refactor cpu measurement utilities and tests (#45)

system_metrics_collector/src/system_metrics_collector/linux_cpu_measurement_node.cpp

@@ -20,6 +20,7 @@
 
 #include "../../src/system_metrics_collector/linux_cpu_measurement_node.hpp"
 #include "../../src/system_metrics_collector/periodic_measurement_node.hpp"
+#include "../../src/system_metrics_collector/utilities.hpp"
 
 #include "rclcpp/rclcpp.hpp"
 #include "rcutils/logging_macros.h"
@@ -30,55 +31,11 @@ namespace
 {
 constexpr const char MEASUREMENT_TYPE[] = "system_cpu_percent_used";
 constexpr const char PROC_STAT_FILE[] = "/proc/stat";
-constexpr const char CPU_LABEL[] = "cpu";
 }  // namespace
 
 namespace system_metrics_collector
 {
 
-system_metrics_collector::ProcCpuData processStatCpuLine(const std::string & stat_cpu_line)
-{
-  system_metrics_collector::ProcCpuData parsed_data;
-
-  if (!stat_cpu_line.empty()) {
-    if (!stat_cpu_line.compare(0, strlen(CPU_LABEL), CPU_LABEL)) {
-      std::istringstream ss(stat_cpu_line);
-
-      if (!ss.good()) {
-        return system_metrics_collector::ProcCpuData();
-      }
-      ss >> parsed_data.cpu_label;
-
-      for (int i = 0;
-        i < static_cast<int>(system_metrics_collector::ProcCpuStates::kNumProcCpuStates); ++i)
-      {
-        if (!ss.good()) {
-          return system_metrics_collector::ProcCpuData();
-        }
-        ss >> parsed_data.times[i];
-      }
-      return parsed_data;
-    }
-  }
-  return parsed_data;
-}
-
-double computeCpuActivePercentage(
-  const system_metrics_collector::ProcCpuData & measurement1,
-  const system_metrics_collector::ProcCpuData & measurement2)
-{
-  if (measurement1.isMeasurementEmpty() || measurement2.isMeasurementEmpty()) {
-    RCUTILS_LOG_ERROR_NAMED("computeCpuActivePercentage",
-      "a measurement was empty, unable to compute cpu percentage");
-    return std::nan("");
-  }
-  const double active_time = measurement2.getActiveTime() - measurement1.getActiveTime();
-  const double total_time = (measurement2.getIdleTime() + measurement2.getActiveTime()) -
-    (measurement1.getIdleTime() + measurement1.getActiveTime());
-
-  return 100.0 * active_time / total_time;
-}
-
 LinuxCpuMeasurementNode::LinuxCpuMeasurementNode(
   const std::string & name,
   const std::chrono::milliseconds measurement_period,

system_metrics_collector/src/system_metrics_collector/linux_cpu_measurement_node.hpp

@@ -26,25 +26,6 @@
 namespace system_metrics_collector
 {
 
-/**
- * Parse a line read from /proc/stat
- *
- * @param stat_cpu_line a line from /proc/stat
- * @return ProcCpuData struct populated if parsed, otherwise empty
- */
-system_metrics_collector::ProcCpuData processStatCpuLine(const std::string & stat_cpu_line);
-
-/**
- * Compute the percentage of CPU active.
- *
- * @param measurement1 the first measurement
- * @param measurement2 the second measurement (made after the first)
- * @return percentage of CPU active
- */
-double computeCpuActivePercentage(
-  const system_metrics_collector::ProcCpuData & measurement1,
-  const system_metrics_collector::ProcCpuData & measurement2);
-
 /**
  * Node that periodically calculates the % of active CPU by
  * reading /proc/stat.

system_metrics_collector/src/system_metrics_collector/utilities.cpp

@@ -28,10 +28,20 @@ namespace system_metrics_collector
 
 namespace
 {
+
+constexpr const char CPU_LABEL[] = "cpu";
 constexpr const char MEM_TOTAL[] = "MemTotal:";
 constexpr const char MEM_AVAILABLE[] = "MemAvailable:";
 constexpr const char EMPTY_FILE[] = "";
 constexpr const int INVALID_MEMORY_SAMPLE = -1;
+
+double computeCpuTotalTime(const ProcCpuData measurement1, const ProcCpuData measurement2)
+{
+  const double total_time = (measurement2.getIdleTime() + measurement2.getActiveTime()) -
+    (measurement1.getIdleTime() + measurement1.getActiveTime());
+  return total_time;
+}
+
 }  // namespace
 
 std::string readFileToString(const std::string & file_name)
@@ -48,6 +58,49 @@ std::string readFileToString(const std::string & file_name)
   return to_return;
 }
 
+ProcCpuData processStatCpuLine(const std::string & stat_cpu_line)
+{
+  ProcCpuData parsed_data;
+
+  if (!stat_cpu_line.empty()) {
+    if (!stat_cpu_line.compare(0, strlen(CPU_LABEL), CPU_LABEL)) {
+      std::istringstream ss(stat_cpu_line);
+
+      if (!ss.good()) {
+        return ProcCpuData();
+      }
+      ss >> parsed_data.cpu_label;
+
+      for (int i = 0;
+        i < static_cast<int>(ProcCpuStates::kNumProcCpuStates); ++i)
+      {
+        if (!ss.good()) {
+          return ProcCpuData();
+        }
+        ss >> parsed_data.times[i];
+      }
+      return parsed_data;
+    }
+  }
+  return parsed_data;
+}
+
+double computeCpuActivePercentage(
+  const ProcCpuData & measurement1,
+  const ProcCpuData & measurement2)
+{
+  if (measurement1.isMeasurementEmpty() || measurement2.isMeasurementEmpty()) {
+    RCUTILS_LOG_ERROR_NAMED("computeCpuActivePercentage",
+      "a measurement was empty, unable to compute cpu percentage");
+    return std::nan("");
+  }
+
+  const double active_time = measurement2.getActiveTime() - measurement1.getActiveTime();
+  const double total_time = computeCpuTotalTime(measurement1, measurement2);
+
+  return 100.0 * active_time / total_time;
+}
+
 double processMemInfoLines(const std::string & lines)
 {
   std::istringstream process_lines_stream(lines);

system_metrics_collector/src/system_metrics_collector/utilities.hpp

@@ -17,6 +17,8 @@
 
 #include <string>
 
+#include "../../src/system_metrics_collector/proc_cpu_data.hpp"
+
 namespace system_metrics_collector
 {
 /**
@@ -28,6 +30,25 @@ namespace system_metrics_collector
  */
 std::string readFileToString(const std::string & file_name);
 
+/**
+ * Parse a line read from /proc/stat
+ *
+ * @param stat_cpu_line a line from /proc/stat
+ * @return ProcCpuData struct populated if parsed, otherwise empty
+ */
+ProcCpuData processStatCpuLine(const std::string & stat_cpu_line);
+
+/**
+ * Compute the percentage of CPU active.
+ *
+ * @param measurement1 the first measurement
+ * @param measurement2 the second measurement (made after the first)
+ * @return percentage of CPU active
+ */
+double computeCpuActivePercentage(
+  const ProcCpuData & measurement1,
+  const ProcCpuData & measurement2);
+
 /**
  * Process input lines from the /proc/meminfo file. The expected format to
  * compute memory used is

system_metrics_collector/test/system_metrics_collector/test_constants.hpp

@@ -24,6 +24,23 @@ constexpr const std::chrono::milliseconds TEST_DURATION{250};
 constexpr const std::chrono::milliseconds MEASURE_PERIOD{50};
 constexpr const std::chrono::milliseconds PUBLISH_PERIOD{80};
 
+constexpr const char PROC_SAMPLE_RESOLUTION_TEST[] =
+  "cpu  57211920 335926 18096939 2526329830 14818556 0 1072048 0 0 0\n";
+constexpr const std::array<const char *, 10> PROC_SAMPLES = {
+  "cpu 22451232 118653 7348045 934943300 5378119 0 419114 0 0 0\n",
+  "cpu 22451360 118653 7348080 934949227 5378120 0 419117 0 0 0\n",
+  "cpu 24343452 61856 6484430 10645595 58695 0 683052 0 0 0\n",
+  "cpu 6051294 43322 1611333 9021635 47400 0 177494 0 0 0\n",
+  "cpu 6092443 6217 1623536 535731 4143 0 232286 0 0 0\n",
+  "cpu 6097071 6498 1612044 544445 3484 0 135942 0 0 0\n",
+  "cpu 6102643 5818 1637516 543782 3666 0 137329 0 0 0\n",
+  "cpu 24513632 62372 6527524 11205004 62394 0 687176 0 0 0\n",
+  "cpu 6093617 43419 1621953 9161570 48047 0 178792 0 0 0\n",
+  "cpu 6134250 6371 1634411 675446 5285 0 233478 0 0 0\n"
+};
+constexpr const double CPU_ACTIVE_PROC_SAMPLE_0_1 = 2.7239908106334099;
+
+
 constexpr const char EMPTY_SAMPLE[] = "";
 constexpr const char GARBAGE_SAMPLE[] = "this is garbage\n";
 constexpr const char INCOMPLETE_SAMPLE[] =