This commit combines a number of cleanups, targeting both the
code structure and the code logic. Large changes include:
- Using more strongly-typed classes for SHAMap nodes, instead of relying
on runtime-time detection of class types. This change saves 16 bytes
of memory per node.
- Improving the interface of SHAMap::addGiveItem and SHAMap::addItem to
avoid the need for passing two bool arguments.
- Documenting the "copy-on-write" semantics that SHAMap uses to
efficiently track changes in individual nodes.
- Removing unused code and simplifying several APIs.
- Improving function naming.
* Document delete_batch, back_off_milliseconds, age_threshold_seconds.
* Convert those time values to chrono types.
* Fix bug that ignored age_threshold_seconds.
* Add a "recovery buffer" to the config that gives the node a chance to
recover before aborting online delete.
* Add begin/end log messages around the SQL queries.
* Add a new configuration section: [sqlite] to allow tuning the sqlite
database operations. Ignored on full/large history servers.
* Update documentation of [node_db] and [sqlite] in the
rippled-example.cfg file.
Resolves#3321
These changes use the hash of the consensus transaction set when
characterizing the mismatch between a locally built ledger and fully
validated network ledger. This allows detection of non-determinism in
transaction process, in which consensus succeeded, but a node somehow
generated a different subsequent ledger.
