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

service/src/main/java/org/whispersystems/textsecuregcm/metrics/NstatCounters.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2021 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.whispersystems.textsecuregcm.metrics;
+
+import static com.codahale.metrics.MetricRegistry.name;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.common.annotations.VisibleForTesting;
+import io.micrometer.core.instrument.Metrics;
+import java.io.IOException;
+import java.time.Duration;
+import java.util.Collections;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class NstatCounters {
+
+  private final Map<String, Long> networkStatistics = new ConcurrentHashMap<>();
+
+  private static final String[] NSTAT_COMMAND_LINE = new String[] { "nstat", "--zero", "--json", "--noupdate", "--ignore" };
+  private static final String[] EXCLUDE_METRIC_NAME_PREFIXES = new String[] { "Icmp", "Udp", "Ip6" };
+
+  private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper()
+      .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
+
+  private static final Logger log = LoggerFactory.getLogger(NstatCounters.class);
+
+  @VisibleForTesting
+  static class NetworkStatistics {
+    private final Map<String, Long> kernelStatistics;
+
+    @JsonCreator
+    private NetworkStatistics(@JsonProperty("kernel") final Map<String, Long> kernelStatistics) {
+      this.kernelStatistics = kernelStatistics;
+    }
+
+    public Map<String, Long> getKernelStatistics() {
+      return kernelStatistics;
+    }
+  }
+
+  public void registerMetrics(final ScheduledExecutorService refreshService, final Duration refreshInterval) {
+    refreshNetworkStatistics();
+
+    networkStatistics.keySet().stream()
+        .filter(NstatCounters::shouldIncludeMetric)
+        .forEach(metricName -> Metrics.globalRegistry.more().counter(name(getClass(), "kernel", metricName),
+            Collections.emptyList(), networkStatistics, statistics -> statistics.get(metricName)));
+
+    refreshService.scheduleAtFixedRate(this::refreshNetworkStatistics,
+        refreshInterval.toMillis(), refreshInterval.toMillis(), TimeUnit.MILLISECONDS);
+  }
+
+  private void refreshNetworkStatistics() {
+    try {
+      networkStatistics.putAll(loadNetworkStatistics().getKernelStatistics());
+    } catch (final InterruptedException | IOException e) {
+      log.warn("Failed to refresh network statistics", e);
+    }
+  }
+
+  @VisibleForTesting
+  static boolean shouldIncludeMetric(final String metricName) {
+    for (final String prefix : EXCLUDE_METRIC_NAME_PREFIXES) {
+      if (metricName.startsWith(prefix)) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  @VisibleForTesting
+  static NetworkStatistics loadNetworkStatistics() throws IOException, InterruptedException {
+    final Process nstatProcess = Runtime.getRuntime().exec(NSTAT_COMMAND_LINE);
+
+    if (nstatProcess.waitFor() == 0) {
+      return OBJECT_MAPPER.readValue(nstatProcess.getInputStream(), NetworkStatistics.class);
+    } else {
+      throw new IOException("nstat process did not exit normally");
+    }
+  }
+}