Added DbLedgerStorage configuration keys with default values in bookkeeper.conf

[merlimat]

Motivation

Added missing configuration keys for BookKeeper DbLedgerStorage

[yahoocla]

CLA is valid!

[sschepens]

@merlimat do you have any recommendations for rocksdb tuning? I believe if we set writeCacheMaxSizeMb very high, a single flush would write a lot of level0 files, which would probably be above rocksDB_numFilesInLevel0 and it will begin to stall writes. Am I correct?

Is there a good ratio between writeCacheMaxSizeMb and rocksDB_writeBufferSizeMB you find useful?

[sschepens]

@merlimat please read my recent comments on #110

[merlimat]

@sschepens In DbLedgerStorage, RocksDB is used to just store the indexes, not the actual entries payloads. All writes to RocksDB are done in a background flush thread, so the stall are not a concern here.

To recap:

• dbStorage_writeCacheMaxSizeMb : Memory portion where payloads are accumulated before flushing. Ideally this should big enough to accumulate ~1min worth of entries
• dbStorage_rocksDB_writeBufferSizeMB : Size of RocksDB memtable. I don't think this need to be increased from the default 64MB
• dbStorage_rocksDB_blockCacheSize : This is the RocksDB cache, used when reading. It should be big enough to hold the "active" portion of database to avoid disk access to read the indexes.

[rdhabalia]

👍