Chapter 12. Slave operation

Currently this is only implemented for the PostgreSQL backend. To test, issue the following on a clean database:

create table domains (
 id		 SERIAL PRIMARY KEY,
 name		 VARCHAR(255) NOT NULL,
 master		 VARCHAR(20) NOT NULL,
 last_check	 INT DEFAULT NULL,
 type		 VARCHAR(6) NOT NULL,
 account         VARCHAR(40) DEFAULT NULL
);
CREATE INDEX name_index ON domains(name);
GRANT UPDATE ON domains TO pdns;
GRANT SELECT ON domains_id_seq TO pdns;
  
CREATE TABLE records (
        id              SERIAL PRIMARY KEY,
        domain_id       INT DEFAULT NULL,
        name            VARCHAR(255) DEFAULT NULL,
        type            VARCHAR(6) DEFAULT NULL,
        content         VARCHAR(255) DEFAULT NULL,
        ttl             INT DEFAULT NULL,
        prio            INT DEFAULT NULL,
        change_data     INT DEFAULT NULL, 
        CONSTRAINT domain_exists 
        FOREIGN KEY(domain_id) REFERENCES domains(id)
        ON DELETE CASCADE
);

CREATE INDEX name_index ON records(name);
CREATE INDEX nametype_index ON records(name,type);
CREATE INDEX domain_id ON records(domain_id);

GRANT ALL ON records TO pdns;
GRANT ALL ON records_id_seq TO pdns;
      
Now launch PDNS with the slave option in pdns.conf. It should launch normally and report that 'All slave domains are fresh'.

Now connect to your database as user pdns. To become a slave of the 'powerdns.com' domain, execute this:

	insert into domains (name,master,type) values ('powerdns.com','213.244.168.217','SLAVE');
      
And wait awhile for PDNS to pick up the addition - which happens within one minute. Typical output is:
	Apr 09 13:34:29 All slave domains are fresh
	Apr 09 13:35:29 1 slave domain needs checking
	Apr 09 13:35:29 Domain powerdns.com is stale, master serial 1, our serial 0
	Apr 09 13:35:30 [gPgSQLBackend] Connecting to database with connect string 'dbname=pdns user=pdns'
	Apr 09 13:35:30 AXFR started for 'powerdns.com'
	Apr 09 13:35:30 AXFR done for 'powerdns.com'
	Apr 09 13:35:30 [gPgSQLBackend] Closing connection
      

12.1. Details

On launch, PDNS requests from all backends a list of domains which have not been checked recently for changes. This should happen every refresh seconds, as specified in the SOA record. All domains that are unfresh are then checked for changes over at their master. If the SOA serial number there is higher, the domain is retrieved and inserted into the database. In any case, after the check the domain is declared 'unstale', and will only be checked again after refresh seconds have passed.

PDNS also reacts to notifies by immediately checking if the zone has updated and if so, retransfering it.

All backends which implement this feature must make sure that they can handle transactions so as to not leave the zone in a half updated state. MySQL configured with either BerkeleyDB or InnoDB meets this requirement, as do PostgreSQL and Oracle. The Bindbackend implements transaction semantics by renaming files if and only if they have been retrieved completely and parsed correctly.