deploy)

okay.. I'm trying to connect the dots as there's a lot of buzzwords but not much connection, or at least, its not so clear to me. Vagrant fires up some virtual machines. You give it a file name as a playbook which is a set of tasks given to a set of roles. Why is there a need for the leiningen role if it is just a single task. I assume when you switch from local to a server, you would edit your playbook and change the role from lein to java, but I'm trying to connect the playbook to the tasks

NB: often you'll get a much better deploy setup with clojure itself by finding the instructions for setting up a java project, then using an uberjar using clojure.main + your source where they would use a java fat jar

I know nothing about ansible roles - based on how they cargo cult the clojure stuff I wouldn't be surprised if they were using ansible weirdly too

So in his example, common role has a task called Install motd. I can see it, it places some data somewhere I assume for the program to grab. However, the playbook is also a list of things. What are these things? So, the only one I have is named Apply common configuration and looks like this:

---
# ansible/provision.yml
# Provision development environment

- name: Apply common configuration
  hosts: all
  sudo: yes
  roles:
    - common

I might actually go and write my own tutorial after I crack this as without a background in networking it's not so easy to get into this

maybe someone else here knows - or maybe someone on an Ansible forum

Yeah. Unfortunately there's no ansible channel as its not a clojure thing

but I'm going to need to ask further

thank you for your time though ❤️

I mean - maybe they have their own slack or IRC or whatever - big parts of what you need to figure out are not clojure related

np

yeah thats the struggle

it should be possible to break this up into domain specific parts: a generic ansible setup with a spot for "construct the artifacts your program needs on deploy" - an ansible expert could help there

then a clojure expert can tell you what goes in that spot

Finding itweird that it's going to require an expert to show me these things, I'm going through the ansible docs for a bit I think

I think one systemic issue is that at most one person needs to sort this out for a given project in most cases, and the task is done once per project and rarely needs to be updated

so there's a lot of "barely familiar" people, and few who really know it well

I get that.. Hopefully I can get the hang of it too so I can help others

https://www.ansible.com/resources/videos/quick-start-video?extIdCarryOver=true&sc_cid=701f2000001OH7YAAW

A role isn't what I thought it was. A Role is a self-contained playbook, so a playbook can contain tasks as well as the roles, and the reason I didn't see the tasks get called before is purely because they're called not by the playbook but by the role

The role isn't a category but an active thing

ah!