Allow module specific monitor parameters to be altered

Module specific parameters can now be altered at runtime. This allows both
the removal and addition of arbitrary monitor parameters.

server/core/config.c

@@ -1070,7 +1070,7 @@ return_p2:
  * Free a configuration parameter
  * @param p1 Parameter to free
  */
-void free_config_parameter(CONFIG_PARAMETER* p1)
+void config_parameter_free(CONFIG_PARAMETER* p1)
 {
     while (p1)
     {
@@ -1089,7 +1089,7 @@ void config_context_free(CONFIG_CONTEXT *context)
     while (context)
     {
         obj = context->next;
-        free_config_parameter(context->parameters);
+        config_parameter_free(context->parameters);
         MXS_FREE(context->object);
         MXS_FREE(context);
         context = obj;

server/core/config_runtime.c

@@ -361,8 +361,27 @@ bool runtime_alter_monitor(MONITOR *monitor, char *key, char *value)
             monitorSetNetworkTimeout(monitor, MONITOR_READ_TIMEOUT, ival);
         }
     }
+    else
+    {
+        /** We're modifying module specific parameters and we need to stop the monitor */
+        monitorStop(monitor);
 
-    if (valid)
+        if (monitorRemoveParameter(monitor, key) || value[0])
+        {
+            /** Either we're removing an existing parameter or adding a new one */
+            valid = true;
+
+            if (value[0])
+            {
+                CONFIG_PARAMETER p = {.name = key, .value = value};
+                monitorAddParameters(monitor, &p);
+            }
+        }
+
+        monitorStart(monitor, monitor->parameters);
+    }
+
+    if (valid && monitor->created_online)
     {
         monitor_serialize(monitor);
     }
@@ -497,9 +516,15 @@ bool runtime_create_monitor(const char *name, const char *module)
     bool rval = false;
     MONITOR *monitor = monitor_alloc((char*)name, (char*)module);
 
-    if (monitor && monitor_serialize(monitor))
+    if (monitor)
     {
-        rval = true;
+        /** Mark that this monitor was created after MaxScale was started */
+        monitor->created_online = true;
+
+        if (monitor_serialize(monitor))
+        {
+            rval = true;
+        }
     }
 
     spinlock_release(&crt_lock);

server/core/monitor.c

@@ -104,6 +104,7 @@ monitor_alloc(char *name, char *module)
     mon->connect_timeout = DEFAULT_CONNECT_TIMEOUT;
     mon->interval = MONITOR_INTERVAL;
     mon->parameters = NULL;
+    mon->created_online = false;
     spinlock_init(&mon->lock);
     spinlock_acquire(&monLock);
     mon->next = allMonitors;
@@ -144,7 +145,7 @@ monitor_free(MONITOR *mon)
         }
     }
     spinlock_release(&monLock);
-    free_config_parameter(mon->parameters);
+    config_parameter_free(mon->parameters);
     monitor_server_free_all(mon->databases);
     MXS_FREE(mon->name);
     MXS_FREE(mon->module_name);
@@ -767,6 +768,32 @@ void monitorAddParameters(MONITOR *monitor, CONFIG_PARAMETER *params)
     }
 }
 
+bool monitorRemoveParameter(MONITOR *monitor, const char *key)
+{
+    CONFIG_PARAMETER *prev = NULL;
+
+    for (CONFIG_PARAMETER *p = monitor->parameters; p; p = p->next)
+    {
+        if (strcmp(p->name, key) == 0)
+        {
+            if (p == monitor->parameters)
+            {
+                monitor->parameters = monitor->parameters->next;
+                p->next = NULL;
+            }
+            else
+            {
+                prev->next = p->next;
+                p->next = NULL;
+            }
+            config_parameter_free(p);
+            return true;
+        }
+        prev = p;
+    }
+    return false;
+}
+
 /**
  * Set a pending status bit in the monitor server
  *

server/core/service.c

@@ -665,7 +665,7 @@ void service_free(SERVICE *service)
     MXS_FREE(service->credentials.name);
     MXS_FREE(service->credentials.authdata);
 
-    free_config_parameter(service->svc_config_param);
+    config_parameter_free(service->svc_config_param);
     serviceClearRouterOptions(service);
 
     MXS_FREE(service);

server/modules/routing/debugcli/debugcmd.c

@@ -1290,6 +1290,13 @@ static void alterMonitor(DCB *dcb, MONITOR *monitor, char *v1, char *v2, char *v
             {
                 dcb_printf(dcb, "Error: Bad key-value parameter: %s=%s\n", key, value);
             }
+            else if (!monitor->created_online)
+            {
+                dcb_printf(dcb, "Warning: Altered monitor '%s' which is in the "
+                           "main\nconfiguration file. These changes will not be "
+                           "persisted and need\nto be manually added or set again"
+                           "after a restart.\n", monitor->name);
+            }
         }
         else
         {
@@ -1316,9 +1323,8 @@ struct subcommand alteroptions[] =
         "monitor", 2, 12, alterMonitor,
         "Alter monitor parameters",
         "Usage: alter monitor NAME KEY=VALUE ...\n"
-        "This will alter an existing parameter of a monitor. The accepted values\n"
-        "for KEY are: 'user', 'password', 'monitor_interval',\n"
-        "'backend_connect_timeout', 'backend_write_timeout', 'backend_read_timeout'\n"
+        "This will alter an existing parameter of a monitor. To remove parameters,\n"
+        "pass an empty value for a key e.g. 'maxadmin alter monitor my-monitor my-key='\n"
         "A maximum of 11 parameters can be changed at one time",
         {ARG_TYPE_MONITOR, ARG_TYPE_STRING, ARG_TYPE_STRING, ARG_TYPE_STRING,
             ARG_TYPE_STRING, ARG_TYPE_STRING, ARG_TYPE_STRING, ARG_TYPE_STRING,