re-frame-10x/README.md

# re-frame-trace

`re-frame-trace` let's you instrument, and then inspect, the inner workings of a running `re-frame` application. It presents as a programmer's dashboard, delivering curated insight and illumination.

### It Is Epoch Oriented

`re-frame` applications are computationally regular. First an event happens,
and then boom, boom, boom go a series of known computational steps (aka dominoes), 
in a known order. When this chain reaction completes, 
a `re-frame` app enters a quiescent state waiting for another 
event to kick off the next iteration of the same process.

Each `re-frame` event and its consequent computation forms a bounded "epoch" 
which can be inspected, analysed and understood independently of other epochs. This 
tool is epoch-oriented - it shows you one at a time.

And, yes, it has "time travel debugger" capabilities - you can go 
[backwards and forwards through epochs](https://condenaststore.com/featured/the-conga-line-of-past-selves-a-string-liana-finck.html) - but that's really not the most interesting or powerful aspect of what `re-frame-trace` delivers.

### It Is About Trace Data

As it runs, `re-frame` logs "trace" as data, and this provides an x-ray (MRI?) of your app's inner
functioning. At its most basic level, `re-frame-trace` is a consumer, processor and presenter
of trace data.

### It Is About The Data Flow

While re-frame is a functional framework, it is
strongly defined by its "data oriented" design. `re-frame`
"flows" data, in a loop, through the functions you provide.
To understand what is happening in a `re-frame` app, you must understand
what data is "happening".

### It Is Always About The Data

So, clearly, data is at the core of `re-frame-trace` for both of the reasons 
just outlined, but its importance is even more base and fundamental than that.

Each time you put a `println` into your program, you are printing out what? 
And why? Invariably, it is data which fuels your debugging investigation, 
confirming your current hypothesis, or not.

And when you write your unittests, you represent your expections as what? Correct
data is the very definition of success.

So, for debugging and understanding activities, more data, more easily is winning. Going back 
and adding a `println` shouldn't be necessary. All the data you need should already
be captured, and it should be readily available in your REPL for further experimentation.

### Data Brings Code To Life

Perhaps you have seen LightTable in action?

In the small, it is a delightfully productive debugging environment because it co-renders 
code and the data generated by running the code. The data provides a "paper trail" which
brings the code to life, revealing its dynamics and enriching 
a programmer's understanding.

`re-frame-trace` has a similar goal, although the method is different.

### It Is A Data Dashboard 

Observing raw data trace is both interesting and valuable, but it isn't enough. 
First, we want to leverage this data for insights. And, second, there's often too much data - you 
can drown in the detail.

So, `re-frame-trace` tries to be a "dashboard" which curates this
"raw data" into "information" through various kinds of analysis 
and "roll ups". It should deliver insight "at a glance", while still allowing 
you to drill down into the detail.

### Which Is Helpful How?

Four ways:

  1. It helps you to learn `re-frame`.  Simply looking at 
     the "raw traces" provides insight into how it operates. Even experienced
     re-framians, er, like me, have learned a lot.
     
  2. It helps you to explore and learn an unfamiliar `re-frame` codebase.
     When I click, over here, on this "X" button, it shows me what event is `dispatch`-ed 
     and in what namespace the associated event handler is registered.  And, 
     "oh look, that's interesting - four subscriptions recalculated". Etc.
     
  3. It helps you with debugging. You see an x-ray of your app's functioning. 
     In particular, it will assist you to write and debug 
     event handlers, which is useful because they hold most of the logic 
     in your `re-frame` apps.
     
  4. It helps you to find performance problems and/or detect where there is 
     unnecessary computation occurring.
     
Point 3, is primary, of course. But Point 2 is almost as important because we all spend a 
lot of our time groking unfamiliar codebases. Being able to observe the inner 
workings of a running app is a great way to bring code to life, reveal key 
features, and build a cognative map of how the code is structured.

### Temporary Warning 

> Some of the claims above are aspirational. `re-frame-trace` [remains a WIP](https://github.com/Day8/re-frame-trace/issues/118).

## Of Sausage And Sizzle

Internal discussion about a name meandered for a while.  Initially, it was `re-frame-trace`, which is accurate, sure, but it is also 100% sausage because it talks about low level function, and not higher level benefit (sizzle, sizzle).  Side stepping the issue, I wanted to call it `vox-datum` (voice of the data) but that was cruelly rejected, for reasons I don't care to remember. The pain. I mean, who the hell doesn't like a Latin name??  Philistines.

Now, the tool's benifits are `-insight` and `-illumination`, but adding either made the name waaaay too long.  Naming things - it really is a nightmare!

Finally, `-10x` cheekily materialised, delivering 100 decibels of audacious sizzle, and consequently a challenge for us to live up to. A 10x programmer starts by having 10x more knowledge and insight - so go make that tool, smarty pants.

## A 1000 words

Slightly out of date, but indicative ...  

<img src="docs/images/re-frame-trace-demo.gif" height="500px">

## Installation

If you are using leiningen, modify `project.clj` in the following ways. When puzzling over the various possible leiningen configurations, it's often helpful to look at a sample [project.clj](https://github.com/technomancy/leiningen/blob/stable/sample.project.clj).

[![Clojars Project](https://img.shields.io/clojars/v/day8.re-frame/trace.svg)](https://clojars.org/day8.re-frame/trace)

- Update your re-frame dependency to at least `0.10.5` - `[re-frame "0.10.5"]`.

- Add re-frame-trace as a dev dependency by placing `[day8.re-frame/trace "VERSION"]` within `:profiles :dev :dependencies`. For example:

  ```cljs
  :profiles
     {:dev
        {:dependencies [[some-other-package  "0.0.0"]
                        [day8.re-frame/trace "0.0.0 (see version above)"]] }}
  ```
  
  If your project uses React 16 and Reagent 0.8.0-alpha2 (or higher) then you will need to add the qualifier `-react16` to the version, e.g. `[day8.re-frame/trace "0.0.0-react16"]`.

- Locate the `:compiler` map under `:dev` and add:

  - `:closure-defines      {"re_frame.trace.trace_enabled_QMARK_" true}`
  - `:preloads             [day8.re-frame.trace.preload]`

  For example:

  ```cljs
  {:builds
     [{:id           "dev"
       :source-paths ["src" "dev"]
       :compiler     {...
                      :closure-defines      {"re_frame.trace.trace_enabled_QMARK_" true}
                      :preloads             [day8.re-frame.trace.preload]
                      }}]}
  ```

[cljs-devtools](https://github.com/binaryage/cljs-devtools) is not required to use re-frame-trace, but it is highly recommended.

## Usage

- **Make sure you have followed all of the installation instructions above.**

- Start up your application.

- Once it is loaded, focus the document window and press `ctrl-h` to slide open the trace panel and enable tracing.

- When the panel is closed, tracing is disabled.

## Use Cases

### app-db

* Inspect a portion of app-db's state with the path inspector, allowing you to focus on just the parts you care about.
* Reset app-db to before an event was run to run it again, instead of resetting the whole application
* Toggle app-db before and after states for running an event, to inspect UI changes. 

### Timing

* Answer the question "Why is my app slow when it runs this event?"
* See whether time is spent in processing an event, or rendering the changes 

## Troubleshooting

* Try a `lein clean`
* Make sure you have followed all the installation steps.

### If re-frame-trace throws an exception on startup

* Reset the settings to factory defaults in the settings panel
* If you can't load the settings panel, run `day8.re_frame.trace.factory_reset_BANG_()` in the JavaScript console.
* If neither of those work, remove all of the keys with the prefix `day8.re-frame.trace` from your browser's Local Storage.

## How does it work?

re-frame is instrumented - all important activity generates trace data. 

`re-frame-trace` consumes this trace data and renders useful visualisations of the `re-frame` process. Currently, re-frame's tracing capabilities are in alpha and are subject to change at any time. We're testing the utility of the the trace by building an app on top. 

By default, re-frame tracing is "compiled out", so it won't impose a performance cost in production. The trade-off here is that you need to explicitly enable it in development.

The [preloads](https://github.com/clojure/clojurescript/wiki/Compiler-Options#preloads) option (`:preloads [day8.re-frame.trace.preload]`) has to be set in order to automatically monkeypatch Reagent to add appropriate lifecycle hooks. Yes this is gross, and yes we will [make a PR to reagent to add proper hooks](https://github.com/Day8/re-frame-trace/issues/115), once we know exactly what we need. The preload namespace also injects a div containing the devtools panel into the DOM.

## Developing/Contributing

If you want to work on re-frame-trace, see [DEVELOPERS.md](DEVELOPERS.md).

## Citations

* [open](https://thenounproject.com/search/?q=popout&i=334227) by Bluetip Design from the Noun Project
* [reload](https://thenounproject.com/adnen.kadri/collection/arrows/?i=798299) by Adnen Kadri from the Noun Project
* [Camera](https://thenounproject.com/search/?q=snapshot&i=200965) by Christian Shannon from the Noun Project
* [Delete](https://thenounproject.com/term/delete/926276) by logan from the Noun Project
* [Settings](https://thenounproject.com/search/?q=settings&i=1169241) by arjuazka from the Noun Project
* [Wrench](https://thenounproject.com/icon/1013218/) by Aleksandr Vector from the Noun Project
* [pause](https://thenounproject.com/icon/1376662/) by Bhuvan from the Noun Project
* [play]() by Bhuvan from the Noun Project
* [Log Out](https://thenounproject.com/icon/54484/) by Arthur Shlain from the Noun Project