- Berkeley DB Reference Guide:
- Berkeley DB Replication
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Connecting to a new site
Connecting to a new site in the replication group happens whenever the
DB_ENV->rep_process_message method returns DB_REP_NEWSITE. The application
should assign the new site a local environment ID number, and all future
messages from the site passed to DB_ENV->rep_process_message should include that
environment ID number. It is possible, of course, for the application
to be aware of a new site before the return of DB_ENV->rep_process_message (for
example, applications using connection-oriented protocols are likely to
detect new sites immediately, while applications using broadcast
protocols may not).
Regardless, in applications supporting the dynamic addition of database
environments to replication groups, environments joining an existing
replication group may need to provide contact information. (For
example, in an application using TCP/IP sockets, a DNS name or IP
address might be a reasonable value to provide.) This can be done using
the cdata parameter to the DB_ENV->rep_start method. The information
referenced by cdata is wrapped in the initial contact message
sent by the new environment, and is provided to the existing members of
the group using the rec parameter returned by DB_ENV->rep_process_message.
If no additional information was provided for Berkeley DB to forward to the
existing members of the group, the data field of the rec
parameter passed to the DB_ENV->rep_process_message method will be NULL after
DB_ENV->rep_process_message returns DB_REP_NEWSITE.
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