wsd: dump the Prometheus metrics with USR1

Change-Id: I51a2dd80bca4aa33a2829f7e8baf87034a654f61
Signed-off-by: Ashod Nakashian <[email protected]>

wsd/Admin.cpp

@@ -13,6 +13,7 @@
 
 #include <chrono>
 #include <iomanip>
+#include <sstream>
 #include <string>
 #include <sys/poll.h>
 #include <unistd.h>
@@ -695,6 +696,17 @@ void Admin::pollingThread()
  }
  }
 
+ bool dumpMetrics = true;
+ if (_dumpMetrics.compare_exchange_strong(dumpMetrics, false))
+ {
+ std::ostringstream oss;
+ oss << "Admin Metrics:\n";
+ getMetrics(oss);
+ const std::string str = oss.str();
+ fprintf(stderr, "%s\n", str.c_str());
+ LOG_TRC(str);
+ }
+
  // Handle websockets & other work.
  const auto timeout = std::chrono::milliseconds(capAndRoundInterval(
  std::min(std::min(std::min(cpuWait, memWait), netWait), cleanupWait)));

wsd/Admin.hpp

@@ -173,6 +173,9 @@ class Admin : public SocketPoll
 
  void getMetrics(std::ostringstream &metrics);
 
+ /// Will dump the metrics in the log and stderr from the Admin SocketPoll.
+ static void dumpMetrics() { instance()._dumpMetrics = true; }
+
  // delete entry from _monitorSocket map
  void deleteMonitorSocket(const std::string &uriWithoutParam);
 
@@ -226,6 +229,9 @@ class Admin : public SocketPoll
  uint64_t _lastRecvCount;
  std::string _forkitLogLevel;
 
+ /// When set, the metrics will be dumped into the log and stderr.
+ std::atomic_bool _dumpMetrics;
+
  struct MonitorConnectRecord
  {
  void setWhen(std::chrono::steady_clock::time_point when) { _when = when; }

wsd/COOLWSD.cpp

@@ -4960,6 +4960,10 @@ void dump_state()
  const std::string msg = oss.str();
  fprintf(stderr, "%s\n", msg.c_str());
  LOG_TRC(msg);
+
+#if !MOBILEAPP
+ Admin::dumpMetrics();
+#endif
 }
 
 void lslr_childroot()