Keep some statistics for the binary cache stores

src/hydra-queue-runner/s3-binary-cache-store.hh

@@ -2,6 +2,8 @@
 
 #include "binary-cache-store.hh"
 
+#include <atomic>
+
 namespace Aws { namespace Client { class ClientConfiguration; } }
 namespace Aws { namespace S3 { class S3Client; } }
 
@@ -24,8 +26,23 @@ public:
 
     void init() override;
 
+    struct Stats
+    {
+        std::atomic<uint64_t> put{0};
+        std::atomic<uint64_t> putBytes{0};
+        std::atomic<uint64_t> putTimeMs{0};
+        std::atomic<uint64_t> get{0};
+        std::atomic<uint64_t> getBytes{0};
+        std::atomic<uint64_t> getTimeMs{0};
+        std::atomic<uint64_t> head{0};
+    };
+
+    const Stats & getS3Stats();
+
 private:
 
+    Stats stats;
+
     ref<Aws::Client::ClientConfiguration> makeConfig();
 
 protected: