System trying to add a second index entry for a given project to the database

[reckart]

Describe the bug
Index metadata is kept in the database. It seems to be possible that situations could occur when the system tries to add a second index metadata entry for a project.

To Reproduce
Not sure. Looks like a race condition.

Expected behavior
Only a single index metadata item for a project should ever be added to a DB. If one already exists, no other one should be added.

Screenshots

2024-08-13 23:07:29 ERROR [inception-worker-1] [SYSTEM] SqlExceptionHelper - (conn=104) Duplicate entry '144' for key 'UK_index_project'
2024-08-13 23:07:29 ERROR [inception-worker-1] [SYSTEM] Task - Task [Rebuilding index...] failed (trigger: [onLayerConfigurationChanged])
javax.persistence.PersistenceException: org.hibernate.exception.ConstraintViolationException: could not execute statement
	at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:154) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
	at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:181) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
	at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:188) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
	at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:762) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
	at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:742) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
	at jdk.internal.reflect.GeneratedMethodAccessor292.invoke(Unknown Source) ~[?:?]
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
	at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
	at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:316) ~[spring-orm-5.3.37.jar:5.3.37]
	at jdk.proxy2/jdk.proxy2.$Proxy193.persist(Unknown Source) ~[?:?]
	at de.tudarmstadt.ukp.inception.search.SearchServiceImpl.loadIndex(SearchServiceImpl.java:264) ~[classes/:?]
	at de.tudarmstadt.ukp.inception.search.SearchServiceImpl.acquireIndex(SearchServiceImpl.java:373) ~[classes/:?]
	at de.tudarmstadt.ukp.inception.search.SearchServiceImpl.reindex(SearchServiceImpl.java:651) ~[classes/:?]
	at de.tudarmstadt.ukp.inception.search.SearchServiceImpl$$FastClassBySpringCGLIB$$d6146f50.invoke(<generated>) ~[classes/:?]
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218) ~[spring-core-5.3.37.jar:5.3.37]
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:792) ~[spring-aop-5.3.37.jar:5.3.37]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.3.37.jar:5.3.37]
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:762) ~[spring-aop-5.3.37.jar:5.3.37]
	at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:123) ~[spring-tx-5.3.37.jar:5.3.37]
	at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:388) ~[spring-tx-5.3.37.jar:5.3.37]
	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) ~[spring-tx-5.3.37.jar:5.3.37]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.37.jar:5.3.37]
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:762) ~[spring-aop-5.3.37.jar:5.3.37]
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:707) ~[spring-aop-5.3.37.jar:5.3.37]
	at de.tudarmstadt.ukp.inception.search.SearchServiceImpl$$EnhancerBySpringCGLIB$$4fefb718.reindex(<generated>) ~[classes/:?]
	at de.tudarmstadt.ukp.inception.search.scheduling.tasks.ReindexTask.execute(ReindexTask.java:71) ~[classes/:?]
	at de.tudarmstadt.ukp.inception.scheduling.Task.runSync(Task.java:203) [classes/:?]
	at de.tudarmstadt.ukp.inception.scheduling.Task.run(Task.java:190) [classes/:?]
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136) [?:?]
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635) [?:?]
	at java.base/java.lang.Thread.run(Thread.java:833) [?:?]

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Additional context
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