create simple snapshot logic for rocksdb

rocks/include/userver/storages/rocks/client.hpp

@@ -64,10 +64,13 @@ class Client final {
    */
   void CheckStatus(rocksdb::Status status, std::string_view method_name);
 
+  Client MakeSnapshot(const std::string& checkpoint_path);
+
  private:
   std::unique_ptr<rocksdb::DB> db_;
   engine::TaskProcessor& blocking_task_processor_;
 };
+
 }  // namespace storages::rocks
 
 USERVER_NAMESPACE_END

rocks/src/storages/rocks/client.cpp

@@ -2,6 +2,8 @@
 
 #include <fmt/format.h>
 
+#include <rocksdb/utilities/checkpoint.h>
+
 #include <userver/storages/rocks/exception.hpp>
 #include <userver/utils/async.hpp>
 
@@ -56,6 +58,26 @@ void Client::CheckStatus(rocksdb::Status status, std::string_view method_name) {
         method_name, status.ToString());
   }
 }
+
+Client Client::MakeSnapshot(const std::string& checkpoint_path) {
+  rocksdb::Checkpoint* checkpoint;
+  rocksdb::Status status = rocksdb::Checkpoint::Create(db_.get(), &checkpoint);
+
+  CheckStatus(status, "Create Checkpoint");
+
+  try {
+    status = checkpoint->CreateCheckpoint(checkpoint_path);
+
+    CheckStatus(status, "Bind Checkpoint to the path");
+
+    delete checkpoint;
+  } catch (...) {
+    delete checkpoint;
+  }
+
+  return Client(checkpoint_path, blocking_task_processor_);
+}
+
 }  // namespace storages::rocks
 
 USERVER_NAMESPACE_END

rocks/src/storages/rocks/client_test.cpp

@@ -23,6 +23,39 @@ UTEST(Rocks, CheckCRUD) {
   client.Delete(key);
   res = client.Get(key);
   EXPECT_EQ("", res);
+
+}
+
+UTEST(RocksSnapshot, CheckCRUD) {
+  storages::rocks::Client client{"/tmp/rocksdb_simple_snapshot",
+                                 engine::current_task::GetTaskProcessor()};
+  std::string key = "key";
+  std::string value = "value";
+
+  client.Put(key, value);
+  std::string res = client.Get(key);
+  EXPECT_EQ(value, res);
+
+  storages::rocks::Client snapshot(client.MakeSnapshot("/tmp/snapshot"));
+  res = snapshot.Get(key);
+  EXPECT_EQ(value, res);
+
+
+  std::string new_value = "new value";
+  snapshot.Put(key, new_value);
+  res = snapshot.Get(key);
+  EXPECT_EQ(new_value, res);
+
+  res = client.Get(key);
+  EXPECT_EQ(value, res);
+
+
+  snapshot.Delete(key);
+  res = snapshot.Get(key);
+  EXPECT_EQ("", res);
+
+  res = client.Get(key);
+  EXPECT_EQ(value, res);
 }
 
 }  // namespace