Enable online modification of monitors

The monitor parameters can now be changed via maxadmin. These changes are
not persisted to disk yet.

include/maxscale/monitor.h

@@ -137,6 +137,9 @@ typedef enum
 #define MONITOR_INTERVAL 10000 // in milliseconds
 #define MONITOR_DEFAULT_ID 1UL // unsigned long value
 
+#define MAX_MONITOR_USER_LEN     512
+#define MAX_MONITOR_PASSWORD_LEN 512
+
 /*
  * Create declarations of the enum for monitor events and also the array of
  * structs containing the matching names. The data is taken from def_monitor_event.h
@@ -177,8 +180,8 @@ typedef struct monitor_servers
 struct monitor
 {
     char *name;                   /**< The name of the monitor module */
-    char *user;                   /*< Monitor username */
-    char *password;               /*< Monitor password */
+    char user[MAX_MONITOR_USER_LEN]; /*< Monitor username */
+    char password[MAX_MONITOR_PASSWORD_LEN]; /*< Monitor password */
     SPINLOCK lock;
     CONFIG_PARAMETER* parameters; /*< configuration parameters */
     MONITOR_SERVERS* databases;   /*< List of databases the monitor monitors */

server/core/monitor.c

@@ -93,9 +93,8 @@ monitor_alloc(char *name, char *module)
     mon->name = name;
     mon->handle = NULL;
     mon->databases = NULL;
-    mon->password = NULL;
-    mon->user = NULL;
-    mon->password = NULL;
+    *mon->password = '\0';
+    *mon->user = '\0';
     mon->read_timeout = DEFAULT_READ_TIMEOUT;
     mon->write_timeout = DEFAULT_WRITE_TIMEOUT;
     mon->connect_timeout = DEFAULT_CONNECT_TIMEOUT;
@@ -377,8 +376,8 @@ void monitorRemoveServer(MONITOR *mon, SERVER *server)
 void
 monitorAddUser(MONITOR *mon, char *user, char *passwd)
 {
-    mon->user = MXS_STRDUP_A(user);
-    mon->password = MXS_STRDUP_A(passwd);
+    snprintf(mon->user, sizeof(mon->user), "%s", user);
+    snprintf(mon->password, sizeof(mon->password), "%s", passwd);
 }
 
 /**

server/modules/routing/debugcli/debugcmd.c

@@ -1098,6 +1098,83 @@ static void alterServer(DCB *dcb, SERVER *server, char *key, char *value)
     }
 }
 
+/**
+ * @brief Convert a string value to a positive integer
+ *
+ * If the value is not a positive integer, an error is printed to @c dcb.
+ *
+ * @param dcb Client DCB
+ * @param value String value
+ * @return 0 on error, otherwise a positive integer
+ */
+static long get_positive_int(DCB *dcb, const char *value)
+{
+    char *endptr;
+    long ival = strtol(value, &endptr, 10);
+
+    if (*endptr == '\0' && ival > 0)
+    {
+        return ival;
+    }
+
+    dcb_printf(dcb, "Invalid value: %s", value);
+    return 0;
+}
+
+static void alterMonitor(DCB *dcb, MONITOR *monitor, char *key, char *value)
+{
+    bool unknown = false;
+    if (strcmp(key, "user") == 0)
+    {
+        monitorAddUser(monitor, value, monitor->password);
+    }
+    else if (strcmp(key, "password") == 0)
+    {
+        monitorAddUser(monitor, monitor->user, value);
+    }
+    else if (strcmp(key, "monitor_interval") == 0)
+    {
+        long ival = get_positive_int(dcb, value);
+        if (ival)
+        {
+            monitorSetInterval(monitor, ival);
+        }
+    }
+    else if (strcmp(key, "backend_connect_timeout") == 0)
+    {
+        long ival = get_positive_int(dcb, value);
+        if (ival)
+        {
+            monitorSetNetworkTimeout(monitor, MONITOR_CONNECT_TIMEOUT, ival);
+        }
+    }
+    else if (strcmp(key, "backend_write_timeout") == 0)
+    {
+        long ival = get_positive_int(dcb, value);
+        if (ival)
+        {
+            monitorSetNetworkTimeout(monitor, MONITOR_READ_TIMEOUT, ival);
+        }
+    }
+    else if (strcmp(key, "backend_read_timeout") == 0)
+    {
+        long ival = get_positive_int(dcb, value);
+        if (ival)
+        {
+            monitorSetNetworkTimeout(monitor, MONITOR_WRITE_TIMEOUT, ival);
+        }
+    }
+    else
+    {
+        unknown = true;
+    }
+
+    if (unknown)
+    {
+        dcb_printf(dcb, "Unknown parameter '%s'", key);
+    }
+}
+
 struct subcommand alteroptions[] =
 {
     {
@@ -1108,6 +1185,15 @@ struct subcommand alteroptions[] =
         "for KEY are: 'address', 'port', 'monuser', 'monpw'",
         {ARG_TYPE_SERVER, ARG_TYPE_STRING, ARG_TYPE_STRING}
     },
+    {
+        "monitor", 3, 3, 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'",
+        {ARG_TYPE_MONITOR, ARG_TYPE_STRING, ARG_TYPE_STRING}
+    },
     {
         EMPTY_OPTION
     }