Blockchain's subscriptions, unsubscriptions and notifications are
handled by a single notificationDispatcher routine. Thus, on attempt
to send the subsequent event to Blockchain's subscribers, dispatcher
can't handle subscriptions\unsubscriptions. Make subscription and
unsubscription to be a non-blocking operation for blockchain on the
server side, otherwise it may cause the dispatcher locks.
To achieve this, use a separate lock for those code that make calls
to blockchain's subscription API and for subscription counters on
the server side.
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.
If VUB-th block is received, we still can't guaranty that transaction
wasn't accepted to chain. Back this situation by rolling back to a
poll-based waiter.
Do not block subscribers until the unsubscription request to RPC server
is completed. Otherwise, another notification may be received from the
RPC server which will block the unsubscription process.
At the same time, fix event-based waiter. We must not block the receiver
channel during unsubscription because there's a chance that subsequent
event will be sent by the server. We need to read this event in order not
to block the WSClient's readloop.
Bad contract -> no contract. Unfortunately we've got a broken
6f1837723768f27a6f6a14452977e3e0e264f2cc contract on the mainnet which can't
be decoded (even though it had been saved successfully), so this is a
temporary fix for #2801 to be able to start mainnet node after shutdown.
v.estack is used throughout the code to work with estack, while ctx.sc.estack
is (theoretically) just a reference to it that is saved on script load and
restored to v.estack on context unload. The problem is that v.estack can grow
as we use it and can be reallocated away from its original slice (saved in the
ctx.sc.estack), so either ctx.sc.estack should be a pointer or we need to
ensure that it's correct when loading a new script. The second approach is a
bit safer for now and it fixes#2798.
client_test.go:1935:
Error Trace: /home/rik/dev/neo-go/pkg/services/rpcsrv/client_test.go:1935
Error: Should NOT be empty, but was 00000000-0000-0000-0000-000000000000
Test: TestClient_Iterator_SessionConfigVariations/sessions_disabled
It's obviously empty, since we have sessions disabled, but it was not
considered to be empty in testify 1.7.0, now it is, see 840cb80149
There is a security issue found in github.com/btcsuite/btcd that we don't care
about (we're only using 256k1 implementation), but GitHub complains about
it. We could update to github.com/btcsuite/btcd/btcec/v2, but it's now just a
thin wrapper over github.com/decred/dcrd/dcrec/secp256k1/v4, so we better use
it directly.
* strip NEP-XX methods before going into generator to avoid unused imports
* nepXX.Invoker types already include Call
* always import util, it's used for Hash
Execution events are followed by block events, not vise versa, thus,
we can wait until VUB block to be accepted to be sure that
transaction wasn't accepted to chain.
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.
When block is being spread through the network we can get a lot of invs with
the same hash. Some more stale nodes may also announce previous or some
earlier block. We can avoid full DB lookup for them and minimize inv handling
time (timeouts in inv handler had happened in #2744).
It doesn't affect tests, just makes node a little less likely to spend some
considerable amount of time in the inv handler.
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.
