Randomly, Confluence has been having connection drops to the PostgreSQL database.
I receive this error:
Whats interesting is that my JIRA set up is running on the same server and same instance of PostgreSQL (9.6) completely fine.
I can provide all the logs you need.
One solution that ive been doing is going to PGadmin(PostgreSQL interface tool) to check on the Databases and seeing if they're connected, which they are. So I leave PGadmin running and i restart Confluence through the service menu in computer management (Windows 10 pro).
Confluence starts to run, however this is a temporary fix, because after a few hours or a day Confluence loses connection to PostgreSQL(Which is still running)
Below is an image of how Confluence DB is configured through PostgreSQL using PGadmin

Again, you can see in the image provided above that JIRAdb is there and running perfectly fine.
The two logs below are Catalina Log and Application Log
14-Nov-2018 00:12:37.386 SEVERE [http-nio-8090-exec-10] org.apache.catalina.core.StandardHostValve.custom Exception Processing ErrorPage[errorCode=404, location=/fourohfour.action]
java.util.concurrent.CompletionException: com.atlassian.confluence.tenant.VacantException: Confluence is vacant, a call to tenanted [public abstract org.hibernate.Session org.hibernate.SessionFactory.getCurrentSession() throws org.hibernate.HibernateException] is not allowed.
at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:273)
at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:280)
at java.util.concurrent.CompletableFuture.uniHandle(CompletableFuture.java:824)
at java.util.concurrent.CompletableFuture.uniHandleStage(CompletableFuture.java:834)
at java.util.concurrent.CompletableFuture.handle(CompletableFuture.java:2155)
at java.util.concurrent.CompletableFuture.handle(CompletableFuture.java:110)
at com.atlassian.confluence.impl.concurrency.CompletionStageUtils.foldResult(CompletionStageUtils.java:19)
at com.atlassian.confluence.impl.vcache.SynchronousExternalCache.get(SynchronousExternalCache.java:236)
at com.atlassian.confluence.setup.bandana.ConfluenceCachingBandanaPersister.retrieve(ConfluenceCachingBandanaPersister.java:78)
at com.atlassian.confluence.setup.bandana.ConfluenceCachingBandanaPersister.retrieve(ConfluenceCachingBandanaPersister.java:71)
at com.atlassian.bandana.DefaultBandanaManager.getValue(DefaultBandanaManager.java:32)
at com.atlassian.confluence.themes.DefaultThemeManager.getThemeSettings(DefaultThemeManager.java:73)
at com.atlassian.confluence.themes.DefaultThemeManager.getGlobalThemeKey(DefaultThemeManager.java:49)
at com.atlassian.confluence.themes.DefaultThemeManager.getGlobalTheme(DefaultThemeManager.java:42)
at com.atlassian.confluence.setup.sitemesh.ConfluenceSpaceDecoratorMapper.getDecorator(ConfluenceSpaceDecoratorMapper.java:80)
at com.atlassian.confluence.setup.sitemesh.ConfluenceSpaceDecoratorMapper.getDecorator(ConfluenceSpaceDecoratorMapper.java:53)
at com.opensymphony.module.sitemesh.mapper.AbstractDecoratorMapper.getDecorator(AbstractDecoratorMapper.java:45)
at com.atlassian.confluence.setup.sitemesh.PluginDecoratorMapper.getDecorator(PluginDecoratorMapper.java:32)
at com.opensymphony.module.sitemesh.mapper.AbstractDecoratorMapper.getDecorator(AbstractDecoratorMapper.java:45)
at com.opensymphony.module.sitemesh.mapper.InlineDecoratorMapper.getDecorator(InlineDecoratorMapper.java:41)
at com.atlassian.confluence.util.profiling.ConfluenceDecoratorSelector.selectDecorator(ConfluenceDecoratorSelector.java:64)
at com.opensymphony.sitemesh.webapp.SiteMeshFilter.doFilter(SiteMeshFilter.java:83)
at com.atlassian.confluence.util.profiling.ProfilingSiteMeshFilter.doFilter(ProfilingSiteMeshFilter.java:50)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at com.atlassian.johnson.plugin.servlet.filter.JohnsonServletFilterModuleContainerFilter.doFilter(JohnsonServletFilterModuleContainerFilter.java:47)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at com.atlassian.confluence.util.UserThreadLocalFilter.doFilter(UserThreadLocalFilter.java:39)
at com.atlassian.core.filters.AbstractHttpFilter.doFilter(AbstractHttpFilter.java:31)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at com.atlassian.confluence.web.filter.ConfluenceSecurityFilter.doFilter(ConfluenceSecurityFilter.java:27)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at com.atlassian.seraph.filter.BaseLoginFilter.doFilter(BaseLoginFilter.java:148)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at com.atlassian.johnson.plugin.servlet.filter.JohnsonServletFilterModuleContainerFilter.doFilter(JohnsonServletFilterModuleContainerFilter.java:47)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at com.atlassian.johnson.plugin.servlet.filter.JohnsonServletFilterModuleContainerFilter.doFilter(JohnsonServletFilterModuleContainerFilter.java:47)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at com.atlassian.confluence.util.RequestCacheThreadLocalFilter.doFilter(RequestCacheThreadLocalFilter.java:65)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at com.atlassian.confluence.web.filter.ZipkinTracingFilter.doFilter(ZipkinTracingFilter.java:54)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at com.atlassian.confluence.web.filter.DebugFilter.doFilter(DebugFilter.java:46)
at com.atlassian.core.filters.AbstractHttpFilter.doFilter(AbstractHttpFilter.java:31)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:712)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:461)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:384)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:312)
at org.apache.catalina.core.StandardHostValve.custom(StandardHostValve.java:394)
at org.apache.catalina.core.StandardHostValve.status(StandardHostValve.java:253)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:175)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:770)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1415)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
Caused by: com.atlassian.confluence.tenant.VacantException: Confluence is vacant, a call to tenanted [public abstract org.hibernate.Session org.hibernate.SessionFactory.getCurrentSession() throws org.hibernate.HibernateException] is not allowed.
at com.atlassian.confluence.tenant.TenantGate$1.lambda$create$0(TenantGate.java:43)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:208)
at com.sun.proxy.$Proxy54.getCurrentSession(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:302)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202)
at com.sun.proxy.$Proxy54.getCurrentSession(Unknown Source)
at org.springframework.orm.hibernate5.HibernateTemplate.doExecute(HibernateTemplate.java:344)
at org.springframework.orm.hibernate5.HibernateTemplate.execute(HibernateTemplate.java:313)
at com.atlassian.confluence.setup.bandana.persistence.dao.hibernate.HibernateConfluenceBandanaRecordDao.getRecord(HibernateConfluenceBandanaRecordDao.java:42)
at com.atlassian.confluence.setup.bandana.ConfluenceDaoBandanaPersister.retrieve(ConfluenceDaoBandanaPersister.java:29)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:302)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:281)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:208)
at com.sun.proxy.$Proxy55.retrieve(Unknown Source)
at com.atlassian.confluence.setup.bandana.ConfluenceCachingBandanaPersister.lambda$retrieve$0(ConfluenceCachingBandanaPersister.java:80)
at com.atlassian.confluence.impl.vcache.SynchronousExternalCache.lambda$get$11(SynchronousExternalCache.java:239)
at com.atlassian.confluence.impl.concurrency.CompletionStageUtils.lambda$foldResult$0(CompletionStageUtils.java:19)
at java.util.concurrent.CompletableFuture.uniHandle(CompletableFuture.java:822)
... 70 more
2018-11-13 23:06:47,676 ERROR [C3P0PooledConnectionPoolManager[identityToken->2rvxtv9z4jp4wl1yl4557|6c2fa18e]-HelperThread-#0] [org.postgresql.Driver] connect Connection error:
org.postgresql.util.PSQLException: FATAL: the database system is starting up
at org.postgresql.core.v3.ConnectionFactoryImpl.doAuthentication(ConnectionFactoryImpl.java:438)
at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:222)
at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49)
at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:194)
at org.postgresql.Driver.makeConnection(Driver.java:450)
at org.postgresql.Driver.connect(Driver.java:252)
at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:175)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:220)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:206)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:203)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1138)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1125)
at com.mchange.v2.resourcepool.BasicResourcePool.access$700(BasicResourcePool.java:44)
at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1870)
at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:696)
2018-11-13 23:06:47,754 WARN [C3P0PooledConnectionPoolManager[identityToken->2rvxtv9z4jp4wl1yl4557|6c2fa18e]-HelperThread-#0] [mchange.v2.resourcepool.BasicResourcePool] log com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@72131583 -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception:
org.postgresql.util.PSQLException: FATAL: the database system is starting up
at org.postgresql.core.v3.ConnectionFactoryImpl.doAuthentication(ConnectionFactoryImpl.java:438)
at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:222)
at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49)
at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:194)
at org.postgresql.Driver.makeConnection(Driver.java:450)
at org.postgresql.Driver.connect(Driver.java:252)
at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:175)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:220)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:206)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:203)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1138)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1125)
at com.mchange.v2.resourcepool.BasicResourcePool.access$700(BasicResourcePool.java:44)
at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1870)
at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:696)