Simple Policies

The static name-to-address mapping policy is implemented directly in the policy-switching component. Apart from being called for sites that are configured to use it, it is also invoked when the site in question has only one replica, or if the original policy cannot choose any replica. It can thus be perceived as a fallback mechanism.

The round-robin policy first allocates a private table of counters, where each counter (one per site) points to the replica from which the next response should start. Each counter in the table is indicated by the identifier of the corresponding site. The table is placed in a shared memory chunk, and protected by a special lock. In this way it can be shared by all response-generating processes.