a flat file. Preserve the BlockstackDB API, but be a lot more rigorous
about checking invariants that must hold across state-preordering,
state-creating, and state-transitioning.
* identify and preserve invariant properties that must hold across name
state-transitions (like no-collisions, or limiting fields that can
change).
* add history validation
* identify consensus-bearing fields, and how each state-creation or
state-transition may affect them (and add runtime checks to see that
they only affect the fields we say they will)
* add decorators that we can apply to name operations to enforce the
above.
* autoincrement peer index
* enable test network methods only if we're a subordinate atlas peer,
and not the main test thread
* locking bugfixes
* remove redundant code
* more debug output
instead of Metropolis-Hastings Random Walk with Backtracking. This is
in light of reading the SIGCOMM 2012 paper by Lee, Xu, and Eun. Also,
update documentation to briefly explain the peer selection and
exploration rationale.
* use metropolis-hastings random walk with random backtracking (variant of MRWB)
to sample the peer graph in as unbiased a way as we can. The only major
difference between this and MRWB is that we don't maintain a peer stack;
we just select a random peer instead of backtracking.
* keep the peer table and the peer database in sync--the table is the
cache-coherent copy.
* keep only 65536 peers. Hash the peer address and a nonce to select a
slot, and ping an old peer before evicting it on collision (and keep the
old peer on collision if it responds)
* a peer can ask for all other peers.
* remove up to 10 peers that are unhealthy per walk; add up to 10 new
peers that we discover on remote peer queries.
* use socket-determined peer address, not RPC-given peer address
* various code cleanups.
