the high-level change is that events matching a rule are now send into a
lua "on_event" function for handling, rather than doing the handling
down in c++.
more specifics:
before, the lua "load_rule" function registered formatters with
associated IDs with the c++ side, which later used this state to
reconcile events with formats and print output accordingly.
now, no such state is kept on the c++ side. the lua "load_rule" function
maintains the id->formatters map, and uses it to print outputs when it
receives events.
this change simplifies the existing flow and will also make the forthcoming
implementation of function outputs far simpler than it would have been
in the current setup.
Before this change, events were only printed if they had all the
fields (same behavior as with sysdig when the output format doesn't have
a leading "*"). With this change, all events are printed; those that
don't have all fields are prefixed with a notification.
Move compiler loading out of libsinsp/lua_parser.cpp and into a new
class in digwatch/rules.cpp.
This way the libsinsp support is strictly about providing a lua API for
scripts to setup filters. Loading the actual parser and rules is logic
that belongs in the app (digwatch in this case, maybe sysdig down the
line) rather than there.
