Implement BoundedChannel and multithreaded logging infra

tooling/pipeline/includes/services/logging/log_consumer.h

@@ -0,0 +1,59 @@
+/**
+ * @file services/logging/log_consumer.h
+ * @brief Dedicated log consumer/drain for asynchronous pipeline logging.
+ *
+ * Intent: Dequeue LogEntry values from a BoundedChannel on a dedicated thread
+ * and forward them to spdlog for I/O and formatting. Decouples application
+ * logic from logging latency.
+ */
+
+#ifndef BIERGARTEN_PIPELINE_INCLUDES_SERVICES_LOGGING_LOG_CONSUMER_H_
+#define BIERGARTEN_PIPELINE_INCLUDES_SERVICES_LOGGING_LOG_CONSUMER_H_
+
+#include <spdlog/spdlog.h>
+
+#include <string>
+
+#include "concurrency/bounded_channel.h"
+#include "services/logging/log_entry.h"
+
+/**
+ * @class LogConsumer
+ * @brief Consumes log entries from channel and forwards to spdlog.
+ *
+ * Non-copyable, non-movable. Designed to run on its own dedicated std::thread.
+ * Drains the channel until closure, then exits cleanly.
+ */
+class LogConsumer {
+ public:
+   /**
+    * @brief Construct a log consumer.
+    *
+    * @param channel Reference to bounded channel for log entry retrieval.
+    *                Channel must outlive this consumer instance.
+    */
+   explicit LogConsumer(BoundedChannel<LogEntry>& channel);
+
+   LogConsumer(const LogConsumer&) = delete;
+   LogConsumer& operator=(const LogConsumer&) = delete;
+   LogConsumer(LogConsumer&&) = delete;
+   LogConsumer& operator=(LogConsumer&&) = delete;
+
+   /**
+    * @brief Main loop: drain channel and forward entries to spdlog.
+    *
+    * Intended to be called once on a dedicated thread. Returns when:
+    * - Channel is closed AND all queued entries are drained.
+    *
+    * Thread-safe for use from multiple ChannelLogger instances on other threads.
+    */
+   void Run();
+
+ private:
+   BoundedChannel<LogEntry>& channel_;
+
+   static spdlog::level::level_enum ToSpdlogLevel(LogLevel level);
+   static std::string ToString(PipelinePhase phase);
+};
+
+#endif  // BIERGARTEN_PIPELINE_INCLUDES_SERVICES_LOGGING_LOG_CONSUMER_H_