Package com.tangosol.net.partition

Class FailoverAccessPolicy

java.lang.Object
com.tangosol.net.partition.FailoverAccessPolicy
All Implemented Interfaces:
ActionPolicy
public class FailoverAccessPolicy extends Object implements ActionPolicy
FailoverAccessPolicy is used to moderate the client request load during a failover event in order to allow cache servers adequate opportunity to re-establish partition backups.

While typically not necessary to ensure the timely recovery to a "safe" state, this access policy could be used in situations where a heavy load of of high-latency requests may prevent or significantly delay cache servers from successfully acquiring exclusive access to partitions needing to be transferred or backed up.

Since:
Coherence 12.1.2
Author:
rhl 09.12.2011

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    protected class 
    FailoverAccessPolicy.MembershipListener
    The MemberListener is used to listen to service membership events to monitor the endangered status of the service.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    long
    m_cLimitMillis
    The amount of time after being in an endangered state after which the quorum policy makes a maximal effort to hold client requests.
    long
    m_cMaxDelayMillis
    The maximum amount of time (in ms) that a request could be delayed by this quorum policy.
    long
    m_cThresholdMillis
    The amount of time after being in an endangered state before the quorum policy should start to hold client requests.
    long
    m_ldtEndangered
    The time at which the service most recently became endangered (or 0 if the service is in the "safe" state).
    int
    m_nState
    One of the STATE_* constants representing the current quorum state.
    protected PartitionedService
    m_service
    The PartitionedService that this quorum policy is bound to.
    static final int
    STATE_ENDANGERED
    Constant used to indicate that the service is in an endangered state.
    static final int
    STATE_SAFE
    Constant used to indicate that the service is "safe" (non-endangered).
    static final int
    STATE_UNKNOWN
    Constant used to indicate that the service is in an unknown (possibly endangered) state.

  • Constructor Summary

    Constructors
    Constructor
    Description
    FailoverAccessPolicy()
    Default constructor.
    FailoverAccessPolicy(long cThresholdMillis, long cLimitMillis, long cMaxDelayMillis)
    Construct a FailoverAccessPolicy according to the specified parameters.

  • Method Summary

    Modifier and Type
    Method
    Description
    protected long
    calculateWaitTime(long cMillisEndangered)
    Return the amount of time that a request should be delayed before being allowed to proceed.
    protected boolean
    checkEndangered()
    Check to see if the associated service is endangered.
    int
    getState()
    Return the current endangered state (one of the STATE_* constants).
    void
    init(Service service)
    Called when the specified service loads and configures this policy.
    boolean
    isAllowed(Service service, Action action)
    Evaluate if the specified action is currently allowed by this policy.
    protected void
    setState(int nState)
    Set the endangered state (one of the STATE_* constants).

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    Methods inherited from interface com.tangosol.net.ActionPolicy

    toString

  • Field Details

    • STATE_SAFE

      public static final int STATE_SAFE
      Constant used to indicate that the service is "safe" (non-endangered).
      See Also:

    • STATE_UNKNOWN

      public static final int STATE_UNKNOWN
      Constant used to indicate that the service is in an unknown (possibly endangered) state.
      See Also:

    • STATE_ENDANGERED

      public static final int STATE_ENDANGERED
      Constant used to indicate that the service is in an endangered state.
      See Also:

    • m_cThresholdMillis

      public long m_cThresholdMillis
      The amount of time after being in an endangered state before the quorum policy should start to hold client requests.

    • m_cLimitMillis

      public long m_cLimitMillis
      The amount of time after being in an endangered state after which the quorum policy makes a maximal effort to hold client requests.

    • m_cMaxDelayMillis

      public long m_cMaxDelayMillis
      The maximum amount of time (in ms) that a request could be delayed by this quorum policy.

    • m_nState

      public int m_nState
      One of the STATE_* constants representing the current quorum state.

      Note: this field is intentionally left non-volatile. The consequence of a "stale" read is that the first request per thread following a transition to endangered could be missed by this quorum (allowed to proceed). As this has no impact, we would rather avoid the additional volatile read on each "normal" operation.

    • m_ldtEndangered

      public long m_ldtEndangered
      The time at which the service most recently became endangered (or 0 if the service is in the "safe" state).

    • m_service

      protected PartitionedService m_service
      The PartitionedService that this quorum policy is bound to.

  • Constructor Details

    • FailoverAccessPolicy

      public FailoverAccessPolicy()
      Default constructor.

    • FailoverAccessPolicy

      public FailoverAccessPolicy(long cThresholdMillis, long cLimitMillis, long cMaxDelayMillis)
      Construct a FailoverAccessPolicy according to the specified parameters.
      Parameters:
      cThresholdMillis - the delay before the policy should start holding requests (after becoming endangered)
      cLimitMillis - the delay before the policy makes a maximal effort to hold requests (after becoming endangered)
      cMaxDelayMillis - the maximum amount of time to hold a request

  • Method Details

    • getState

      public int getState()
      Return the current endangered state (one of the STATE_* constants).
      Returns:
      the current endangered state

    • setState

      protected void setState(int nState)
      Set the endangered state (one of the STATE_* constants).
      Parameters:
      nState - the new endangered state

    • init

      public void init(Service service)
      Called when the specified service loads and configures this policy.

      Note: A policy could be applied to multiple services.

      Specified by:
      init in interface ActionPolicy
      Parameters:
      service - the service that this policy applies to

    • isAllowed

      public boolean isAllowed(Service service, Action action)
      Evaluate if the specified action is currently allowed by this policy.

      Note: for forward compatibility, implementations should generally return true for actions that are not recognized.

      Specified by:
      isAllowed in interface ActionPolicy
      Parameters:
      service - the service that is performing the action
      action - the action that is being performed
      Returns:
      true iff the specified action is currently allowed by this policy

    • calculateWaitTime

      protected long calculateWaitTime(long cMillisEndangered)
      Return the amount of time that a request should be delayed before being allowed to proceed.
      Parameters:
      cMillisEndangered - the amount of time that the service has been endangered
      Returns:
      the amount of time (in ms) to delay the client request

    • checkEndangered

      protected boolean checkEndangered()
      Check to see if the associated service is endangered.

      Note: the caller must hold synchronization on this quorum policy.

      Returns:
      true iff the service is endangered