Fix bugs in block polling logic and serialization

internal/orchestrator/poller.go

@@ -98,7 +98,7 @@ func (p *Poller) Start() {
 						return
 					}
 				}
-				log.Debug().Msgf("Polling blocks %s to %s", blockNumbers[0], endBlock)
+				log.Debug().Msgf("Polling %d blocks starting from %s to %s", len(blockNumbers), blockNumbers[0], endBlock)
 
 				worker := worker.NewWorker(p.rpc)
 				results := worker.Run(blockNumbers)
@@ -131,11 +131,15 @@ func (p *Poller) getBlockRange() ([]*big.Int, error) {
 	startBlock := new(big.Int).Add(p.lastPolledBlock, big.NewInt(1))
 	endBlock := new(big.Int).Add(startBlock, big.NewInt(p.blocksPerPoll-1))
 
+	if startBlock.Cmp(latestBlock) > 0 {
+		log.Debug().Msgf("Start block %s is greater than latest block %s, skipping", startBlock, latestBlock)
+		return nil, nil
+	}
 	if endBlock.Cmp(latestBlock) > 0 {
 		endBlock = latestBlock
 	}
 
-	blockCount := endBlock.Sub(endBlock, startBlock).Int64() + 1
+	blockCount := new(big.Int).Sub(endBlock, startBlock).Int64() + 1
 	blockNumbers := make([]*big.Int, blockCount)
 	for i := int64(0); i < blockCount; i++ {
 		blockNumbers[i] = new(big.Int).Add(startBlock, big.NewInt(i))

internal/worker/serializer.go

@@ -2,6 +2,7 @@ package worker
 
 import (
 	"encoding/json"
+	"fmt"
 	"math/big"
 	"strconv"
 
@@ -10,7 +11,7 @@ import (
 )
 
 func SerializeWorkerResults(chainId *big.Int, blocks []BatchFetchResult[RawBlock], logs []BatchFetchResult[RawLogs], traces []BatchFetchResult[RawTraces]) []WorkerResult {
-	results := make([]WorkerResult, len(blocks))
+	results := make([]WorkerResult, 0, len(blocks))
 
 	rawLogsMap := make(map[string]BatchFetchResult[RawLogs])
 	for _, rawLogs := range logs {
@@ -22,14 +23,20 @@ func SerializeWorkerResults(chainId *big.Int, blocks []BatchFetchResult[RawBlock
 		rawTracesMap[rawTraces.BlockNumber.String()] = rawTraces
 	}
 
-	for i, rawBlock := range blocks {
+	for _, rawBlock := range blocks {
 		result := WorkerResult{
 			BlockNumber: rawBlock.BlockNumber,
 		}
+		if rawBlock.Result == nil {
+			log.Warn().Msgf("Received a nil block result for block %s.", rawBlock.BlockNumber.String())
+			result.Error = fmt.Errorf("received a nil block result from RPC")
+			results = append(results, result)
+			continue
+		}
 
 		if rawBlock.Error != nil {
 			result.Error = rawBlock.Error
-			results[i] = result
+			results = append(results, result)
 			continue
 		}
 
@@ -55,7 +62,7 @@ func SerializeWorkerResults(chainId *big.Int, blocks []BatchFetchResult[RawBlock
 			}
 		}
 
-		results[i] = result
+		results = append(results, result)
 	}
 
 	return results