PersistenceService

Class astutedds::dcps::PersistenceService

ClassList > astutedds > dcps > PersistenceService

OMG-compliant DDS Persistence Service. More...

  • #include <persistence_service.hpp>

Public Functions

Type Name
PersistenceService (const PersistenceService &) = delete
PersistenceService (PersistenceService &&) = delete
std::vector< PersistedSample > get_samples (const std::string & topic_name)
Return all stored samples for the given topic.
bool has_samples (const std::string & topic_name) const
Return true when the service has any samples for the topic.
void notify_writer_deleted (const std::string & topic_name)
Notify the service that all writers for a topic have been deleted.
PersistenceService & operator= (const PersistenceService &) = delete
PersistenceService & operator= (PersistenceService &&) = delete
const std::string & persistence_dir () const
Return the current persistence directory.
void purge_persistent_store (const std::string & topic_name)
Permanently delete the on-disk store for a PERSISTENT topic.
void remove_topic (const std::string & topic_name)
Remove the in-memory store for a topic immediately.
std::size_t sample_count (const std::string & topic_name) const
Return the number of stored samples for the topic.
void set_persistence_dir (const std::string & dir)
Set the directory used for PERSISTENT storage.
void store_sample (const std::string & topic_name, DurabilityQosPolicyKind durability, const DurabilityServiceQosPolicy & service_qos, const CacheChange & change)
Store a data sample for the given topic.

Public Static Functions

Type Name
PersistenceService & instance ()
Return the process-level singleton instance.

Detailed Description

Acts as the backend storage for DataWriters with TRANSIENT or PERSISTENT durability QoS (DDS 1.4 ยง2.2.3.4). The service is a process-level singleton; applications interact with it via the static instance() method.

TRANSIENT mode

Samples are kept in an in-memory ring-buffer governed by the DurabilityServiceQosPolicy of the DataWriter. Data does not outlive the current process.

PERSISTENT mode

Samples are additionally written to a per-topic binary file in persistence_dir_. On startup, or the first time a topic is requested, the service automatically loads any previously persisted samples so that late-joining readers receive data written in earlier process runs.

Cleanup

The DurabilityServiceQosPolicy::service_cleanup_delay field is honoured: after all local writers for a topic are deleted, the service waits that long before purging the in-memory cache (TRANSIENT) or truncating the on-disk file (PERSISTENT).

Thread safety: all public methods are guarded by an internal mutex.

Public Functions Documentation

function PersistenceService [1/3]

astutedds::dcps::PersistenceService::PersistenceService (
    const PersistenceService &
) = delete

function PersistenceService [2/3]

astutedds::dcps::PersistenceService::PersistenceService (
    PersistenceService &&
) = delete

function get_samples

Return all stored samples for the given topic. 

std::vector< PersistedSample > astutedds::dcps::PersistenceService::get_samples (
    const std::string & topic_name
)

Called by DomainParticipant when a late-joining DataReader with TRANSIENT or PERSISTENT durability is matched against a writer.

For PERSISTENT topics, the service will load data from disk if the in-memory cache is empty (e.g. first access after a restart).

Parameters:

  • topic_name Name of the DDS topic.

Returns:

Ordered (oldest-first) vector of persisted samples.

function has_samples

Return true when the service has any samples for the topic. 

bool astutedds::dcps::PersistenceService::has_samples (
    const std::string & topic_name
) const

function notify_writer_deleted

Notify the service that all writers for a topic have been deleted. 

void astutedds::dcps::PersistenceService::notify_writer_deleted (
    const std::string & topic_name
)

After the service_cleanup_delay elapses, the in-memory cache is purged. For PERSISTENT topics the on-disk file is NOT removed, ensuring data survives across restarts.

Parameters:

  • topic_name Name of the DDS topic.

function operator=

PersistenceService & astutedds::dcps::PersistenceService::operator= (
    const PersistenceService &
) = delete

function operator=

PersistenceService & astutedds::dcps::PersistenceService::operator= (
    PersistenceService &&
) = delete

function persistence_dir

Return the current persistence directory. 

inline const std::string & astutedds::dcps::PersistenceService::persistence_dir () const

function purge_persistent_store

Permanently delete the on-disk store for a PERSISTENT topic. 

void astutedds::dcps::PersistenceService::purge_persistent_store (
    const std::string & topic_name
)

Parameters:

  • topic_name Name of the DDS topic.

function remove_topic

Remove the in-memory store for a topic immediately. 

void astutedds::dcps::PersistenceService::remove_topic (
    const std::string & topic_name
)

For PERSISTENT topics the on-disk file is preserved so data can be recovered on the next process start.

Parameters:

  • topic_name Name of the DDS topic.

function sample_count

Return the number of stored samples for the topic. 

std::size_t astutedds::dcps::PersistenceService::sample_count (
    const std::string & topic_name
) const

function set_persistence_dir

Set the directory used for PERSISTENT storage. 

void astutedds::dcps::PersistenceService::set_persistence_dir (
    const std::string & dir
)

Defaults to <cwd>/.astutedds_persistence. Must be called before any PERSISTENT topic is first accessed.

Parameters:

  • dir Absolute or relative path to the persistence directory.

function store_sample

Store a data sample for the given topic. 

void astutedds::dcps::PersistenceService::store_sample (
    const std::string & topic_name,
    DurabilityQosPolicyKind durability,
    const DurabilityServiceQosPolicy & service_qos,
    const CacheChange & change
)

Called by DataWriter::write() when the writer's Durability QoS is TRANSIENT_DURABILITY_QOS or PERSISTENT_DURABILITY_QOS.

The DurabilityServiceQosPolicy governs the in-memory cache limits (history kind, depth, max_samples, max_instances, max_samples_per_instance).

Parameters:

  • topic_name Name of the DDS topic.
  • durability Durability kind (must be TRANSIENT or PERSISTENT).
  • service_qos DurabilityServiceQosPolicy from the DataWriter.
  • change The cache-change to store.

Public Static Functions Documentation

function instance

Return the process-level singleton instance. 

static PersistenceService & astutedds::dcps::PersistenceService::instance ()

The documentation for this class was generated from the following file include/astutedds/dcps/persistence_service.hpp