MXS-1300: Add link/unlink command to MaxCtrl

The link/unlink commands are similar to the add/remove commands in
MaxAdmin but they link services and monitors to a list of servers instead
of linking servers to a list of either services or monitors. This can
reduce the number of required calls to alter the configuration while
making the process easier for MaxCtrl to do via the REST API.

Also fixed a false negative where a service alteration which results in a
no-op would be counted as an error.

client/maxctrl/lib/link.js

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2020-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+require('../common.js')()
+
+function addServer(path, targets) {
+    doRequest(path, function(res) {
+        var servers =_.get(res, 'data.relationships.servers.data', [])
+
+        targets.forEach(function(i){
+            servers.push({id: i, type: 'servers'})
+        })
+
+        // Update relationships and remove unnecessary parts
+        _.set(res, 'data.relationships.servers.data', servers)
+        delete res.data.attributes
+
+        doRequest(path, null, {method: 'PATCH', body: res})
+    })
+}
+
+exports.command = 'link <command>'
+exports.desc = 'Link objects'
+exports.handler = function() {}
+exports.builder = function(yargs) {
+    yargs
+        .command('service <name> <server...>', 'Link servers to a service', {}, function(argv) {
+            addServer('services/' + argv.name, argv.server)
+        })
+        .command('monitor <name> <server...>', 'Link servers to a monitor', {}, function(argv) {
+            addServer('monitors/' + argv.name, argv.server)
+        })
+        .usage('Usage: link <command>')
+        .help()
+        .command('*', 'the default command', {}, () => {
+            console.log('Unknown command. See output of `help link` for a list of commands.')
+        })
+}

client/maxctrl/lib/unlink.js

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2020-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+require('../common.js')()
+
+function removeServer(path, targets) {
+    doRequest(path, function(res) {
+        var servers =_.get(res, 'data.relationships.servers.data', [])
+
+        _.remove(servers, function(i) {
+            return targets.indexOf(i.id) != -1
+        })
+
+        // Update relationships and remove unnecessary parts
+        _.set(res, 'data.relationships.servers.data', servers)
+        delete res.data.attributes
+
+        doRequest(path, null, {method: 'PATCH', body: res})
+    })
+}
+
+exports.command = 'unlink <command>'
+exports.desc = 'Unlink objects'
+exports.handler = function() {}
+exports.builder = function(yargs) {
+    yargs
+        .command('service <name> <server...>', 'Unlink servers from a service', {}, function(argv) {
+            removeServer('services/' + argv.name, argv.server)
+        })
+        .command('monitor <name> <server...>', 'Unlink servers from a monitor', {}, function(argv) {
+            removeServer('monitors/' + argv.name, argv.server)
+        })
+        .usage('Usage: unlink <command>')
+        .help()
+        .command('*', 'the default command', {}, () => {
+            console.log('Unknown command. See output of `help unlink` for a list of commands.')
+        })
+}

client/maxctrl/maxctrl.js

@@ -58,6 +58,8 @@ program
     .command(require('./lib/disable.js'))
     .command(require('./lib/create.js'))
     .command(require('./lib/destroy.js'))
+    .command(require('./lib/link.js'))
+    .command(require('./lib/unlink.js'))
     .help()
     .demandCommand(1, 'At least one command is required')
     .command('*', 'the default command', {}, () => {

server/core/config_runtime.cc

@@ -1377,7 +1377,7 @@ bool runtime_alter_service_from_json(SERVICE* service, json_t* new_json)
     if (is_valid_resource_body(new_json) &&
         object_to_server_relations(service->name, old_json.get(), new_json))
     {
-        bool changed = false;
+        rval = true;
         json_t* parameters = mxs_json_pointer(new_json, MXS_JSON_PTR_PARAMETERS);
         json_t* old_parameters = mxs_json_pointer(old_json.get(), MXS_JSON_PTR_PARAMETERS);
 
@@ -1395,7 +1395,6 @@ bool runtime_alter_service_from_json(SERVICE* service, json_t* new_json)
                 }
             }
 
-            rval = true;
             const char* key;
             json_t* value;