Introduce a final check in the event of any weirdness with message du…

cmd/microservice-ethereum-worker-server/main.go

@@ -19,6 +19,7 @@ import (
 	"github.com/fluidity-money/fluidity-app/common/ethereum/chainlink"
 	"github.com/fluidity-money/fluidity-app/common/ethereum/fluidity"
 
+	"github.com/fluidity-money/fluidity-app/lib/databases/postgres/failsafe"
 	worker_config "github.com/fluidity-money/fluidity-app/lib/databases/postgres/worker"
 	"github.com/fluidity-money/fluidity-app/lib/log"
 	"github.com/fluidity-money/fluidity-app/lib/queue"
@@ -489,6 +490,15 @@ func main() {
 					fluidClients = baseFluidClients
 				)
 
+				if logIndex == nil {
+					log.Fatal(func(k *log.Log) {
+						k.Format(
+							"Log index for transaction hash %v is nil!",
+							transactionHash,
+						)
+					})
+				}
+
 				// if the amount transferred was exactly 0, then we skip to the next transfer
 
 				if isDecoratedTransferZeroVolume(transfer) {
@@ -678,11 +688,17 @@ func main() {
 						secondsSinceLastEpoch,
 						emission,
 					)
+
 					payouts = append(payouts, specialPayout)
 				}
 
 				tokenDetails := fluidTokenDetails
 
+				// check if we've processed this before as a final failsafe before we submit
+				// the balls via a message and store an emission
+
+				failsafe.CommitTransactionHashIndex(transactionHash, *logIndex)
+
 				for _, payoutDetails := range payouts {
 
 					log.Debug(func(k *log.Log) {

database/101-up-postgres/20231214171310-failsafe_add_transaction_hash_index.sql

@@ -0,0 +1,13 @@
+
+-- migrate:up
+
+CREATE TABLE failsafe_transaction_hash (
+	transaction_hash VARCHAR,
+	log_index BIGINT,
+	worker_id VARCHAR,
+	PRIMARY KEY(transaction_hash, log_index, worker_id)
+);
+
+-- migrate:down
+
+DROP TABLE failsafe_transaction_hash;

lib/databases/postgres/failsafe/failsafe.go

@@ -0,0 +1,13 @@
+// Copyright 2022 Fluidity Money. All rights reserved. Use of this
+// source code is governed by a GPL-style license that can be found in the
+// LICENSE.md file.
+
+package failsafe
+
+// Context to use for when failsafe acquisition goes wrong
+const Context = "POSTGRES/FAILSAFE"
+
+// TableFailsafeTransactionHashIndex to be used as the final check before
+// a side effectful action where duplication could possibly happen at the
+// infra level
+const TableFailsafeTransactionHashIndex = "failsafe_transaction_hash_index"

lib/databases/postgres/failsafe/transaction_hash_index.go

@@ -0,0 +1,57 @@
+// Copyright 2022 Fluidity Money. All rights reserved. Use of this
+// source code is governed by a GPL-style license that can be found in the
+// LICENSE.md file.
+
+package failsafe
+
+import (
+	"fmt"
+
+	"github.com/fluidity-money/fluidity-app/lib/log"
+	"github.com/fluidity-money/fluidity-app/lib/postgres"
+	"github.com/fluidity-money/fluidity-app/lib/types/ethereum"
+	"github.com/fluidity-money/fluidity-app/lib/types/misc"
+	"github.com/fluidity-money/fluidity-app/lib/util"
+)
+
+// CommitTransactionHashIndex using the transactionHash given, the
+// logIndex, and the worker ID, forming a composite primary key
+// that guarantees uniqueness. Will Fatal if the insertion fails, with a
+// reason. Useful for identifying duplication-related issues.
+func CommitTransactionHashIndex(transactionHash ethereum.Hash, logIndex misc.BigInt) {
+	postgresClient := postgres.Client()
+
+	statementText := fmt.Sprintf(`
+		INSERT INTO %v (
+			transaction_hash,
+			log_index,
+			worker_id
+		)
+		VALUES (
+			$1,
+			$2,
+			$3
+		)`,
+
+		TableFailsafeTransactionHashIndex,
+	)
+
+	workerId := util.GetWorkerId()
+
+	_, err := postgresClient.Exec(statementText, transactionHash, logIndex, workerId)
+
+	if err != nil {
+		log.Fatal(func(k *log.Log) {
+			k.Context = Context
+
+			k.Format(
+				"Failed to acquire a failsafe for transaction hash %v, log index %v, worker id %v",
+				transactionHash,
+				logIndex,
+				workerId,
+			)
+
+			k.Payload = err
+		})
+	}
+}