Expose some RocksDB stats

cpp/cdc/CDC.cpp

@@ -762,6 +762,7 @@ private:
     CDCShared& _shared;
     XmonNCAlert _alert;
     MetricsBuilder _metricsBuilder;
+    std::unordered_map<std::string, uint64_t> _rocksDBStats;
 public:
     CDCMetricsInserter(Logger& logger, std::shared_ptr<XmonAgent>& xmon, CDCShared& shared):
         PeriodicLoop(logger, xmon, "metrics_inserter", {1_sec, 1.0, 1_mins, 0.1}),
@@ -796,6 +797,15 @@ public:
             _metricsBuilder.fieldFloat("size", (double)sum / (double)_shared.inFlightTxnsWindow.size());
             _metricsBuilder.timestamp(now);
         }
+        {
+            _rocksDBStats.clear();
+            _shared.db.rocksDBStats(_rocksDBStats);
+            for (const auto& [name, value]: _rocksDBStats) {
+                _metricsBuilder.measurement("eggsfs_cdc_rocksdb");
+                _metricsBuilder.fieldU64(name, value);
+                _metricsBuilder.timestamp(now);
+            }
+        }
         std::string err = sendMetrics(10_sec, _metricsBuilder.payload());
         _metricsBuilder.reset();
         if (err.empty()) {

cpp/cdc/CDCDB.cpp

@@ -1666,6 +1666,10 @@ struct CDCDBImpl {
          
         commitTransaction(*dbTxn);
     }
+
+    void rocksDBStats(std::unordered_map<std::string, uint64_t>& stats) {
+        ::rocksDBStats(_env, _db, stats);
+    }
 };
 
 CDCDB::CDCDB(Logger& logger, std::shared_ptr<XmonAgent>& xmon, const std::string& path) {
@@ -1695,3 +1699,7 @@ void CDCDB::startNextTransaction(bool sync, EggsTime time, uint64_t logIndex, CD
 uint64_t CDCDB::lastAppliedLogEntry() {
     return ((CDCDBImpl*)_impl)->_lastAppliedLogEntry();
 }
+
+void CDCDB::rocksDBStats(std::unordered_map<std::string, uint64_t>& values) {
+    return ((CDCDBImpl*)_impl)->rocksDBStats(values);
+}

cpp/cdc/CDCDB.hpp

@@ -1,5 +1,7 @@
 #pragma once
 
+#include "unordered_map"
+
 #include "Bincode.hpp"
 #include "Msgs.hpp"
 #include "Env.hpp"
@@ -129,4 +131,6 @@ public:
 
     // The index of the last log entry persisted to the DB
     uint64_t lastAppliedLogEntry();
+
+    void rocksDBStats(std::unordered_map<std::string, uint64_t>& values);
 };