lua plugin: Make it possible to register more than one reader/writer.

lua_tostring(), used to identify readers/writers, doesn't work
on functions (it returns NULL). So, callback name is not unique and
its registration fail.

Added code to store script path and callback index in LUA Registry and
to build callback name based on them.

Added possibility to pass LUA callback as global-scope function name.
In this case callback name is built using function name, not callback
index.

Closes: #2379
Closes: #3139

diff --git a/src/collectd-lua.pod b/src/collectd-lua.pod
index f5e43aa..eccd71f 100644 (file)
--- a/src/collectd-lua.pod
+++ b/src/collectd-lua.pod
@@ -72,8 +72,8 @@ These are used to collect the actual data. It is called once
 per interval (see the B<Interval> configuration option of collectd). Usually
 it will call B<collectd.dispatch_values> to dispatch the values to collectd
 which will pass them on to all registered B<write functions>. If this function
-does not return 0 the plugin will be skipped for an increasing
-amount of time until it returns normally again.
+does not return 0, interval between its calls will grow until function returns
+0 again. See the B<MaxReadInterval> configuration option of collectd.
 
 =item write functions
 
@@ -90,12 +90,14 @@ The following functions are provided to Lua modules:
 
 =item register_read(callback)
 
+Function to register read callbacks.
 The callback will be called without arguments.
 If this callback function does not return 0 the next call will be delayed by
 an increasing interval.
 
-=item register_write
+=item register_write(callback)
 
+Function to register write callbacks.
 The callback function will be called with one argument passed, which will be a
 table of values.
 If this callback function does not return 0 next call will be delayed by
@@ -136,8 +138,8 @@ A very simple write function might look like:
 
 To register those functions with collectd:
 
-  collectd.register_read(read)
-  collectd.register_write(write)
+  collectd.register_read(read)     -- pass function as variable
+  collectd.register_write("write") -- pass by global-scope function name
 
 =back
 

diff --git a/src/lua.c b/src/lua.c
index 5f8f964..9a1ceed 100644 (file)
--- a/src/lua.c
+++ b/src/lua.c
@@ -40,6 +40,9 @@
 
 #include <pthread.h>
 
+#define PLUGIN_READ 1
+#define PLUGIN_WRITE 2
+
 typedef struct lua_script_s {
   lua_State *lua_state;
   struct lua_script_s *next;
@@ -265,62 +268,39 @@ static void lua_cb_free(void *data) {
   free(cb);
 }
 
-static int lua_cb_register_read(lua_State *L) /* {{{ */
+static int lua_cb_register_generic(lua_State *L, int type) /* {{{ */
 {
   int nargs = lua_gettop(L);
 
   if (nargs != 1)
     return luaL_error(L, "Invalid number of arguments (%d != 1)", nargs);
 
-  luaL_checktype(L, 1, LUA_TFUNCTION);
-
-  char function_name[DATA_MAX_NAME_LEN];
-  snprintf(function_name, sizeof(function_name), "lua/%s", lua_tostring(L, 1));
-
-  int callback_id = clua_store_callback(L, 1);
-  if (callback_id < 0)
-    return luaL_error(L, "%s", "Storing callback function failed");
-
-  lua_State *thread = lua_newthread(L);
-  if (thread == NULL)
-    return luaL_error(L, "%s", "lua_newthread failed");
-  clua_store_thread(L, -1);
-  lua_pop(L, 1);
-
-  clua_callback_data_t *cb = calloc(1, sizeof(*cb));
-  if (cb == NULL)
-    return luaL_error(L, "%s", "calloc failed");
-
-  cb->lua_state = thread;
-  cb->callback_id = callback_id;
-  cb->lua_function_name = strdup(function_name);
-  pthread_mutex_init(&cb->lock, NULL);
-
-  int status =
-      plugin_register_complex_read(/* group = */ "lua",
-                                   /* name      = */ function_name,
-                                   /* callback  = */ clua_read,
-                                   /* interval  = */ 0,
-                                   &(user_data_t){
-                                       .data = cb, .free_func = lua_cb_free,
-                                   });
-
-  if (status != 0)
-    return luaL_error(L, "%s", "plugin_register_complex_read failed");
-  return 0;
-} /* }}} int lua_cb_register_read */
-
-static int lua_cb_register_write(lua_State *L) /* {{{ */
-{
-  int nargs = lua_gettop(L);
+  char subname[DATA_MAX_NAME_LEN];
+  if (!lua_isfunction(L, 1) && lua_isstring(L, 1)) {
+    const char *fname = lua_tostring(L, 1);
+    snprintf(subname, sizeof(subname), "%s()", fname);
 
-  if (nargs != 1)
-    return luaL_error(L, "Invalid number of arguments (%d != 1)", nargs);
+    lua_getglobal(L, fname); // Push function into stack
+    lua_remove(L, 1);        // Remove string from stack
+    if (!lua_isfunction(L, -1)) {
+      return luaL_error(L, "Unable to find function '%s'", fname);
+    }
+  } else {
+    lua_getfield(L, LUA_REGISTRYINDEX, "collectd:callback_num");
+    int tmp = lua_tointeger(L, -1);
+    snprintf(subname, sizeof(subname), "callback_%d", tmp);
+    lua_pop(L, 1); // Remove old value from stack
+    lua_pushinteger(L, tmp + 1);
+    lua_setfield(L, LUA_REGISTRYINDEX, "collectd:callback_num"); // pops value
+  }
 
   luaL_checktype(L, 1, LUA_TFUNCTION);
 
-  char function_name[DATA_MAX_NAME_LEN] = "";
-  snprintf(function_name, sizeof(function_name), "lua/%s", lua_tostring(L, 1));
+  lua_getfield(L, LUA_REGISTRYINDEX, "collectd:script_path");
+  char function_name[DATA_MAX_NAME_LEN];
+  snprintf(function_name, sizeof(function_name), "lua/%s/%s",
+           lua_tostring(L, -1), subname);
+  lua_pop(L, 1);
 
   int callback_id = clua_store_callback(L, 1);
   if (callback_id < 0)
@@ -341,16 +321,41 @@ static int lua_cb_register_write(lua_State *L) /* {{{ */
   cb->lua_function_name = strdup(function_name);
   pthread_mutex_init(&cb->lock, NULL);
 
-  int status = plugin_register_write(/* name = */ function_name,
-                                     /* callback  = */ clua_write,
+  if (PLUGIN_READ == type) {
+    int status =
+        plugin_register_complex_read(/* group = */ "lua",
+                                     /* name      = */ function_name,
+                                     /* callback  = */ clua_read,
+                                     /* interval  = */ 0,
                                      &(user_data_t){
                                          .data = cb, .free_func = lua_cb_free,
                                      });
 
-  if (status != 0)
-    return luaL_error(L, "%s", "plugin_register_write failed");
-  return 0;
-} /* }}} int lua_cb_register_write */
+    if (status != 0)
+      return luaL_error(L, "%s", "plugin_register_complex_read failed");
+    return 0;
+  } else if (PLUGIN_WRITE == type) {
+    int status = plugin_register_write(/* name = */ function_name,
+                                       /* callback  = */ clua_write,
+                                       &(user_data_t){
+                                           .data = cb, .free_func = lua_cb_free,
+                                       });
+
+    if (status != 0)
+      return luaL_error(L, "%s", "plugin_register_write failed");
+    return 0;
+  } else {
+    return luaL_error(L, "%s", "lua_cb_register_generic unsupported type");
+  }
+} /* }}} int lua_cb_register_generic */
+
+static int lua_cb_register_read(lua_State *L) {
+  return lua_cb_register_generic(L, PLUGIN_READ);
+}
+
+static int lua_cb_register_write(lua_State *L) {
+  return lua_cb_register_generic(L, PLUGIN_WRITE);
+}
 
 static const luaL_Reg collectdlib[] = {
     {"log_debug", lua_cb_log_debug},
@@ -457,6 +462,11 @@ static int lua_script_load(const char *script_path) /* {{{ */
     return -1;
   }
 
+  lua_pushstring(script->lua_state, script_path);
+  lua_setfield(script->lua_state, LUA_REGISTRYINDEX, "collectd:script_path");
+  lua_pushinteger(script->lua_state, 0);
+  lua_setfield(script->lua_state, LUA_REGISTRYINDEX, "collectd:callback_num");
+
   status = lua_pcall(script->lua_state,
                      /* nargs = */ 0,
                      /* nresults = */ LUA_MULTRET,
@@ -469,8 +479,8 @@ static int lua_script_load(const char *script_path) /* {{{ */
             "In addition, no error message could be retrieved from the stack.",
             status);
     else
-      ERROR("Lua plugin: Executing script \"%s\" failed: %s",
-            script_path, errmsg);
+      ERROR("Lua plugin: Executing script \"%s\" failed: %s", script_path,
+            errmsg);
   }
 
   /* Append this script to the global list of scripts. */