The basic design of the multi-threader is to move packets of data from one thread to another. By giving threads the power to communicate through pipes to other processes, and through sockets to other systems it was easy to build a generic packet switch which will route the packet to whichever thread it is addressed. All threads have the same interface so basically any thread will connect anywhere. Without this packet switch technique the nonstop functionality would have been ten times harder.
The other major design breakthrough that enabled the nonstop functionality was the 'double-ended thread'. Half the thread is in one system and the other half in the backup system. However, because the backup system needs an identical thread, the two halves in the same system are joined to form one thread with a PIPS interface through the middle of it.
Back to our main page