Expose GetTotalTrashSize in SstFileManager interface (#4206)

Summary:
Hi, it would be great if we could expose this API, so that LogDevice can use it to track the total size of trash files and alarm if it grows too large in relation to disk size. There's probably other customers that would be interested in this as well. :)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4206

Differential Revision: D9115516

Pulled By: gdavidsson

fbshipit-source-id: f34993a940e39cb0a0b544ae8298546499b7e047

include/rocksdb/sst_file_manager.h

@@ -75,6 +75,10 @@ class SstFileManager {
   // Update trash/DB size ratio where new files will be deleted immediately
   // thread-safe
   virtual void SetMaxTrashDBRatio(double ratio) = 0;
+
+  // Return the total size of trash files
+  // thread-safe
+  virtual uint64_t GetTotalTrashSize() = 0;
 };
 
 // Create a new SstFileManager that can be shared among multiple RocksDB

util/sst_file_manager_impl.cc

@@ -162,6 +162,10 @@ void SstFileManagerImpl::SetMaxTrashDBRatio(double r) {
   return delete_scheduler_.SetMaxTrashDBRatio(r);
 }
 
+uint64_t SstFileManagerImpl::GetTotalTrashSize() {
+  return delete_scheduler_.GetTotalTrashSize();
+}
+
 Status SstFileManagerImpl::ScheduleFileDeletion(
     const std::string& file_path, const std::string& path_to_sync) {
   return delete_scheduler_.DeleteFile(file_path, path_to_sync);

util/sst_file_manager_impl.h

@@ -93,6 +93,9 @@ class SstFileManagerImpl : public SstFileManager {
   // Update trash/DB size ratio where new files will be deleted immediately
   virtual void SetMaxTrashDBRatio(double ratio) override;
 
+  // Return the total size of trash files
+  uint64_t GetTotalTrashSize() override;
+
   // Mark file as trash and schedule it's deletion.
   virtual Status ScheduleFileDeletion(const std::string& file_path,
                                       const std::string& dir_to_sync);