Package org.apache.zookeeper.server

Enum EphemeralType

  • All Implemented Interfaces:
    Serializable, Comparable<EphemeralType>
    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).

    • Field Detail

      • CONTAINER_EPHEMERAL_OWNER

        public static final long CONTAINER_EPHEMERAL_OWNER
        See Also:
        Constant Field Values

      • MAX_EXTENDED_SERVER_ID

        public static final long MAX_EXTENDED_SERVER_ID
        See Also:
        Constant Field Values

    • Method Detail

      • values

        public static EphemeralType[] values()
        Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows: 
        for (EphemeralType c : EphemeralType.values())
    System.out.println(c);
        Returns:
        an array containing the constants of this enum type, in the order they are declared

      • valueOf

        public static EphemeralType valueOf​(String name)
        Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (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 type 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