Should Seed/Bootstrap Nodes Run Only the PEX Reactor, or All Reactors?

[tzdybal]

Context

The current implementation starts all reactors even in “seed mode,” despite ADR-052 specifying that seed nodes should run only the PEX reactor (peer exchange). There is ongoing ambiguity about the ideal role for bootstrap/seed nodes, especially as features like reactor-specific peers are introduced.

We need to make an explicit decision: Should seed/bootstrap nodes run only PEX, or should they enable all reactors and act like regular nodes?

Options:

1. Seeds/Bootstrap Nodes Run ONLY PEX

• Pros:
  • Simplifies code & logic: Seeds are always open for peer exchange, do not participate in consensus, state sync, blocksync, etc. This is straightforward, especially with new "reactor-specific peers" designs.
  • Clear security posture: Easier to reason about attack surface, since only peer exchange is handled.
  • Aligns with ADR-052: Matches current architectural documentation.
• Cons:
  • Low incentive to run: Operators might not see direct network benefit for running a "PEX-only" node.
  • No contribution to mempool/block propagation: Seed nodes can't help with block or transaction dissemination – they're just address books.

2. Seeds/Bootstrap Nodes Run ALL Reactors (Like Regular Nodes)

• Pros:
  • More value for operators: Seed nodes can help with mempool, block sync, gossipping, and overall network resilience; this might motivate more community-provided seeds (since they are also full participants).
  • Improved network quality: More nodes actively propagating data, especially beneficial in smaller or less-connected networks.
• Cons:
  • Potential security/exposure: Seed nodes are more exposed to various reactor-related attacks / DoS.
  • Drifts from ADR-052 goal: Would need to update documentation/spec to reflect the new reality.

The Question

What should our implementation do? Should seed/bootstrap nodes only handle peer exchange as prescribed in ADR-052, or should they act as regular nodes with all reactors enabled by default?

Please share your thoughts, concerns, etc

Related links:

• ADR-052: PEX/Seeds
• Modify the Pex Reactor to act as a seed node #1882
• Reactor specific peers #1728