public synchronized boolean isFailedServer(final Address address) {
    if (failedServers.isEmpty()) {
      return false;
    }
    final long now = EnvironmentEdgeManager.currentTime();
    if (now > this.latestExpiry) {
      failedServers.clear();
      return false;
    }
    Long expiry = this.failedServers.get(address);
    if (expiry == null) {
      return false;
    }
    if (expiry >= now) {
      return true;
    } else {
      this.failedServers.remove(address);
    }
    return false;
  }
Check if the server should be considered as bad. Clean the old entries of the list.
@return true if the server is in the failed servers list
hbase-client/src/main/java/org/apache/hadoop/hbase/ipc/FailedServers.java