Enum Class EphemeralType

java.lang.Object
java.lang.Enum<EphemeralType>
org.apache.zookeeper.server.EphemeralType
All Implemented Interfaces:
Serializable, Comparable<EphemeralType>, Constable

public enum EphemeralType extends Enum<EphemeralType>

Abstraction that interprets the ephemeralOwner field of a ZNode. Originally, the ephemeralOwner noted that a ZNode is ephemeral and which session created the node. Through an optional system property (zookeeper.extendedTypesEnabled) "extended" features such as TTL Nodes can be enabled. Special bits of the ephemeralOwner are used to denote which feature is enabled and the remaining bits of the ephemeralOwner are feature specific.

When the system property zookeeper.extendedTypesEnabled is true, extended types are enabled. An extended ephemeralOwner is defined as an ephemeralOwner whose high 8 bits are set (0xff00000000000000L). The two bytes that follow the high 8 bits are used to denote which extended feature the ephemeralOwner represents. The remaining 5 bytes are used by the feature for whatever purpose is needed

Currently, the only extended feature is TTL Nodes. It is denoted by the extended feature value of 0. i.e. for TTL Nodes, the ephemeralOwner has the high byte set to 0xff and the next 2 bytes are 0 followed by 5 bytes that represent the TTL value in milliseconds. So, an ephemeralOwner with a TTL value of 1 millisecond is: 0xff00000000000001.

To add new extended features: a) Add a new name to the enum, b) define a constant EXTENDED_BIT_xxxx that's next in line (after TTLs, that would be 0x0001), c) add a mapping to the extendedFeatureMap via the static initializer

NOTE: "Container" nodes technically are extended types but as it was implemented before this feature they are denoted specially. An ephemeral owner with only the high bit set (0x8000000000000000L) is by definition a container node (irrespective of whether or not extended types are enabled).

  • Enum Constant Details

    • VOID

      public static final EphemeralType VOID
      Not ephemeral
    • NORMAL

      public static final EphemeralType NORMAL
      Standard, pre-3.5.x EPHEMERAL
    • CONTAINER

      public static final EphemeralType CONTAINER
      Container node
    • TTL

      public static final EphemeralType TTL
      TTL node
  • Field Details

    • CONTAINER_EPHEMERAL_OWNER

      public static final long CONTAINER_EPHEMERAL_OWNER
      See Also:
    • MAX_EXTENDED_SERVER_ID

      public static final long MAX_EXTENDED_SERVER_ID
      See Also:
  • Method Details

    • values

      public static EphemeralType[] values()
      Returns an array containing the constants of this enum class, in the order they are declared.
      Returns:
      an array containing the constants of this enum class, in the order they are declared
    • valueOf

      public static EphemeralType valueOf(String name)
      Returns the enum constant of this class with the specified name. The string must match exactly an identifier used to declare an enum constant in this class. (Extraneous whitespace characters are not permitted.)
      Parameters:
      name - the name of the enum constant to be returned.
      Returns:
      the enum constant with the specified name
      Throws:
      IllegalArgumentException - if this enum class has no constant with the specified name
      NullPointerException - if the argument is null
    • maxValue

      public long maxValue()
      For types that support it, the maximum extended value
      Returns:
      0 or max
    • toEphemeralOwner

      public long toEphemeralOwner(long value)
      For types that support it, convert a value to an extended ephemeral owner
      Returns:
      0 or extended ephemeral owner
    • getValue

      public long getValue(long ephemeralOwner)
      For types that support it, return the extended value from an extended ephemeral owner
      Returns:
      0 or extended value
    • extendedEphemeralTypesEnabled

      public static boolean extendedEphemeralTypesEnabled()
      Return true if extended ephemeral types are enabled
      Returns:
      true/false
    • get

      public static EphemeralType get(long ephemeralOwner)
      Convert a ZNode ephemeral owner to an ephemeral type. If extended types are not enabled, VOID or NORMAL is always returned
      Parameters:
      ephemeralOwner - the ZNode's ephemeral owner
      Returns:
      type
    • validateServerId

      public static void validateServerId(long serverId)
      Make sure the given server ID is compatible with the current extended ephemeral setting
      Parameters:
      serverId - Server ID
      Throws:
      RuntimeException - extendedTypesEnabled is true but Server ID is too large
    • validateTTL

      public static void validateTTL(CreateMode mode, long ttl)
      Utility to validate a create mode and a ttl
      Parameters:
      mode - create mode
      ttl - ttl
      Throws:
      IllegalArgumentException - if the ttl is not valid for the mode