add conf for blockChainOnlyPeers pool size

Author: adamsmo

src/main/resources/application.conf

@@ -294,6 +294,10 @@ grothendieck {
     # same peer for previous blocks, until we find one that we have a parent for. This setting determines the batch size
     # of such query (number of blocks returned in a single query).
     block-resolving-depth = 20
+
+    # size of the list that keeps track of peers that are failing to provide us with mpt node
+    # we switch them to download only blockchain elements
+    fastsync-block-chain-only-peers-pool = 100
   }
 
   pruning {

src/main/scala/io/iohk/ethereum/blockchain/sync/FastSync.scala

@@ -5,7 +5,7 @@ import scala.concurrent.ExecutionContext.Implicits.global
 import akka.actor._
 import akka.util.ByteString
 import io.iohk.ethereum.domain.BlockHeader
-import io.iohk.ethereum.network.{EtcPeerManagerActor, Peer, PeerActor}
+import io.iohk.ethereum.network.{EtcPeerManagerActor, Peer}
 import io.iohk.ethereum.network.PeerEventBusActor.PeerEvent.MessageFromPeer
 import io.iohk.ethereum.network.PeerEventBusActor.{PeerSelector, Subscribe, Unsubscribe}
 import io.iohk.ethereum.network.PeerEventBusActor.SubscriptionClassifier.MessageClassifier
@@ -235,7 +235,7 @@ trait FastSync {
 
     private def handleFailingMptPeers: Receive ={
       case BlockChainOnlyDownload(peer) =>
-        blockChainOnlyPeers = blockChainOnlyPeers + peer
+        blockChainOnlyPeers = (blockChainOnlyPeers + peer).take(blockChainOnlyPeersPoolSize)
     }
 
     private def printStatus() = {

src/main/scala/io/iohk/ethereum/utils/Config.scala

@@ -116,6 +116,7 @@ object Config {
 
     val checkForNewBlockInterval: FiniteDuration = syncConfig.getDuration("check-for-new-block-interval").toMillis.millis
     val blockResolveDepth: Int = syncConfig.getInt("block-resolving-depth")
+    val blockChainOnlyPeersPoolSize: Int = syncConfig.getInt("fastsync-block-chain-only-peers-pool")
   }
 
   trait DbConfig {