refactor(userspace/engine): strengthen and document thread-safety guarantees of falco_engine::process_event #2082
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/milestone 0.33.0 |
jasondellaluce
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Jun 21, 2022
| std::vector<uint64_t> m_by_priority; | ||
| std::vector<uint64_t> m_by_rule_id; | ||
| atomic<uint64_t> m_total; | ||
| std::vector<std::unique_ptr<atomic<uint64_t>>> m_by_priority; |
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Note: the usage of unique_ptr is required because atomic<> does not have copy nor move constructors, which makes them unusable in vectors as simple values.
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…nt method Signed-off-by: Jason Dellaluce <[email protected]>
…e::process_event Signed-off-by: Jason Dellaluce <[email protected]>
Signed-off-by: Jason Dellaluce <[email protected]>
Signed-off-by: Jason Dellaluce <[email protected]>
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LGTM label has been added. Git tree hash: 722c6bad23695db9ab69de98bb4de599ab91fbdc
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[APPROVALNOTIFIER] This PR is APPROVED This pull-request has been approved by: FedeDP, jasondellaluce The full list of commands accepted by this bot can be found here. The pull request process is described here
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What type of PR is this?
/kind feature
Any specific area of the project related to this PR?
/area engine
What this PR does / why we need it:
This PR is focused on guaranteeing (and documenting) that concurrent access to
falco_engine::process_event()is safe for different event sources.Since the new plugin system got implemented, and due to the recent refactoring of the Falco engine for Falco v0.32, the engine is not internally split by event sources. This means that the engine contains multiple rulesets, each mapped 1-1 with an event source. Accordingly, it is possible to assume that
falco_engine::process_event()is now thread-safe with some assumptions:source_idxsource_idxacross subsequent calls tofalco_engine::process_event()Considering the above, the only synchronization point is
stats_manager::on_event(), which has been modified to be thread-safe and lock-free.Which issue(s) this PR fixes:
Special notes for your reviewer:
Thread safety is not a requirement for Falco, but future developments such as the ones described in #2074 could require it. Among the many things that can be useful to make thread safe, the most crucial one is the rule-event matching routine, of which
falco_engine::process_event()is entrypoint. With this implementation, it is possible to consider processing events coming from different event sources in different parallel threads.Assuming a single-threaded scenario, the changes involved in
stats_manager::on_event()are a no-op in both expected behavior and performance. This is true becausestats_manager::on_event()is invoked when an event matches a given rule exclusively, which happens with less frequency than the production of events by some orders of magnitude. As such, we can consider these changes as non-noticeable for single-thread scenarios (which is what we have right now). Moreover, when events are matched with a rule we then have to queue them in the Falco output engine, which is still an asynchronous sequential synchronization point.Does this PR introduce a user-facing change?: