Multi-tenancy Mode: Schema, java.sql.SQLException: PooledConnection has already been closed

Ours is a multitenant application running in `SCHEMA` mode on Postgres database.
We are continuously facing `java.sql.SQLException: PooledConnection` has already been closed issue.

Here is the stacktrace for it:
--------------------------------------------------------------------------------------------------------------
```groovy
ERROR org.hibernate.engine.jdbc.spi.SqlExceptionHelper - PooledConnection has already been closed.
ERROR org.grails.web.errors.GrailsExceptionResolver - SQLException occurred when processing request: [GET] /login/auth
PooledConnection has already been closed.. Stacktrace follows:
org.springframework.jdbc.UncategorizedSQLException: Hibernate operation: could not prepare statement; uncategorized SQLException for SQL [select this_.id as id1_84_0_, this_.version as version2_84_0_, this_.date_created as date_cre3_84_0_, this_.logo as logo4_84_0_, this_.organization as organiza5_84_0_, this_.username as username6_84_0_, this_.password as password7_84_0_, this_.status as status8_84_0_, this_.is_infra_provider as is_infra9_84_0_, this_.domain as domain10_84_0_, this_.identifier as identif11_84_0_, this_.email as email12_84_0_ from public.tenant this_ where this_.domain=? limit ?]; SQL state [null]; error code [0]; PooledConnection has already been closed.; nested exception is java.sql.SQLException: PooledConnection has already been closed.
at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:84)
at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:81)
at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:81)
at org.grails.orm.hibernate.GrailsHibernateTemplate.convertJdbcAccessException(GrailsHibernateTemplate.java:723)
at org.grails.orm.hibernate.GrailsHibernateTemplate.convertHibernateAccessException(GrailsHibernateTemplate.java:711)
at org.grails.orm.hibernate.GrailsHibernateTemplate.doExecute(GrailsHibernateTemplate.java:302)
at org.grails.orm.hibernate.GrailsHibernateTemplate.execute(GrailsHibernateTemplate.java:242)
at org.grails.orm.hibernate.GrailsHibernateTemplate.executeWithNewSession(GrailsHibernateTemplate.java:149)
at org.grails.orm.hibernate.GrailsHibernateTemplate.executeWithExistingOrCreateNewSession(GrailsHibernateTemplate.java:208)
at org.grails.orm.hibernate.AbstractHibernateDatastore.withNewSession(AbstractHibernateDatastore.java:362)
at grails.gorm.multitenancy.Tenants$_withId_closure1.doCall(Tenants.groovy:218)
at grails.gorm.multitenancy.Tenants$CurrentTenant.withTenant(Tenants.groovy:318)
at grails.gorm.multitenancy.Tenants.withId(Tenants.groovy:196)
at grails.gorm.multitenancy.Tenants.withId(Tenants.groovy:166)
at grails.plugin.springsecurity.LoginController.auth(LoginController.groovy:62)
at org.grails.core.DefaultGrailsControllerClass$MethodHandleInvoker.invoke(DefaultGrailsControllerClass.java:223)
at org.grails.core.DefaultGrailsControllerClass.invoke(DefaultGrailsControllerClass.java:188)
at org.grails.web.mapping.mvc.UrlMappingsInfoHandlerAdapter.handle(UrlMappingsInfoHandlerAdapter.groovy:90)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85)
at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:129)
at org.springframework.boot.web.filter.ApplicationContextHeaderFilter.doFilterInternal(ApplicationContextHeaderFilter.java:55)
at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61)
at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131)
at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61)
at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:317)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:127)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:91)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:115)
at grails.plugin.springsecurity.web.UpdateRequestContextHolderExceptionTranslationFilter.doFilter(UpdateRequestContextHolderExceptionTranslationFilter.groovy:64)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at grails.plugin.springsecurity.web.filter.GrailsAnonymousAuthenticationFilter.doFilter(GrailsAnonymousAuthenticationFilter.groovy:53)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter.doFilter(RememberMeAuthenticationFilter.java:150)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:169)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:200)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at grails.plugin.springsecurity.web.authentication.logout.MutableLogoutFilter.doFilter(MutableLogoutFilter.groovy:62)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:105)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at grails.plugin.springsecurity.web.SecurityRequestHolderFilter.doFilter(SecurityRequestHolderFilter.groovy:58)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:214)
at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:177)
at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61)
at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131)
at org.grails.web.servlet.mvc.GrailsWebRequestFilter.doFilterInternal(GrailsWebRequestFilter.java:77)
at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61)
at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131)
at org.grails.web.filters.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:67)
at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61)
at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131)
at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61)
at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131)
at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61)
at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131)
at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61)
at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131)
at io.undertow.servlet.handlers.FilterHandler.handleRequest(FilterHandler.java:84)
at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:131)
at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60)
at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77)
at io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:285)
at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:264)
at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81)
at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:175)
at io.undertow.server.Connectors.executeRootHandler(Connectors.java:209)
at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:802)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.sql.SQLException: PooledConnection has already been closed.
at org.springframework.jdbc.datasource.LazyConnectionDataSourceProxy$LazyConnectionInvocationHandler.invoke(LazyConnectionDataSourceProxy.java:376)
at org.springframework.jdbc.datasource.TransactionAwareDataSourceProxy$TransactionAwareInvocationHandler.invoke(TransactionAwareDataSourceProxy.java:240)
at org.springframework.jdbc.datasource.TransactionAwareDataSourceProxy$TransactionAwareInvocationHandler.invoke(TransactionAwareDataSourceProxy.java:240)
at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$5.doPrepare(StatementPreparerImpl.java:146)
at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$StatementPreparationTemplate.prepareStatement(StatementPreparerImpl.java:172)
at org.hibernate.engine.jdbc.internal.StatementPreparerImpl.prepareQueryStatement(StatementPreparerImpl.java:148)
at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1934)
at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1903)
at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1881)
at org.hibernate.loader.Loader.doQuery(Loader.java:925)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:342)
at org.hibernate.loader.Loader.doList(Loader.java:2622)
at org.hibernate.loader.Loader.doList(Loader.java:2605)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2434)
at org.hibernate.loader.Loader.list(Loader.java:2429)
at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:109)
at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1787)
at org.hibernate.internal.CriteriaImpl.list(CriteriaImpl.java:363)
at org.grails.orm.hibernate.query.AbstractHibernateQuery.singleResultViaListCall(AbstractHibernateQuery.java:801)
at org.grails.orm.hibernate.query.AbstractHibernateQuery.singleResult(AbstractHibernateQuery.java:791)
at org.grails.datastore.gorm.finders.AbstractFindByFinder.invokeQuery(AbstractFindByFinder.java:35)
at org.grails.datastore.gorm.finders.AbstractFindByFinder$1.doInSession(AbstractFindByFinder.java:29)
at org.grails.datastore.mapping.core.DatastoreUtils.execute(DatastoreUtils.java:319)
at org.grails.datastore.gorm.finders.AbstractFinder.execute(AbstractFinder.java:42)
at org.grails.datastore.gorm.finders.AbstractFindByFinder.doInvokeInternal(AbstractFindByFinder.java:27)
at org.grails.datastore.gorm.finders.DynamicFinder.invoke(DynamicFinder.java:252)
at org.grails.datastore.gorm.finders.DynamicFinder.invoke(DynamicFinder.java:390)
at org.grails.datastore.gorm.GormStaticApi.methodMissing(GormStaticApi.groovy:172)
at org.grails.datastore.gorm.GormEntity$Trait$Helper.staticMethodMissing(GormEntity.groovy:757)
at grails.plugin.springsecurity.LoginController$_auth_closure1.doCall(LoginController.groovy:63)
at grails.gorm.multitenancy.Tenants$_withId_closure1$_closure3.doCall(Tenants.groovy:225)
at org.grails.orm.hibernate.GrailsHibernateTemplate$1.doInHibernate(GrailsHibernateTemplate.java:152)
at org.grails.orm.hibernate.GrailsHibernateTemplate.doExecute(GrailsHibernateTemplate.java:298)
... 83 common frames omitted
```
--------------------------------------------------------------------------------------------------------------------------------
**Some pointers on this:**

1. **Production environment Configuration:**
```yaml
---
hibernate:
cache:
queries: false
use_second_level_cache: false
use_query_cache: false
region.factory_class: 'org.hibernate.cache.ehcache.EhCacheRegionFactory'

dataSource:
pooled: true
jmxExport: true
driverClassName: org.h2.Driver
username: sa
password:

environments:
production:
dataSource:
dbCreate: none
pooled: true
jmxExport: true
driverClassName: 'org.postgresql.Driver'
dialect: net.kaleidos.hibernate.PostgresqlExtensionsDialect
username: 'root'
password: 'root'
url: 'jdbc:postgresql://someHostname:5432/database'
logSql: true
schemaHandler: flint.forms.TenantSchemaHandler
properties:
jmxEnabled: true
initialSize: 5
maxActive: 50
minIdle: 5
maxIdle: 25
maxWait: 10000
maxAge: 600000
timeBetweenEvictionRunsMillis: 5000
minEvictableIdleTimeMillis: 60000
validationQuery: SELECT 1
validationQueryTimeout: 3
validationInterval: 15000
testOnBorrow: true
testWhileIdle: true
testOnReturn: false
jdbcInterceptors: ConnectionState
defaultTransactionIsolation: 2 # TRANSACTION_READ_COMMITTED

---
grails:
gorm:
multiTenancy:
mode: SCHEMA
tenantResolverClass:
```
**2. Environment Information:**

Operating System: Ubuntu 16.04/CentOS 7
GORM Version: 6.1.4.RELEASE
Grails Version: 3.2.10
JDK Version: 1.8

**3. Libraries Included:**
```groovy
org.grails:grails-datastore-web:6.0.11.RELEASE"
'org.grails', name: 'grails-datastore-gorm-async', version: '6.1.4.RELEASE'
org.postgresql:postgresql:9.4.1212.jre7
org.grails.plugins:postgresql-extensions:5.1.0
org.grails.plugins:hibernate5:6.1.4
org.hibernate:hibernate-core:5.1.2.Final
org.hibernate:hibernate-ehcache:5.1.2.Final
org.hibernate:hibernate-java8:5.1.2.Final
org.springframework.boot:spring-boot-starter-tomcat
```

Start with the stack trace around grails.gorm.multitenancy.Tenants.groovy at lines 166-218 and 318, then inspect grails.plugin.springsecurity.LoginController.groovy at line 62 and the PostgreSQL schema-mode setup. Reproduce the login request and determine why the pooled connection is closed; done means the reported query completes successfully without the SQLException.

Written by the indexing model from the issue text.