Support for Genesis consensus mode alternate big ledger peer targets

This change equips peer selection and churn governor to
appropriately respond to change in ledger state judgment
when diffusion is running in Genesis consensus mode. A
separate targets basis is made available in this mode
which uses more hot big ledger peers when a node is syncing
up.

Additional changes in support of this were made to
the configuration module, and some other minor refactorings
were applied as well.

CONTRIBUTING.md

@@ -213,6 +213,9 @@ will make it easier for others to rebase on top of your committed changes).  If
 you need to rebase your branch we prefer to rebase over merge (since then the
 actually merged changes are more explicit).
 
+We also keep the convention that a source branch's name for a pull request
+includes github user name of the contributor.
+
 Since the code base of `ouroboros-network` is quite large, we don't require
 that every commit is buildable across all included packages.  You can update
 upstream dependencies later in the commit history; although note that if you do

ouroboros-network-api/CHANGELOG.md

@@ -17,6 +17,8 @@
 * Renamed:
   * `accBigPoolStake` -> `accumulateBigLedgerStake`
      and `reRelativeStake` -> `recomputeRelativeStake`
+* Added `ConsensusMode` which must be passed to start diffusion in the
+  appropriate mode 
 
 * Added `Measure` and `BoundedMeasure` instances for `SizeInBytes`.
 

ouroboros-network-api/ouroboros-network-api.cabal

@@ -29,6 +29,7 @@ library
                        Ouroboros.Network.BlockFetch.ConsensusInterface
 
                        Ouroboros.Network.CodecCBORTerm
+                       Ouroboros.Network.ConsensusMode
                        Ouroboros.Network.ControlMessage
                        Ouroboros.Network.Handshake
                        Ouroboros.Network.Handshake.Acceptable

ouroboros-network-api/src/Ouroboros/Network/ConsensusMode.hs

@@ -0,0 +1,29 @@
+{-# LANGUAGE DeriveAnyClass #-}
+{-# LANGUAGE DeriveGeneric  #-}
+
+module Ouroboros.Network.ConsensusMode where
+
+import Data.Aeson
+import GHC.Generics (Generic)
+
+-- | Diffusion layer configuration parameter.
+--
+-- The two modes determine which `PeerSelectionTargets` basis is used
+-- by churn and OG. The node's configuration sets this, and diffusion
+-- is initiated and remains only in this mode.
+--
+data ConsensusMode =
+    GenesisMode
+  -- ^ When `LedgerStateJudgement` is `TooOld`, the targets basis is changed
+  -- from default to one specific for this mode, which uses more big ledger peers
+  -- until syncing is complete.
+
+  | PraosMode
+  -- ^ The legacy mode which depends on official relays and/or bootstrap peers
+  -- configuration. This mode uses only the default target basis irrespective
+  -- ledger state.
+  deriving (Eq, Show, Generic, FromJSON)
+
+
+defaultConsensusMode :: ConsensusMode
+defaultConsensusMode = PraosMode

ouroboros-network/CHANGELOG.md

@@ -13,6 +13,16 @@
   bootstrapping a node in Genesis consensus mode, or in general when 
   LedgerStateJudgement = TooOld, subject to conditions in
   `LedgerPeers.ledgerPeersThread`.
+* Diffusion run function in P2P mode has new paramaters:
+    * `daPeerTargets` - replaces daPeerSelectionTargets. `Configuration`
+        module provides an API. Used by peer selection & churn governors. Given
+        required arguments, it returns the correct target basis to use for churn
+        and peer selection governors.
+    * `daConsensusMode` - flag indicating whether diffusion should run in Praos
+      or Genesis mode, which influences what `PeerSelectionTargets` both
+      governors should use. Genesis may use two different sets of targets
+      depending on ledger state, while Praos uses only one set. Either set
+      once active is appropriately churned. 
 
 ### Non-Breaking changes
 
@@ -25,6 +35,9 @@
 * Added property tests checking if `LedgerPeerSnapshot` CBOR encoding is valid,
   and decode/encode = id, as well as some property tests for calculating big ledger
   peers
+* Implemented separate configurable peer selection targets for Praos and
+  Genesis consensus modes. Genesis mode may use more big ledger peers when
+  a node is syncing up. 
 
 ## 0.16.1.1 -- 2024-06-28
 

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

@@ -72,7 +72,7 @@ import Ouroboros.Network.Diffusion.P2P qualified as Diff.P2P
 import Ouroboros.Network.ExitPolicy (RepromoteDelay (..))
 import Ouroboros.Network.NodeToNode.Version (DiffusionMode (..))
 import Ouroboros.Network.PeerSelection.Governor (PeerSelectionTargets (..),
-           PublicPeerSelectionState (..))
+           PublicPeerSelectionState (..), ConsensusModePeerTargets)
 import Ouroboros.Network.PeerSelection.PeerMetric
            (PeerMetricsConfiguration (..), newPeerMetric)
 import Ouroboros.Network.Protocol.Handshake (HandshakeArguments (..))
@@ -112,6 +112,7 @@ import Test.Ouroboros.Network.Diffusion.Node.NodeKernel (NodeKernel (..),
 import Test.Ouroboros.Network.Diffusion.Node.NodeKernel qualified as Node
 import Test.Ouroboros.Network.PeerSelection.RootPeersDNS (DNSLookupDelay,
            DNSTimeout, mockDNSActions)
+import Ouroboros.Network.ConsensusMode (ConsensusMode)
 
 
 data Interfaces m = Interfaces
@@ -141,13 +142,14 @@ data Arguments m = Arguments
     , aShouldChainSyncExit  :: BlockHeader -> m Bool
     , aChainSyncEarlyExit   :: Bool
 
-    , aPeerSelectionTargets :: PeerSelectionTargets
+    , aPeerTargets          :: ConsensusModePeerTargets
     , aReadLocalRootPeers   :: STM m [( HotValency
                                       , WarmValency
                                       , Map RelayAccessPoint ( PeerAdvertise
                                                              , PeerTrustable))]
     , aReadPublicRootPeers  :: STM m (Map RelayAccessPoint PeerAdvertise)
     , aReadUseBootstrapPeers :: Script UseBootstrapPeers
+    , aConsensusMode        :: ConsensusMode
     , aOwnPeerSharing       :: PeerSharing
     , aReadUseLedgerPeers   :: STM m UseLedgerPeers
     , aProtocolIdleTimeout  :: DiffTime
@@ -390,7 +392,7 @@ run blockGeneratorArgs limits ni na tracersExtra tracerBlockFetch =
     mkArgsExtra :: StrictTVar m (Script UseBootstrapPeers)
                 -> Diff.P2P.ArgumentsExtra m
     mkArgsExtra ubpVar = Diff.P2P.ArgumentsExtra
-      { Diff.P2P.daPeerSelectionTargets   = aPeerSelectionTargets na
+      { Diff.P2P.daPeerTargets            = aPeerTargets na
       , Diff.P2P.daReadLocalRootPeers     = aReadLocalRootPeers na
       , Diff.P2P.daReadPublicRootPeers    = aReadPublicRootPeers na
       , Diff.P2P.daReadUseBootstrapPeers  = stepScriptSTM' ubpVar
@@ -401,6 +403,7 @@ run blockGeneratorArgs limits ni na tracersExtra tracerBlockFetch =
       , Diff.P2P.daDeadlineChurnInterval  = 3300
       , Diff.P2P.daBulkChurnInterval      = 300
       , Diff.P2P.daReadLedgerPeerSnapshot = pure Nothing -- ^ tested independently
+      , Diff.P2P.daConsensusMode          = aConsensusMode na
       }
 
     appArgs :: Node.AppArgs BlockHeader Block m