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KnownPeers.hs
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KnownPeers.hs
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{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE ScopedTypeVariables #-}
module Ouroboros.Network.PeerSelection.Governor.KnownPeers
( belowTarget
, aboveTarget
) where
import Data.Maybe (fromMaybe)
import Data.Semigroup (Min(..))
import qualified Data.Map.Strict as Map
import qualified Data.Set as Set
import Control.Concurrent.JobPool (Job(..))
import Control.Monad.Class.MonadAsync
import Control.Monad.Class.MonadSTM
import Control.Monad.Class.MonadTime
import Control.Monad.Class.MonadTimer
import Control.Exception (Exception(..), SomeException)
import Ouroboros.Network.PeerSelection.Types
import qualified Ouroboros.Network.PeerSelection.KnownPeers as KnownPeers
import Ouroboros.Network.PeerSelection.Governor.Types
---------------------------
-- Known peers below target
--
-- | If we are below the target of /known peers/ we gossip (if we are above the
-- gossip request threashold).
--
belowTarget :: (MonadAsync m, MonadTimer m, Ord peeraddr)
=> PeerSelectionActions peeraddr peerconn m
-> MkGuardedDecision peeraddr peerconn m
belowTarget actions
policy@PeerSelectionPolicy {
policyMaxInProgressGossipReqs,
policyPickKnownPeersForGossip,
policyGossipRetryTime
}
st@PeerSelectionState {
knownPeers,
inProgressGossipReqs,
targets = PeerSelectionTargets {
targetNumberOfKnownPeers
}
}
-- Are we under target for number of known peers?
| numKnownPeers < targetNumberOfKnownPeers
-- Are we at our limit for number of gossip requests?
, numGossipReqsPossible > 0
-- Are there any known peers that we can send a gossip request to?
-- We can only ask ones where we have not asked them within a certain time.
, not (Set.null availableForGossip)
= Guarded Nothing $ do
selectedForGossip <- pickPeers
policyPickKnownPeersForGossip
(KnownPeers.toMap knownPeers
`Map.restrictKeys` availableForGossip)
numGossipReqsPossible
let numGossipReqs = Set.size selectedForGossip
return $ \now -> Decision {
decisionTrace = TraceGossipRequests
targetNumberOfKnownPeers
numKnownPeers
availableForGossip
selectedForGossip,
decisionState = st {
inProgressGossipReqs = inProgressGossipReqs
+ numGossipReqs,
knownPeers = KnownPeers.setGossipTime
selectedForGossip
(addTime policyGossipRetryTime now)
knownPeers
},
decisionJobs = [jobGossip actions policy
(Set.toList selectedForGossip)]
}
-- If we could gossip except that there are none currently available
-- then we return the next wakeup time (if any)
| numKnownPeers < targetNumberOfKnownPeers
, numGossipReqsPossible > 0
, Set.null availableForGossip
= GuardedSkip (Min <$> KnownPeers.minGossipTime knownPeers)
| otherwise
= GuardedSkip Nothing
where
numKnownPeers = KnownPeers.size knownPeers
numGossipReqsPossible = policyMaxInProgressGossipReqs
- inProgressGossipReqs
availableForGossip = KnownPeers.availableForGossip knownPeers
jobGossip :: forall m peeraddr peerconn.
(MonadAsync m, MonadTimer m, Ord peeraddr)
=> PeerSelectionActions peeraddr peerconn m
-> PeerSelectionPolicy peeraddr m
-> [peeraddr]
-> Job m (Completion m peeraddr peerconn)
jobGossip PeerSelectionActions{requestPeerGossip}
PeerSelectionPolicy{..} =
\peers -> Job (jobPhase1 peers) (handler peers) "gossipPhase1"
where
handler :: [peeraddr] -> SomeException -> Completion m peeraddr peerconn
handler peers e =
Completion $ \st _ ->
Decision {
decisionTrace = TraceGossipResults [ (p, Left e) | p <- peers ],
decisionState = st {
inProgressGossipReqs = inProgressGossipReqs st
- length peers
},
decisionJobs = []
}
jobPhase1 :: [peeraddr] -> m (Completion m peeraddr peerconn)
jobPhase1 peers = do
-- In the typical case, where most requests return within a short
-- timeout we want to collect all the responses into a batch and
-- add them to the known peers set in one go.
--
-- So fire them all off in one go:
gossips <- sequence [ async (requestPeerGossip peer) | peer <- peers ]
-- First to finish synchronisation between /all/ the gossips completing
-- or the timeout (with whatever partial results we have at the time)
results <- waitAllCatchOrTimeout gossips policyGossipBatchWaitTime
case results of
Right totalResults -> do
let peerResults = zip peers totalResults
newPeers = [ p | Right ps <- totalResults, p <- ps ]
return $ Completion $ \st _ -> Decision {
decisionTrace = TraceGossipResults peerResults,
decisionState = st {
--TODO: also update with the failures
knownPeers = KnownPeers.insert
PeerSourceGossip
(const DoAdvertisePeer)
(Set.fromList newPeers)
(knownPeers st),
inProgressGossipReqs = inProgressGossipReqs st
- length peers
},
decisionJobs = []
}
-- But if any don't make the first timeout then they'll be added later
-- when they do reply or never if we hit the hard timeout.
Left partialResults -> do
-- We have to keep track of the relationship between the peer
-- addresses and the gossip requests, completed and still in progress:
let peerResults = [ (p, r)
| (p, Just r) <- zip peers partialResults ]
newPeers = [ p
| Just (Right ps) <- partialResults
, p <- ps ]
peersRemaining = [ p
| (p, Nothing) <- zip peers partialResults ]
gossipsRemaining = [ a
| (a, Nothing) <- zip gossips partialResults ]
return $ Completion $ \st _ -> Decision {
decisionTrace = TraceGossipResults peerResults,
decisionState = st {
--TODO: also update with the failures
knownPeers = KnownPeers.insert
PeerSourceGossip
(const DoAdvertisePeer)
(Set.fromList newPeers)
(knownPeers st),
inProgressGossipReqs = inProgressGossipReqs st
- length peerResults
},
decisionJobs = [Job (jobPhase2 peersRemaining gossipsRemaining)
(handler peersRemaining)
"gossipPhase2"]
}
jobPhase2 :: [peeraddr] -> [Async m [peeraddr]]
-> m (Completion m peeraddr peerconn)
jobPhase2 peers gossips = do
-- Wait again, for all remaining to finish or a timeout.
results <- waitAllCatchOrTimeout
gossips
(policyGossipOverallTimeout
- policyGossipBatchWaitTime)
let peerResults =
case results of
Right totalResults -> zip peers totalResults
Left partialResults -> [ (p, fromMaybe err r)
| (p, r) <- zip peers partialResults ]
where err = Left (toException AsyncCancelled)
newPeers =
case results of
Right totalResults -> [ p | Right ps <- totalResults, p <- ps ]
Left partialResults -> [ p | Just (Right ps) <- partialResults, p <- ps ]
gossipsIncomplete =
case results of
Right _totalResults -> []
Left partialResults ->
[ a | (a, Nothing) <- zip gossips partialResults ]
mapM_ cancel gossipsIncomplete
return $ Completion $ \st _ -> Decision {
decisionTrace = TraceGossipResults peerResults,
decisionState = st {
--TODO: also update with the failures
knownPeers = KnownPeers.insert
PeerSourceGossip
(const DoAdvertisePeer)
(Set.fromList newPeers)
(knownPeers st),
inProgressGossipReqs = inProgressGossipReqs st
- length peers
},
decisionJobs = []
}
---------------------------
-- Known peers above target
--
-- | If we are above the target of /known peers/ (i.e. /cold/, /warm/ and /hot/
-- combined), we drop some of the /cold peers/ but we protect the
-- 'targetNumberOfRootPeers' (from combined sets of /local/ and /public root/
-- peers). 'policyPickColdPeersToForget' policy is used to pick the peers.
--
aboveTarget :: (MonadSTM m, Ord peeraddr)
=> MkGuardedDecision peeraddr peerconn m
aboveTarget PeerSelectionPolicy {
policyPickColdPeersToForget
}
st@PeerSelectionState {
localRootPeers,
publicRootPeers,
knownPeers,
establishedPeers,
inProgressPromoteCold,
targets = PeerSelectionTargets {
targetNumberOfKnownPeers,
targetNumberOfRootPeers
}
}
-- Are we above the target for number of known peers?
| numKnownPeers > targetNumberOfKnownPeers
-- Are there any cold peers we could pick to forget?
-- As a first cheap approximation, check if there are any cold peers.
, numKnownPeers > numEstablishedPeers
-- Beyond this it gets more complicated, and it is not clear that there
-- are any precise cheap checks. So we just do the full calculation.
-- In particular there can be overlap between cold peers and root peers
-- and we have constraints on forgetting root peers.
--
-- We must never pick local root peers to forget as this would violate
-- our invariant that the localRootPeers is a subset of the knownPeers.
--
-- We also need to avoid picking public root peers if that would put us
-- below the target for root peers.
--
, let numRootPeersCanForget = Map.size localRootPeers
+ Set.size publicRootPeers
- targetNumberOfRootPeers
protectedRootPeers = Map.keysSet localRootPeers
<> Set.drop numRootPeersCanForget publicRootPeers
availableToForget = KnownPeers.toMap knownPeers
Map.\\ establishedPeers
`Map.withoutKeys` protectedRootPeers
`Map.withoutKeys` inProgressPromoteCold
, not (Map.null availableToForget)
= Guarded Nothing $ do
let numPeersToForget = numKnownPeers - targetNumberOfKnownPeers
selectedToForget <- pickPeers
policyPickColdPeersToForget
availableToForget
numPeersToForget
return $ \_now -> Decision {
decisionTrace = TraceForgetColdPeers
targetNumberOfKnownPeers
numKnownPeers
selectedToForget,
decisionState = st {
knownPeers = KnownPeers.delete
selectedToForget
knownPeers,
publicRootPeers = publicRootPeers
Set.\\ selectedToForget
},
decisionJobs = []
}
| otherwise
= GuardedSkip Nothing
where
numKnownPeers, numEstablishedPeers :: Int
numKnownPeers = KnownPeers.size knownPeers
numEstablishedPeers = Map.size establishedPeers
-------------------------------
-- Utils
--
-- | Perform a first-to-finish synchronisation between:
--
-- * /all/ the async actions completing; or
-- * the timeout with whatever partial results we have at the time
--
-- The result list is the same length and order as the asyncs, so the results
-- can be paired up.
--
waitAllCatchOrTimeout :: (MonadAsync m, MonadTimer m)
=> [Async m a]
-> DiffTime
-> m (Either [Maybe (Either SomeException a)]
[Either SomeException a])
waitAllCatchOrTimeout as time = do
t <- newTimeout time
results <- atomically $
(Right <$> mapM waitCatchSTM as)
`orElse` (Left <$> (awaitTimeout t >> mapM pollSTM as))
case results of
Right{} -> cancelTimeout t
_ -> return ()
return results