There was a deadlock while trying to finalize transaction during
PostBlock:
1) (*Notary).PostBlock is called under the blockchain lock
2) (*Notary).onTransaction is called inside the PostBlock
3) (*Notary).onTransaction needs to RLock the blockchain to add
completed transaction to the memory pool (and the blockchain is Lock'ed
by this moment)
The problem is fixed by using notifications subsistem, because it's not
required to call (*Notary).PostBlock under the blockchain lock.
And stop dropping connections if we're to receive them. Proper handling is
subject of #1701, but we need at least some connection-level stability for
now.
Node receiving extensible payload from the future is confused and drops
connection. Note that this can still happen if the node is to loose its
synchrony.
Calling `IsInSync()` is quite expensive, so we stop doing that once synchrony
is reached (hence bool flag).
1. Initialization is performed via `Blockchain` methods.
2. Native Oracle contract updates list of oracle nodes
and in-fly requests in `PostPersist`.
3. RPC uses Oracle module directly.
1) It duplicates registration in `version` message handler and no valid
connection can work without version exchange.
2) On public networks we have seed nodes defined by names, so we register
connections to them using these names, but then if connection is dropped we
delist them by IP:PORT combinations which can lead to zero PeerCount() with
all seeds still being registered as connected in the discovery subsystem
and thus no reconnection attempts being made.
It could be the case that checks are performed simultaneosly and
peers connections goes down from 2 to 0. We must take such case into
account and register address as good in discovery.
Right now a single slow peer can slow down whole network.
Do broadcast in 2 parts:
1. Perform non-blocking send to all peers if possible.
2. Perform blocking sends until message is sent to 2/3 of good peers.
Prices are defined in as a coefficients to `BaseExecFee` which
is defined by Policy contract (TBD later).
Native method prices are defined without need to multiply.
It happens from time to time in a four-node private network where there are
seeds (aka CNs) and not a lot of other nodes to connect to.
I don't know how to test for an infinite loop that has no side-effects, so no
test added here.
