Use cdb_set_object to set a leaf in a container

harminder · April 6, 2021, 7:23am

Hi, I am using some autogen code above cdb APIs which currently supports only cdb_set_elem, when i subscribe for list with container having N leafs, i get N notifications.

I want to replace cdb_set_element with cdb_set_object, but now the question is, for some lists i need to update individual leafs.
can i update individual leafs using cdb_set_object?

eaksu · April 6, 2021, 12:16pm

Hi,

To set arbitrary (sub)elements of a container or list-entry you can use cdb_set_values. The omitted elements will remain unchanged.
If I understood your use case correctly, I would also look into an alternative way in which the generated code performs commits after some batch of cdb_set_elem calls.

Regards,
Erdem

cohult · April 9, 2021, 7:03am

Hi,

@harminder, I would use either the CDB API cdb_set_values() as a single operation for changes so that the CDB operational subscriber is invoked just once (or at least a minimum number of times), or even better, as @eaksu hints, use MAAPI towards the operational datastore where there can be multiple operations but the CDB operational subscriber will not be invoked until maapi_apply_trans() (commit) is called by the application. I would still use maapi_set_values() instead of set_elem() or set_object() operations as set_values() is more efficient.

See examples.confd/intro/13-c_stats_push for a simple maapi_set_values() to the operational datastore example. cdb_set_values() work the same way. See the confd_lib_cdb(3) and confd_lib_maapi(3) man pages for details.

The ConfD Developer GitHub also has a couple of examples:

github.com

ConfD-Developer/ConfD-Demos/blob/6afa025e74a0ee87dc877de66c867af984deb5b4/oper-performance/app/src/per-cdb-w.c#L131


        sprintf(id[k], "%07d", pos);
        CONFD_SET_TAG_XMLBEGIN(&v[j], r_route, r__ns); j++;
        CONFD_SET_TAG_STR(&v[j], r_id, id[k]); j++;
        CONFD_SET_TAG_INT32(&v[j], r_leaf1, 1+pos); j++;
        CONFD_SET_TAG_INT32(&v[j], r_leaf2, 2); j++;
        CONFD_SET_TAG_INT32(&v[j], r_leaf3, 3); j++;
        CONFD_SET_TAG_INT32(&v[j], r_leaf4, 4); j++;
        CONFD_SET_TAG_XMLEND(&v[j], r_route, r__ns); j++;
        pos++;
      }
      if ((ret = cdb_set_values(rwsock, v, j, SUBPATH)) < 0) {
#if 0
        print_tag_value_array(v, j, NULL, 0);
#endif
        confd_fatal("cdb_set_values() failed ret=%d nobj=%d iter=%d j=%d pos=%d\n", ret, nobj, iter, j, pos);
      }
      free(v);
    }
    cdb_end_session(rwsock);
  }
  return cdb_close(rwsock);

github.com

ConfD-Developer/ConfD-Demos/blob/6afa025e74a0ee87dc877de66c867af984deb5b4/active-active/consistent-sync/app/aasync.c#L922


	    }
	    for(node = aasync_nodes; node != NULL; node = node->next) {
	      if(node->nodeid != local_nodeid) {
		if (((node->th = maapi_start_trans(node->maapi_socket, CONFD_RUNNING, CONFD_READ_WRITE))) < 0) {
		  DEBUG_LOG("aasync%d: maapi_start_trans to node%d failed", local_nodeid, node->nodeid);
		  goto abort_local_trans;
		}
		  
		/* Write the CDB modifications we got in tag value format and write them to the other active ConfDs */
		if ((ret = maapi_set_values(node->maapi_socket, node->th, tvals, nvals, ACTIVE_CFG_PATH)) != CONFD_OK) {
		  DEBUG_LOG("aasync%d: maapi_set_values to node %d failed", local_nodeid, node->nodeid);
		  goto abort_local_trans;
		}
		  
		if (maapi_validate_trans(node->maapi_socket, node->th, 0, 0) != CONFD_OK) {
		  DEBUG_LOG("aasync%d: maapi_validate_trans to node %d failed", local_nodeid, node->nodeid);
		  goto abort_local_trans;
		}
	      }
	    }

harminder · April 13, 2021, 4:50am

Thanks for the help. i am using maapi apis now.