Reindexing takes too much time with com.atlassian.jira.issue.index.SearchUnavailableException exceptions

The Problem

After upgrading Jira, some clients are faced with a reindexing problem. It can take too much time because of SLA fields in JEP.
Here is a sample stacktrace:
Error indexing issue ABC-123: Dropping 'customfield_10100'
com.atlassian.jira.issue.index.SearchUnavailableException
	at com.atlassian.jira.issue.index.DefaultIndexManager.getEntitySearcher(DefaultIndexManager.java:878)
	at com.atlassian.jira.issue.index.DefaultIndexManager.getIssueSearcher(DefaultIndexManager.java:858)
	at sun.reflect.GeneratedMethodAccessor542.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.atlassian.jira.config.component.SwitchingInvocationHandler.invoke(SwitchingInvocationHandler.java:22)
	at com.sun.proxy.$Proxy12.getIssueSearcher(Unknown Source)
	at com.atlassian.jira.issue.search.SearchProviderFactoryImpl.getSearcher(SearchProviderFactoryImpl.java:18)
	at com.atlassian.jira.issue.search.providers.LuceneSearchProvider.getIssueSearcher(LuceneSearchProvider.java:148)
	at com.atlassian.jira.issue.search.providers.LuceneSearchProvider.searchCount(LuceneSearchProvider.java:117)
	... 2 filtered
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.atlassian.plugin.util.ContextClassLoaderSettingInvocationHandler.invoke(ContextClassLoaderSettingInvocationHandler.java:26)
	at com.sun.proxy.$Proxy376.searchCount(Unknown Source)
	... 2 filtered
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:302)
	at org.eclipse.gemini.blueprint.service.importer.support.internal.aop.ServiceInvoker.doInvoke(ServiceInvoker.java:56)
	at org.eclipse.gemini.blueprint.service.importer.support.internal.aop.ServiceInvoker.invoke(ServiceInvoker.java:60)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:133)
	at org.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:121)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.eclipse.gemini.blueprint.service.util.internal.aop.ServiceTCCLInterceptor.invokeUnprivileged(ServiceTCCLInterceptor.java:70)
	at org.eclipse.gemini.blueprint.service.util.internal.aop.ServiceTCCLInterceptor.invoke(ServiceTCCLInterceptor.java:53)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.eclipse.gemini.blueprint.service.importer.support.LocalBundleContextAdvice.invoke(LocalBundleContextAdvice.java:57)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:133)
	at org.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:121)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:208)
	at com.sun.proxy.$Proxy3151.searchCount(Unknown Source)
	at com.tuncaysenturk.jira.plugins.enhancer.customfield.sla.e.a(TimeToSlaCFType.java:190)
	at com.tuncaysenturk.jira.plugins.enhancer.customfield.sla.e.a(TimeToSlaCFType.java:176)
	at com.tuncaysenturk.jira.plugins.enhancer.customfield.sla.e.a(TimeToSlaCFType.java:163)
	at com.tuncaysenturk.jira.plugins.enhancer.customfield.sla.e.a(TimeToSlaCFType.java:123)
	at com.tuncaysenturk.jira.plugins.enhancer.customfield.sla.e.a(TimeToSlaCFType.java:225)
The Solution

Go to JEP Menu > Advanced.
Click on Hold reindex.