appmap-ruby is a Ruby Gem for recording
AppMaps of your code.
"AppMap" is a data format which records code structure (modules, classes, and methods), code execution events
(function calls and returns), and code metadata (repo name, repo URL, commit
SHA, labels, etc). It's more granular than a performance profile, but it's less
granular than a full debug trace. It's designed to be optimal for understanding the design intent and structure of code and key data flows.
Visit the AppMap for Ruby reference page on AppLand.com for a complete reference guide.
Configuration
appmap.yml is loaded into an AppMap::Config.
Hooking
Once configuration is loaded, AppMap::Hook is enabled. "Hooking" refers to the process of replacing a method
with a "hooked" version of the method. The hooked method checks to see if tracing is enabled. If so, it wraps the original
method with calls that record the parameters and return value.
Builtins
Hook begins by iterating over builtin classes and modules defined in the Config. Builtins include code
like openssl and net/http. This code is not dependent on any external libraries being present, and
appmap cannot guarantee that it will be loaded before builtins. Therefore, it's necessary to require it and
hook it by looking up the classes and modules as constants in the Object namespace.
User code and gems
After hooking builtins, Hook attaches a TracePoint to :begin events.
This TracePoint is notified each time a new class or module is being evaluated. When this happens, Hook uses the Config
to determine whether any code within the evaluated file is configured for hooking. If so, a TracePoint is attached to
:end events. Each :end event is fired when a class or module definition is completed. When this happens, the Hook enumerates
the public methods of the class or module, hooking the ones that are targeted by the Config. Once the :end TracePoint leaves
the scope of the :begin, the :end TracePoint is disabled.
Before running tests, configure local.appmap to point to your local appmap-ruby directory.
$ bundle config local.appmap $(pwd)
Run the tests via rake:
$ bundle exec rake test
The test target will build the native extension first, then run the tests. If you need
to build the extension separately, run
$ bundle exec rake compile
The fixture apps in test/fixtures are plain Ruby projects that exercise the basic functionality of the
appmap gem. To develop in a fixture, simply enter the fixture directory and bundle.
The fixture apps in spec/fixtures are simple Rack, Rails5, and Rails6 apps.
You can use them to interactively develop and test the recording features of the appmap gem.
These fixture apps are more sophisticated than test/fixtures, because they include additional
resources such as a PostgreSQL database. Still, you can simply enter the fixture directory and bundle.
If you don't have PostgreSQL on the local (default) socket, you can export DATABASE_URL to
point to the database server you want to use.
You can launch a database like this:
➜ docker-compose -p appmap-ruby up -d
... stuff
➜ docker-compose port pg 5432
0.0.0.0:64479
➜ export DATABASE_URL=postgres://postgres@localhost:64479