And include some node-specific configurations there with backwards
compatibility. Note that in the future we'll remove Ledger's
fields from the ProtocolConfiguration and it'll be possible to access them in
Blockchain directly (not via .Ledger).
The other option tried was using two configuration types separately, but that
incurs more changes to the codebase, single structure that behaves almost like
the old one is better for backwards compatibility.
Fixes#2676.
It's more generic and convenient than MillisecondsPerBlock. This setting is
made in backwards-compatible fashion, but it'll override SecondsPerBlock if
both are used. Configurations are specifically not changed here, it's
important to check compatibility.
Fixes#2675.
Small (especially dockerized/virtualized) networks often start all nodes at
ones and then we see a lot of connection flapping in the log. This happens
because nodes try to connect to each other simultaneously, establish two
connections, then each one finds a duplicate and drops it, but this can be
different duplicate connections on other sides, so they retry and it all
happens for some time. Eventually everything settles, but we have a lot of
garbage in the log and a lot of useless attempts.
This random waiting timeout doesn't change the logic much, adds a minimal
delay, but increases chances for both nodes to establish a proper single
connection on both sides to only then see another one and drop it on both
sides as well. It leads to almost no flapping in small networks, doesn't
affect much bigger ones. The delay is close to unnoticeable especially if
there is something in the DB for node to process during startup.
Consider mainnet, it has an AttemptConnPeers of 20, so may already have 3
peers and request 20 more, then have 4th connected and attemtp 20 more again,
this leads to a huge number of connections easily.
Consider initial connection phase for public networks:
* simultaneous connections to seeds
* very quick handshakes
* got five handshaked peers and some getaddr requests sent
* but addr replies won't trigger new connections
* so we can stay with just five connections until any of them breaks or a
(long) address checking timer fires
This new timers solves the problem, it's adaptive at the same time. If we have
enough peers we won't be waking up often.
* treat connected/handshaked peers separately in the discoverer, save
"original" address for connected ones, it can be a name instead of IP and
it's important to keep it to avoid reconnections
* store name->IP mapping for seeds if and when they're connected to avoid
reconnections
* block seed if it's detected to be our own node (which is often the case for
small private networks)
* add an event for handshaked peers in the server, connected but
non-handshaked ones are not really helpful for MinPeers or GetAddr logic
Fixes#2796.
Every 1000 blocks seems to be OK for big networks (that only had done some
initial requests previously and then effectively never requested addresses
again because there was a sufficient number of addresses), won't hurt smaller
ones as well (that effectively keep doing this on every connect/disconnect,
peer changes are very rare there, but when they happen we want to have some
quick reaction to these changes).
32 is a very good number, but we all know 42 is a better one. And it can even
be proven by tests with higher peaking TPS values.
You may wonder why is it so good? Because we're using packet-switching
networks mostly and a packet is a packet almost irrespectively of how bit it
is. Yet a packet has some maximum possible size (hi, MTU) and this size most
of the time is 1500 (or a little less than that, hi VPN). Subtract IP header
(20 for IPv4 or 40 for IPv6 not counting options), TCP header (another 20) and
Neo message/payload headers (~8 for this case) and we have just a little more
than 1400 bytes for our dear hashes. Which means that in a single packet most
of the time we can have 42-44 of them, maybe 45. Choosing between these
numbers is not hard then.
We have AttemptConnPeers that is closely related, the more we have there the
bigger the network supposedly is, so it's much better than magic minPoolCount.
Sometimes we already have it, but it's not yet processed, so we can save on
getdata request. It only affects very high-speed networks like 4-1 scenario
and it doesn't affect it a lot, but still we can do it.
This is not exactly the protocol-level batching as was tried in #1770 and
proposed by neo-project/neo#2365, but it's a TCP-level change in that we now
Write() a set of messages and given that Go sets up TCP sockets with
TCP_NODELAY by default this is a substantial change, we have less packets
generated with the same amount of data. It doesn't change anything on properly
connected networks, but the ones with delays benefit from it a lot.
This also improves queueing because we no longer generate 32 messages to
deliver on transaction's GetData, it's just one stream of bytes with 32
messages inside.
Do the same with GetBlocksByIndex, we can have a lot of messages there too.
But don't forget about potential peer DoS attacks, if a peer is to request a
lot of big blocks we need to flush them before we process the whole set.
This allows to naturally scale transaction processing if we have some peer
that is sending a lot of them while others are mostly silent. It also can help
somewhat in the event we have 50 peers that all send transactions. 4+1
scenario benefits a lot from it, while 7+2 slows down a little. Delayed
scenarios don't care.
Surprisingly, this also makes disconnects (#2744) much more rare, 4-node
scenario almost never sees it now. Most probably this is the case where peers
affect each other a lot, single-threaded transaction receiver can be slow
enough to trigger some timeout in getdata handler of its peer (because it
tries to push a number of replies).
It makes sense in general (further narrowing down the time window when
transactions are processed by consensus thread) and it improves block times a
little too, especially in the 7+2 scenario.
Related to #2744.
Until the consensus process starts for a new block and until it really needs
some transactions we can spare some cycles by not delivering transactions to
it. In tests this doesn't affect TPS, but makes block delays a bit more
stable. Related to #2744, I think it also may cause timeouts during
transaction processing (waiting on the consensus process channel while it does
something dBFT-related).
When the network is big enough, MinPeers may be suboptimal for good network
connectivity, but if we know the network size we can do some estimation on the
number of sufficient peers.
They can fail right in the getPeers or they can fail later when packet send
is attempted. Of course they can complete handshake in-between these events,
but most likely they won't and we'll waste more resources on this attempt. So
rule out bad peers immediately.
Drop EnqueueP2PPacket, replace EnqueueHPPacket with EnqueueHPMessage. We use
Enqueue* when we have a specific per-peer message, it makes zero sense
duplicating serialization code for it (unlike Broadcast*).
Follow the general rules of broadcasts, even though it's somewhat different
from Inv, we just want to get some reply from our neighbors to see if we're
behind. We don't strictly need all neighbors for it.
