Hello, we are using Camunda 7.10.0 on multi-pod environment on production. Unfortunately, We are facing a critical problem with OptimisticLockingException - “ENGINE-03005 Execution of ‘UPDATE VariableInstanceEntity[…]’ failed. Entity was updated by another transaction concurrently.”.
Application allows for read-only API calls to retrieve process variables (using RuntimeService.createExecutionQuery()), even during processing the flow execution. On single-pod application everything works fine, but on multi-instance environment, the error mentioned before occurs.
After investigation we have located the source of the problem, which seems to be a json serialization.
Class org.camunda.bpm.engine.impl.persistence.entity.util.TypedValueField has method isValuedImplicitlyUpdated which compares two bytearray values of serialized json values. Unfortunetly, in case of storing list, the order of elements are not guaranteed so set of strings/enums can be serialized to diffrent values. The main effect of above is treating values from get operation as dirty and flush of data occurs:
org.camunda.bpm.engine.OptimisticLockingException: ENGINE-03005 Execution of ‘UPDATE VariableInstanceEntity[c22fb029-6c75-11ea-abf9-0242ac113b08]’ failed. Entity was updated by another transaction concurrently.
at org.camunda.bpm.engine.impl.db.EnginePersistenceLogger.concurrentUpdateDbEntityException(EnginePersistenceLogger.java:134)
at org.camunda.bpm.engine.impl.db.entitymanager.DbEntityManager.handleOptimisticLockingException(DbEntityManager.java:498)
at org.camunda.bpm.engine.impl.db.entitymanager.DbEntityManager.checkFlushResults(DbEntityManager.java:450)
at org.camunda.bpm.engine.impl.db.entitymanager.DbEntityManager.flushDbOperations(DbEntityManager.java:366)
at org.camunda.bpm.engine.impl.db.entitymanager.DbEntityManager.flushDbOperationManager(DbEntityManager.java:324)
at org.camunda.bpm.engine.impl.db.entitymanager.DbEntityManager.flush(DbEntityManager.java:296)
at org.camunda.bpm.engine.impl.interceptor.CommandContext.flushSessions(CommandContext.java:207)
at org.camunda.bpm.engine.impl.interceptor.CommandContext.close(CommandContext.java:136)
at org.camunda.bpm.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:115)
One of workaround we have found is to use @JsonDeserialize(as = LinkedHashSet.class) annotation. But it must be added to every single list and with complex DTO object with multi-layer inner dependency hierarchy.
But is there any way to have more global solution to this problem?
Thanks for reply in advance