re-frame provides a data driven architecture, but we need to be able to inspect it. re-frame-trace takes inspiration from [redux-devtools](https://github.com/gaearon/redux-devtools), and provides several ways to visualise the structure and state of your re-frame application.
re-frame has instrumentation to collect traces throughout various important points in the lifecycle of a re-frame app. re-frame-trace is a consumer of these traces, and provides visualisations of the traces. These traces have a well-defined structure, and will eventually be standardised, allowing other developers to create their own tooling to work against the traces. Currently, re-frame's tracing and re-frame-trace are in alpha and are subject to change at any time.
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 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.
Now you can start up your application. Once it is loaded, press Ctrl+H to slide open the trace panel and enable tracing. When the panel is closed, tracing is disabled.
- Go into the root directory of a project you'd like to use as a host to test re-frame-trace with. For example, you can use the [todo-mvc](https://github.com/Day8/re-frame/tree/master/examples/todomvc) project.
- Add re-frame-trace into this project using the [instructions](#getting-started) above.
- Create a folder called `checkouts:`
```
mkdir checkouts
```
- Create a symlink from your local re-frame-trace project in the checkouts folder:
