[GitHub] [incubator-doris] morningman commented on a change in pull request #2983: Add block layer to storage-engine

[GitBox <gi...@apache.org>]

morningman commented on a change in pull request #2983: Add block layer to storage-engine
URL: https://github.com/apache/incubator-doris/pull/2983#discussion_r386032512
 
 

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 File path: be/src/olap/fs/file_block_manager.h
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+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#pragma once
+
+#include <cstdint>
+#include <memory>
+#include <string>
+#include <unordered_set>
+#include <vector>
+
+#include "common/status.h"
+#include "olap/fs/block_manager.h"
+
+namespace doris {
+
+class BlockId;
+class Env;
+class MemTracker;
+class RandomAccessFile;
+
+namespace fs {
+namespace internal {
+
+class FileReadableBlock;
+class FileWritableBlock;
+struct BlockManagerMetrics;
+
+} // namespace internal
+
+// TODO(lingbin): When we create a batch of blocks(blocks are created one by one),
+// eg, when we do a compaction,  multiple files will be generated in sequence.
+// For this scenario, we should have a mechanism that can give the Operating System
+// more opportunities to perform IO merge.
+
+// A file-backed block storage implementation.
+//
+// This is a naive block implementation which maps each block to its own
+// file on disk.
+//
+// The block manager can take advantage of multiple filesystem paths.
+//
+// When creating blocks, the block manager will place blocks based on the
+// provided CreateBlockOptions.
+
+// The file-backed block manager.
+class FileBlockManager : public BlockManager {
+public:
+    // Note: all objects passed as pointers should remain alive for the lifetime
+    // of the block manager.
+    FileBlockManager(Env* env, BlockManagerOptions opts);
+    virtual ~FileBlockManager();
+
+    Status open() override;
+
+    Status create_block(const CreateBlockOptions& opts,
+                        std::unique_ptr<WritableBlock>* block) override;
+    Status open_block(const std::string& path, std::unique_ptr<ReadableBlock>* block) override;
+
+    Status get_all_block_ids(std::vector<BlockId>* block_ids) override {
+        // TODO(lingbin): to be implemented after we assign each block an id
+        return Status::OK();
+    };
+
+private:
+    friend class internal::FileReadableBlock;
+    friend class internal::FileWritableBlock;
+
+    // Deletes an existing block, allowing its space to be reclaimed by the
+    // filesystem. The change is immediately made durable.
+    //
+    // Blocks may be deleted while they are open for reading or writing;
+    // the actual deletion will take place after the last open reader or
+    // writer is closed.
+    Status _delete_block(const std::string& path);
+
+    // Synchronizes the metadata for a block with the given location.
+    Status _sync_metadata(const std::string& path);
+
+    Env* env() const { return _env; }
 
 Review comment:
   Why there is a private env() method?

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