The pending_block member of database was a premature optimization and had an
unfortunate tendency to get out of sync, especially when switching forks.
This commit removes it, and substantially improves the handling of transactions
when switching forks. Specifically, flooding or forking no longer causes nodes to
discard valid transactions.
- with this change the fork database now caches blocks that do not link
and attempts to link the unlinked blocks after every new block is
successfully linked.
- with this change the fork database only tracks blocks as far back as
the undo history allows. This significantly reduces memory usage when
there is high witness participation.
The blockchain now has a minimal participation requirement that can only
be overridden with checkpoints. Any time participation falls below a
minimal level no new blocks may be added.
Currently it requires 66% participation and tolerates short periods of
time below 66% participation with a maximum of 500 consecutive blocks
missed. For every two blocks produced 1 can be missed with a slack of
999 bias.
This is done to comply with the policy that transactions should be self
describing and not depend upon implied state. This makes things easier
for everyone to understand exactly when a transaction will be invalid
without having to refer to chain state.
- remove circular dependency with fee_schedule
- unitiy build db_* as database.cpp
- move protocol definitions in separate directory
- combined some objects/evaluators
- combined limit/call evaluator/objects into market_evaluator.*
Core exchange rate is now redundantly stored in price feed for
bitassets, and updated when the median feed changes. This allows feed
producers to update the core exchange rate. Redundant storage is
necessary, because the core exchange rate is needed for user-issued
assets as well as market issued assets.
