DatabaseQosPolicy Class Reference

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

Inheritance diagram for DatabaseQosPolicy:

Public Attributes
final ThreadSettings_t	thread
	Database thread settings.
final Duration_t	shutdown_timeout
	The maximum wait time during a shutdown.
final Duration_t	cleanup_period
	The database thread will wake up at this rate to clean up the database.
final Duration_t	shutdown_cleanup_period
	The clean-up period used during database shut-down.
int	initial_records
	The initial number of total records.
int	max_skiplist_level
	The maximum level of the skiplist.
int	initial_weak_references
	The initial number of weak references.
int	max_weak_references
	The maximum number of weak references.
Public Attributes inherited from QosPolicy
final QosPolicyId_t	id
	The ID of this QoS policy.
final String	policy_name
	The name of this QoS policy.

Additional Inherited Members
Public Member Functions inherited from Struct
abstract boolean	equals (Object obj)
abstract int	hashCode ()
String	toString ()
Protected Member Functions inherited from Struct
	Struct ()
abstract void	pull_from_nativeI (long native_status)
abstract void	push_to_nativeI (long native_status)

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 com.rti.dds.domain.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 com.rti.dds.infrastructure.DatabaseQosPolicy.shutdown_timeout and com.rti.dds.infrastructure.DatabaseQosPolicy.shutdown_cleanup_period parameters to decrease the time it takes to delete a com.rti.dds.domain.DomainParticipant when your application is shutting down.

The com.rti.dds.infrastructure.DomainParticipantResourceLimitsQosPolicy controls the memory allocation for elements stored in the database.

This QoS policy is an extension to the DDS standard.

Entity:

com.rti.dds.domain.DomainParticipant

Properties:

RxO = N/A
Changeable NO

Member Data Documentation

final ThreadSettings_t 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: com.rti.dds.infrastructure.ThreadSettingsKind.THREAD_SETTINGS_STDIO

final Duration_t 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,com.rti.dds.infrastructure.Duration_t.INFINITE]

final Duration_t cleanup_period

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

[default] 61 seconds

[range] [0,1 year]

final Duration_t shutdown_cleanup_period

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

[default] 1 second

[range] [0,1 year]

int initial_records

The initial number of total records.

[default] 1024

[range] [1,10 million]

int 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]

int initial_weak_references

The initial number of weak references.

See com.rti.dds.infrastructure.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 com.rti.dds.infrastructure.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

com.rti.dds.infrastructure.DatabaseQosPolicy.max_weak_references

int 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 com.rti.dds.infrastructure.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 com.rti.dds.infrastructure.ResourceLimitsQosPolicy.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] com.rti.dds.infrastructure.ResourceLimitsQosPolicy.LENGTH_UNLIMITED

[range] [1, 100 million] or com.rti.dds.infrastructure.ResourceLimitsQosPolicy.LENGTH_UNLIMITED, >= initial_weak_references

See Also

com.rti.dds.infrastructure.DatabaseQosPolicy.initial_weak_references