Summary:
The patch adds statistics support to the integrated BlobDB implementation,
namely the tickers `BLOB_DB_BLOB_FILE_BYTES_READ` and
`BLOB_DB_GC_{NUM_KEYS,BYTES}_RELOCATED`, and the histograms
`BLOB_DB_(DE)COMPRESSION_MICROS`. (Some other statistics, like
`BLOB_DB_BLOB_FILE_BYTES_WRITTEN`, `BLOB_DB_BLOB_FILE_SYNCED`,
`BLOB_DB_BLOB_FILE_{READ,WRITE,SYNC}_MICROS` were already supported.)
Note that the vast majority of the old BlobDB's tickers/histograms are not
really applicable to the new implementation, since they e.g. pertain to calling
dedicated BlobDB APIs (which the integrated BlobDB does not have) or are
tied to the legacy BlobDB's design of writing blob files synchronously when
a write API is called. Such statistics are marked "legacy BlobDB only" in
`statistics.h`.
Fixes https://github.com/facebook/rocksdb/issues/8645 .
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8667
Test Plan: Ran `make check` and tested the new statistics using `db_bench`.
Reviewed By: riversand963
Differential Revision: D30356884
Pulled By: ltamasi
fbshipit-source-id: 5f8a833faee60401c5643c2f0a6c0415488190a4
Levi Tamasi