DDS_DatabaseQosPolicy Struct Reference

Various threads and resource limits settings used by RTI Connext to control its internal database. More...

Data Fields
struct DDS_ThreadSettings_t	thread
	Database thread settings.
struct DDS_Duration_t	shutdown_timeout
	The maximum wait time during a shutdown.
struct DDS_Duration_t	cleanup_period
	The database thread will wake up at this rate to clean up the database.
struct DDS_Duration_t	shutdown_cleanup_period
	The clean-up period used during database shut-down.
DDS_Long	initial_records
	The initial number of total records.
DDS_Long	max_skiplist_level
	The maximum level of the skiplist.
DDS_Long	max_weak_references
	The maximum number of weak references.
DDS_Long	initial_weak_references
	The initial number of weak references.

Detailed Description

Various threads and resource limits settings used by RTI Connext to control its internal database.

RTI uses an internal in-memory "database" to store information about entities created locally as well as remote entities found during the discovery process. This database uses a background thread to garbage-collect records related to deleted entities. When the DDS_DomainParticipant that maintains this database is deleted, it shuts down this thread.

The Database QoS policy is used to configure how RTI Connext manages its database, including how often it cleans up, the priority of the database thread, and limits on resources that may be allocated by the database.

You may be interested in modifying the DDS_DatabaseQosPolicy::shutdown_timeout and DDS_DatabaseQosPolicy::shutdown_cleanup_period parameters to decrease the time it takes to delete a DDS_DomainParticipant when your application is shutting down.

The DDS_DomainParticipantResourceLimitsQosPolicy controls the memory allocation for elements stored in the database.

This QoS policy is an extension to the DDS standard.

Entity:

DDS_DomainParticipant

Properties:

RxO = N/A
Changeable NO

Field Documentation

struct DDS_ThreadSettings_t DDS_DatabaseQosPolicy::thread

Database thread settings.

There is only one database thread: the clean-up thread.

[default] Priority: LOW.
The actual value depends on your architecture:

For Windows: -3
For Linux: OS default priority
For a complete list of platform specific values, please refer to Platform Notes.

[default] Stack Size: The actual value depends on your architecture:

For Windows: OS default stack size
For Linux: OS default stack size
For a complete list of platform specific values, please refer to Platform Notes.

[default] Mask: DDS_THREAD_SETTINGS_STDIO

struct DDS_Duration_t DDS_DatabaseQosPolicy::shutdown_timeout

The maximum wait time during a shutdown.

The domain participant will exit after the timeout, even if the database has not been fully cleaned up.

[default] 15 seconds

[range] [0,DDS_DURATION_INFINITE]

struct DDS_Duration_t DDS_DatabaseQosPolicy::cleanup_period

The database thread will wake up at this rate to clean up the database.

[default] 61 seconds

[range] [0,1 year]

struct DDS_Duration_t DDS_DatabaseQosPolicy::shutdown_cleanup_period

The clean-up period used during database shut-down.

[default] 1 second

[range] [0,1 year]

DDS_Long DDS_DatabaseQosPolicy::initial_records

The initial number of total records.

[default] 1024

[range] [1,10 million]

DDS_Long DDS_DatabaseQosPolicy::max_skiplist_level

The maximum level of the skiplist.

The skiplist is used to keep records in the database. Usually, the search time is log2(N), where N is the total number of records in one skiplist. However, once N exceeds 2^n, where n is the maximum skiplist level, the search time will become more and more linear. Therefore, the maximum level should be set such that 2^n is larger than the maximum(N among all skiplists). Usually, the maximum N is the maximum number of remote and local writers or readers.

[default] 14

[range] [1,31]

DDS_Long DDS_DatabaseQosPolicy::max_weak_references

The maximum number of weak references.

A weak reference is an internal data structure that refers to a record within RTI Connext' internal database. This field configures the maximum number of such references that RTI Connext may create.

The actual number of weak references is permitted to grow from an initial value (indicated by DDS_DatabaseQosPolicy::initial_weak_references) to this maximum. To prevent RTI Connext from allocating any weak references after the system has reached a steady state, set the initial and maximum values equal to one another. To indicate that the number of weak references should continue to grow as needed indefinitely, set this field to DDS_LENGTH_UNLIMITED. Be aware that although a single weak reference occupies very little memory, allocating a very large number of them can have a significant impact on your overall memory usage.

Tuning this value precisely is difficult without intimate knowledge of the structure of RTI Connext' database; doing so is an advanced feature not required by most applications. The default value has been chosen to be sufficient for reasonably large systems. If you believe you may need to modify this value, please consult with RTI support personnel for assistance.

[default] DDS_LENGTH_UNLIMITED

[range] [1, 100 million] or DDS_LENGTH_UNLIMITED, >= initial_weak_references

See Also

DDS_DatabaseQosPolicy::initial_weak_references

DDS_Long DDS_DatabaseQosPolicy::initial_weak_references

The initial number of weak references.

See DDS_DatabaseQosPolicy::max_weak_references for more information about what a weak reference is.

If the QoS set contains an initial_weak_references value that is too small to ever grow to DDS_DatabaseQosPolicy::max_weak_references using RTI Connext' internal algorithm, this value will be adjusted upwards as necessary. Subsequent accesses of this value will reveal the actual initial value used.

Changing the value of this field is an advanced feature; it is recommended that you consult with RTI support personnel before doing so.

[default] 2049, which is the minimum initial value imposed by REDA when the maximum is unlimited. If a lower value is specified, it will simply be increased to 2049 automatically.

[range] [1, 100 million], <= max_weak_references

See Also

DDS_DatabaseQosPolicy::max_weak_references