A beginner needs help

Elastic Stack Logstash
3

Thank you for your help,if I can learn how to create filter for one of my log files I'm sure I can continue doing this for others as well.Here is the part of log file:

2013-08-13 16:05:10,241 [1] ERROR NHibernate.Util.ADOExceptionReporter - Session is currently disconnected
2013-08-13 16:05:10,469 [1] ERROR LogExceptionHandler - Unhandled Exception
NHibernate.HibernateException: Session is currently disconnected
at NHibernate.AdoNet.ConnectionManager.GetConnection()
at NHibernate.AdoNet.AbstractBatcher.Prepare(IDbCommand cmd)
at NHibernate.AdoNet.AbstractBatcher.ExecuteReader(IDbCommand cmd)
at NHibernate.Loader.Loader.GetResultSet(IDbCommand st, Boolean autoDiscoverTypes, Boolean callable, RowSelection selection, ISessionImplementor session)
at NHibernate.Loader.Loader.DoQuery(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies)
at NHibernate.Loader.Loader.DoQueryAndInitializeNonLazyCollections(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies)
at NHibernate.Loader.Loader.LoadEntity(ISessionImplementor session, Object id, IType identifierType, Object optionalObject, String optionalEntityName, Object optionalIdentifier, IEntityPersister persister)
at NHibernate.Loader.Entity.AbstractEntityLoader.Load(ISessionImplementor session, Object id, Object optionalObject, Object optionalId)
at NHibernate.Loader.Entity.AbstractEntityLoader.Load(Object id, Object optionalObject, ISessionImplementor session)
at NHibernate.Event.Default.DefaultLoadEventListener.LoadFromDatasource(LoadEvent event, IEntityPersister persister, EntityKey keyToLoad, LoadType options)
at NHibernate.Event.Default.DefaultLoadEventListener.Load(LoadEvent event, IEntityPersister persister, EntityKey keyToLoad, LoadType options)
at NHibernate.Event.Default.DefaultLoadEventListener.OnLoad(LoadEvent event, LoadType loadType)
at NHibernate.Impl.SessionImpl.FireLoad(LoadEvent event, LoadType loadType)
at NHibernate.Impl.SessionImpl.Get(String entityName, Object id)
at NHibernate.Impl.SessionImpl.Get(Type entityClass, Object id)
at NHibernate.Impl.SessionImpl.Get[T](Object id)

I've tried to use Grok constructor but I was not successful.
Thank you for your help