Handling plugin extraction errors #125
Description
Motivation
Currently, errors are ignored during field extraction in the plugin framework. In theory, a plugin might fail extracting a field for two main reasons:
- The field is not present in the given event, for which the
ss_plugin_extract_field.field_presentflag is set to false - The
extract_fieldsexported plugin function encounters some error and returns a code different thanSS_PLUGIN_SUCCESS.
In the current implementation, in both cases the filtercheck returns a NULL pointer, which is interpreted as a not-available field. This is visible here 👇🏼
libs/userspace/libsinsp/plugin.cpp
Line 630 in 83f460c
libs/userspace/libsinsp/plugin.cpp
Line 304 in 83f460c
Although this is semantically correct, the two failure paths have a quite different meaning. In the second case, the plugin returns a failure code and the framework silently ignores it to maintain a non-blocking extraction flow. This is makes error handling efforts useless for plugin developers, and generally makes it harder to debug plugins at runtime.
Feature
I propose to catch the error and make it visible somehow.
I agree that maintaining field extraction non-blocking might be a priority here, so maybe throwing an exception might not be a viable option. We can consider some weaker error propagation methods, or maybe logging to stderr. To the bare minimum, we might log the error if a debug mode is enabled.
Alternatives
Keep things as they are, and just ignore plugin failures for extract_fields.