Our own devp2p node on Polygon (Frankfurt). It sees relay TXs and blocks straight from ~30 peers, sends our TXs, and keeps a verified index of the CargoX contracts' logs and the relay TXs' receipts. Every switch below is live and falls back to the RPCs on its own when the listener is down or behind.
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Connection
where the relayer reaches the listener
Features
each one on its own; off = the RPC path as before
Listener box
the node itself
Log index
blocks, logs and receipts verified against the block headers
On the listener
Used by the relayer
Mempool race
relay TXs seen by both sources, judged on the first arrival
P2P send
our relay TXs also pushed through the listener
Relayer
Owner
State
Mempool
P2P send
The first TX, every rebid and every batch also go to the listener when the RPC fan-out starts. The RPCs still decide and report errors; the listener is never waited for.