1. The Reliable Server Pooling Framework
RSerPool Features:
Lightweight
Realtime
Scalable
Extendable
Simple
RSerPool Terminology:
Pool Element (PE): Server
Pool: Set of PEs
PE ID: Unique ID of PE
Pool Handle: Unique ID of pool
Handlespace: Set of pools
Registrar (PR)
Pool User (PU): Client
RSerPool Protocols:
ASAP (Aggregate Server Access Protocol)
ENRP (Endpoint HaNdlespace Redundancy Protocol)
Our Demo System
Usage of SCTP for:
Multi-Homing
Network Path Redundancy
Dynamic Address Reconfiguration
Message Framing
Thomas Dreibholz's Reliable Server Pooling Page
Application Example
Policy-Based Server Selection
Session Establishment (PU requests service from a pool):
PU asks any PR (e.g. local PR in its LAN) to resolve pool handle to list of PEs
PR selects set of PEs by pool's selection policy (e.g. round robin)
PU puts PE set into its local cache
PU selects one PE, again by policy, and establishes application connection
Subsequent requests may be satisfied from cache (default timeout: 30s)
Failover (PU handles a PE failure):
PU should report the PE's failure to its PR
(PR may decide to remove this PE from the handlespace)
PU selects a new PE (from its cache , or by PR query )
PU invokes an application-specific failover procedure
(Example: file download - tell new PE the file name and last position)
Selections 1 2
SS7 Gateway for Telephone
Signalling over IP Networks
Client-Based Application State Sharing
Our Research Activity
Fast
Server
Selection Policy Performance:
Which server should be selected?
Different capacities
Current load status
=> Definition of appropriate pool policies
Our Prototype Implementation
Our New Policies
Existing Policies
Our New Policies
Weighted Random
Static
Non-Deterministic
Priority Least Used
Dynamic
PE provides information ''How much does a new job increase my load?''
Use PE that will be least loaded after it gets a new job
Design Decisions
Open Source (GPL License)
Platform independence
Currently: Linux, FreeBSD, Darwin, Solaris
Implemented in ANSI-C
Basic Components
rsplib Library
ASAP protocol
Basic Mode API for PE/PU <-> PR communication
Enhanced Mode API: The RSerPool Session Layer
Registrar
ENRP protocol
New policies achieve significant performance gain
Contribution to the standard -> Internet Draft (Status: IETF RSerPool Working Group Document)