Merge pull request #402 from iExecBlockchainComputing/feature/5.1.0-rc3

Make the couple (chainDealId+taskIndex) unique

src/main/java/com/iexec/core/task/Task.java

@@ -25,6 +25,7 @@
 import lombok.*;
 import org.springframework.data.annotation.Id;
 import org.springframework.data.annotation.Version;
+import org.springframework.data.mongodb.core.index.CompoundIndex;
 import org.springframework.data.mongodb.core.index.Indexed;
 
 import java.util.ArrayList;
@@ -39,6 +40,16 @@
 @NoArgsConstructor
 @AllArgsConstructor
 @Builder
+/**
+ * We need this index to make sure that we don't
+ * add two tasks with the same combination:
+ * (chainDealId + taskIndex).
+ * This can appear when multiple threads call
+ * the method {@link TaskService#addTask()}.
+ */
+@CompoundIndex(name = "unique_deal_idx",
+        def = "{'chainDealId': 1, 'taskIndex': 1}",
+        unique = true)
 public class Task {
 
     @Id