pp. 129-134, Vila Velha, ES, Brazil, Oct, 2008. [pdf]
This work presents SAPOTI (Dependable TCP/IP Application Servers - in
Portuguese: Servidores de
APlicações cOnfiáveis Tcp/Ip), a distributed tool that
guarantees the availability of TCP/IP application servers,
in particular of Web
servers. The tool is based on the SNMP framework and is executed on a group of
Web servers running on a set of hosts that are monitored by a dependable
distributed network management tool based on the hierarchical diagnosis
algorithm Hi-ADSD with Timestamps. One server is elected to be responsible for
the service. After this server becomes faulty and this event is diagnosed, the
service is automatically recovered by electing another server among those that
are fault-free. A priority scheme based on identifiers is defined. The service
is available even if only one host/server is fault-free. Experiments are
described obtained from a implementation of SAPOTI on a LAN with real Apache
servers. Experiments that involved the injection of 210 faults distributed among
a group of six servers were run, the measured availability was at least 97.3%.
In another experiment with five servers, where 27 faults were injected, the
availability was 99.5% during the whole experiment time.
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