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.
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.
If the node is to start with seeds unavailable it will try connecting to each
of them three times, blacklist them and then sit forever waiting for
something. It's not a good behavior, it should always try connecting to seeds
if nothing else works.
GetBlockByIndex handler starts sending blocks right from the start index and
if that index is s.chain.BlockHeight() then we're requesting and receiving a
block we already have.
Turns out, C# node no longer broadcasts an Inv when it's creating a block,
instead it sends a ping and if we're not paying attention to the height
specified there we're technically missing a new block. Of course we'll get it
later after ping timer expiration and regular ping/pong sequence, but that's
delaying it for no good reason.
