Description:
We found a occasionally node hang issue on BSC, I think Geth may
also have the issue, so pick the fix patch here.
The fix on BSC repo: https://github.com/bnb-chain/bsc/pull/3347
When the hang occurs, there are two routines stuck.
- routine 1: AsyncFilter(...)
On node start, it will run part of the DiscoveryV4 protocol, which could
take considerable time, here is its hang callstack:
```
goroutine 9711 [chan receive]: // this routine was stuck on read channel: `<-f.slots`
github.com/ethereum/go-ethereum/p2p/enode.AsyncFilter.func1()
github.com/ethereum/go-ethereum/p2p/enode/iter.go:206 +0x125
created by github.com/ethereum/go-ethereum/p2p/enode.AsyncFilter in goroutine 1
github.com/ethereum/go-ethereum/p2p/enode/iter.go:192 +0x205
```
- Routine 2: Node Stop
It is the main routine to shutdown the process, but it got stuck when it
tries to shutdown the discovery components, as it tries to drain the
channel of `<-f.slots`, but the extra 1 slot will never have chance to
be resumed.
```
goroutine 11796 [chan receive]:
github.com/ethereum/go-ethereum/p2p/enode.(*asyncFilterIter).Close.func1()
github.com/ethereum/go-ethereum/p2p/enode/iter.go:248 +0x5c
sync.(*Once).doSlow(0xc032a97cb8?, 0xc032a97d18?)
sync/once.go:78 +0xab
sync.(*Once).Do(...)
sync/once.go:69
github.com/ethereum/go-ethereum/p2p/enode.(*asyncFilterIter).Close(0xc092ff8d00?)
github.com/ethereum/go-ethereum/p2p/enode/iter.go:244 +0x36
github.com/ethereum/go-ethereum/p2p/enode.(*bufferIter).Close.func1()
github.com/ethereum/go-ethereum/p2p/enode/iter.go:299 +0x24
sync.(*Once).doSlow(0x11a175f?, 0x2bfe63e?)
sync/once.go:78 +0xab
sync.(*Once).Do(...)
sync/once.go:69
github.com/ethereum/go-ethereum/p2p/enode.(*bufferIter).Close(0x30?)
github.com/ethereum/go-ethereum/p2p/enode/iter.go:298 +0x36
github.com/ethereum/go-ethereum/p2p/enode.(*FairMix).Close(0xc0004bfea0)
github.com/ethereum/go-ethereum/p2p/enode/iter.go:379 +0xb7
github.com/ethereum/go-ethereum/eth.(*Ethereum).Stop(0xc000997b00)
github.com/ethereum/go-ethereum/eth/backend.go:960 +0x4a
github.com/ethereum/go-ethereum/node.(*Node).stopServices(0xc0001362a0, {0xc012e16330, 0x1, 0xc000111410?})
github.com/ethereum/go-ethereum/node/node.go:333 +0xb3
github.com/ethereum/go-ethereum/node.(*Node).Close(0xc0001362a0)
github.com/ethereum/go-ethereum/node/node.go:263 +0x167
created by github.com/ethereum/go-ethereum/cmd/utils.StartNode.func1.1 in goroutine 9729
github.com/ethereum/go-ethereum/cmd/utils/cmd.go:101 +0x78
```
The rootcause of the hang is caused by the extra 1 slot, which was
designed to make sure the routines in `AsyncFilter(...)` can be
finished. This PR fixes it by making sure the extra 1 shot can always be
resumed when node shutdown.
This PR improves the speed of Disc/v4 and Disc/v5 based discovery by
adding a prefetch buffer to discovery sources, eliminating slowdowns
due to timeouts and rate mismatch between the two processes.
Since we now want to filter the discv4 nodes iterator, it is being removed
from the default discovery mix in p2p.Server. To keep backwards-compatibility,
the default unfiltered discovery iterator will be utilized by the server when
no protocol-specific discovery is configured.
---------
Signed-off-by: Csaba Kiraly <csaba.kiraly@gmail.com>
Co-authored-by: Felix Lange <fjl@twurst.com>
This adds support for naming the source iterators of FairMix, like so:
mix.AddSource(enode.WithSourceName("mySource", iter))
The source that produced the latest node is returned by the new NodeSource method.
