History Expiry (from "drop day" to 4444)

[ScottyPoi]

WIP

Meta Issue for History Expiry / EIP-4444 tasks

https://github.com/ethereum/EIPs/blob/master/EIPS/eip-4444.md

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Informal timeline for history expiry:

flowchart LR
    subgraph N[Today]
    direction TB
    A[Full History] -.- D[Nodes expected to store full chain history]
    end
    subgraph DD[May 1, 2025]
    direction TB
    B[''Drop Day''] -.- D2[Nodes may drop pre-merge Block and Receipts]
    end
    subgraph EIP[Unknown 2026 Hardfork]
    C[EIP-4444] -.- D3[Rolling window History Expiry]
    direction TB
    end
    subgraph ALT[DevConnect???]
    direction TB
    DD2[Off with their Heads!] -.- D4[Nodes may drop pre-merge Headers]
    end
    N --> DD
    DD --> ALT
    ALT --> EIP

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"Drop-Day" - May 1, 2025

EL Clients have agreed to May 1, 2025 date for first phase of History Expiry.

After May 1:

• Clients are no longer expected to store pre-merge Blocks and Receipts
• Client: purge history helper  #3934

DevP2P

• No guarantee of retrieving pre-merge Blocks and Receipts
• Not required to serve pre-merge Blocks and Receipts

Full Genesis Sync:

• Not guaranteed via DevP2P
  • Can still retrieve Headers, but not Block-Bodies or Receipts
• Available via Era1
  • Client: sync from era1 #3869
• Available via Portal HistoryNetwork

RPC Requests (blocks and receipts)

• Can serve from local DB if present
• Can serve from Era1 if present
• Can serve from Portal HistoryNetwork