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welcome mount

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anatoly 2015-10-19 21:33:56 -04:00
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/target
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*.jar
*.class
/.lein-*
/.nrepl-port
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syntax: glob
target/**
classes/**
checkouts/**
pom.xml
pom.xml.asc
*.jar
*.class
/.lein-*
/.nrepl-port
.gitignore
.git/**

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# mount
riding side by side with [tools.namespace](https://github.com/clojure/tools.namespace) to manage application state during development.
## why?
Clojure is
* powerful
* simple
* and _fun_
Depending on how application state is managed during development, the above three superpowers can either stay,
go somewhat or go completely.
If Clojure REPL (i.e. `lein repl`, `boot repl`) fired up instantly, the need to reload application state
inside the REPL would go away. But at the moment, and for some time in the future, managing state by making it
reloadable within the same REPL session is important to retain all the Clojure superpowers.
[Here](http://blog.ndk.io/2014/02/25/clojure-bootstrapping.html) is a good break down on the Clojure REPL
startup time, and it is [not because of JVM](http://blog.ndk.io/2014/02/11/jvm-slow-startup.html).
`mount` is here to preserve all the Clojure superpowers while making application state enjoyably reloadable.
There is another Clojure superpower that `mount` is made to retain: Clojure community.
Pull request away, let's solve this thing!
## how
```clojure
(require '[mount :refer [defstate]])
```
### Creating State
Creating state is easy:
```clojure
(defstate conn :start (create-conn))
```
where `(create-conn)` is defined elsewhere, can be right above it.
In case this state needs to be cleaned / destryed between reloads, there is also a `:stop`
```clojure
(defstate conn :start (create-conn)
:stop (disconnect conn))
```
That is pretty much it. But wait, there is more.. this state is a top level being, which means it can be simply
`required` by other namespaces.
### Using State
For example let's say an `app` needs a connection above. No problem:
```clojure
(ns app
(:require [above :refer [conn]]))
```
where `above` is an arbitrary namespace that have the above state / connection.
## Dependencies
If the whole app is one big application context (or `system`), cross dependencies with a solid dependency graph
is an integral part of the system.
But if a state is a simple top level being, these beings can coexist with each other and with other
namespaces by being `required` instead.
If a managing state library requires a whole app buy-in, where everything is a bean or a component,
it is a framework, and dependency graph is usually quite large and complex,
since it has _everything_ (every piece of the application) in it.
But if stateful things are kept lean and low level (i.e. I/O, queues, etc.), dependency graphs are simple
and small, and everything else is just namespaces and functions: the way it shuold be.
### Talking States
There are of course direct dependecies that `mount` respects:
```clojure
(ns app.config
(:require [mount :refer [defstate]]))
(defstate app-config
:start (load-config "test/resources/config.edn"))
```
this app-config, being top level, can be used in other namespaces, including the ones that create states:
```clojure
(ns app.database
(:require [mount :refer [defstate]]
[app.config :refer [app-config]]))
(defstate conn :start (create-connection app-config))
```
[here](https://github.com/tolitius/mount/blob/master/test/mount/nyse.clj)
is an example of Datomic connection that "depends" on the app config.
## The Importance of Being Reloadable
`mount` has start and stop functions that will walk all the states created with `defstate` and start / stop them
accordingly: i.e. will call their `:start` and `:stop` defined functions.
This can be easily hooked up to [tool.namespace](https://github.com/clojure/tools.namespace), to make the whole
application reloadable. Here is a [dev.clj](https://github.com/tolitius/mount/blob/master/dev/dev.clj) as
an example.
## mount and develop!
`mount` comes with an example [app](https://github.com/tolitius/mount/blob/master/test/mount/app.clj)
that has two states:
* config, loaded from the files and refreshed on each `(reset)`
* datamic connection that uses the config to create connection
### Running New York Stock Exchange
To try it out, clone `mount`, get to REPL and switch to `(dev)`:
```clojure
$ lein repl
user=> (dev)
20:37:29.461 [nREPL-worker-0] INFO mount.config - loading config from test/resources/config.edn
20:37:29.477 [nREPL-worker-0] INFO mount.nyse - creating a connection to datomic: datomic:mem://mount
dev=>
```
everything is started and can be played with:
```clojure
dev=> (create-nyse-schema)
dev=> (add-order "GOOG" 665.51M 665.59M 100)
dev=> (add-order "GOOG" 665.50M 665.58M 300)
dev=> (find-orders "GOOG")
({:db/id 17592186045418, :order/symbol "GOOG", :order/bid 665.51M, :order/qty 100, :order/offer 665.59M}
{:db/id 17592186045420, :order/symbol "GOOG", :order/bid 665.50M, :order/qty 300, :order/offer 665.58M})
```
once something changed in the code, or you just need to reload everything `(reset)`:
```clojure
dev=> (reset)
20:38:43.244 [nREPL-worker-1] INFO mount.nyse - disconnecting from datomic:mem://mount
:reloading (mount mount.config mount.nyse mount.utils.datomic mount.app dev)
20:38:43.287 [nREPL-worker-1] INFO mount.config - loading config from test/resources/config.edn
20:38:43.296 [nREPL-worker-1] INFO mount.nyse - creating a connection to datomic: datomic:mem://mount
:ready
```
notice that it stopped and started again.
Since the schema was not there roght after the start, it is not there now as well:
```clojure
dev=> (find-orders "GOOG")
IllegalArgumentExceptionInfo :db.error/not-an-entity Unable to resolve entity: :order/symbol datomic.error/arg (error.clj:57)
```
hence the app is in its "clean" state, and ready to rock and roll as right after the REPL started:
```clojure
dev=> (create-nyse-schema)
dev=> (find-orders "GOOG")
()
dev=> (add-order "AAPL" 111.712M 111.811M 250)
dev=> (find-orders "AAPL")
({:db/id 17592186045418, :order/symbol "AAPL", :order/bid 111.712M, :order/qty 250, :order/offer 111.811M})
```
## license
Copyright © 2015 tolitius
Distributed under the Eclipse Public License either version 1.0 or (at
your option) any later version.

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(ns dev
"Tools for interactive development with the REPL. This file should
not be included in a production build of the application."
;; (:use [cljs.repl :only [repl]]
;; [cljs.repl.browser :only [repl-env]])
(:require [clojure.java.io :as io]
[clojure.java.javadoc :refer [javadoc]]
[clojure.pprint :refer [pprint]]
[clojure.reflect :refer [reflect]]
[clojure.repl :refer [apropos dir doc find-doc pst source]]
[clojure.set :as set]
[clojure.string :as str]
[clojure.test :as test]
;; [clojure.core.async :refer [>!! <!! >! <! go-loop alt! timeout]]
[clojure.tools.namespace.repl :refer [refresh refresh-all]]
[mount.app :refer :all]
[mount :as app]))
(defn start []
(app/start))
(defn stop []
(app/stop))
(defn go
"Initializes and starts the system running."
[]
;; (refresh) would redefine "defstates" which will call "start" on them
:ready)
(defn reset
"Stops the system, reloads modified source files, and restarts it."
[]
(stop)
(refresh :after 'dev/go))

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(defn dev
[]
(require 'dev)
(in-ns 'dev))

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# Introduction to statuo
TODO: write [great documentation](http://jacobian.org/writing/what-to-write/)

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(defproject mount "0.1.0-SNAPSHOT"
:description "managing Clojure app state since (reset)"
:url "https://github.com/tolitius/mount"
:license {:name "Eclipse Public License"
:url "http://www.eclipse.org/legal/epl-v10.html"}
:source-paths ["src" "src/mount"]
:dependencies [[org.clojure/clojure "1.7.0"]]
:profiles {:dev {:source-paths ["dev"]
:dependencies [[yesql "0.5.1"]
[org.clojure/tools.namespace "0.2.11"]
[com.datomic/datomic-free "0.9.5327" :exclusions [joda-time]]
[ch.qos.logback/logback-classic "1.1.3"]
[org.clojure/tools.logging "0.3.1"]]}})

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(ns mount
(:require [clojure.tools.macro :as macro]
[clojure.tools.logging :refer [info]]))
;;TODO validate stop and the fact that start and stop are fns
(defn- validate [{:keys [start stop]}]
(when-not start
(throw (IllegalArgumentException. "can't start a stateful thing without a start function. (i.e. missing :start fn)")))
{:start start :stop stop})
(defmacro defstate [state & body]
(let [[state [c cf d df]] (macro/name-with-attributes state body)
{:keys [start stop]} (validate {c cf d df})]
(let [s-meta (-> {:state (str `~state) :start `(fn [] (~@start))}
(cond-> df (assoc :stop `(fn [] (~@stop)))))]
`(defonce ~(with-meta state (merge (meta state) s-meta))
(~@start)))))
(defn- up [{:keys [ns name start]}]
(intern ns (symbol name) (start)))
(defn- down [{:keys [stop]}]
(when stop
(stop)))
(defn- f-states [f]
(->> (all-ns)
(mapcat ns-interns)
(map second)
(filter #(:state (meta %)))
(map (comp f meta))))
(defn start []
(doall
(f-states up)))
(defn stop []
(doall
(f-states down)))

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(ns mount.app
(:require [datomic.api :as d]
[mount.utils.datomic :refer [touch]]
[mount.config :refer [app-config]]
[mount.nyse :as nyse]))
(defn create-schema [conn]
(let [schema [{:db/id #db/id [:db.part/db]
:db/ident :order/symbol
:db/valueType :db.type/string
:db/cardinality :db.cardinality/one
:db/index true
:db.install/_attribute :db.part/db}
{:db/id #db/id [:db.part/db]
:db/ident :order/bid
:db/valueType :db.type/bigdec
:db/cardinality :db.cardinality/one
:db.install/_attribute :db.part/db}
{:db/id #db/id [:db.part/db]
:db/ident :order/qty
:db/valueType :db.type/long
:db/cardinality :db.cardinality/one
:db.install/_attribute :db.part/db}
{:db/id #db/id [:db.part/db]
:db/ident :order/offer
:db/valueType :db.type/bigdec
:db/cardinality :db.cardinality/one
:db.install/_attribute :db.part/db}]]
@(d/transact conn schema)))
(defn add-order [ticker bid offer qty] ;; can take connection as param
@(d/transact nyse/conn [{:db/id (d/tempid :db.part/user)
:order/symbol ticker
:order/bid bid
:order/offer offer
:order/qty qty}]))
(defn find-orders [ticker] ;; can take connection as param
(let [orders (d/q '[:find ?e :in $ ?ticker
:where [?e :order/symbol ?ticker]]
(d/db nyse/conn) ticker)]
(touch nyse/conn orders)))
(defn create-nyse-schema []
(create-schema nyse/conn))

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(ns mount.config
(:require [mount :refer [defstate]]
[clojure.edn :as edn]
[clojure.tools.logging :refer [info]]))
(defn load-config [path]
(info "loading config from" path)
(-> path
slurp
edn/read-string))
(defstate app-config
:start (load-config "test/resources/config.edn"))

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(ns mount.nyse
(:require [mount :refer [defstate]]
[mount.config :refer [app-config]]
[datomic.api :as d]
[clojure.tools.logging :refer [info]]))
(defn- new-connection [conf]
(info "conf: " conf)
(let [uri (get-in conf [:datomic :uri])]
(info "creating a connection to datomic:" uri)
(d/create-database uri)
(d/connect uri)))
(defn disconnect [conf conn]
(let [uri (get-in conf [:datomic :uri])]
(info "disconnecting from " uri)
(.release conn) ;; usually it's no released, here just to illustrate the access to connection on (stop)
(d/delete-database uri)))
(defstate conn :start (new-connection app-config)
:stop (disconnect app-config conn))

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(ns mount.utils.datomic
(:require [datomic.api :as d]))
(defn entity [conn id]
(d/entity (d/db conn) id))
(defn touch [conn results]
"takes 'entity ids' results from a query
e.g. '#{[272678883689461] [272678883689462] [272678883689459] [272678883689457]}'"
(let [e (partial entity conn)]
(map #(-> % first e d/touch) results)))

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{:datomic
{:uri "datomic:mem://mount"}
:h2
{:classname "org.h2.Driver"
:subprotocol "h2"
:subname "jdbc:h2:mem:mount"
:user "sa"
:password ""}
:rabbit
{:host "192.168.1.1"
:port 5672
:api-port 15672
:node "jabit"
:exchange "foo"
:queue "r-queue"
:routing-key ""
:auto-delete-q? true
:exchange-type "direct"
:vhost "/captoman"
:username "guest"
:password "guest"}}