Reliable Server PoolingArchitecture

Michael Tüxen

tuexen@fh-muenster.de

The Motivation

• Build systems without a single point of failure by using servers not being highly reliable.

• SCTP addresses network failures.

• RSerPool addresses host failures (as much as possible).

Server Pools

• Use a set of servers instead of one.

• Identify them by a Pool Handle (PH).

• Provide a mechanism to resolve PH to transport addresses.

• State sharing between the servers is out of scope of RSerPool

Entities in the Architecture

• Pool Elements (PEs)– the servers in a server pool.

• Pool Users (PUs)– the clients.

• Name Servers (NSs)– the entities performing the name resolution.

Communication relations

PU

PE PE PE PE PE

NS NS

PU

Protocols

• Aggregate Server Access Protocol (ASAP)– PE <-> NS– PU <-> NS– PU <-> PE (Enhanced Mode)

• Endpoint Name Resolution Protocol (ENRP)– NS <-> NS

What are the protocols used for?

• ASAP– Registration of PEs.– Re-registration of PEs.– Supervision of PEs.– Name resolution.– Failover support.

• ENRP– Complete state sharing between the NSs.

General Considerations

• Lightweight Client have to be supported.

• Two entities are in the transport address selection involved.

• There are other applications for RSerPool: distributed computing, support for transport layer mobility, ...

Failover Support

• Business Cards for PUs being PEs.

• Last Will for preferred PEs to fail over.

• State Cookie for state synchronization.

• Only available in Advanced Mode.