2.1 Overview

The sample application described in this chapter demonstrates how to make a data service application highly available. This sample is for illustrative purposes only. There is no guarantee that this particular application will be highly available.

This chapter assumes that you have read the Sun Cluster Data Services API man pages describing hareg(1M) and haget(1M).

This sample application demonstrates many, but not all, of the features included in the API. Note these aspects of the sample application:

• The data used in the sample application cannot be split easily into disjoint sets, so only one data set (one logical host) is used.

• The in.named data service supports a command line option -b, which points to data in a file system residing on the logical host's disk set.

• In the client-server protocol for a data service, the server sometimes will return its own host name to the client as part of the contents of a message to the client. For such protocols, the client might be depending on this returned host name as the host name to use in the future for contacting the server. For the in.named sample, these issues do not arise. The in.named data service does not need the host name of the server and does not return the host name to clients.

• The in.named data service works off-the-shelf with multihomed hosts.

• The in.named data service works off-the-shelf with the additional IP addresses for the logical hosts. Its stopping and starting methods kill and restart the in.named daemon.