From 488309b5a932372878d5f10e51dabc9ea69edb43 Mon Sep 17 00:00:00 2001
From: i-norden <iansnorden@gmail.com>
Date: Wed, 29 Dec 2021 01:05:24 -0600
Subject: [PATCH] port retry on deadlock detection feature

---
 statediff/service.go | 34 ++++++++++++++++++++++++++++------
 1 file changed, 28 insertions(+), 6 deletions(-)

diff --git a/statediff/service.go b/statediff/service.go
index 5334b4b3113f..c8c7649fd426 100644
--- a/statediff/service.go
+++ b/statediff/service.go
@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"math/big"
 	"strconv"
+	"strings"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -46,8 +47,12 @@ import (
 	types2 "github.com/ethereum/go-ethereum/statediff/types"
 )
 
-const chainEventChanSize = 20000
-const genesisBlockNumber = 0
+const (
+	chainEventChanSize = 20000
+	genesisBlockNumber = 0
+	defaultRetryLimit  = 3                   // default retry limit once deadlock is detected.
+	deadlockDetected   = "deadlock detected" // 40P01 https://www.postgresql.org/docs/current/errcodes-appendix.html
+)
 
 var writeLoopParams = Params{
 	IntermediateStateNodes:   true,
@@ -122,6 +127,8 @@ type Service struct {
 	enableWriteLoop bool
 	// Size of the worker pool
 	numWorkers uint
+	// Number of retry for aborted transactions due to deadlock.
+	maxRetry uint
 }
 
 // BlockCache caches the last block for safe access from different service loops
@@ -174,6 +181,7 @@ func New(stack *node.Node, ethServ *eth.Ethereum, cfg *ethconfig.Config, params
 		indexer:           indexer,
 		enableWriteLoop:   params.EnableWriteLoop,
 		numWorkers:        workers,
+		maxRetry:          defaultRetryLimit,
 	}
 	stack.RegisterLifecycle(sds)
 	stack.RegisterAPIs(sds.APIs())
@@ -266,7 +274,7 @@ func (sds *Service) WriteLoop(chainEventCh chan core.ChainEvent) {
 func (sds *Service) writeGenesisStateDiff(currBlock *types.Block, workerId uint) {
 	// For genesis block we need to return the entire state trie hence we diff it with an empty trie.
 	log.Info("Writing state diff", "block height", genesisBlockNumber, "worker", workerId)
-	err := sds.writeStateDiff(currBlock, common.Hash{}, writeLoopParams)
+	err := sds.writeStateDiffWithRetry(currBlock, common.Hash{}, writeLoopParams)
 	if err != nil {
 		log.Error("statediff.Service.WriteLoop: processing error", "block height",
 			genesisBlockNumber, "error", err.Error(), "worker", workerId)
@@ -295,7 +303,7 @@ func (sds *Service) writeLoopWorker(params workerParams) {
 			}
 
 			log.Info("Writing state diff", "block height", currentBlock.Number().Uint64(), "worker", params.id)
-			err := sds.writeStateDiff(currentBlock, parentBlock.Root(), writeLoopParams)
+			err := sds.writeStateDiffWithRetry(currentBlock, parentBlock.Root(), writeLoopParams)
 			if err != nil {
 				log.Error("statediff.Service.WriteLoop: processing error", "block height", currentBlock.Number().Uint64(), "error", err.Error(), "worker", params.id)
 				continue
@@ -632,7 +640,7 @@ func (sds *Service) WriteStateDiffAt(blockNumber uint64, params Params) error {
 		parentBlock := sds.BlockChain.GetBlockByHash(currentBlock.ParentHash())
 		parentRoot = parentBlock.Root()
 	}
-	return sds.writeStateDiff(currentBlock, parentRoot, params)
+	return sds.writeStateDiffWithRetry(currentBlock, parentRoot, params)
 }
 
 // WriteStateDiffFor writes a state diff for the specific blockhash directly to the database
@@ -645,7 +653,7 @@ func (sds *Service) WriteStateDiffFor(blockHash common.Hash, params Params) erro
 		parentBlock := sds.BlockChain.GetBlockByHash(currentBlock.ParentHash())
 		parentRoot = parentBlock.Root()
 	}
-	return sds.writeStateDiff(currentBlock, parentRoot, params)
+	return sds.writeStateDiffWithRetry(currentBlock, parentRoot, params)
 }
 
 // Writes a state diff from the current block, parent state root, and provided params
@@ -689,3 +697,17 @@ func (sds *Service) writeStateDiff(block *types.Block, parentRoot common.Hash, p
 	}
 	return nil
 }
+
+// Wrapper function on writeStateDiff to retry when the deadlock is detected.
+func (sds *Service) writeStateDiffWithRetry(block *types.Block, parentRoot common.Hash, params Params) error {
+	var err error
+	for i := uint(0); i < sds.maxRetry; i++ {
+		err = sds.writeStateDiff(block, parentRoot, params)
+		if err != nil && strings.Contains(err.Error(), deadlockDetected) {
+			// Retry only when the deadlock is detected.
+			continue
+		}
+		break
+	}
+	return err
+}