How to use

backpressureStormRoot

method

in

org.apache.storm.cluster.ClusterUtils

/**
 * Get the backpressure znode full path.
 *
 * @param stormId   The topology id
 * @param shortPath A string in the form of "node-port"
 * @return The backpressure znode path
 */
public static String backpressurePath(String stormId, String shortPath) {
  return backpressureStormRoot(stormId) + ZK_SEPERATOR + shortPath;
}

public static String backpressurePath(String stormId, String node, Long port) {
  return backpressureStormRoot(stormId) + ZK_SEPERATOR + node + "-" + port;
}

@Override
public void removeBackpressure(String stormId) {
  try {
    stateStorage.delete_node(ClusterUtils.backpressureStormRoot(stormId));
  } catch (Exception e) {
    if (Utils.exceptionCauseIsInstanceOf(KeeperException.class, e)) {
      // do nothing
      LOG.warn("Could not teardown backpressure node for {}.", stormId);
    } else {
      throw e;
    }
  }
}

@Override
public void setupBackpressure(String stormId, Map<String, Object> topoConf) {
  stateStorage.mkdirs(ClusterUtils.BACKPRESSURE_SUBTREE, defaultAcls);
  stateStorage.mkdirs(ClusterUtils.backpressureStormRoot(stormId), ClusterUtils.mkTopoReadWriteAcls(topoConf));
}

/**
 * Check whether a topology is in throttle-on status or not: if the backpresure/storm-id dir is not empty, this topology has
 * throttle-on, otherwise throttle-off. But if the backpresure/storm-id dir is not empty and has not been updated for more than
 * timeoutMs, we treat it as throttle-off. This will prevent the spouts from getting stuck indefinitely if something wrong happens.
 *
 * @param stormId   The topology Id
 * @param timeoutMs How long until the backpressure znode is invalid.
 * @param callback  The callback function
 * @return True is backpresure/storm-id dir is not empty and at least one of the backpressure znodes has not timed out; false otherwise.
 */
@Override
public boolean topologyBackpressure(String stormId, long timeoutMs, Runnable callback) {
  if (callback != null) {
    backPressureCallback.put(stormId, callback);
  }
  String path = ClusterUtils.backpressureStormRoot(stormId);
  long mostRecentTimestamp = 0;
  if (stateStorage.node_exists(path, false)) {
    List<String> children = stateStorage.get_children(path, callback != null);
    mostRecentTimestamp = children.stream()
                   .map(childPath -> stateStorage.get_data(ClusterUtils.backpressurePath(stormId, childPath), false))
                   .filter(data -> data != null)
                   .mapToLong(data -> ByteBuffer.wrap(data).getLong())
                   .max()
                   .orElse(0);
  }
  boolean ret = ((System.currentTimeMillis() - mostRecentTimestamp) < timeoutMs);
  LOG.debug("topology backpressure is {}", ret ? "on" : "off");
  return ret;
}

public static String backpressurePath(String stormId, String node, Long port) {
  return backpressureStormRoot(stormId) + ZK_SEPERATOR + node + "-" + port;
}

@Override
public void removeBackpressure(String stormId) {
  try {
    stateStorage.delete_node(ClusterUtils.backpressureStormRoot(stormId));
  } catch (Exception e) {
    if (Utils.exceptionCauseIsInstanceOf(KeeperException.class, e)) {
      // do nothing
      LOG.warn("Could not teardown backpressure node for {}.", stormId);
    } else {
      throw e;
    }
  }
}

/**
 * Check whether a topology is in throttle-on status or not:
 * if the backpresure/storm-id dir is not empty, this topology has throttle-on, otherwise throttle-off.
 * 
 * @param stormId
 * @param callback
 * @return
 */
@Override
public boolean topologyBackpressure(String stormId, Runnable callback) {
  if (callback != null) {
    backPressureCallback.put(stormId, callback);
  }
  String path = ClusterUtils.backpressureStormRoot(stormId);
  List<String> childrens = null;
  if(stateStorage.node_exists(path, false)) {
    childrens = stateStorage.get_children(path, callback != null);
  } else {
    childrens = new ArrayList<>();
  }
  return childrens.size() > 0;
}

@Override
public void setupBackpressure(String stormId, Map<String, Object> topoConf) {
  stateStorage.mkdirs(ClusterUtils.BACKPRESSURE_SUBTREE, acls);
  stateStorage.mkdirs(ClusterUtils.backpressureStormRoot(stormId), ClusterUtils.mkTopoReadWriteAcls(topoConf));
}