#include <db_cxx.h>

int
DbEnv::rep_set_request(u_int32_t min, u_int32_t max);

int
DbEnv::rep_get_request(u_int32_t *minp, u_int32_t *maxp);

The DbEnv::rep_set_request method sets a threshold for the minimum and maximum time that a client waits before requesting retransmission of a missing message. Specifically, if the client detects a gap in the sequence of incoming log records or database pages, Berkeley DB will wait for at least min microseconds before requesting retransmission of the missing record. Berkeley DB will double that amount before requesting the same missing record again, and so on, up to a maximum threshold of max microseconds.

These values are thresholds only. Since Berkeley DB has no thread available in the library as a timer, the threshold is only checked when a thread enters the Berkeley DB library to process an incoming replication message. Any amount of time may have passed since the last message arrived and Berkeley DB only checks whether the amount of time since a request was made is beyond the threshold value or not.

By default the minimum is 40000 and the maximum is 1280000 (1.28 seconds). These defaults are fairly arbitrary and the application likely needs to adjust these. The values should be based on expected load and performance characteristics of the master and client host platforms and transport infrastructure as well as round-trip message time.

The database environment's replication subsystem may also be configured using the environment's DB_CONFIG file. The syntax of the entry in that file is a single line with the string "rep_set_request", one or more whitespace characters, and the request times specified in two parts: the min and the max. For example, "rep_set_request 40000 1280000". Because the DB_CONFIG file is read when the database environment is opened, it will silently overrule configuration done before that time.

The DbEnv::rep_set_request method configures a database environment, not only operations performed using the specified DbEnv handle.

The DbEnv::rep_set_request method may be called at any time during the life of the application.

The DbEnv::rep_set_request method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success.

• The maximum number of microseconds a client waits before requesting retransmission.

• The minimum number of microseconds a client waits before requesting retransmission.

The DbEnv::rep_set_request method may fail and throw DbException, encapsulating one of the following non-zero errors, or return one of the following non-zero errors:

• An invalid flag value or parameter was specified.

The DbEnv::rep_get_request method returns the minimum and maximum number of microseconds a client waits before requesting retransmission.

The DbEnv::rep_get_request method may be called at any time during the life of the application.

The DbEnv::rep_get_request method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success.

• The maxp parameter references memory into which the maximum number of microseconds a client will wait before requesting retransmission is copied.

• The minp parameter references memory into which the minimum number of microseconds a client will wait before requesting retransmission is copied.