src/ProcStats.cpp

#include "ProcStats.h"
#include "yagpcc_metrics.pb.h"
#include <string>
#include <fstream>
#include <unistd.h>

extern "C" {
#include "postgres.h"
#include "utils/elog.h"
}

namespace {
#define FILL_IO_STAT(stat_name)                                                \
  uint64_t stat_name;                                                          \
  proc_stat >> tmp >> stat_name;                                               \
  stats->set_##stat_name(stat_name - stats->stat_name());

void fill_io_stats(yagpcc::SystemStat *stats) {
  std::ifstream proc_stat("/proc/self/io");
  std::string tmp;
  FILL_IO_STAT(rchar);
  FILL_IO_STAT(wchar);
  FILL_IO_STAT(syscr);
  FILL_IO_STAT(syscw);
  FILL_IO_STAT(read_bytes);
  FILL_IO_STAT(write_bytes);
  FILL_IO_STAT(cancelled_write_bytes);
}

void fill_cpu_stats(yagpcc::SystemStat *stats) {
  static const int UTIME_ID = 13;
  static const int STIME_ID = 14;
  static const int VSIZE_ID = 22;
  static const int RSS_ID = 23;
  static const double tps = sysconf(_SC_CLK_TCK);

  std::ifstream proc_stat("/proc/self/stat");
  std::string trash;
  for (int i = 0; i <= RSS_ID; ++i) {
    switch (i) {
    case UTIME_ID:
      double utime;
      proc_stat >> utime;
      stats->set_usertimeseconds(utime / tps - stats->usertimeseconds());
      break;
    case STIME_ID:
      double stime;
      proc_stat >> stime;
      stats->set_kerneltimeseconds(stime / tps - stats->kerneltimeseconds());
      break;
    case VSIZE_ID:
      uint64_t vsize;
      proc_stat >> vsize;
      stats->set_vsize(vsize);
      break;
    case RSS_ID:
      uint64_t rss;
      proc_stat >> rss;
      // NOTE: this is a double AFAIU, need to double-check
      stats->set_rss(rss);
      break;
    default:
      proc_stat >> trash;
    }
  }
}

void fill_status_stats(yagpcc::SystemStat *stats) {
  std::ifstream proc_stat("/proc/self/status");
  std::string key, measure;
  while (proc_stat >> key) {
    if (key == "VmPeak:") {
      uint64_t value;
      proc_stat >> value;
      stats->set_vmpeakkb(value);
      proc_stat >> measure;
      if (measure != "kB") {
        ereport(FATAL, (errmsg("Expected memory sizes in kB, but got in %s",
                               measure.c_str())));
      }
    } else if (key == "VmSize:") {
      uint64_t value;
      proc_stat >> value;
      stats->set_vmsizekb(value);
      if (measure != "kB") {
        ereport(FATAL, (errmsg("Expected memory sizes in kB, but got in %s",
                               measure.c_str())));
      }
    }
  }
}
} // namespace

void fill_self_stats(yagpcc::SystemStat *stats) {
  static yagpcc::SystemStat prev_stats;
  fill_io_stats(&prev_stats);
  fill_cpu_stats(&prev_stats);
  fill_status_stats(&prev_stats);
  *stats = prev_stats;
}