$ show falcosecurity/falco
Falco is a cloud-native runtime security daemon that monitors Linux system calls, Kubernetes audit logs, and plugin-supplied events in real time. It applies a flexible rule engine to detect anomalous behavior and generates alerts via multiple output channels (stdout, file, syslog, HTTP, program). The codebase is a monolithic C++ application with a modular internal architecture: a sequenced action pipeline (app/app.cpp) drives startup, configuration, plugin loading, rule compilation, event processing, and output dispatch. The rule engine (userspace/engine/) parses YAML rule definitions, resolves macros and filters, indexes rules by event type, and matches events efficiently. The output subsystem uses a thread-safe worker queue with a watchdog. Falco supports hot-reload via inotify file watching and a Unix socket control endpoint. It is deployed as a Helm chart on Kubernetes (DaemonSet/Deployment) and is packaged as DEB, RPM, and Docker images. The repository includes extensive unit tests (Google Test), end-to-end event generator tests, and CI/CD pipelines for building, testing, and publishing. External dependencies include falcosecurity/libs (sinsp), falcoctl, OpenSSL, cURL, yaml-cpp, and jemalloc. The architecture demonstrates strong engineering practices with clean abstractions (indexed_vector, atomic_signal_handler, yaml_helper) and composable action steps.
The LLM identified 3 files worth highlighting for reuse:
Provides a lock-free trigger/handle pattern for safe signal delivery in multi-threaded daemons. Uses std::atomic<bool> for the trigger flag and a separate std::atomic<int> for pending signals, ensuring that signal handlers (which can only use async-signal-safe operations) can safely notify the main thread. The pattern is generic and can be extracted into any C++ project requiring reliable signal handling without mutexes.
A generic container template that provides O(1) access to elements by both string name and numeric index. Internally maintains a vector for positional access and an unordered_map for name lookup. Supports insertion, removal, and re-indexing. This pattern is reusable in any project needing dual-key access to a dynamic collection, such as plugin registries, rule stores, or configuration tables.
A utility library for YAML configuration handling that extends yaml-cpp with environment variable expansion, escaped key navigation (supporting dots and brackets in keys), typed scalar/sequence access, set/modify operations, include strategies (append/override/add-only), and JSON schema validation via valijson. This component is self-contained and can be reused in any C++ project that needs robust YAML configuration management with validation.