@Override
  public int checkZooKeeper() throws Exception {
    zookeeperMode = true;
    LOG.info("Canary tool is running in ZooKeeper mode");
    return runMonitor(null);
  }
HBase Canary Tool for "canary monitoring" of a running HBase cluster. There are three modes:
<ol>
<li>region mode (Default): For each region, try to get one row per column family outputting
information on failure (ERROR) or else the latency.</li>
<li>regionserver mode: For each regionserver try to get one row from one table selected randomly
outputting information on failure (ERROR) or else the latency.</li>
<li>zookeeper mode: for each zookeeper instance, selects a znode outputting information on
failure (ERROR) or else the latency.</li>
</ol>
hbase-server/src/main/java/org/apache/hadoop/hbase/tool/CanaryTool.java