fix(tiering): Remove disk store files on exit

Author: dranikpg

src/server/tiering/disk_storage.cc

@@ -74,6 +74,7 @@ error_code DiskStorage::Open(string_view path) {
   if (absl::GetFlag(FLAGS_backing_file_direct))
     kFlags |= O_DIRECT;
 
+  backing_file_path_ = path;
   auto res = OpenLinux(path, kFlags, 0666);
   if (!res)
     return res.error();
@@ -104,8 +105,13 @@ void DiskStorage::Close() {
   while (pending_ops_ > 0 || grow_.pending)
     util::ThisFiber::SleepFor(10ms);
 
-  backing_file_->Close();
+  auto ec = backing_file_->Close();
+  LOG_IF(ERROR, ec) << "Failed to close backing file: " << ec;
   backing_file_.reset();
+
+  int errc = unlink(backing_file_path_.c_str());
+  LOG_IF(ERROR, errc != 0) << "Failed to unlink backing file: "
+                           << std::error_code{errc, std::system_category()};
 }
 
 void DiskStorage::Read(DiskSegment segment, ReadCb cb) {

src/server/tiering/disk_storage.h

@@ -70,6 +70,7 @@ class DiskStorage {
     util::fb2::EventCount ev;  // woken up when in-progress op finishes
   } grow_;                     // status of latest blocking Grow() operation
 
+  std::string backing_file_path_;
   std::unique_ptr<util::fb2::LinuxFile> backing_file_;
   ExternalAllocator alloc_;
 };

src/server/tiering/disk_storage_test.cc

@@ -32,7 +32,9 @@ struct DiskStorageTest : public PoolTestBase {
   void Close() {
     storage_->Close();
     storage_.reset();
-    unlink(filename_.c_str());
+
+    // Disk storage deletes its files on exit
+    EXPECT_FALSE(std::filesystem::exists(filename_));
   }
 
   void Stash(size_t index, string value) {