org.apache.storm.cluster

## Interface IStateStorage

- All Superinterfaces:
    AutoCloseable, Closeable
  All Known Implementing Classes:
    PaceMakerStateStorage, ZKStateStorage

      public interface IStateStorage
      extends Closeable

  StateStorage provides the API for the pluggable state store used by the Storm daemons. Data is stored in path/value format, and the store supports listing sub-paths at a given path. All data should be available across all nodes with eventual consistency.

  IMPORTANT NOTE: Heartbeats have different api calls used to interact with them. The root path (/) may or may not be the same as the root path for the other api calls.

  For example, performing these two calls: set_data(“/path”, data, acls); void set_worker_hb(“/path”, heartbeat, acls); may or may not cause a collision in “/path”. Never use the same paths with the _hb methods as you do with the others.

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `add_listener(org.apache.storm.shade.org.apache.curator.framework.state.ConnectionStateListener listener)` Add a StateStorageListener to the connection.
    `void` | `close()` Close the connection to the data store.
    `String` | `create_sequential(String path, byte[] data, List<org.apache.storm.shade.org.apache.zookeeper.data.ACL> acls)` Path will be appended with a monotonically increasing integer, a new node will be created there, and data will be put at that node.
    `void` | `delete_node_blobstore(String path, String nimbusHostPortInfo)` Allows us to delete the znodes within /storm/blobstore/key_name whose znodes start with the corresponding nimbusHostPortInfo.
    `void` | `delete_node(String path)` Deletes the node at a given path, and any child nodes that may exist.
    `void` | `delete_worker_hb(String path)` Deletes the heartbeat at a given path, and any child nodes that may exist.
    `List<String>` | `get_children(String path, boolean watch)` Get a list of paths of all the child nodes which exist immediately under path.
    `VersionedData<byte[]>` | `get_data_with_version(String path, boolean watch)` Get the data at the node along with its version.
    `byte[]` | `get_data(String path, boolean watch)` Get the data from the node at path
    `Integer` | `get_version(String path, boolean watch)` Gets the ‘version’ of the node at a path.
    `List<String>` | `get_worker_hb_children(String path, boolean watch)` Get a list of paths of all the child nodes which exist immediately under path.
    `byte[]` | `get_worker_hb(String path, boolean watch)` Get the heartbeat from the node at path
    `void` | `mkdirs(String path, List<org.apache.storm.shade.org.apache.zookeeper.data.ACL> acls)` Creates nodes for path and all its parents.
    `boolean` | `node_exists(String path, boolean watch)` Check if a node exists and optionally set a watch on the path.
    `String` | `register(ZKStateChangedCallback callback)` Registers a callback function that gets called when CuratorEvents happen.
    `void` | `set_data(String path, byte[] data, List<org.apache.storm.shade.org.apache.zookeeper.data.ACL> acls)` Set the value of the node at path to data.
    `void` | `set_ephemeral_node(String path, byte[] data, List<org.apache.storm.shade.org.apache.zookeeper.data.ACL> acls)` Creates an ephemeral node at path.
    `void` | `set_worker_hb(String path, byte[] data, List<org.apache.storm.shade.org.apache.zookeeper.data.ACL> acls)` Write a worker heartbeat at the path.
    `void` | `sync_path(String path)` Force consistency on a path.
    `void` | `unregister(String id)` Unregisters a callback function that was registered with register(…).

- - ### Method Detail

    - #### register

          String register(ZKStateChangedCallback callback)

      Registers a callback function that gets called when CuratorEvents happen.

      Parameters:
        `callback` - is a clojure IFn that accepts the type - translated to clojure keyword as in zookeeper - and the path: (callback type path)
      Returns:
        is an id that can be passed to unregister(…) to unregister the callback.

    - #### unregister

          void unregister(String id)

      Unregisters a callback function that was registered with register(…).

      Parameters:
        `id` - is the String id that was returned from register(…).

    - #### create_sequential

          String create_sequential(String path,
                                   byte[] data,
                                   List<org.apache.storm.shade.org.apache.zookeeper.data.ACL> acls)

      Path will be appended with a monotonically increasing integer, a new node will be created there, and data will be put at that node.

      Parameters:
        `path` - The path that the monotonically increasing integer suffix will be added to.
        `data` - The data that will be written at the suffixed path’s node.
        `acls` - The acls to apply to the path. May be null.
      Returns:
        The path with the integer suffix appended.

    - #### mkdirs

          void mkdirs(String path,
                      List<org.apache.storm.shade.org.apache.zookeeper.data.ACL> acls)

      Creates nodes for path and all its parents. Path elements are separated by a “/”, as in *nix filesystem notation. Equivalent to mkdir -p in *nix.

      Parameters:
        `path` - The path to create, along with all its parents.
        `acls` - The acls to apply to the path. May be null.

    - #### delete_node

          void delete_node(String path)

      Deletes the node at a given path, and any child nodes that may exist.

      Parameters:
        `path` - The path to delete

    - #### set_ephemeral_node

          void set_ephemeral_node(String path,
                                  byte[] data,
                                  List<org.apache.storm.shade.org.apache.zookeeper.data.ACL> acls)

      Creates an ephemeral node at path. Ephemeral nodes are destroyed by the store when the client disconnects.

      Parameters:
        `path` - The path where a node will be created.
        `data` - The data to be written at the node.
        `acls` - The acls to apply to the path. May be null.

    - #### get_version

          Integer get_version(String path,
                              boolean watch)
                       throws Exception

      Gets the ‘version’ of the node at a path. Optionally sets a watch on that node. The version should increase whenever a write happens.

      Parameters:
        `path` - The path to get the version of.
        `watch` - Whether or not to set a watch on the path. Watched paths emit events which are consumed by functions registered with the register method. Very useful for catching updates to nodes.
      Returns:
        The integer version of this node.
      Throws:
        `Exception`

    - #### node_exists

          boolean node_exists(String path,
                              boolean watch)

      Check if a node exists and optionally set a watch on the path.

      Parameters:
        `path` - The path to check for the existence of a node.
        `watch` - Whether or not to set a watch on the path. Watched paths emit events which are consumed by functions registered with the register method. Very useful for catching updates to nodes.
      Returns:
        Whether or not a node exists at path.

    - #### get_children

          List<String> get_children(String path,
                                    boolean watch)

      Get a list of paths of all the child nodes which exist immediately under path.

      Parameters:
        `path` - The path to look under
        `watch` - Whether or not to set a watch on the path. Watched paths emit events which are consumed by functions registered with the register method. Very useful for catching updates to nodes.
      Returns:
        list of string paths under path.

    - #### close

          void close()

      Close the connection to the data store.

      Specified by:
        `close` in interface `AutoCloseable`
      Specified by:
        `close` in interface `Closeable`

    - #### set_data

          void set_data(String path,
                        byte[] data,
                        List<org.apache.storm.shade.org.apache.zookeeper.data.ACL> acls)

      Set the value of the node at path to data.

      Parameters:
        `path` - The path whose node we want to set.
        `data` - The data to put in the node.
        `acls` - The acls to apply to the path. May be null.

    - #### get_data

          byte[] get_data(String path,
                          boolean watch)

      Get the data from the node at path

      Parameters:
        `path` - The path to look under
        `watch` - Whether or not to set a watch on the path. Watched paths emit events which are consumed by functions registered with the register method. Very useful for catching updates to nodes.
      Returns:
        The data at the node.

    - #### get_data_with_version

          VersionedData<byte[]> get_data_with_version(String path,
                                                      boolean watch)

      Get the data at the node along with its version. Data is returned in an Map with the keys data and version.

      Parameters:
        `path` - The path to look under
        `watch` - Whether or not to set a watch on the path. Watched paths emit events which are consumed by functions registered with the register method. Very useful for catching updates to nodes.
      Returns:
        the data with a version

    - #### set_worker_hb

          void set_worker_hb(String path,
                             byte[] data,
                             List<org.apache.storm.shade.org.apache.zookeeper.data.ACL> acls)

      Write a worker heartbeat at the path.

      Parameters:
        `path` - The path whose node we want to set.
        `data` - The data to put in the node.
        `acls` - The acls to apply to the path. May be null.

    - #### get_worker_hb

          byte[] get_worker_hb(String path,
                               boolean watch)

      Get the heartbeat from the node at path

      Parameters:
        `path` - The path to look under
        `watch` - Whether or not to set a watch on the path. Watched paths emit events which are consumed by functions registered with the register method. Very useful for catching updates to nodes.
      Returns:
        The heartbeat at the node.

    - #### get_worker_hb_children

          List<String> get_worker_hb_children(String path,
                                              boolean watch)

      Get a list of paths of all the child nodes which exist immediately under path. This is similar to get_children, but must be used for any nodes

      Parameters:
        `path` - The path to look under
        `watch` - Whether or not to set a watch on the path. Watched paths emit events which are consumed by functions registered with the register method. Very useful for catching updates to nodes.
      Returns:
        list of string paths under path.

    - #### delete_worker_hb

          void delete_worker_hb(String path)

      Deletes the heartbeat at a given path, and any child nodes that may exist.

      Parameters:
        `path` - The path to delete.

    - #### add_listener

          void add_listener(org.apache.storm.shade.org.apache.curator.framework.state.ConnectionStateListener listener)

      Add a StateStorageListener to the connection.

      Parameters:
        `listener` - A StateStorageListener to handle changing cluster state events.

    - #### sync_path

          void sync_path(String path)

      Force consistency on a path. Any writes committed on the path before this call will be completely propagated when it returns.

      Parameters:
        `path` - The path to synchronize.

    - #### delete_node_blobstore

          void delete_node_blobstore(String path,
                                     String nimbusHostPortInfo)

      Allows us to delete the znodes within /storm/blobstore/key_name whose znodes start with the corresponding nimbusHostPortInfo.

      Parameters:
        `path` - /storm/blobstore/key_name
        `nimbusHostPortInfo` - Contains the host port information of a nimbus node.

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