memcached plugin: Fix backwards compatibility.

Register a default callback in the init() phase if no configuration is
provided for the plugin. This way doing just "LoadPlugin memcached" will
result in the old behavior i.e. localhost being queried.

diff --git a/src/memcached.c b/src/memcached.c
index 5cfd823..b96845e 100644 (file)
--- a/src/memcached.c
+++ b/src/memcached.c
@@ -57,9 +57,10 @@ struct memcached_s
   char *host;
   char *port;
 };
-
 typedef struct memcached_s memcached_t;
 
+static _Bool memcached_have_instances = 0;
+
 static int memcached_read (user_data_t *user_data);
 
 static void memcached_free (memcached_t *st)
@@ -75,14 +76,15 @@ static void memcached_free (memcached_t *st)
 
 static int memcached_query_daemon (char *buffer, int buffer_size, user_data_t *user_data)
 {
-  int fd;
+  int fd = -1;
   ssize_t status;
   int buffer_fill;
   int i = 0;
 
   memcached_t *st;
   st = user_data->data;
-  if (st->socket != NULL) {
+  if (st->socket != NULL)
+  {
     struct sockaddr_un serv_addr;
 
      memset (&serv_addr, 0, sizeof (serv_addr));
@@ -99,7 +101,8 @@ static int memcached_query_daemon (char *buffer, int buffer_size, user_data_t *u
        return -1;
      }
   }
-  else {
+  else
+  {
     const char *host;
     const char *port;
 
@@ -243,6 +246,27 @@ static int memcached_query_daemon (char *buffer, int buffer_size, user_data_t *u
   return 0;
 }
 
+static int memcached_add_read_callback (memcached_t *st)
+{
+  user_data_t ud;
+  char callback_name[3*DATA_MAX_NAME_LEN];
+  int status;
+
+  memset (&ud, 0, sizeof (ud));
+  ud.data = st;
+  ud.free_func = (void *) memcached_free;
+
+  assert (st->name != NULL);
+  ssnprintf (callback_name, sizeof (callback_name), "memcached/%s", st->name);
+
+  status = plugin_register_complex_read (/* group = */ "memcached",
+      /* name      = */ callback_name,
+      /* callback  = */ memcached_read,
+      /* interval  = */ NULL,
+      /* user_data = */ &ud);
+  return (status);
+} /* int memcached_add_read_callback */
+
 /* Configuration handling functiions
  * <Plugin memcached>
  *   <Instance "instance_name">
@@ -255,30 +279,28 @@ static int config_add_instance(oconfig_item_t *ci)
 {
   memcached_t *st;
   int i;
-  int status;
+  int status = 0;
 
-  if ((ci->values_num != 1)
-    || (ci->values[0].type != OCONFIG_TYPE_STRING))
-  {
-    WARNING ("memcached plugin: The `%s' config option "
-      "needs exactly one string argument.", ci->key);
-    return (-1);
-  }
+  /* Disable automatic generation of default instance in the init callback. */
+  memcached_have_instances = 1;
 
-  st = (memcached_t *) malloc (sizeof (*st));
+  st = malloc (sizeof (*st));
   if (st == NULL)
   {
     ERROR ("memcached plugin: malloc failed.");
     return (-1);
   }
 
+  memset (st, 0, sizeof (*st));
   st->name = NULL;
   st->socket = NULL;
   st->host = NULL;
   st->port = NULL;
-  memset (st, 0, sizeof (*st));
 
-  status = cf_util_get_string (ci, &st->name);
+  if (strcasecmp (ci->key, "Plugin") == 0) /* default instance */
+    st->name = sstrdup ("default");
+  else /* <Instance /> block */
+    status = cf_util_get_string (ci, &st->name);
   if (status != 0)
   {
     sfree (st);
@@ -308,26 +330,7 @@ static int config_add_instance(oconfig_item_t *ci)
   }
 
   if (status == 0)
-  {
-    user_data_t ud;
-    char callback_name[3*DATA_MAX_NAME_LEN];
-
-    memset (&ud, 0, sizeof (ud));
-    ud.data = st;
-    ud.free_func = (void *) memcached_free;
-
-    memset (callback_name, 0, sizeof (callback_name));
-    ssnprintf (callback_name, sizeof (callback_name),
-        "memcached/%s/%s",
-        (st->host != NULL) ? st->host : MEMCACHED_DEF_HOST,
-        (st->port != NULL) ? st->port : MEMCACHED_DEF_PORT)
-
-    status = plugin_register_complex_read (/* group = */ "memcached",
-        /* name      = */ callback_name,
-        /* callback  = */ memcached_read,
-        /* interval  = */ NULL,
-        /* user_data = */ &ud);
-  }
+    status = memcached_add_read_callback (st);
 
   if (status != 0)
   {
@@ -341,6 +344,7 @@ static int config_add_instance(oconfig_item_t *ci)
 static int memcached_config (oconfig_item_t *ci)
 {
   int status = 0;
+  _Bool have_instance_block = 0;
   int i;
 
   for (i = 0; i < ci->children_num; i++)
@@ -348,7 +352,16 @@ static int memcached_config (oconfig_item_t *ci)
     oconfig_item_t *child = ci->children + i;
 
     if (strcasecmp ("Instance", child->key) == 0)
+    {
       config_add_instance (child);
+      have_instance_block = 1;
+    }
+    else if (!have_instance_block)
+    {
+      /* Non-instance option: Assume legacy configuration (without <Instance />
+       * blocks) and call config_add_instance() with the <Plugin /> block. */
+      return (config_add_instance (ci));
+    }
     else
       WARNING ("memcached plugin: The configuration option "
           "\"%s\" is not allowed here. Did you "
@@ -360,6 +373,33 @@ static int memcached_config (oconfig_item_t *ci)
   return (status);
 }
 
+static int memcached_init (void)
+{
+  memcached_t *st;
+  int status;
+
+  if (memcached_have_instances)
+    return (0);
+
+  /* No instances were configured, lets start a default instance. */
+  st = malloc (sizeof (*st));
+  if (st == NULL)
+    return (ENOMEM);
+  memset (st, 0, sizeof (*st));
+  st->name = sstrdup ("default");
+  st->socket = NULL;
+  st->host = NULL;
+  st->port = NULL;
+
+  status = memcached_add_read_callback (st);
+  if (status == 0)
+    memcached_have_instances = 1;
+  else
+    memcached_free (st);
+
+  return (status);
+} /* int memcached_init */
+
 static void submit_derive (const char *type, const char *type_inst,
     derive_t value, memcached_t *st)
 {
@@ -610,4 +650,5 @@ static int memcached_read (user_data_t *user_data)
 void module_register (void)
 {
   plugin_register_complex_config ("memcached", memcached_config);
+  plugin_register_init ("memcached", memcached_init);
 }