feat(otlp): expose export counters via logger params

docs/OtlpHttpLogger.md

@@ -64,6 +64,24 @@ LogIt++ -> OtlpHttpLogger -> kurlyk::HttpClient -> OpenTelemetry Collector / Lok
 
 Resource attributes are configured through `OtlpHttpLoggerConfig`, including `service.name`, `service.namespace`, `service.instance.id`, and `deployment.environment.name`.
 
+## Diagnostics
+
+`OtlpHttpLogger` exposes its internal counters through the generic logger parameter API:
+
+```cpp
+const auto dropped = LOGIT_GET_INT_PARAM(otlp_index, logit::LoggerParam::DroppedLogCount);
+const auto failed = LOGIT_GET_INT_PARAM(otlp_index, logit::LoggerParam::FailedExportCount);
+```
+
+Available diagnostic params:
+
+| Parameter | Meaning |
+| --- | --- |
+| `LoggerParam::DroppedLogCount` | Number of records dropped because the backend queue overflowed or the logger was stopping. |
+| `LoggerParam::FailedExportCount` | Number of failed OTLP export attempts. |
+
+These values are also available through `get_string_param()` and `get_float_param()`. Integer retrieval saturates at `int64_t` max if the underlying unsigned counter ever exceeds that range.
+
 ## Notes
 
 - `OtlpHttpLogger` is an outbound client/exporter, not a server.

include/logit_cpp/logit/enums.hpp

@@ -48,7 +48,9 @@ namespace logit {
         LastFileName,          ///< The name of the last file written to.
         LastFilePath,          ///< The full path of the last file written to.
         LastLogTimestamp,      ///< The timestamp of the last log.
-        TimeSinceLastLog       ///< The time elapsed since the last log in seconds.
+        TimeSinceLastLog,      ///< The time elapsed since the last log in seconds.
+        DroppedLogCount,       ///< Number of log records dropped by the backend.
+        FailedExportCount      ///< Number of failed export attempts reported by the backend.
     };
 
     /// \enum CompressType

include/logit_cpp/logit/loggers/OtlpHttpLogger.hpp

@@ -27,6 +27,7 @@
 #include <cstdint>
 #include <deque>
 #include <future>
+#include <limits>
 #include <mutex>
 #include <string>
 #include <thread>
@@ -126,6 +127,8 @@ namespace logit {
             switch (param) {
             case LoggerParam::LastLogTimestamp: return std::to_string(get_last_log_ts());
             case LoggerParam::TimeSinceLastLog: return std::to_string(get_time_since_last_log());
+            case LoggerParam::DroppedLogCount: return std::to_string(dropped_count());
+            case LoggerParam::FailedExportCount: return std::to_string(failed_export_count());
             default:
                 break;
             }
@@ -139,6 +142,8 @@ namespace logit {
             switch (param) {
             case LoggerParam::LastLogTimestamp: return get_last_log_ts();
             case LoggerParam::TimeSinceLastLog: return get_time_since_last_log();
+            case LoggerParam::DroppedLogCount: return counter_to_int64(dropped_count());
+            case LoggerParam::FailedExportCount: return counter_to_int64(failed_export_count());
             default:
                 break;
             }
@@ -147,13 +152,17 @@ namespace logit {
 
         /// \brief Retrieves a floating-point parameter from the logger.
         /// \param param Parameter to retrieve.
-        /// \return Parameter value in seconds, or 0.0 when unsupported.
+        /// \return Parameter value in seconds for time params, raw count for counter params, or 0.0 when unsupported.
         double get_float_param(const LoggerParam& param) const override {
             switch (param) {
             case LoggerParam::LastLogTimestamp:
                 return static_cast<double>(get_last_log_ts()) / 1000.0;
             case LoggerParam::TimeSinceLastLog:
                 return static_cast<double>(get_time_since_last_log()) / 1000.0;
+            case LoggerParam::DroppedLogCount:
+                return static_cast<double>(dropped_count());
+            case LoggerParam::FailedExportCount:
+                return static_cast<double>(failed_export_count());
             default:
                 break;
             }
@@ -317,6 +326,14 @@ namespace logit {
             const int64_t now = LOGIT_CURRENT_TIMESTAMP_MS();
             return now > last ? now - last : 0;
         }
+
+        /// \brief Converts unsigned counter value to int64_t with saturation.
+        /// \param value Counter value.
+        /// \return Counter value clamped to int64_t max.
+        static int64_t counter_to_int64(uint64_t value) {
+            const uint64_t max_value = static_cast<uint64_t>((std::numeric_limits<int64_t>::max)());
+            return value > max_value ? (std::numeric_limits<int64_t>::max)() : static_cast<int64_t>(value);
+        }
     };
 
 } // namespace logit