>3) Users session is on that machine. The url for that machine is machine123.msn.com.
You missed a few steps which outlines the problem with clustered servers not being able to use session scope for a user : -a user types in their login details on www.msn.com and hits "GO". -the request hits www.msn.com and the load balancer assigns the request to a low load box and rewrites the url and forwards the request on ie serv1.msn.com -the request lands at serv1.msn.com and the application on serv1.msn.com services the request and pops a few things in session scope for use later now it knows who the user is because they just logged on, it then sends back a valid response with the users page. -the user gets his response and decides to click their personalised news link www.msn.com/news - we are then submitting a new request to www.msn.com. The load balancer(front processor) may decide that serv1.msn.com is under load or is not available for this request and sends to serv24.msn.com. - The users session is not on this machine so the application cannot obtain the info it needs about the user to proceed with the request. The application has to : a, get the user to relogin b, fail horribly or with a nice smiley message :P The ways around this have been to : c, use black magic to retrieve the users session by black magic I mean cookies with a state id in/a sessionid in the httpheader/session id in a url parameter/hidden form field on a page that matches to a database/file/static storage record containing the users session information. The point is if you use load balanced application server clustering its not straight forward to implement session handling and everyone does it differently subject to their applications needs. Chris McCormack -----Original Message----- From: Bryan Hunt [mailto:[EMAIL PROTECTED] Sent: 08 July 2004 13:00 To: Struts Users Mailing List Subject: Re: some best practices questions The main arguments that people have against session storage is the following a) Excessive memory consumption limits scallability. True, just don't go crazy storing whole db's and stuff in there. b) Sessions can not be shared by webservers in clustered environment. Clustered webservers with shared sessions are such a myth/stupid idea. Do it like hotmail. 1) Request comes in to one of the front processor machines selected by DNS server with multiple resolves for the same address. 2) Choose a machine that that has resources to spare. 3) Users session is on that machine. The url for that machine is machine123.msn.com. 4) User logs off, the next time they come back their session is on some other machine. I fail to see what the point of sharing sessions between machines is ? Even if the machine crashes, they just enter in the initial address (ie hotmail.com ) and get sent to a working machine. So my point is ... what's so bad about sessions ? Also if session ties you to a machine then file storage is twice as bad. --b *********************************************** This e-mail and its attachments are confidential and are intended for the above named recipient only. If this has come to you in error, please notify the sender immediately and delete this e-mail from your system. You must take no action based on this, nor must you copy or disclose it or any part of its contents to any person or organisation. Statements and opinions contained in this email may not necessarily represent those of Littlewoods. Please note that e-mail communications may be monitored. The registered office of Littlewoods Limited and its subsidiaries is 100 Old Hall Street, Liverpool, L70 1AB. Registered number of Littlewoods Limited is 262152. ************************************************ --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
