Thanks for the words of encouragement. Glenn
On Fri, Apr 30, 2004 at 03:27:00PM -0600, Tom Anderson wrote: > I'm just a list lurker (so my opinion doesn't "count") but I'm really > happy to see these fixes. I have had to override JDBCStore and > PersistentManagerBase at my site to make similar fixes so that things > work acceptably (yes, I submitted patches but they weren't accepted). > Having these fixes in would allow me to upgrade to 4.1.x and get rid of > my old overridden classes. > > Thanks Glenn! > ~Tom > > On Apr 30, 2004, at 1:15 PM, [EMAIL PROTECTED] wrote: > > >glenn 2004/04/30 12:15:26 > > > > Modified: catalina/src/share/org/apache/catalina/session > > JDBCStore.java PersistentManagerBase.java > > StandardManager.java StandardSession.java > > StoreBase.java > > Log: > > The JDBCStore required a great deal of unnecessary db > > queries to manage the persisted data. This could severly > > impact its ability to scale to large numbers of sessions. > > > > 1. When a JSESSIONID cookie was submitted with a request where > > the Session no longer exists multiple queries of the db occurred > > to try and load a persisted Session from the Store. I was > > seeing four attempts to load from the persistence store > > each request when a Session did not exist for a JSESSIONID. > > > > PersistentManagerBase swapIn() and swapOut() were patched > > to maintain a Hashtable of JSESSIONID's which do not exist > > in the Store so that they don't have to be checked multiple > > times. Each checkInterval the Hashtable is cleared to > > prevent it from consuming too much memory. > > > > 2. The StoreBase.processExpires() method triggers a load of > > each Session persisted to the db each checkInterval to > > perform its test to determine if the Session has expired. > > This incurred alot of overhead on the db, especially > > if there was a large amount of session data. The number > > of queries performed each checkInterval is 1 + number of > > sessions persisted to the db + number of expired sessions > > removed. > > > > The StoreBase.processExpires() method was overridden > > in JDBCStore. The method in JDBCStore performs a > > query of the db to find only those Sessions which should > > be expired. The number of queries performed here is 1 + > > 2 * the number of expired sessions (load then remove > > of expired session). > > > > 3. JDBCStore.remove() is being called sometimes with a null > > sessionid String causing an unnecessary synchronization > > and db query. > > > > Added a check for a null sessionid String at top of method. > > > > Problems with expiring sessions have been reported numerous times. > > The basic problem is as follows, starting at time 0 min and with > > a max inactive interval of 30 minutes: > > > > 00 min: First request, new session created, LastAccessedTime 0 > > 02 min: Second request, reuse session, LastAccessedTime 0 > > 31 min: Third request, reuse session, LastAccessedTime now 2 > > 33 min: Background manager thread expires session even though > > it has only been two minutes since the remote clients > > last request. > > > > The argument for not changing how this works is based on how > > the Servlet Spec defines Session.getLastAccessedTime(). > > > > But I agree with all those who have complained about this > > behaviour that Tomcat session timeouts are buggy. > > > > So I came up with a compromise that still allows the > > HttpSession.getLastAccessedTime() to return the time of the > > previous request for those who are Servlet Spec purists. > > > > But internally sessions are expired when > > current time > last request + max inactive interval. > > > > When we do a major revision we should consider adding > > the StandardSession.getLastUsedTime() method to the > > org.apache.catalina.Session interface. > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] ---------------------------------------------------------------------- Glenn Nielsen [EMAIL PROTECTED] | /* Spelin donut madder | MOREnet System Programming | * if iz ina coment. | Missouri Research and Education Network | */ | ---------------------------------------------------------------------- --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
