Calculate memory usage percentage instead of using ps command (#59)

Author: awegrzyn

README.md

@@ -104,6 +104,8 @@ See table below to find out how to create `URI` for each backend:
 | InfoLogger   | -         | `infologger`           | -                |
 | Flume        | UDP       | `flume`                | -                |
 
+Multiple backends may be used at the same time, URLs should be separated by `,` (comma).
+
 ### Sending metric
 
 ```cpp
@@ -197,16 +199,13 @@ Glabal tags are tags that are added to each metric. The following tags are set t
 You can add your own global tag by calling `addGlobalTag(std::string name, std::string value)`.
 
 ### Monitoring process
-Currently process monitoring is supported only on Linux. To enable it use:
 ```cpp
 enableProcessMonitoring([interval in seconds]);
 ```
 The following metrics are generated every interval:
-+ **cpuUsedPercentage** - percentage of a core usage over time interval (from `gerrusage`)
-+ **involuntaryContextSwitches** - involuntary context switches over time interval (from `gerrusage`)
-+ **memoryUsagePercentage** - ratio of the process's resident set size  to the physical memory on the machine, expressed as a percentage (from `ps`)
-+ **bytesReceived** - the total number of bytes of data received by the process per interface (from `/proc/[PID]/net/dev`)
-+ **bytesTransmitted** - the total number of bytes of data transmitted by the process per interface (from `/proc/[PID]/net/dev`).
++ **cpuUsedPercentage** - percentage of a core usage over time interval
++ **involuntaryContextSwitches** - involuntary context switches over time interval
++ **memoryUsagePercentage** - ratio of the process's resident set size  to the physical memory on the machine, expressed as a percentage (Linux only)
 
 ## Code snippets
 Code snippets are available in [examples](examples/) directory.

include/Monitoring/ProcessMonitor.h

@@ -47,8 +47,11 @@ class ProcessMonitor
     /// PIDs that are monitored
     unsigned int mPid;
 
-    /// Executes terminal command
-    std::string exec(const char* cmd);
+    /// Total memory size
+    unsigned int mTotalMemory;
+
+    /// Retrievs total memory size from /proc/meminfo
+    void setTotalMemory();
 
     /// 'getrusage' values from last execution
     struct rusage mPreviousGetrUsage;

src/Monitoring.cxx

@@ -59,12 +59,12 @@ void Monitoring::flushBuffer() {
 }
 
 void Monitoring::enableProcessMonitoring(const unsigned int interval) {
-#ifdef _OS_LINUX
   mMonitorRunning = true;
   mMonitorThread = std::thread(&Monitoring::processMonitorLoop, this, interval);
+#ifdef _OS_LINUX
   MonLogger::Get() << "Process Monitor : Automatic updates enabled" << MonLogger::End();
 #else
-  MonLogger::Get() << "!! Process Monitor : Automatic updates not supported" << MonLogger::End();
+  MonLogger::Get() << "!! Process Monitor : Limited metrics available" << MonLogger::End();
 #endif
 }
 
@@ -123,8 +123,9 @@ void Monitoring::processMonitorLoop(int interval)
     std::this_thread::sleep_for (std::chrono::milliseconds(interval*10));
     if ((++loopCount % 100) != 0) continue;
     send(mProcessMonitor->getCpuAndContexts());
-    send(mProcessMonitor->getNetworkUsage());
+#ifdef _OS_LINUX
     send(mProcessMonitor->getMemoryUsage());
+#endif
     loopCount = 0;
   }
 }

src/ProcessMonitor.cxx

@@ -24,14 +24,36 @@ ProcessMonitor::ProcessMonitor()
   mPid = static_cast<unsigned int>(::getpid());
   getrusage(RUSAGE_SELF, &mPreviousGetrUsage);
   mTimeLastRun = std::chrono::high_resolution_clock::now();
+#ifdef _OS_LINUX
+  setTotalMemory();
+#endif
+}
+
+void ProcessMonitor::setTotalMemory()
+{
+  std::ifstream memInfo("/proc/meminfo");
+  std::string totalString;
+  std::getline(memInfo, totalString);
+  std::istringstream iss(totalString);
+  std::vector<std::string> tokens{std::istream_iterator<std::string>{iss},
+                                  std::istream_iterator<std::string>{}};
+  mTotalMemory = std::stoi(tokens[1]);
 }
 
 Metric ProcessMonitor::getMemoryUsage()
 {
-  std::string command = "ps --no-headers -o pmem --pid " + std::to_string(mPid);
-  std::string output = exec(command.c_str());
-  boost::trim(output);
-  return Metric{std::stod(output), "memoryUsagePercentage"};
+  std::ifstream statusStream("/proc/self/status");
+  std::string rssString;
+  rssString.reserve(50);
+
+  // Scan for VmRSS
+  for(int i = 0; i < 18; i++) {
+       std::getline(statusStream, rssString);
+  }
+  std::istringstream iss(rssString);
+  std::vector<std::string> tokens{std::istream_iterator<std::string>{iss},
+                                  std::istream_iterator<std::string>{}};
+  return Metric{(std::stod(tokens[1])*100)/mTotalMemory, "memoryUsagePercentage"};
 }
 
 std::vector<Metric> ProcessMonitor::getCpuAndContexts() {
@@ -85,20 +107,5 @@ std::vector<Metric> ProcessMonitor::getNetworkUsage()
 return metrics;
 }
 
-std::string ProcessMonitor::exec(const char* cmd)
-{
-  char buffer[128];
-  std::string result = "";
-  std::shared_ptr<FILE> pipe(popen(cmd, "r"), pclose);
-  if (!pipe) {
-    throw MonitoringInternalException("Process Monitor exec", "Issue encountered when running 'ps' (popen)");
-  }
-  while (!feof(pipe.get())) {
-    if (fgets(buffer, 128, pipe.get()) != NULL)
-      result += buffer;
-  }
-  return result;
-}
-
 } // namespace monitoring
 } // namespace o2