erigon-pulse/cmd/observer
Mark Holt 509a7af26a
Discovery zero refresh timer (#8661)
This fixes an issue where the mumbai testnet node struggle to find
peers. Before this fix in general test peer numbers are typically around
20 in total between eth66, eth67 and eth68. For new peers some can
struggle to find even a single peer after days of operation.

These are the numbers after 12 hours or running on a node which
previously could not find any peers: eth66=13, eth67=76, eth68=91.

The root cause of this issue is the following:

- A significant number of mumbai peers around the boot node return
network ids which are different from those currently available in the
DHT
- The available nodes are all consequently busy and return 'too many
peers' for long periods

These issues case a significant number of discovery timeouts, some of
the queries will never receive a response.

This causes the discovery read loop to enter a channel deadlock - which
means that no responses are processed, nor timeouts fired. This causes
the discovery process in the node to stop. From then on it just
re-requests handshakes from a relatively small number of peers.

This check in fixes this situation with the following changes:

- Remove the deadlock by running the timer in a separate go-routine so
it can run independently of the main request processing.
- Allow the discovery process matcher to match on port if no id match
can be established on initial ping. This allows subsequent node
validation to proceed and if the node proves to be valid via the
remainder of the look-up and handshake process it us used as a valid
peer.
- Completely unsolicited responses, i.e. those which come from a
completely unknown ip:port combination continue to be ignored.
-
2023-11-07 08:48:58 +00:00
..
database
observer
reports
utils
main.go
README.md

Observer - P2P network crawler

Observer crawls the Ethereum network and collects information about the nodes.

Build

make observer

Run

observer --datadir ... --nat extip:<IP> --port <PORT>

Where IP is your public IP, and PORT has to be open for incoming UDP traffic.

See observer --help for available options.

Report

To get the report about the currently known network state run:

observer report --datadir ...

Description

Observer uses discv4 protocol to discover new nodes. Starting from a list of preconfigured "bootnodes" it uses FindNode to obtain their "neighbor" nodes, and then recursively crawls neighbors of neighbors and so on. Each found node is re-crawled again a few times. If the node fails to be pinged after maximum attempts, it is considered "dead", but still re-crawled less often.

A separate "diplomacy" process is doing "handshakes" to obtain information about the discovered nodes. It tries to get RLPx Hello and Eth Status from each node. The handshake repeats a few times according to the configured delays.