Learning what BBL is
Before diving into a more specific topic, we should demystify the BBL process. Tuxedo uses all three System V interprocess communication mechanisms: message queues as a transport mechanism, semaphores for synchronization, and shared memory for keeping application configuration and dynamic information about the state of the application.
The shared memory region is called the Bulletin Board and the administration process that runs in each Tuxedo application is called the Bulletin Board Liaison (BBL). Because the Tuxedo application consists of many Unix processes starting, working, stopping, and sometimes crashing at different moments in time, it is important to keep the Bulletin Board up to date and ensure consistency despite misbehaving clients and servers.
Monitoring server processes and restarting them as needed is one of several tasks assigned to the BBL process. To investigate, we start with the Tuxedo application developed in the previous chapter and...