aggregation plugin: Improve two error messages.

diff --git a/src/aggregation.c b/src/aggregation.c
index e50557d..db33c17 100644 (file)
--- a/src/aggregation.c
+++ b/src/aggregation.c
@@ -192,13 +192,21 @@ static int agg_instance_update (agg_instance_t *inst, /* {{{ */
   gauge_t *rate;
 
   if (ds->ds_num != 1)
-    return (-1);
+  {
+    ERROR ("aggregation plugin: The \"%s\" type (data set) has more than one "
+        "data source. This is currently not supported by this plugin. "
+        "Sorry.", ds->type);
+    return (EINVAL);
+  }
 
   rate = uc_get_rate (ds, vl);
   if (rate == NULL)
   {
-    ERROR ("aggregation plugin: uc_get_rate() failed.");
-    return (-1);
+    char ident[6 * DATA_MAX_NAME_LEN];
+    FORMAT_VL (ident, sizeof (ident), vl);
+    ERROR ("aggregation plugin: Unable to read the current rate of \"%s\".",
+        ident);
+    return (ENOENT);
   }
 
   if (isnan (rate[0]))