Check if epoch rewards are frozen and avoid putting errors in the logs (

#839)

consensus/istanbul/backend/engine.go

@@ -471,6 +471,7 @@ func (sb *Backend) Finalize(chain consensus.ChainReader, header *types.Header, s
 		snapshot = state.Snapshot()
 		err = sb.distributeEpochRewards(header, state)
 		if err != nil {
+			sb.logger.Error("Failed to distribute epoch rewards", "blockNumber", header.Number, "err", err)
 			state.RevertToSnapshot(snapshot)
 		}
 	}

consensus/istanbul/backend/pos.go

@@ -41,6 +41,15 @@ import (
 func (sb *Backend) distributeEpochRewards(header *types.Header, state *state.StateDB) error {
 	start := time.Now()
 	defer sb.rewardDistributionTimer.UpdateSince(start)
+	logger := sb.logger.New("func", "Backend.distributeEpochPaymentsAndRewards", "blocknum", header.Number.Uint64())
+
+	// Check if reward distribution has been frozen and return early without error if it is.
+	if frozen, err := epoch_rewards.EpochRewardsIsFrozen(header, state); err != nil {
+		logger.Warn("Failed to determine if epoch rewards are frozen", "err", err)
+	} else if frozen {
+		logger.Debug("Epoch rewards are frozen, skipping distribution")
+		return nil
+	}
 
 	err := epoch_rewards.UpdateTargetVotingYield(header, state)
 	if err != nil {
@@ -50,14 +59,16 @@ func (sb *Backend) distributeEpochRewards(header *types.Header, state *state.Sta
 	if err != nil {
 		return err
 	}
-	log.Debug("Calculated target rewards", "validatorReward", validatorReward, "totalVoterRewards", totalVoterRewards, "communityReward", communityReward)
+
+	logger.Debug("Calculated target rewards", "validatorReward", validatorReward, "totalVoterRewards", totalVoterRewards, "communityReward", communityReward)
 
 	// The validator set that signs off on the last block of the epoch is the one that we need to
 	// iterate over.
 	valSet := sb.GetValidators(big.NewInt(header.Number.Int64()-1), header.ParentHash)
 	if len(valSet) == 0 {
+
 		err := errors.New("Unable to fetch validator set to update scores and distribute rewards")
-		sb.logger.Error(err.Error())
+		logger.Error(err.Error())
 		return err
 	}
 

contract_comm/epoch_rewards/epoch_rewards.go

@@ -91,6 +91,20 @@ const epochRewardsABIString string = `[
       "payable": false,
       "stateMutability": "view",
       "type": "function"
+    },
+    {
+      "constant": true,
+      "inputs": [],
+      "name": "frozen",
+      "outputs": [
+        {
+          "name": "",
+          "type": "bool"
+        }
+      ],
+      "payable": false,
+      "stateMutability": "view",
+      "type": "function"
     }
 ]
 `
@@ -135,3 +149,12 @@ func GetCarbonOffsettingPartnerAddress(header *types.Header, state vm.StateDB) (
 	}
 	return carbonOffsettingPartner, nil
 }
+
+func EpochRewardsIsFrozen(header *types.Header, state vm.StateDB) (bool, error) {
+	var frozen bool
+	_, err := contract_comm.MakeStaticCall(params.EpochRewardsRegistryId, epochRewardsABI, "frozen", []interface{}{}, &[]interface{}{&frozen}, params.MaxGasForIsFrozen, header, state)
+	if err != nil {
+		return false, err
+	}
+	return frozen, nil
+}