109 lines
6.0 KiB
Markdown
109 lines
6.0 KiB
Markdown
# re-frame-trace
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`re-frame-trace` is a programmer's dashboard
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for inspecting a running `re-frame` application. It should assist you to both understand and debug your application.
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**Status:** Alpha. [](https://clojars.org/day8.re-frame/trace) [](https://versions.deps.co/Day8/re-frame-trace)
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**Note** [the latest version 0.1.13](https://github.com/Day8/re-frame-trace/releases/tag/0.1.13) ALSO requires the latest version of re-frame itself - `v0.10.3-alpha1`.
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## Dashboard Overview
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`re-frame` applications are computationally regular. First an event happens,
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and then boom, boom, boom go a series of known steps (dominos), in a known order. At the end of
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it, a `re-frame` app lapses into a quiescent state waiting for another event to kick
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off the next iteration of the same cycle.
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Each `re-frame` event and its consequent computation forms a discrete "epoch" which can be analysed and inspected independently of other epochs. As a result, this tool is epoch-oriented.
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As it runs, `re-frame` generates detailed "trace data", but much of it will be low level and uninteresting a lot of the time.
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`re-frame-trace` is a "dashboard" in the sense that it shows useful, "rolled up" information "at a glance", and allows you to drill down and explore the detail as necessary. All the data you want should ultimately be available, but you shouldn't initially drown in it.
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Not only is the underlying trace "just data", but so is much of the observed `re-frame` proecess. Much of what `re-frame` does on your behalf is the move data from one domino to another. You write the dominos (functions) and `re-frame` will flow data through them.
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So, yeah, this tool an epoch-oriented, interactive data dashboard for gaining insights and assisting debugging. It is also a work in progress, so this grand descrption runs well ahead of what is delivered right now.
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## More Aspirational goals
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Here's the vision for how we'd like `re-frame-trace` to help (eventually):
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- Help in learning `re-frame`. If I'm new to `re-frame`, the dashboard should assist me to understand the
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dominoes and the data flows involved.
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- Help in learning a new code base. It should help me to explore how an unfamiliar application is wired together. When I click
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on this button "X", it shows me what event is `dispatch`-ed and in what namespace the associated event handler is registered. And,
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"oh look, that's interesting - four subscriptions recalculated". Etc.
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- Help with debugging. Particularly assistance for writing event handlers as they hold most of the application logic.
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- Help with finding performance problems and/or detecting where there is unnecessary computation occuring.
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## A Visual Sampler
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<img src="docs/images/trace-window.gif" height="400px">
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## Installation
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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).
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[](https://clojars.org/day8.re-frame/trace)
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- Add re-frame-trace as a dev dependency by placing `[day8.re-frame/trace "VERSION"]` within `:profiles :dev :dependencies`. For example:
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```cljs
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:profiles
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{:dev
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{:dependencies [[some-other-package "0.0.0"]
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[day8.re-frame/trace "0.0.0 (see version above)"]] }}
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```
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- Locate the `:compiler` map under `:dev` and add:
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- `:closure-defines {"re_frame.trace.trace_enabled_QMARK_" true}`
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- `:preloads [day8.re-frame.trace.preload]`
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For example:
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```cljs
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{:builds
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[{:id "dev"
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:source-paths ["src" "dev"]
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:compiler {...
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:closure-defines {"re_frame.trace.trace_enabled_QMARK_" true}
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:preloads [day8.re-frame.trace.preload]}}]}
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```
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[cljs-devtools](https://github.com/binaryage/cljs-devtools) is not required to use re-frame-trace, but it is highly recommended.
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## Usage
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- **Make sure you have followed all of the installation instructions above.**
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- Start up your application.
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- Once it is loaded, focus the document window and press `ctrl-h` to slide open the trace panel and enable tracing.
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- When the panel is closed, tracing is disabled.
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## Troubleshooting
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* Try a `lein clean`
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* Make sure you have followed all the installation steps.
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## How does it work?
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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.
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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.
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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 try and make a PR to reagent to add proper hooks, once we know exactly what we need. The preload namespace also injects a div containing the devtools panel into the DOM.
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## Developing/Contributing
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If you want to work on re-frame-trace, see [DEVELOPERS.md](DEVELOPERS.md).
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## Citations
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* [open](https://thenounproject.com/search/?q=popout&i=334227) by Bluetip Design from the Noun Project
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* [reload](https://thenounproject.com/adnen.kadri/collection/arrows/?i=798299) by Adnen Kadri from the Noun Project
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* [Camera](https://thenounproject.com/search/?q=snapshot&i=200965) by Christian Shannon from the Noun Project
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* [Delete](https://thenounproject.com/term/delete/926276) by logan from the Noun Project
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