Cheng Chang 00ee89b584 Track WAL in MANIFEST: update WalMetadata for WAL syncing (#7414)
Summary:
There are some tricky behaviors related to WAL sync:

- When creating a WAL, the WAL might not be synced, if the WAL directory is not synced, the WAL file's metadata may not even be synced to disk, so during recovery, when listing the WAL directory, the WAL may not even show up.
- During each DB::Write, the WriteOption can control whether the WAL should be synced, so a WAL previously not synced on creation can be synced during Write.

For each `SyncWAL`, we'll track the synced status and the current WAL size. Previously, we only track the WAL size on closing.
During recovery, we check that the on-disk WAL size is >= the last synced size.

So this PR introduces `synced_size` and `closed` to `WalMetadata` for the above design update.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7414

Test Plan:
- updated wal_edit_test
- updated version_edit_test

Reviewed By: riversand963

Differential Revision: D23796127

Pulled By: cheng-chang

fbshipit-source-id: 5498ab80f537c48a10157e71a4745716aef5cf30
2020-09-22 14:35:14 -07:00
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