Add host system metrics.

src/main/java/org/whispersystems/textsecuregcm/metrics/CpuUsageGauge.java

@@ -0,0 +1,16 @@
+package org.whispersystems.textsecuregcm.metrics;
+
+import com.sun.management.OperatingSystemMXBean;
+import com.yammer.metrics.core.Gauge;
+
+import java.lang.management.ManagementFactory;
+
+public class CpuUsageGauge extends Gauge<Integer> {
+  @Override
+  public Integer value() {
+    OperatingSystemMXBean mbean = (com.sun.management.OperatingSystemMXBean)
+        ManagementFactory.getOperatingSystemMXBean();
+
+    return (int) Math.ceil(mbean.getSystemCpuLoad() * 100);
+  }
+}

src/main/java/org/whispersystems/textsecuregcm/metrics/FreeMemoryGauge.java

@@ -0,0 +1,20 @@
+package org.whispersystems.textsecuregcm.metrics;
+
+import com.sun.management.OperatingSystemMXBean;
+import com.yammer.metrics.core.Gauge;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.lang.management.ManagementFactory;
+
+public class FreeMemoryGauge extends Gauge<Long> {
+
+  @Override
+  public Long value() {
+    OperatingSystemMXBean mbean = (com.sun.management.OperatingSystemMXBean)
+        ManagementFactory.getOperatingSystemMXBean();
+
+    return mbean.getFreePhysicalMemorySize();
+  }
+}

src/main/java/org/whispersystems/textsecuregcm/metrics/NetworkGauge.java

@@ -0,0 +1,37 @@
+package org.whispersystems.textsecuregcm.metrics;
+
+
+import com.yammer.metrics.core.Gauge;
+import org.whispersystems.textsecuregcm.util.Pair;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileReader;
+import java.io.IOException;
+
+public abstract class NetworkGauge extends Gauge<Long> {
+
+  protected Pair<Long, Long> getSentReceived() throws IOException {
+    File           proc          = new File("/proc/net/dev");
+    BufferedReader reader        = new BufferedReader(new FileReader(proc));
+    String         header        = reader.readLine();
+    String         header2       = reader.readLine();
+
+    long           bytesSent     = 0;
+    long           bytesReceived = 0;
+
+    String interfaceStats;
+
+      while ((interfaceStats = reader.readLine()) != null) {
+        String[] stats = interfaceStats.split("\\s+");
+
+        if (!stats[1].equals("lo:")) {
+          bytesReceived += Long.parseLong(stats[2]);
+          bytesSent     += Long.parseLong(stats[10]);
+        }
+      }
+
+    return new Pair<>(bytesSent, bytesReceived);
+  }
+}

src/main/java/org/whispersystems/textsecuregcm/metrics/NetworkReceivedGauge.java

@@ -0,0 +1,36 @@
+package org.whispersystems.textsecuregcm.metrics;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.whispersystems.textsecuregcm.util.Pair;
+
+import java.io.IOException;
+
+public class NetworkReceivedGauge extends NetworkGauge {
+
+  private final Logger logger = LoggerFactory.getLogger(NetworkSentGauge.class);
+
+  private long lastTimestamp;
+  private long lastReceived;
+
+  @Override
+  public Long value() {
+    try {
+      long             timestamp       = System.currentTimeMillis();
+      Pair<Long, Long> sentAndReceived = getSentReceived();
+      long             result          = 0;
+
+      if (lastTimestamp != 0) {
+        result       = sentAndReceived.second() - lastReceived;
+        lastReceived = sentAndReceived.second();
+      }
+
+      lastTimestamp = timestamp;
+      return result;
+    } catch (IOException e) {
+      logger.warn("NetworkReceivedGauge", e);
+      return -1L;
+    }
+  }
+
+}

src/main/java/org/whispersystems/textsecuregcm/metrics/NetworkSentGauge.java

@@ -0,0 +1,35 @@
+package org.whispersystems.textsecuregcm.metrics;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.whispersystems.textsecuregcm.util.Pair;
+
+import java.io.IOException;
+
+public class NetworkSentGauge extends NetworkGauge {
+
+  private final Logger logger = LoggerFactory.getLogger(NetworkSentGauge.class);
+
+  private long lastTimestamp;
+  private long lastSent;
+
+  @Override
+  public Long value() {
+    try {
+      long             timestamp       = System.currentTimeMillis();
+      Pair<Long, Long> sentAndReceived = getSentReceived();
+      long             result          = 0;
+
+      if (lastTimestamp != 0) {
+        result        = sentAndReceived.first() - lastSent;
+        lastSent      = sentAndReceived.first();
+      }
+
+      lastTimestamp = timestamp;
+      return result;
+    } catch (IOException e) {
+      logger.warn("NetworkSentGauge", e);
+      return -1L;
+    }
+  }
+}