Feed peer selection governor with big ledger peers obtained from a snapshot #4850

crocodile-dentist · 2024-04-11T14:18:13Z

Description

Consensus Genesis syncing mode relies on having at least one honest peer to ensure a syncing node will finish on a good chain. Largest stake pools are a good proxy for honesty, and therefore these peers are the big ledger peers, which a syncing node may not be aware of when its ledger state may still be too stale. A snapshot file of these peers can be provided in a node's topology configuration, and this set will be provided to peer selection governor so it has an opportunity to make these connections.

This change modifies ledgerPeersThread to leverage this data, and appropriately randomly pick from this set and respond to peer selection governor when it makes a request for big ledger peers.

Checklist

Branch
- Updated changelog files.
- Commit sequence broadly makes sense
- Commits have useful messages
- The documentation has been properly updated
- New tests are added if needed and existing tests are updated
- If serialization changes, user-facing consequences (e.g. replay from genesis) are confirmed to be intentional.
Pull Request
- Self-reviewed the diff
- Useful pull request description at least containing the following information:
  - What does this PR change?
  - Why these changes were needed?
  - How does this affect downstream repositories and/or end-users?
  - Which ticket does this PR close (if any)? If it does, is it linked?
- Reviewer requested

coot

We also need to add some tests where the simulation nodes are using ledger snapshot rather as a source of big ledger peers. Network simulation tests are located here.

ouroboros-network-api/src/Ouroboros/Network/PeerSelection/LedgerPeers/Utils.hs

ouroboros-network-api/src/Ouroboros/Network/PeerSelection/RelayAccessPoint.hs

ouroboros-network/sim-tests-lib/Test/Ouroboros/Network/LedgerPeers.hs

ouroboros-network-api/src/Ouroboros/Network/PeerSelection/LedgerPeers/Utils.hs

ouroboros-network-api/src/Ouroboros/Network/PeerSelection/LedgerPeers/Type.hs

ouroboros-network/src/Ouroboros/Network/PeerSelection/LedgerPeers.hs

ouroboros-network-api/src/Ouroboros/Network/PeerSelection/LedgerPeers/Type.hs

ouroboros-network-api/src/Ouroboros/Network/PeerSelection/RelayAccessPoint.hs

ouroboros-network-api/src/Ouroboros/Network/PeerSelection/LedgerPeers/Type.hs

bolt12

LGTM just stylistic comments!

bolt12 · 2024-07-23T09:18:29Z

ouroboros-network/src/Ouroboros/Network/PeerSelection/LedgerPeers.hs

+                 let (peersStakeMap, bigPeersStakeMap, lastSnapshotSlot'') =
+                       stakeMapWithSlotOverSource StakeMapOverSource {
+                                                    ledgerSlotNo, ledgerPools, peerSnapshot,
+                                                    lastSnapshotSlot, peerMap, bigPeerMap, ula}


Suggested change

let (peersStakeMap, bigPeersStakeMap, lastSnapshotSlot'') =

stakeMapWithSlotOverSource StakeMapOverSource {

ledgerSlotNo, ledgerPools, peerSnapshot,

lastSnapshotSlot, peerMap, bigPeerMap, ula}

let (peersStakeMap, bigPeersStakeMap, lastSnapshotSlot'') =

stakeMapWithSlotOverSource

StakeMapOverSource {

ledgerSlotNo

, ledgerPools

, peerSnapshot

, lastSnapshotSlot

, peerMap

, bigPeerMap

, ula

}

or

Suggested change

let (peersStakeMap, bigPeersStakeMap, lastSnapshotSlot'') =

stakeMapWithSlotOverSource StakeMapOverSource {

ledgerSlotNo, ledgerPools, peerSnapshot,

lastSnapshotSlot, peerMap, bigPeerMap, ula}

let stakeMapOverSource =

StakeMapOverSource {

ledgerSlotNo

, ledgerPools

, peerSnapshot

, lastSnapshotSlot

, peerMap

, bigPeerMap

, ula

}

(peersStakeMap, bigPeersStakeMap, lastSnapshotSlot'') =

stakeMapWithSlotOverSource stakeMapOverSource

bolt12 · 2024-07-23T09:22:17Z

ouroboros-network/src/Ouroboros/Network/PeerSelection/LedgerPeers.hs

+  case (ledgerWithOrigin, ledgerPeers, peerSnapshot) of
+    (At ledgerSlotNo, LedgerPeers _ ledgerRelays, Just (LedgerPeerSnapshot (At snapshotSlotNo, accSnapshotRelays)))
+      | snapshotSlotNo >= ledgerSlotNo -> -- we cache the peers from the snapshot to avoid unnecessary work
+        case cachedSlot of
+          Just thatSlot | thatSlot == snapshotSlotNo ->
+                          (peerMap, bigPeerMap, cachedSlot)
+          _otherwise -> (accPoolStake (map snd accSnapshotRelays), Map.fromAscList accSnapshotRelays, Just snapshotSlotNo)
+      | otherwise -> (accPoolStake ledgerRelays, accBigPoolStakeMap ledgerRelays, Nothing)
+
+    (_, LedgerPeers _ ledgerRelays, Nothing) -> (accPoolStake ledgerRelays, accBigPoolStakeMap ledgerRelays, Nothing)
+
+    (_, _, Just (LedgerPeerSnapshot (At snapshotSlotNo, accSnapshotRelays)))
+      | After slot <- ula, snapshotSlotNo >= slot -> do
+        case cachedSlot of
+          Just thatSlot | thatSlot == snapshotSlotNo ->
+                          (peerMap, bigPeerMap, cachedSlot)
+          _otherwise -> (accPoolStake (map snd accSnapshotRelays), Map.fromAscList accSnapshotRelays, Just snapshotSlotNo)
+
+    _otherwise -> (Map.empty, Map.empty, Nothing)


Try to keep to 80 character width lines

Depending on its topology configuration, a node may provide diffusion layer with a snapshot of big ledger peers from some slot. This value is provided as an argument when diffusion is initialized, and is provided to ledgerPeersThread function, which contains the logic when these peers, if any, can be provided to peer selection governor when it requests them. This is especially useful when consensus is ran in Genesis mode and when the node is bootstrapping so it may have opportunity to connect to these trustworthy peers when they may not be yet available on its own ledger.

encoding, as well as checking that ToCBOR and FromCBOR are working together correctly.

Test is modified such that ledger peer pool relays are equal modulo fully qualified domain names to pool relays restored from snapshot. Also, since stake is serialised in floating point format, comparison to original Rational values is approximate.

Improved naming of functions related to calculating big ledger stake distribution which were to moved public ouroboros-network-api component.

crocodile-dentist requested a review from a team as a code owner April 11, 2024 14:18

crocodile-dentist force-pushed the mwojtowicz/provide-peers-from-snapshot branch from 4c893c8 to e3cf273 Compare April 11, 2024 15:27

crocodile-dentist self-assigned this Apr 12, 2024

amesgen mentioned this pull request Apr 18, 2024

Support for responding to a LocalStateQuery demand for a snapshot of big ledger peers IntersectMBO/ouroboros-consensus#1067

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crocodile-dentist mentioned this pull request Apr 22, 2024

Introduction of serialization instances in support of ledger peer snapshot #4851

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crocodile-dentist added 4 commits July 23, 2024 13:10

Review - improve naming

33d47bb

Added a property test that verifies validity of peer snapshot CBOR

b494d2d

encoding, as well as checking that ToCBOR and FromCBOR are working together correctly.

Added ledger peer snapshot property tests

748fcf7

Improved naming of functions related to calculating big ledger stake distribution which were to moved public ouroboros-network-api component.

crocodile-dentist force-pushed the mwojtowicz/provide-peers-from-snapshot branch from 170ae15 to 748fcf7 Compare July 23, 2024 11:11

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Merged via the queue into master with commit 88bf776 Jul 23, 2024

crocodile-dentist deleted the mwojtowicz/provide-peers-from-snapshot branch July 23, 2024 12:14

Feed peer selection governor with big ledger peers obtained from a snapshot #4850

Feed peer selection governor with big ledger peers obtained from a snapshot #4850

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crocodile-dentist commented Apr 11, 2024 •

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