#include <db.h>
int
DB_ENV->rep_set_transport(DB_ENV *env, int envid,
int (*send)(DB_ENV *dbenv,
const DBT *control, const DBT *rec, const DB_LSN *lsnp,
int envid, u_int32_t flags));
The DB_ENV->rep_set_transport() method initializes the communication
infrastructure for a database environment participating in a replicated application.
The DB_ENV->rep_set_transport() method is not called by most
replication applications. It should only be called by Base API applications
implementing their own network transport layer, explicitly holding
replication group elections and handling replication messages outside
of the Replication Manager framework.
The DB_ENV->rep_set_transport() method configures operations
performed using the specified DB_ENV handle,
not all operations performed on the underlying database environment.
The DB_ENV->rep_set_transport() method may be called at any time
during the life of the application.
The DB_ENV->rep_set_transport()
method returns a non-zero error value on failure and 0 on success.
Berkeley DB is not re-entrant. The callback function for this method should not attempt to make library calls (for example, to release locks or close open handles). Re-entering Berkeley DB is not guaranteed to work correctly, and the results are undefined.
The envid parameter is the local environment's ID. It must be a non-negative integer and uniquely identify this Berkeley DB database environment (see Replication environment IDs for more information).
The send callback function is used to transmit data using the replication application's communication infrastructure. The parameters to send are as follows:
dbenv
The dbenv parameter is the enclosing database environment handle.
control
The control parameter is the first of the two data elements to be transmitted by the send function.
rec
The rec parameter is the second of the two data elements to be transmitted by the send function.
lsnp
If the type of message to be sent has an LSN associated with it, then the lsnp parameter contains the LSN of the record being sent. This LSN can be used to determine that certain records have been processed successfully by clients.
envid
The envid parameter is a positive integer identifier that specifies the replication environment to which the message should be sent (see Replication environment IDs for more information).
The special identifier DB_EID_BROADCAST indicates that a message
should be broadcast to every environment in the replication group. The application
may use a true broadcast protocol or may send the message in sequence to each
machine with which it is in communication. In both cases, the sending site should
not be asked to process the message.
The special identifier DB_EID_INVALID indicates an invalid environment ID. This may be used to initialize values that are subsequently checked for validity.
flags
The flags parameter must be set to 0 or by bitwise inclusively OR'ing together one or more of the following values:
The message is a client request that can be satisfied by another client as well as by the master.
The record being sent should be transmitted immediately and not buffered or delayed.
The record being sent is critical for maintaining database integrity (for example, the message includes a transaction commit). The application should take appropriate action to enforce the reliability guarantees it has chosen, such as waiting for acknowledgement from one or more clients.
The message is a client request that has already been made and to which no response was received.
It may sometimes be useful to pass application-specific data to the send function; see Environment FAQ for a discussion on how to do this.
The send function must return 0 on success and non-zero on failure. If the send function fails, the message being sent is necessary to maintain database integrity, and the local log is not configured for synchronous flushing, the local log will be flushed; otherwise, any error from the send function will be ignored.
The DB_ENV->rep_set_transport()
method may fail and return one of the following non-zero errors: