Add z_liveliness_declare_background_subscriber

docs/api.rst

@@ -1299,6 +1299,7 @@ Functions
 .. autocfunction:: liveliness.h::z_liveliness_undeclare_token
 .. autocfunction:: liveliness.h::z_liveliness_subscriber_options_default
 .. autocfunction:: liveliness.h::z_liveliness_declare_subscriber
+.. autocfunction:: liveliness.h::z_liveliness_declare_background_subscriber
 .. autocfunction:: liveliness.h::z_liveliness_get
 
 

include/zenoh-pico/api/liveliness.h

@@ -111,6 +111,23 @@ z_result_t z_liveliness_subscriber_options_default(z_liveliness_subscriber_optio
 z_result_t z_liveliness_declare_subscriber(const z_loaned_session_t *zs, z_owned_subscriber_t *sub,
                                            const z_loaned_keyexpr_t *keyexpr, z_moved_closure_sample_t *callback,
                                            z_liveliness_subscriber_options_t *options);
+/**
+ * Declares a background subscriber on liveliness tokens that intersect `keyexpr`.
+ * Subscriber callback will be called to process the messages, until the corresponding session is closed or dropped.
+ *
+ * Parameters:
+ *   zs: The Zenoh session.
+ *   keyexpr: The key expression to subscribe to.
+ *   callback: The callback function that will be called each time a liveliness token status is changed.
+ *   options: The options to be passed to the liveliness subscriber declaration.
+ *
+ * Return:
+ *   ``0`` if declare is successful, ``negative value`` otherwise.
+ */
+z_result_t z_liveliness_declare_background_subscriber(const z_loaned_session_t *zs, const z_loaned_keyexpr_t *keyexpr,
+                                                      z_moved_closure_sample_t *callback,
+                                                      z_liveliness_subscriber_options_t *options);
+
 #endif  // Z_FEATURE_SUBSCRIPTION == 1
 
 /**************** Liveliness Query ****************/

src/api/liveliness.c

@@ -116,6 +116,15 @@ z_result_t z_liveliness_declare_subscriber(const z_loaned_session_t *zs, z_owned
 
     return _Z_RES_OK;
 }
+
+z_result_t z_liveliness_declare_background_subscriber(const z_loaned_session_t *zs, const z_loaned_keyexpr_t *keyexpr,
+                                                      z_moved_closure_sample_t *callback,
+                                                      z_liveliness_subscriber_options_t *options) {
+    z_owned_subscriber_t sub;
+    _Z_RETURN_IF_ERR(z_liveliness_declare_subscriber(zs, &sub, keyexpr, callback, options));
+    _z_subscriber_clear(&sub._val);
+    return _Z_RES_OK;
+}
 #endif  // Z_FEATURE_SUBSCRIPTION == 1
 
 /**************** Liveliness Query ****************/

src/session/liveliness.c

@@ -244,9 +244,8 @@ z_result_t _z_liveliness_pending_query_drop(_z_session_t *zn, uint32_t interest_
         ret = _Z_ERR_ENTITY_UNKNOWN;
     }
 
-    _Z_DEBUG("Liveliness pending query drop %i resolve result %i", (int)interest_id, ret);
-
     if (ret == _Z_RES_OK) {
+        _Z_DEBUG("Liveliness pending query drop %i", (int)interest_id);
         _z_liveliness_pending_query_intmap_remove(&zn->_liveliness_pending_queries, interest_id);
     }