Make ldmsd continue startup on producer's hostname resolution failure

Change producer's hostname resolution failure at config time from an
error to a warning, allowing ldmsd to continue starting up. The hostname
will be resolved again before establishing the connection and retired at
the reconnect interval if the resolution fails.

ldms/src/ldmsd/ldmsd.h

@@ -289,6 +289,11 @@ typedef struct ldmsd_prdcr {
 	 * quick lookup by the logic that handles update schedule.
 	 */
 	struct rbt hint_set_tree;
+
+	/**
+	 * Not-resolved counter. Reset to zero when the hostname is resolved.
+	 */
+	int not_resolved_cnt;
 } *ldmsd_prdcr_t;
 
 struct ldmsd_strgp;

ldms/src/ldmsd/ldmsd_prdcr.c

@@ -845,6 +845,17 @@ static void prdcr_connect(ldmsd_prdcr_t prdcr)
 {
 	int ret;
 
+	if (prdcr_resolve(prdcr->host_name, prdcr->port_no, &prdcr->ss, &prdcr->ss_len)) {
+		if (0 == prdcr->not_resolved_cnt) {
+			ldmsd_log(LDMSD_LERROR, "Producer '%s' connection failed. Unable to resolve hostname '%s:%u'.\n",
+				prdcr->obj.name, prdcr->host_name,(unsigned) prdcr->port_no);
+		}
+		prdcr->not_resolved_cnt++;
+		return;
+	} else {
+		prdcr->not_resolved_cnt = 0;
+	}
+
 	switch (prdcr->type) {
 	case LDMSD_PRDCR_TYPE_ACTIVE:
 	case LDMSD_PRDCR_TYPE_ADVERTISER:
@@ -1006,11 +1017,9 @@ ldmsd_prdcr_new_with_auth(const char *name, const char *xprt_name,
 		}
 	}
 
-	if (prdcr_resolve(host_name, port_no, &prdcr->ss, &prdcr->ss_len)) {
-		errno = EAFNOSUPPORT;
-		ldmsd_log(LDMSD_LERROR, "ldmsd_prdcr_new: %s:%u not resolved.\n",
-			host_name,(unsigned) port_no);
-		goto out;
+	if (prdcr_resolve(prdcr->host_name, prdcr->port_no, &prdcr->ss, &prdcr->ss_len)) {
+		ldmsd_log(LDMSD_LWARNING, "Producer '%s': %s:%u not resolved.\n",
+			prdcr->obj.name, prdcr->host_name,(unsigned) prdcr->port_no);
 	}
 
 	if (!auth)