Tuesday, February 24, 2009

DBFS Coordinator

DBFS Coordinator is the central DBFS System Management process. DBFS Co-ord is the gateway to the DBFS system. Co-ord acts as a proxy to the underlying DBFS subsystems and provides a connection which can be used to carry out various file system CRUD operations.

The architecture of the DBFS Co-ord is show below:
Architecture of DBFS Co-ordinator

Bootstrap Manager
Bootstrap Manager is responsible for initializing all the DBFS sub-systems. The inter process communication between various DBFS sub-systems requires each DBFS sub-system to run a listener on a TCP port that is registered with the DBFS Coord. The ports required by each DBFS sub-system is not fixed and therefore, each sub-system is free to choose their port during the bootstrap process and the sub-system is required to communicate the port address to the DBFS sub-system before the Bootstrap Manager finishes the sub-system initialization phase.

DBFS Health Monitor
DBFS Health Monitor is responsible for communicating with each of the DBFS sub-systems to monitor the health of the component and also manages the health of the DBFS system as a whole. DBFS Health Monitor has a heart beat monitor which listens to the DBFS sub-systems during their active lifetime and if there is any anomaly, Health Monitor initiates the failover operation and hands in the control to the FailOver Manager.

FailOver Manager
When the DBFS Health Monitor activates the FailOver Manager, the FailOver Manager calls the Bootstrap Manager to re-initialize the failed sub-system. Also, the FailOver Manager recreates the DBFS state before the component failed. FailOver Manager switches the control from the failed component to the newly activated component in a transparent manner which the DBFS clients are unaware of.

Unified Connection Manager
The Unified Connection Manager is the gateway or the entry point to the DBFS system. The Unified Connection Manager runs at a TCP port that is known to the DBFS clients and all the DBFS clients communicates with the DBFS System through this port. The UCon Manager accepts the incoming requests and creates a new session for each of the DBFS client connection and the DBFS clients can perform various file system related operations through the connection handle. The UCon Manager is responsible for providing a connection handle to the authenticated DBFS clients. It is essential that the UCon Manager runs at a very well known TCP port that the DBFS client is aware of. When the DBFS is shutdown, the UCon Manager terminates all the client connections and waits for the clients to exit if required and carries out the termination in a graceful manner.

No comments: