Add optional support for Prometheus

Add optional support for Prometheus using file xsns_91_prometheus.ino (#7216)

RELEASENOTES.md

@@ -58,6 +58,7 @@ The following binary downloads have been compiled with ESP8266/Arduino library c
 - Fix Sonoff Bridge, Sc, L1, iFan03 and CSE7766 serial interface to forced speed, config and disable logging
 - Fix commands ``Display`` and ``Counter`` from overruling command processing (#7322)
 - Fix ``White`` added to light status (#7142)
+- Fix Improved fade linearity with gamma correction
 - Fix LCD line and column positioning (#7387)
 - Fix Display handling of hexadecimal escape characters (#7387)
 - Add command ``SetOption79 0/1`` to enable reset of counters at teleperiod time by Andre Thomas (#7355)
@@ -66,3 +67,4 @@ The following binary downloads have been compiled with ESP8266/Arduino library c
 - Add support for DS1624, DS1621 Temperature sensor by Leonid Myravjev
 - Add Zigbee attribute decoder for Xiaomi Aqara Cube
 - Add support for ``AdcParam`` parameters to control ADC0 Current Transformer Apparent Power formula by Jodi Dillon (#7100)
+- Add optional support for Prometheus using file xsns_91_prometheus.ino (#7216)

tasmota/CHANGELOG.md

@@ -3,6 +3,7 @@
 ### 8.1.0.2 20191230
 
 - Add support for ``AdcParam`` parameters to control ADC0 Current Transformer Apparent Power formula by Jodi Dillon (#7100)
+- Add optional support for Prometheus using file xsns_91_prometheus.ino (#7216)
 - Fix LCD line and column positioning (#7387)
 - Fix Display handling of hexadecimal escape characters (#7387)
 - Fix Improved fade linearity with gamma correction

tasmota/xsns_91_prometheus.ino

@@ -0,0 +1,84 @@
+/*
+  xsns_91_prometheus.ino - Web based information for Tasmota
+
+  Copyright (C) 2020  Theo Arends
+
+  This program is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+//#define USE_PROMETHEUS                         // Enable retrieval of metrics
+
+#ifdef USE_PROMETHEUS
+/*********************************************************************************************\
+ * Prometheus support
+\*********************************************************************************************/
+
+#define XSNS_91                    91
+
+void HandleMetrics(void)
+{
+  if (!HttpCheckPriviledgedAccess()) { return; }
+
+  AddLog_P(LOG_LEVEL_DEBUG, S_LOG_HTTP, PSTR("Prometheus"));
+
+  WSContentBegin(200, CT_PLAIN);
+
+  char parameter[FLOATSZ];
+
+  if (global_temperature != 9999) {
+    dtostrfd(global_temperature, Settings.flag2.temperature_resolution, parameter);
+    WSContentSend_P(PSTR("# TYPE global_temperature gauge\nglobal_temperature %s\n"), parameter);
+  }
+  if (global_humidity != 0) {
+    dtostrfd(global_humidity, Settings.flag2.humidity_resolution, parameter);
+    WSContentSend_P(PSTR("# TYPE global_humidity gauge\nglobal_humidity %s\n"), parameter);
+  }
+  if (global_pressure != 0) {
+    dtostrfd(global_pressure, Settings.flag2.pressure_resolution, parameter);
+    WSContentSend_P(PSTR("# TYPE global_pressure gauge\nglobal_pressure %s\n"), parameter);
+  }
+
+#ifdef USE_ENERGY_SENSOR
+  dtostrfd(Energy.voltage[0], Settings.flag2.voltage_resolution, parameter);
+  WSContentSend_P(PSTR("# TYPE voltage gauge\nvoltage %s\n"), parameter);
+  dtostrfd(Energy.current[0], Settings.flag2.current_resolution, parameter);
+  WSContentSend_P(PSTR("# TYPE current gauge\ncurrent %s\n"), parameter);
+  dtostrfd(Energy.active_power[0], Settings.flag2.wattage_resolution, parameter);
+  WSContentSend_P(PSTR("# TYPE active_power guage\nactive_power %s\n"), parameter);
+  dtostrfd(Energy.daily, Settings.flag2.energy_resolution, parameter);
+  WSContentSend_P(PSTR("# TYPE energy_daily counter\nenergy_daily %s\n"), parameter);
+  dtostrfd(Energy.total, Settings.flag2.energy_resolution, parameter);
+  WSContentSend_P(PSTR("# TYPE energy_total counter\nenergy_total %s\n"), parameter);
+#endif
+
+  WSContentEnd();
+}
+
+/*********************************************************************************************\
+ * Interface
+\*********************************************************************************************/
+
+bool Xsns91(uint8_t function)
+{
+  bool result = false;
+
+  switch (function) {
+    case FUNC_WEB_ADD_HANDLER:
+      WebServer->on("/metrics", HandleMetrics);
+      break;
+  }
+  return result;
+}
+
+#endif  // USE_PROMETHEUS