Re: [SSI-users] migration

[Brian J. W. <Bri...@hp...>]

Vladimir Yu. Tereshchenko wrote:
>  In documentation at SSI www page I found this:
> 
>                      6. IPC
>                            * all IPC objects/mechanisms are
>                              clusterwide:
>                                 * pipes
>                                 * fifos
>                                 * signalling
>                                 * message queues
>                                 * semaphore
> ->                              * shared memory
>                                 * Unix-domain sockets
>                                 * Internet-domain sockets

This feature list refers to System V shared memory being clusterwide. 
Another form of shared memory is done via the clone() system call, which 
is not clusterwide. This form is used to implement "multi-threaded" 
processes on Linux, and might be used to share data between Apache's 
master process and its slaves.

Another potential problem is that clusterwide Unix-domain sockets do not 
yet support sending fds between nodes, which Apache might use to pass 
new connections from the master to one of its slaves. This clusterwide 
fd passing feature will be added sometime in the future.

If you want to set up a web-serving cluster, I suggest you run a 
separate copy of Apache on each node and use our integrated version of 
LVS to load-level connections among them. Aneesh can tell you more about 
this.

Hope this helps,

Brian