NEW: otr_publish() from Lua reuses Recorder's authenticated, TLS-enabled MQTT connection

closes #140

doc/HOOKS.md

@@ -91,3 +91,13 @@ An optional function you provide is called `otr_httpobject(u, d, t, data)` where
 After running `otr_hook()`, the Recorder attempts to invoke a Lua function for each of the elements in the extended JSON. If, say, your Lua script contains a function called `hooklet_lat`, it will be invoked every time a `lat` is received as part of the JSON payload. Similarly with `hooklet_addr`, `hooklet_cc`, `hooklet_tst`, etc. These _hooklets_ are invoked with the same parameters as `otr_hook()`.
 
 You define a hooklet function only if you're interested in expressly triggering on a particular JSON element.
+
+In addition to compiling with Lua support, if Recorder is built with MQTT support, a function `otr_publish()` is surfaced into your Lua script.
+
+```
+otr_publish(topic, payload, qos, retain)
+```
+
+`topic` and `payload` are mandatory and must be strings. `qos` and `retain` are optional and specify the QoS for publishing as well as a retain flag; `qos` must be specified if `retain` is to be.
+
+This function allows your code to publish via MQTT from the Recorder, using the same MQTT connection (including TLS, authentication, etc) as the Recorder uses.

hooks.c

@@ -40,6 +40,11 @@ static int otr_log(lua_State *lua);
 static int otr_strftime(lua_State *lua);
 static int otr_putdb(lua_State *lua);
 static int otr_getdb(lua_State *lua);
+#ifdef WITH_MQTT
+# include <mosquitto.h>
+static int otr_publish(lua_State *lua);
+static struct mosquitto *MQTTconn = NULL;
+#endif
 
 static struct gcache *LuaDB = NULL;
 
@@ -102,6 +107,9 @@ struct luadata *hooks_init(struct udata *ud, char *script)
 		lua_pushcfunction(ld->L, otr_getdb);
 		lua_setfield(ld->L, -2, "getdb");
 
+		lua_pushcfunction(ld->L, otr_publish);
+		lua_setfield(ld->L, -2, "publish");
+
 	lua_setglobal(ld->L, "otr");
 
 	LuaDB = ud->luadb;
@@ -130,6 +138,13 @@ struct luadata *hooks_init(struct udata *ud, char *script)
 	return (ld);
 }
 
+#ifdef WITH_MQTT
+void hooks_setmosq(struct mosquitto *mosq)
+{
+	MQTTconn = mosq;
+}
+#endif
+
 void hooks_exit(struct luadata *ld, char *reason)
 {
 	if (ld && ld->script) {
@@ -448,4 +463,34 @@ static int otr_getdb(lua_State *lua)
 	}
 	return (rc);
 }
+
+#ifdef WITH_MQTT
+
+/*
+ * Requires two string arguments: topic, payload
+ * and two numeric args: qos and retain
+ * Will be published via MQTT to the Recorder's
+ * open connection.
+ */
+
+int otr_publish(lua_State *lua)
+{
+	const char *topic, *payload;
+	int qos = 0, retain = 0;
+	int rc = 0;
+
+	if (lua_gettop(lua) >= 1) {
+		topic =  lua_tostring(lua, 1);
+		payload =  lua_tostring(lua, 2);
+		qos =  lua_tonumber(lua, 3);
+		retain =  lua_tonumber(lua, 4);
+
+		rc = mosquitto_publish(MQTTconn, NULL, topic,
+		                                strlen(payload), payload, qos, retain);
+		olog(LOG_DEBUG, "LUA_PUBLISH (%s, %s, %d, %d) == %d\n", topic, payload, qos, retain, rc);
+	}
+	return (rc);
+}
+#endif
+
 #endif /* WITH_LUA */

hooks.h

@@ -3,6 +3,9 @@
 
 #ifdef WITH_LUA
 # include <lua.h>
+#  ifdef WITH_MQTT
+#   include <mosquitto.h>
+#  endif
 
 
 struct luadata {
@@ -16,6 +19,11 @@ void hooks_hook(struct udata *ud, char *topic, JsonNode *obj);
 int hooks_norec(struct udata *ud, char *user, char *device, char *payload);
 JsonNode *hooks_http(struct udata *ud, char *user, char *device, char *payload);
 
+#ifdef WITH_MQTT
+# include <mosquitto.h>
+void hooks_setmosq(struct mosquitto *);
+#endif
+
 #endif /* WITH_LUA */
 
 #endif

recorder.c

@@ -1621,6 +1621,8 @@ int main(int argc, char **argv)
 			mosquitto_lib_cleanup();
 			return rc;
 		}
+		/* Explicitly set MQTT connection for Lua's otr_publish() */
+		hooks_setmosq(mosq);
 	} else {
 		olog(LOG_INFO, "Not using MQTT: disabled by port=0");
 	}