Introduce a set of gauges for various network statistics as reported by nstat.

service/src/test/java/org/whispersystems/textsecuregcm/metrics/NstatCountersTest.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2021 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.whispersystems.textsecuregcm.metrics;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.EnabledOnOs;
+import org.junit.jupiter.api.condition.OS;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.whispersystems.textsecuregcm.metrics.NstatCounters.NetworkStatistics;
+
+import java.io.IOException;
+import java.util.stream.Stream;
+
+import static org.junit.jupiter.api.Assertions.*;
+import static org.junit.jupiter.api.Assumptions.assumeTrue;
+
+class NstatCountersTest {
+
+  @Test
+  @EnabledOnOs(OS.LINUX)
+  void loadNetworkStatistics() throws IOException, InterruptedException {
+    final NetworkStatistics networkStatistics = NstatCounters.loadNetworkStatistics();
+
+    assertNotNull(networkStatistics.getKernelStatistics());
+    assertFalse(networkStatistics.getKernelStatistics().isEmpty());
+  }
+
+  @ParameterizedTest
+  @MethodSource("shouldIncludeMetricNameProvider")
+  void shouldIncludeMetric(final String metricName, final boolean expectInclude) {
+    assertEquals(expectInclude, NstatCounters.shouldIncludeMetric(metricName));
+  }
+
+  static Stream<Arguments> shouldIncludeMetricNameProvider() {
+    return Stream.of(Arguments.of("IpInReceives", true),
+        Arguments.of("TcpActiveOpens", true),
+        Arguments.of("UdpInDatagrams", false),
+        Arguments.of("Ip6InReceives", false),
+        Arguments.of("Udp6InDatagrams", false),
+        Arguments.of("TcpExtSyncookiesSent", true),
+        Arguments.of("IpExtInNoRoutes", true));
+  }
+}