refactor(userspace/engine): make stats manager thread-safe for on_event method

Signed-off-by: Jason Dellaluce <jasondellaluce@gmail.com>

userspace/engine/falco_engine.cpp

@@ -194,6 +194,15 @@ std::unique_ptr<load_result> falco_engine::load_rules(const std::string &rules_c
 		m_rule_loader.compile(cfg, m_rules);
 	}
 
+	if (cfg.res->successful())
+	{
+		m_rule_stats_manager.clear();
+		for (const auto &r : m_rules)
+		{
+			m_rule_stats_manager.on_rule_loaded(r);
+		}
+	}
+
 	return std::move(cfg.res);
 }
 

userspace/engine/stats_manager.cpp

@@ -45,37 +45,48 @@ void stats_manager::format(
 	out += "Rule counts by severity:\n";
 	for (size_t i = 0; i < m_by_priority.size(); i++)
 	{
-		if (m_by_priority[i] > 0)
+		auto val = m_by_priority[i].get()->load();
+		if (val > 0)
 		{
 			falco_common::format_priority(
 				(falco_common::priority_type) i, fmt, true);
 			transform(fmt.begin(), fmt.end(), fmt.begin(), ::toupper);
-			out += "   " + fmt;
-			out += ": " + to_string(m_by_priority[i]) + "\n";
+			out += "   " + fmt + ": " + to_string(val) + "\n";
 		}
 	}
 	out += "Triggered rules by rule name:\n";
 	for (size_t i = 0; i < m_by_rule_id.size(); i++)
 	{
-		if (m_by_rule_id[i] > 0)
+		auto val = m_by_rule_id[i].get()->load();
+		if (val > 0)
 		{
-			out += "   " + rules.at(i)->name;
-			out += ": " + to_string(m_by_rule_id[i]) + "\n";
+			out += "   " + rules.at(i)->name + ": " + to_string(val) + "\n";
 		}
 	}
 }
 
+void stats_manager::on_rule_loaded(const falco_rule& rule)
+{
+	while (m_by_rule_id.size() <= rule.id)
+	{
+		m_by_rule_id.emplace_back();
+		m_by_rule_id[m_by_rule_id.size() - 1].reset(new atomic<uint64_t>(0));
+	}
+	while (m_by_priority.size() <= (size_t) rule.priority)
+	{
+		m_by_priority.emplace_back();
+		m_by_priority[m_by_priority.size() - 1].reset(new atomic<uint64_t>(0));
+	}
+}
+
 void stats_manager::on_event(const falco_rule& rule)
 {
-	if (m_by_rule_id.size() <= rule.id)
+	if (m_by_rule_id.size() <= rule.id
+		|| m_by_priority.size() <= (size_t) rule.priority)
 	{
-		m_by_rule_id.resize(rule.id + 1, (uint64_t) 0);
+		throw falco_exception("rule id or priority is out of boubnds");
 	}
-	if (m_by_priority.size() <= (size_t) rule.priority)
-	{
-		m_by_priority.resize((size_t) rule.priority + 1, (uint64_t) 0);
-	}
-	m_total++;
-	m_by_rule_id[rule.id]++;
-	m_by_priority[(size_t) rule.priority]++;
+	m_total.fetch_add(1, std::memory_order_relaxed);
+	m_by_rule_id[rule.id]->fetch_add(1, std::memory_order_relaxed);
+	m_by_priority[(size_t) rule.priority]->fetch_add(1, std::memory_order_relaxed);
 }

userspace/engine/stats_manager.h

@@ -18,11 +18,16 @@ limitations under the License.
 
 #include <vector>
 #include <string>
+#include <atomic>
+#include <memory>
 #include "falco_rule.h"
 #include "indexed_vector.h"
 
 /*!
-	\brief Manager for the internal statistics of the rule engine
+	\brief Manager for the internal statistics of the rule engine.
+	The on_event() is thread-safe and non-blocking, and it can be used
+	concurrently across many callers in parallel.
+	All the other methods are not thread safe.
 */
 class stats_manager
 {
@@ -36,19 +41,29 @@ public:
 	virtual void clear();
 
 	/*!
-		\brief Callback for when a given rule matches an event
+		\brief Callback for when a new rule is loaded in the engine.
+		Rules must be passed through this method before submitting them as
+		an argument of on_event().
+	*/
+	virtual void on_rule_loaded(const falco_rule& rule);
+
+	/*!
+		\brief Callback for when a given rule matches an event.
+		This method is thread-safe.
+		\throws falco_exception if rule has not been passed to
+		on_rule_loaded() first
 	*/
 	virtual void on_event(const falco_rule& rule);
 
 	/*!
-		\brief Formats the internal statistics into the out string
+		\brief Formats the internal statistics into the out string.
 	*/
 	virtual void format(
 		const indexed_vector<falco_rule>& rules,
 		std::string& out) const;
 
 private:
-	uint64_t m_total;
-	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;
+	std::vector<std::unique_ptr<atomic<uint64_t>>> m_by_rule_id;
 };