Merge pull request #5 from nilsding/add-prometheus-metrics

Add /metrics endpoint which can be used with Prometheus

TWANG32/TWANG32.ino

@@ -1196,7 +1196,6 @@ void getInput(){
 // -------------- SFX --------------
 // ---------------------------------
 
-/*
 /*
    This is used sweep across (up or down) a frequency range for a specified duration.
    A sin based warble is added to the frequency. This function is meant to be called

TWANG32/config.h

@@ -64,6 +64,8 @@
 	#define MIN_REDRAW_INTERVAL  	1000.0 / 60.0    // divide by frames per second..if you tweak adjust player speed
 #endif
 
-
+// Comment or remove the next #define to disable the /metrics endpoint on the HTTP server.
+// This endpoint provides the Twang32 stats for ingestion via Prometheus.
+#define ENABLE_PROMETHEUS_METRICS_ENDPOINT
 
 #endif

TWANG32/wifi_ap.h

@@ -9,7 +9,14 @@ WiFiServer server(80);
 char linebuf[80];
 int charcount=0;
 
+enum PAGE_TO_SEND
+{
+  Stats,
+  Metrics
+};
+
 void ap_setup() {
+
     bool ret;
     
     
@@ -30,8 +37,7 @@ void ap_setup() {
 	Serial.println(passphrase);
 	Serial.println("Web Server Address: http://192.168.4.1");
 	
-	
+	}
-}
 
 void sendStatsPage(WiFiClient client) {
 	// HTTP headers always start with a response code (e.g. HTTP/1.1 200 OK)
@@ -44,7 +50,6 @@ void sendStatsPage(WiFiClient client) {
 	client.println("<h1>TWANG32 Play Stats</h1>");
 	client.println("<ul>");
 
-  
 	client.print("<li>Games played: "); client.print(user_settings.games_played); client.println("</li>");
 	if (user_settings.games_played > 0) {  // prevent divide by 0
 		client.print("<li>Average score: "); client.print(user_settings.total_points / user_settings.games_played); client.println("</li>");
@@ -90,41 +95,76 @@ void sendStatsPage(WiFiClient client) {
 
 	client.print("</table>");
 
+#ifdef ENABLE_PROMETHEUS_METRICS_ENDPOINT
+	client.println("<ul><li><a href=\"/metrics\">Metrics</a></li></ul>");
+#endif // ENABLE_PROMETHEUS_METRICS_ENDPOINT
+
 	client.println("</body>");
 	client.println("</html>");
 	client.println();
 
 }
 
+#ifdef ENABLE_PROMETHEUS_METRICS_ENDPOINT
+// We need to use print() here since println() prints newlines as CR/LF, which
+// Prometheus cannot handle.
+#define __prom_metric(metric_name, metric_description, value) \
+	client.print("# HELP " metric_name " " metric_description "\n");   \
+	client.print("# TYPE " metric_name " gauge\n");                    \
+	client.print(metric_name " ");                                     \
+	client.print(value);                                               \
+	client.print("\n");
+
+static void sendMetricsPage(WiFiClient client)
+{
+	client.println("HTTP/1.1 200 OK");
+	client.println("Content-Type: text/plain; charset=utf-8");
+	client.println("Server: twang_exporter");
+	client.println();
+	__prom_metric("twang_games_played", "Number of games played", user_settings.games_played);
+	__prom_metric("twang_total_points", "Total points", user_settings.total_points);
+	__prom_metric("twang_high_score", "High score", user_settings.high_score);
+	__prom_metric("twang_boss_kills", "Boss kills", user_settings.boss_kills);
+}
+
+#undef __prom_metric
+#endif // ENABLE_PROMETHEUS_METRICS_ENDPOINT
+
 void ap_client_check(){
 	int cnt;
 	bool newconn=false;
 	int stat;
 	WiFiClient client = server.available();   // listen for incoming clients
 
-  //if (client) {                             // if you get a client,
-  //   sendStatsPage(client);
-  //   Serial.println("printUploadForm");
-  //}
 	bool currentLineIsBlank = true;
+	PAGE_TO_SEND page_to_send = Stats;
 
 	while (client.connected()) {
 		if (client.available()) {
 			char c = client.read();
-				//Serial.write(c);
 			linebuf[charcount]=c;
 			if (charcount<sizeof(linebuf)-1)
 				charcount++;
 
-				if (c == '\n' && currentLineIsBlank) {
+			if (c == '\n' && currentLineIsBlank)
+			{
+				switch (page_to_send)
+				{
+				case Stats:
 					sendStatsPage(client);
 					break;
+#ifdef ENABLE_PROMETHEUS_METRICS_ENDPOINT
+				case Metrics:
+					sendMetricsPage(client);
+					break;
+#endif // ENABLE_PROMETHEUS_METRICS_ENDPOINT
+				}
+				break;
 			}
 			if (c == '\n') {
 				// you're starting a new line
 				currentLineIsBlank = true;
 
-					
 				if (strstr(linebuf,"GET /?") > 0)
 				{
 					String line = String(linebuf);
@@ -140,8 +180,14 @@ void ap_client_check(){
 
 					change_setting(paramCode, val.toInt());
 
-						
+					page_to_send = Stats;
 				}
+#ifdef ENABLE_PROMETHEUS_METRICS_ENDPOINT
+				else if (strstr(linebuf, "GET /metrics"))
+				{
+					page_to_send = Metrics;
+				}
+#endif // ENABLE_PROMETHEUS_METRICS_ENDPOINT
 
 				// you're starting a new line
 				currentLineIsBlank = true;
@@ -151,8 +197,6 @@ void ap_client_check(){
 				// you've gotten a character on the current line
 				currentLineIsBlank = false;
 			}
-				
 		}
 	}
-  
 }