improve race condition handling

src/main/java/zw/qantra/tm/domain/services/processors/integrations/StewardIntegrationProcessor.java

@@ -46,6 +46,10 @@ public class StewardIntegrationProcessor implements TransactionProcessorInterfac
     @Transactional
     public Object process(Transaction transaction) throws Exception {
 
+        if(settingService.getBooleanSetting("SIMULATE_INTEGRATION_DELAY")){
+            Thread.sleep(5000);
+        }
+
         if(settingService.getBooleanSetting("SIMULATE_INTEGRATION_FAILURE")){
             transaction.setStatus(Status.FAILED);
             transaction.setResponseCode("92");

src/main/java/zw/qantra/tm/domain/workflows/handlers/IntegrationHandler.java

@@ -15,6 +15,9 @@ import zw.qantra.tm.domain.services.processors.TransactionProcessorInterface;
 import zw.qantra.tm.exceptions.ApiException;
 import zw.qantra.tm.utils.Utils;
 
+import java.util.ArrayList;
+import java.util.List;
+
 @Service("integration")
 @RequiredArgsConstructor
 public class IntegrationHandler implements HandlerInterface {
@@ -26,6 +29,8 @@ public class IntegrationHandler implements HandlerInterface {
     private final TransactionEventService transactionEventService;
     private final TransactionService transactionService;
 
+    List<String> lock = new ArrayList<>();
+
     @Override
     public Object process(Transaction transaction) throws Exception {
         transaction.setType(RequestType.INTEGRATION);
@@ -34,6 +39,14 @@ public class IntegrationHandler implements HandlerInterface {
         if(transaction.getIntegrationStatus().equals(Status.SUCCESS))
             return transaction;
 
+        // prevent race condition
+        if (isLocked(transaction.getId().toString())) {
+            logger.info("Transaction already processing - {}", transaction.getId());
+            transaction.setStatus(Status.PROCESSING);
+            return transaction;
+        }
+
+        addLock(transaction.getId().toString());
         TransactionEvent transactionEvent = TransactionEvent.builder()
                 .transactionId(transaction.getId().toString())
                 .event(transaction.getType().name())
@@ -70,6 +83,7 @@ public class IntegrationHandler implements HandlerInterface {
 
         transaction.setIntegrationStatus(transaction.getStatus());
 
+        removeLock(transaction.getId().toString());
         if(transaction.getStatus() != Status.SUCCESS){
             transactionService.save(transaction);
             throw new ApiException("Transaction failed: " + transaction.getErrorMessage() );
@@ -84,4 +98,16 @@ public class IntegrationHandler implements HandlerInterface {
         transactionService.save(transaction);
         return t1;
     }
+
+    private void addLock(String uid) {
+        lock.add(uid);
+    }
+
+    private boolean removeLock(String uid) {
+        return lock.remove(uid);
+    }
+
+    private boolean isLocked(String uid) {
+        return lock.contains(uid);
+    }
 }

src/main/resources/application-vusa.properties

@@ -1,11 +1,11 @@
-sbz.merchant.url=http://localhost:24000/v1
+#sbz.merchant.url=http://localhost:24000/v1
-#sbz.merchant.url=https://api.stewardpay.co.zw/lab/v2
+sbz.merchant.url=https://api.stewardpay.co.zw/lab/v2
 
-#spring.datasource.url=jdbc:postgresql://localhost:5432/qpay?useLegacyDatetimeCode=false
+spring.datasource.url=jdbc:postgresql://localhost:5432/qpay?useLegacyDatetimeCode=false
-#spring.datasource.username=postgres
+spring.datasource.username=postgres
-#spring.datasource.password=example
+spring.datasource.password=example
 
-#nflow.db.postgresql.driver=org.postgresql.Driver
+nflow.db.postgresql.driver=org.postgresql.Driver
-#nflow.db.postgresql.url=jdbc:postgresql://localhost:5432/qpay
+nflow.db.postgresql.url=jdbc:postgresql://localhost:5432/qpay
-#nflow.db.postgresql.user=postgres
+nflow.db.postgresql.user=postgres
-#nflow.db.postgresql.password=example
+nflow.db.postgresql.password=example