Added LoadAverageCollector class

src/main/java/nu/ltd/fp/se/Constant.java

@@ -6,4 +6,5 @@ public class Constant {
   public static final String METRICS_PATH = "/metrics";
   public static final Integer LISTEN_PORT = 18089;
   public static final String EXPORTER_NAMESPACE = "node_";
+  public static final String LXPROC_PATH = "/system/lxproc";
 }

src/main/java/nu/ltd/fp/se/SystemMetrics.java

@@ -4,6 +4,7 @@ import io.prometheus.client.Counter;
 import io.prometheus.client.Gauge;
 import io.prometheus.client.Histogram;
 import io.prometheus.client.Summary;
+import nu.ltd.fp.se.collector.LoadAverageCollector;
 import nu.ltd.fp.se.collector.MetricCollector;
 import nu.ltd.fp.se.collector.SmartOSCollector;
 import nu.ltd.fp.se.collector.UnameCollector;
@@ -15,9 +16,10 @@ public class SystemMetrics {
   public SystemMetrics() {
     MetricCollector smartOSCollector = new SmartOSCollector();
     MetricCollector unameCollector = new UnameCollector(smartOSCollector);
+    MetricCollector loadAverageCollector = new LoadAverageCollector(unameCollector);
 
     // this.metricCollector should be set to the last one
-    this.metricCollector = unameCollector;
+    this.metricCollector = loadAverageCollector;
   }
 
   public void pollCollectorChain() {

src/main/java/nu/ltd/fp/se/collector/LoadAverageCollector.java

@@ -0,0 +1,61 @@
+package nu.ltd.fp.se.collector;
+
+import io.prometheus.client.Gauge;
+import nu.ltd.fp.se.Constant;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileReader;
+
+public class LoadAverageCollector extends AbstractMetricCollector implements MetricCollector {
+  static final Gauge load1mGauge = Gauge.build()
+    .name(Constant.EXPORTER_NAMESPACE + "load1")
+    .help("1m load average.")
+    .register();
+
+  static final Gauge load5mGauge = Gauge.build()
+    .name(Constant.EXPORTER_NAMESPACE + "load5")
+    .help("5m load average.")
+    .register();
+
+  static final Gauge load15mGauge = Gauge.build()
+    .name(Constant.EXPORTER_NAMESPACE + "load15")
+    .help("15m load average.")
+    .register();
+
+  public LoadAverageCollector() { }
+
+  public LoadAverageCollector(MetricCollector nextCollector) {
+    this();
+    this.setNextCollector(nextCollector);
+  }
+
+  private double getLoadAverage(Integer m) {
+    File loadAverageFile = new File(Constant.LXPROC_PATH + "/loadavg");
+    Double loadAverageValue = 0.0;
+    BufferedReader reader = null;
+    try {
+      reader = new BufferedReader(new FileReader(loadAverageFile));
+      String line = null;
+      while ((line = reader.readLine()) != null) {
+        String[] tokens = line.split(" ");
+        loadAverageValue = Double.parseDouble(tokens[m]);
+      }
+    } catch (Exception e) {
+      loadAverageValue = 0.0;
+    } finally {
+      try { if (reader != null) { reader.close(); } } catch (Exception e) {}
+    }
+    return loadAverageValue;
+  }
+
+  public void collectMetric() {
+    load1mGauge.set(getLoadAverage(0));
+    load5mGauge.set(getLoadAverage(1));
+    load15mGauge.set(getLoadAverage(2));
+    // Nothing to be done, call next collector
+    if (this.getNextCollector() != null) {
+      this.getNextCollector().collectMetric();
+    }
+  }
+}