Only remove explicitly deleted relationships

Only when a relationship is defined as a null JSON value, it should be
deleted. If it is missing, it should be ignored.

server/core/config_runtime.cc

@@ -973,14 +973,11 @@ bool runtime_destroy_monitor(MXS_MONITOR *monitor)
 }
 
 static bool extract_relations(json_t* json, StringSet& relations,
-                              const char** relation_types,
+                              const char* relation_type,
                               bool (*relation_check)(const std::string&, const std::string&))
 {
     bool rval = true;
-
+    json_t* arr = mxs_json_pointer(json, relation_type);
-    for (int i = 0; relation_types[i]; i++)
-    {
-        json_t* arr = mxs_json_pointer(json, relation_types[i]);
 
     if (arr && json_is_array(arr))
     {
@@ -1013,11 +1010,24 @@ static bool extract_relations(json_t* json, StringSet& relations,
             }
         }
     }
-    }
 
     return rval;
 }
 
+static inline bool is_null_relation(json_t* json, const char* relation)
+{
+    std::string str(relation);
+    size_t pos = str.rfind("/data");
+
+    ss_dassert(pos != std::string::npos);
+    str = str.substr(0, pos);
+
+    json_t* data = mxs_json_pointer(json, relation);
+    json_t* base = mxs_json_pointer(json, str.c_str());
+
+    return (data && json_is_null(data)) || (base && json_is_null(base));
+}
+
 static inline const char* get_string_or_null(json_t* json, const char* path)
 {
     const char* rval = NULL;
@@ -1133,13 +1143,6 @@ static bool server_contains_required_fields(json_t* json)
     return rval;
 }
 
-const char* server_relation_types[] =
-{
-    MXS_JSON_PTR_RELATIONSHIPS_SERVICES,
-    MXS_JSON_PTR_RELATIONSHIPS_MONITORS,
-    NULL
-};
-
 static bool server_relation_is_valid(const std::string& type, const std::string& value)
 {
     return (type == CN_SERVICES && service_find(value.c_str())) ||
@@ -1289,7 +1292,8 @@ SERVER* runtime_create_server_from_json(json_t* json)
 
         StringSet relations;
 
-        if (extract_relations(json, relations, server_relation_types, server_relation_is_valid))
+        if (extract_relations(json, relations, MXS_JSON_PTR_RELATIONSHIPS_SERVICES, server_relation_is_valid) &&
+            extract_relations(json, relations, MXS_JSON_PTR_RELATIONSHIPS_MONITORS, server_relation_is_valid))
         {
             if (runtime_create_server(name, address, port.c_str(), protocol, authenticator, authenticator_options))
             {
@@ -1322,12 +1326,33 @@ bool server_to_object_relations(SERVER* server, json_t* old_json, json_t* new_js
         return true;
     }
 
-    bool rval = false;
+    const char* server_relation_types[] =
+    {
+        MXS_JSON_PTR_RELATIONSHIPS_SERVICES,
+        MXS_JSON_PTR_RELATIONSHIPS_MONITORS,
+        NULL
+    };
+
+    bool rval = true;
     StringSet old_relations;
     StringSet new_relations;
 
-    if (extract_relations(old_json, old_relations, server_relation_types, server_relation_is_valid) &&
+    for (int i = 0; server_relation_types[i]; i++)
-        extract_relations(new_json, new_relations, server_relation_types, server_relation_is_valid))
+    {
+        // Extract only changed or deleted relationships
+        if (is_null_relation(new_json, server_relation_types[i]) ||
+            mxs_json_pointer(new_json, server_relation_types[i]))
+        {
+            if (!extract_relations(new_json, new_relations, server_relation_types[i], server_relation_is_valid) ||
+                !extract_relations(old_json, old_relations, server_relation_types[i], server_relation_is_valid))
+            {
+                rval = false;
+                break;
+            }
+        }
+    }
+
+    if (rval)
     {
         StringSet removed_relations;
         StringSet added_relations;
@@ -1340,10 +1365,10 @@ bool server_to_object_relations(SERVER* server, json_t* old_json, json_t* new_js
                             old_relations.begin(), old_relations.end(),
                             std::inserter(added_relations, added_relations.begin()));
 
-        if (unlink_server_from_objects(server, removed_relations) &&
+        if (!unlink_server_from_objects(server, removed_relations) ||
-            link_server_to_objects(server, added_relations))
+            !link_server_to_objects(server, added_relations))
         {
-            rval = true;
+            rval = false;
         }
     }
 
@@ -1434,7 +1459,7 @@ static bool validate_monitor_json(json_t* json)
         else
         {
             StringSet relations;
-            if (extract_relations(json, relations, object_relation_types, object_relation_is_valid))
+            if (extract_relations(json, relations, MXS_JSON_PTR_RELATIONSHIPS_SERVERS, object_relation_is_valid))
             {
                 rval = true;
             }
@@ -1517,9 +1542,10 @@ bool object_to_server_relations(const char* target, json_t* old_json, json_t* ne
     bool rval = false;
     StringSet old_relations;
     StringSet new_relations;
+    const char* object_relation = MXS_JSON_PTR_RELATIONSHIPS_SERVERS;
 
-    if (extract_relations(old_json, old_relations, object_relation_types, object_relation_is_valid) &&
+    if (extract_relations(old_json, old_relations, object_relation, object_relation_is_valid) &&
-        extract_relations(new_json, new_relations, object_relation_types, object_relation_is_valid))
+        extract_relations(new_json, new_relations, object_relation, object_relation_is_valid))
     {
         StringSet removed_relations;
         StringSet added_relations;

server/core/test/rest-api/test/server.js

@@ -68,8 +68,8 @@ describe("Server Relationships", function() {
     });
 
     it("remove relationships", function() {
-        delete rel_server.data.relationships["services"]
+        rel_server.data.relationships["services"] = null
-        delete rel_server.data.relationships["monitors"]
+        rel_server.data.relationships["monitors"] = null
         return request.patch(base_url + "/servers/" + rel_server.data.id, {json: rel_server})
             .should.be.fulfilled
     });