AsyncHttpClient ClientStats源码流程解读

/**
 * A record class representing the state of an (@link org.asynchttpclient.AsyncHttpClient).
 */
public class ClientStats {
  private final Map<String, HostStats> statsPerHost;
  public ClientStats(Map<String, HostStats> statsPerHost) {
    this.statsPerHost = Collections.unmodifiableMap(statsPerHost);
  }
  /**
   * @return A map from hostname to statistics on that host's connections.
   * The returned map is unmodifiable.
   */
  public Map<String, HostStats> getStatsPerHost() {
    return statsPerHost;
  }
  /**
   * @return The sum of {@link #getTotalActiveConnectionCount()} and {@link #getTotalIdleConnectionCount()},
   * a long representing the total number of connections in the connection pool.
   */
  public long getTotalConnectionCount() {
    return statsPerHost
            .values()
            .stream()
            .mapToLong(HostStats::getHostConnectionCount)
            .sum();
  }
  /**
   * @return A long representing the number of active connections in the connection pool.
   */
  public long getTotalActiveConnectionCount() {
    return statsPerHost
            .values()
            .stream()
            .mapToLong(HostStats::getHostActiveConnectionCount)
            .sum();
  }
  /**
   * @return A long representing the number of idle connections in the connection pool.
   */
  public long getTotalIdleConnectionCount() {
    return statsPerHost
            .values()
            .stream()
            .mapToLong(HostStats::getHostIdleConnectionCount)
            .sum();
  }
  @Override
  public String toString() {
    return "There are " + getTotalConnectionCount() +
            " total connections, " + getTotalActiveConnectionCount() +
            " are active and " + getTotalIdleConnectionCount() + " are idle.";
  }
  @Override
  public boolean equals(final Object o) {
    if (this == o) return true;
    if (o == null || getClass() != o.getClass()) return false;
    final ClientStats that = (ClientStats) o;
    return Objects.equals(statsPerHost, that.statsPerHost);
  }
  @Override
  public int hashCode() {
    return Objects.hashCode(statsPerHost);
  }
}

/**
 * A record class representing the status of connections to some host.
 */
public class HostStats {
  private final long activeConnectionCount;
  private final long idleConnectionCount;
  public HostStats(long activeConnectionCount,
                   long idleConnectionCount) {
    this.activeConnectionCount = activeConnectionCount;
    this.idleConnectionCount = idleConnectionCount;
  }
  /**
   * @return The sum of {@link #getHostActiveConnectionCount()} and {@link #getHostIdleConnectionCount()},
   * a long representing the total number of connections to this host.
   */
  public long getHostConnectionCount() {
    return activeConnectionCount + idleConnectionCount;
  }
  /**
   * @return A long representing the number of active connections to the host.
   */
  public long getHostActiveConnectionCount() {
    return activeConnectionCount;
  }
  /**
   * @return A long representing the number of idle connections in the connection pool.
   */
  public long getHostIdleConnectionCount() {
    return idleConnectionCount;
  }
  @Override
  public String toString() {
    return "There are " + getHostConnectionCount() +
            " total connections, " + getHostActiveConnectionCount() +
            " are active and " + getHostIdleConnectionCount() + " are idle.";
  }
  @Override
  public boolean equals(final Object o) {
    if (this == o) return true;
    if (o == null || getClass() != o.getClass()) return false;
    final HostStats hostStats = (HostStats) o;
    return activeConnectionCount == hostStats.activeConnectionCount &&
            idleConnectionCount == hostStats.idleConnectionCount;
  }
  @Override
  public int hashCode() {
    return Objects.hash(activeConnectionCount, idleConnectionCount);
  }
}

public ClientStats getClientStats() {
    Map<String, Long> totalConnectionsPerHost = openChannels.stream().map(Channel::remoteAddress).filter(a -> a.getClass() == InetSocketAddress.class)
            .map(a -> (InetSocketAddress) a).map(InetSocketAddress::getHostName).collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
    Map<String, Long> idleConnectionsPerHost = channelPool.getIdleChannelCountPerHost();
    Map<String, HostStats> statsPerHost = totalConnectionsPerHost.entrySet().stream().collect(Collectors.toMap(Entry::getKey, entry -> {
      final long totalConnectionCount = entry.getValue();
      final long idleConnectionCount = idleConnectionsPerHost.getOrDefault(entry.getKey(), 0L);
      final long activeConnectionCount = totalConnectionCount - idleConnectionCount;
      return new HostStats(activeConnectionCount, idleConnectionCount);
    }));
    return new ClientStats(statsPerHost);
  }