SEC. 9.1 CORBA 521
Interoperable Object Group Reference( IOGR)
Repository identifier |
Profile ID |
Profile-1 |
Profile ID |
Profile-N |
IIOP ver. |
Host-1 |
Port-1 |
Object key-1 |
Components |
IIOP ver. |
Host-N |
Port-N |
Object key-N |
Components |
TAG PRIMARY |
Other groupspecific information |
TAG BACKUP |
Other groupspecific information |
Figure 9-17. A possible organization of an IOGR for an object group having a primary and backups.
An Example Architecture
To support object groups and to handle additional failure management, it is necessary to add components to CORBA. One possible architecture of a faulttolerant version of CORBA is shown in Fig. 9-18. This architecture is derived from the Eternal system( Moser et al., 1998; Narasimhan et al., 2000), which provides a fault tolerance infrastructure constructed on top of the Totem reliable group communication system( Moser et al., 1996).
Replication manager |
Object group manager
Property manager
|
Object |
Client or object server |
|
ORB |
|
|
Logging & Recovery
Log
Interceptor Replication
Reliable multicasting
To other replicas
Figure 9-18. An example architecture of a fault-tolerant CORBA system.
There are several components that play an important role in this architecture. By far the most important one is the replication manager, which is responsible for creating and managing a group of replicated objects. In principle, there is only one replication manager, although it may be replicated for fault tolerance.