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Revision 0ce0edbe120f0ec5c17b3cf7d54a09b1f911e8db authored by Yanqin Jin on 21 November 2019, 00:32:17 UTC, committed by Facebook Github Bot on 21 November 2019, 00:36:29 UTC 
Fix a data race between GetColumnFamilyMetaData and MarkFilesBeingCompacted (#6056)
 
Summary:
Use db mutex to protect the execution of Version::GetColumnFamilyMetaData()
called in DBImpl::GetColumnFamilyMetaData().
Without mutex, GetColumnFamilyMetaData() races with MarkFilesBeingCompacted()
for access to FileMetaData::being_compacted.
Other than mutex, there are several more alternatives.

- Make FileMetaData::being_compacted an atomic variable. This will make
  FileMetaData non-copy-able.

- Separate being_compacted from FileMetaData. This requires re-organizing data
  structures that are already used in many places.

Test Plan (dev server):
```
make check
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6056

Differential Revision: D18620488

Pulled By: riversand963

fbshipit-source-id: 87f89660b5d5e2ab4ef7962b7b2a7d00e346aa3b
1 parent c0983d0
Raw File
DUMP_FORMAT.md 
## RocksDB dump format

The version 1 RocksDB dump format is fairly simple:

1) The dump starts with the magic 8 byte identifier "ROCKDUMP"

2) The magic is followed by an 8 byte big-endian version which is 0x00000001.

3) Next are arbitrarily sized chunks of bytes prepended by 4 byte little endian number indicating how large each chunk is.

4) The first chunk is special and is a json string indicating some things about the creation of this dump.  It contains the following keys:
* database-path: The path of the database this dump was created from.
* hostname: The hostname of the machine where the dump was created.
* creation-time: Unix seconds since epoc when this dump was created.

5) Following the info dump the slices paired into are key/value pairs.
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