refactor: introduce mutation_log::replay_block #302
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| replay_callback callback, | ||
| /*out*/ int64_t &end_offset) | ||
| { | ||
| end_offset = log->start_offset(); |
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end_offset的值是在replay_block里面被修改的，初值设为0更直观一些吧
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这个是原来的代码，这里是照顾到 code review
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我看了一下现在replay的用法，其实没有用到end_offset，可以写个todo考虑后续重构这块
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小改动，就没必要写 todo 了
neverchanje
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| return err; | ||
| } | ||
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| // TODO(wutao1): move it to mutation_log_replay.cpp |
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为什么要把replay函数都移到mutation_log_replay.cpp中？如果要移，就这个pr移过去吧，现在两个在mutation_log.cpp，两个在mutation_log_replay.cpp
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这个 PR 重构关键路径，另外两个虽然没有移但已经加了 TODO。移是因为这个代码已经两千行了。
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mutation_log.cpp文件有2000多行了，replay_log的代码最多500行，如果是为了精简文件行数，可以后面来拆，可能有更好的精简方法，这个pr就专注重构
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嗯，这里拆成两个文件也是方便对比，我发现直接在原来文件改反而更不容易看
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我觉得这个pr的描述和代码有点不一致，我理解原来的replay其实就是以block的方式replay log中的mutation的，这个pr只是重构写法，并不是把replay改成以block的方式replay log，没有大改 |
neverchanje
changed the title
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@hycdong 我修改了标题，你可以再看 |
mutation_log_utils is a set of utilities for mutation log operations. Some of them are used in the refactoring of mutation_log, but some are not. Leave them here for future usage (for duplication).
mutation_log::replaywas used simply for replica recovering, that is, iterating through the whole set of log files and replaying. However, for duplication, the replay of mutation_log becomes a block by block operation. Because it will impose much pressure on this replica to read the entire file once. So we add a new functionmutation_log::replay_block. Actually,replayis originally implemented on a block by block behavior, but replaying a block is not taken as a function.The unit test is committed formerly, see this file.
https://github.com/XiaoMi/rdsn/blob/master/src/dist/replication/test/replica_test/unit_test/mutation_log_test.cpp
mutation_log::replay_blockmay start from a specified offset, not from the offset point to the last replayed mutation. Therefore we modifiedmutation_log::reset_stream, to make it able to reset thestart_offset.