@contrast/patcher

@contrast/patcher

Monkey patching.

Notes on v5 Parity

This was ported directly from the node-agent but code with every dependency commented out. As a result there are differences in parity.

1. Removed dependency on AsyncStorage.

   Old Behavior

   Pre and post hooks only run when async storage context indicates an active request scope.

   New Behavior

   Hooks always run, independent of request scope.

2. Removed dependency on agent and perf-logger.

   Old Behavior

   A configuration setting would allow for logging of perf data of hooks and original function calls.

   New Behavior

   Performance logging of hooks is non-funcitonal.

3. Removed the dependency on scopes.

   Old Behavior

   One could specify a scope in the hook options and the original function would be run in that scope. This allowed control over when to run instrumentaion based on current scope value.

   Also, the alwaysRun option forced hooks to run independent of scope state.

   New Behavior

   There are no notions of scopes yet in v5. Patcher instrumentation always runs.

   The scope and alwaysRun options are effectively ignored.

4. Removed the dependency on tracker.

   Old Behavior

   We used to short-circuit __add function if tracker showed all arguments to be untracked.

   New Behavior

   We do not make this check; no short-circuiting.