From 6375c8e2c0be4ff50da8b29f8bfbdd16ba4213a5 Mon Sep 17 00:00:00 2001
From: Georg Gadinger <nilsding@nilsding.org>
Date: Thu, 10 Oct 2019 20:18:17 +0200
Subject: [PATCH] Add /metrics endpoint to be used with Prometheus

---
 TWANG32/config.h  |   4 +-
 TWANG32/wifi_ap.h | 248 +++++++++++++++++++++++++++-------------------
 2 files changed, 147 insertions(+), 105 deletions(-)
diff --git a/TWANG32/config.h b/TWANG32/config.h
index fa93e1e..a52cbb4 100644
--- a/TWANG32/config.h
+++ b/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
diff --git a/TWANG32/wifi_ap.h b/TWANG32/wifi_ap.h
index d880693..faf6a24 100644
--- a/TWANG32/wifi_ap.h
+++ b/TWANG32/wifi_ap.h
@@ -1,7 +1,7 @@
 #include <WiFi.h>
 #include "settings.h"
 
-const char* ssid     = "TWANG_AP";
+const char* ssid       = "TWANG_AP";
 const char* passphrase = "esp32rocks";
 
 WiFiServer server(80);
@@ -9,146 +9,186 @@ WiFiServer server(80);
 char linebuf[80];
 int charcount=0;
 
+enum PAGE_TO_SEND
+{
+  Stats,
+  Metrics
+};
+
 void ap_setup() {
-    bool ret;
-    
-    
+	bool ret;
 
-  /*
-   * Set up an access point
-   * @param ssid          Pointer to the SSID (max 63 char).
-   * @param passphrase    (for WPA2 min 8 char, for open use NULL)
-   * @param channel       WiFi channel number, 1 - 13.
-   * @param ssid_hidden   Network cloaking (0 = broadcast SSID, 1 = hide SSID)
-   */
-    ret = WiFi.softAP(ssid, passphrase, 2, 0);
-    
-    //Serial.println("\r\nWiFi AP online ...");    
-    server.begin();
-	
+	/*
+	 * Set up an access point
+	 * @param ssid          Pointer to the SSID (max 63 char).
+	 * @param passphrase    (for WPA2 min 8 char, for open use NULL)
+	 * @param channel       WiFi channel number, 1 - 13.
+	 * @param ssid_hidden   Network cloaking (0 = broadcast SSID, 1 = hide SSID)
+	 */
+	ret = WiFi.softAP(ssid, passphrase, 2, 0);
 
+	//Serial.println("\r\nWiFi AP online ...");
+	server.begin();
 }
 
 void sendStatsPage(WiFiClient client) {
-  // HTTP headers always start with a response code (e.g. HTTP/1.1 200 OK)
-  // and a content-type so the client knows what's coming, then a blank line:
-  client.println("HTTP/1.1 200 OK");
-  client.println("Content-type:text/html");
-  client.println();
-  client.println("<html>");
-  client.println("<body>");
-  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
+	// HTTP headers always start with a response code (e.g. HTTP/1.1 200 OK)
+	// and a content-type so the client knows what's coming, then a blank line:
+	client.println("HTTP/1.1 200 OK");
+	client.println("Content-type:text/html");
+	client.println();
+	client.println("<html>");
+	client.println("<body>");
+	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>");
-  }
-  client.print("<li>High score: "); client.print(user_settings.high_score); client.println("</li>");
-  client.print("<li>Boss kills: "); client.print(user_settings.boss_kills); client.println("</li>");
-	
+	}
+	client.print("<li>High score: "); client.print(user_settings.high_score); client.println("</li>");
+	client.print("<li>Boss kills: "); client.print(user_settings.boss_kills); client.println("</li>");
+
 	client.print("<button onClick=\"location.href = 'http://192.168.4.1'\">Refresh</button>");
-  
+
 	client.print("<h2>Adjustable Settings </h2>");
-	
+
 	client.print("<table>");
-	
-	
-	client.print("<tr><td>");	
+
+
+	client.print("<tr><td>");
 	client.print("LED Count (60-");
-  client.print(MAX_LEDS); 
-  client.print(")</td><td><form><input type='number' name='C' value='"); 	
+	client.print(MAX_LEDS);
+	client.print(")</td><td><form><input type='number' name='C' value='");
 	client.print(user_settings.led_count);
 	client.print ("' min='60' max='");
 	client.print (MAX_LEDS);
 	client.print ("'><input type='submit'></form></td></tr>");
-	
-	client.print("<tr><td>Brightness (10-255)</td><td><form><input type='number' name='B' value='"); 
+
+	client.print("<tr><td>Brightness (10-255)</td><td><form><input type='number' name='B' value='");
 	client.print(user_settings.led_brightness);
 	client.print ("' min='10' max='255'><input type='submit'></form></td></tr>");
-		
+
 	client.print("<tr><td>Sound Volume (0-255)</td><td><form><input type='number' name='S' value='");
 	client.print(user_settings.audio_volume);
 	client.print("' min='0' max='255'><input type='submit'></form></td></tr>");
-	
+
 	client.print("<tr><td>Joystick Deadzone (3-12)</td><td><form><input type='number' name='D' value='");
 	client.print(user_settings.joystick_deadzone);
 	client.print("' min='3' max='12'><input type='submit'></form></td></tr>");
-	
+
 	client.print("<tr><td>Attack Sensitivity (20000-35000)</td><td><form><input type='number' name='A' value='");
 	client.print(user_settings.attack_threshold);
 	client.print("' min='2000' max='35000'><input type='submit'></form></td></tr>");
-	
+
 	client.print("<tr><td>Lives Per Level (3-9)</td><td><form><input type='number' name='L' value='");
 	client.print(user_settings.lives_per_level);
 	client.print("' min='3' max='9'><input type='submit'></form></td></tr>");
-	
-  client.print("</table>");
-	
-  client.println("</body>");
-  client.println("</html>");  
-  client.println();
-  
+
+	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
+	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 (client.available()) {
+			char c = client.read();
+			linebuf[charcount]=c;
+			if (charcount<sizeof(linebuf)-1)
+				charcount++;
+
+			if (c == '\n' && currentLineIsBlank)
+			{
+				switch (page_to_send)
+				{
+				case Stats:
 					sendStatsPage(client);
-					break;					
+					break;
+#ifdef ENABLE_PROMETHEUS_METRICS_ENDPOINT
+				case Metrics:
+					sendMetricsPage(client);
+					break;
+#endif // ENABLE_PROMETHEUS_METRICS_ENDPOINT
 				}
-				if (c == '\n') {
-          // you're starting a new line
-          currentLineIsBlank = true;
-					
-					
-					if (strstr(linebuf,"GET /?") > 0)
-					{						
-					  String line = String(linebuf);		
-
-						int start = line.indexOf('=', 0);
-
-						char paramCode = line.charAt(start - 1);
-						
-						int finish = line.indexOf('H', start+1)-1;
-						String val = line.substring(start+1, finish);		
-						// if it is not numeric, it will convert to 0. 
-						// The the change_setting function will make sure the range is OK
-						
-						change_setting(paramCode, val.toInt());
-						
-						
-					}
-					
-					// you're starting a new line
-					currentLineIsBlank = true;
-					memset(linebuf,0,sizeof(linebuf));
-					charcount=0;
-				} else if (c != '\r') {
-					// you've gotten a character on the current line
-					currentLineIsBlank = false;
-				}
-				
+				break;
 			}
+			if (c == '\n') {
+				// you're starting a new line
+				currentLineIsBlank = true;
+
+				if (strstr(linebuf,"GET /?") > 0)
+				{
+					String line = String(linebuf);
+
+					int start = line.indexOf('=', 0);
+
+					char paramCode = line.charAt(start - 1);
+
+					int finish = line.indexOf('H', start+1)-1;
+					String val = line.substring(start+1, finish);
+					// if it is not numeric, it will convert to 0.
+					// The the change_setting function will make sure the range is OK
+
+					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;
+				memset(linebuf,0,sizeof(linebuf));
+				charcount=0;
+			} else if (c != '\r') {
+				// you've gotten a character on the current line
+				currentLineIsBlank = false;
+			}
+		}
 	}
-  
 }

"); + + + client.print("
"); client.print("LED Count (60-"); - client.print(MAX_LEDS); - client.print(")
Brightness (10-255)
Sound Volume (0-255)
Joystick Deadzone (3-12)
Attack Sensitivity (20000-35000)
Lives Per Level (3-9)