Mathias; Thanks for your very informative reply. From your reply, it seems that mod_jk comes close to doing what I want, and should actually provide the fail-over I'm looking for, however not in the most optimal way.
What would be involved in adding (optionally configured) logic to mod_jk that would prefer another running instance over a downed instance, and then remember this as the 'jvmroute' for the given JSESSIONID? Can you provide any insights into mod_webapp? Tom ----- Original Message ----- From: "Mathias Herberts" <[EMAIL PROTECTED]> To: "Tomcat Developers List" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Tuesday, December 18, 2001 10:28 AM Subject: Re: Load balancing - fail-over support with mod_webapp | Hi, I have been working on load balancing Apache/Tomcat clusters. | | In mod_jk, the fail-over is done in the function | get_most_suitable_worker. Basically if the worker who initiated the | session is available (i.e. not in error state), use it, otherwise loop | through the workers and select either the one with the lowest load | balancing value OR one that has been in error for at least | WAIT_BEFORE_RECOVER seconds if such worker exists. Thus the faulted | workers are privileged when selecting a worker for a request whose | worker designated by the jvmroute is not available. | | There is though no algorithm implemented which will map all requests to | the same 'backup' worker, thus either the worker which created the | session (the one in the jvmroute) is available, either another worker | will be selected, but in the latter case there is no guarantee that | 'second choice' will be the same for the next requests. | | Therefore re-routing does exist in mod_jk and works, but it is not | optimal for your case, the worst thing being the | dispatching of incoming requests to a different worker each time, your | distributed session management would therefore give the parenting of the | session to a different worker each time, far from optimal! | | Mathias. | | -- | To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> | For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> | | | -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
