com.sleepycat.je.rep
Class ReplicationMutableConfig

java.lang.Object
  com.sleepycat.je.rep.ReplicationMutableConfig

All Implemented Interfaces:

Serializable, Cloneable

Direct Known Subclasses:

ReplicationConfig

public class ReplicationMutableConfig
extends Object
implements Cloneable, Serializable

Specifies the attributes that may be changed after a ReplicatedEnvironment has been created. ReplicationMutableConfig is a parameter to Environment.setMutableConfig(com.sleepycat.je.EnvironmentMutableConfig) and is returned by Environment.getMutableConfig().

See Also:

Serialized Form

Field Summary

static String	DESIGNATED_PRIMARY Identifies the Primary node in a two node group.
static String	ELECTABLE_GROUP_SIZE_OVERRIDE An escape mechanism to modify the way in which the number of electable nodes, and consequently the quorum requirements for elections and commit acknowledgments, is calculated.
static String	LOG_FLUSH_TASK_INTERVAL The interval that JE HA will do a log buffer flush.
static String	NODE_PRIORITY The election priority associated with this node.
static String	RUN_LOG_FLUSH_TASK If true, JE HA (replication) will flush all committed transactions to disk at the specified time interval.

Constructor Summary

ReplicationMutableConfig()
Create a ReplicationMutableConfig initialized with the system default settings.

Method Summary

String	getConfigParam(String paramName) Return the value for this parameter.
boolean	getDesignatedPrimary() Determines whether this node is the currently designated Primary.
int	getElectableGroupSizeOverride() Returns the value associated with the override.
int	getNodePriority() Returns the election priority associated with the node.
ReplicationMutableConfig	setConfigParam(String paramName, String value) Set this configuration parameter with this value.
ReplicationMutableConfig	setDesignatedPrimary(boolean isPrimary) If isPrimary is true, designate this node as a Primary.
ReplicationMutableConfig	setElectableGroupSizeOverride(int override) Sets the size used to determine the number of electable nodes.
ReplicationMutableConfig	setNodePriority(int priority) Sets the election priority for the node.
String	toString() List the configuration parameters and values that have been set in this configuration object.

Methods inherited from class java.lang.Object

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

Field Detail

DESIGNATED_PRIMARY

public static final transient String DESIGNATED_PRIMARY

Identifies the Primary node in a two node group. See the discussion of issues when configuring two node groups

Name	Type	Mutable	Default
"je.rep.designatedPrimary"	Boolean	Yes	False

See Also:

Constant Field Values

ELECTABLE_GROUP_SIZE_OVERRIDE

public static final transient String ELECTABLE_GROUP_SIZE_OVERRIDE

An escape mechanism to modify the way in which the number of electable nodes, and consequently the quorum requirements for elections and commit acknowledgments, is calculated. The override is accomplished by specifying the quorum size via this mutable configuration parameter.

When this parameter is set to a non-zero value at a member node, the member will use this value as the electable group size, instead of using the metadata stored in the RepGroup database for its quorum calculations. This parameter's value should be set to the number of nodes known to be available. The default value is zero, which indicates normal operation with the electable group size being calculated from the metadata.

Please keep in mind that this is an escape mechanism, only for use in exceptional circumstances, to be used with care. Since JE HA is no longer maintaining quorum requirements automatically, there is the possibility that the simple majority of unavailable nodes could elect their own Master, which would result in a diverging set of changes to the same environment being made by multiple Masters. It is essential to ensure that the problematic nodes are in fact down before making this temporary configuration change. See the discussion in Appendix: Managing a Failure of the Majority.

Name	Type	Mutable	Default
"je.rep.electableGroupSizeOverride"	Integer	Yes	0

See Also:

QuorumPolicy, Durability.ReplicaAckPolicy, Constant Field Values

NODE_PRIORITY

public static final transient String NODE_PRIORITY

The election priority associated with this node. The election algorithm for choosing a new master will pick the participating node that has the most current set of log files. When there is a tie, the election priority is used as a tie-breaker to select amongst these nodes.

A priority of zero is used to ensure that this node is never elected master, even if it has the most up to date log files. Note that the node still votes for a Master and participates in quorum requirements. Please use this option with care, since it means that some node with less current log files could be elected master. As a result, this node would be forced to rollback committed data and must be prepared to handle any RollbackException exceptions that might be thrown.

Name	Type	Mutable	Default	Minimum	Maximum
"je.rep.node.priority"	Integer	Yes	1	0	Integer.MAX_VALUE

See Also:

RollbackException, Constant Field Values

RUN_LOG_FLUSH_TASK

public static final transient String RUN_LOG_FLUSH_TASK

If true, JE HA (replication) will flush all committed transactions to disk at the specified time interval. This is of interest because the default durability for replicated transactions of Durability.COMMIT_NO_SYNC. The default for this behavior is true.

When using Durability.COMMIT_NO_SYNC, continued activity will naturally cause the steady flush of committed transactions, but a pause in activity may cause the latest commits to stay in memory. In such a case, it is unlikely but possible that all members of the replication group have these last transactions in memory and that no members have persisted them to disk. A catastrophic failure of all nodes in the replication group would cause a loss of these transactions, in this unlikely scenario. This background flush task will reduce such a possibility.

Note that enabling this feature when using Durability.COMMIT_NO_SYNC, does not constitute a guarantee that updates made by a transaction are persisted. For an explicit guarantee, transactions should use Durability.COMMIT_SYNC or Durability.COMMIT_WRITE_NO_SYNC. These more stringent, persistent Durability options can be set at the environment or per-transaction scope. Using one of these Durability settings for a given transaction will also flush all commits that occurred earlier in time.

Name	Type	Mutable	Default
"je.rep.runLogFlushTask"	Boolean	No	true

See Also:

Constant Field Values

LOG_FLUSH_TASK_INTERVAL

public static final transient String LOG_FLUSH_TASK_INTERVAL

The interval that JE HA will do a log buffer flush.

Name	Type	Mutable	Default	Minimum	Maximum
"je.rep.logFlushTaskInterval"	Duration	Yes	5 min	1 s	-none-

See Also:

Time Duration Properties, Constant Field Values

Constructor Detail

ReplicationMutableConfig

public ReplicationMutableConfig()

Create a ReplicationMutableConfig initialized with the system default settings. Parameter defaults are documented with the string constants in this class.

Method Detail

setDesignatedPrimary

public ReplicationMutableConfig setDesignatedPrimary(boolean isPrimary)

If isPrimary is true, designate this node as a Primary. The application must ensure that exactly one node is designated to be a Primary at any given time. Primary node configuration is only a concern when the group has two nodes, and there cannot be a simple majority. See the overview on configuring two node groups

Parameters:

isPrimary - true if this node is to be made the Primary.

Returns:

this;

getDesignatedPrimary

public boolean getDesignatedPrimary()

Determines whether this node is the currently designated Primary. See the overview on issues around two node groups

Returns:

true if this node is a Primary, false otherwise.

getElectableGroupSizeOverride

public int getElectableGroupSizeOverride()

Returns the value associated with the override. A value of zero means that the number of electable nodes is determined as usual, that is, from the contents of the group metadata.

Returns:

the number of electable nodes as specified by the override

See Also:

ELECTABLE_GROUP_SIZE_OVERRIDE

setElectableGroupSizeOverride

public ReplicationMutableConfig setElectableGroupSizeOverride(int override)

Sets the size used to determine the number of electable nodes.

Parameters:

override - the number of electable nodes. A value of zero means that the number of electable nodes is determined as usual, that is, from the contents of the group metadata.

Returns:

this

See Also:

ELECTABLE_GROUP_SIZE_OVERRIDE

getNodePriority

public int getNodePriority()

Returns the election priority associated with the node.

Returns:

the priority for this node

See Also:

NODE_PRIORITY

setNodePriority

public ReplicationMutableConfig setNodePriority(int priority)

Sets the election priority for the node. The algorithm for choosing a new master will pick the participating node that has the most current set of log files. When there is a tie, the priority is used as a tie-breaker to select amongst these nodes.

A priority of zero is used to ensure that a node is never elected master, even if it has the most current set of files. Please use this option with caution, since it means that a node with less current log files could be elected master potentially forcing this node to rollback data that had been committed.

Parameters:

priority - the priority to be associated with the node. It must be zero, or a positive number.

See Also:

NODE_PRIORITY

setConfigParam

public ReplicationMutableConfig setConfigParam(String paramName,
                                               String value)
                                        throws IllegalArgumentException

Set this configuration parameter with this value. Values are validated before setting the parameter.

Parameters:

paramName - the configuration parameter name, one of the String constants in this class

value - the configuration value.

Returns:

this;

Throws:

IllegalArgumentException - if the paramName or value is invalid.

getConfigParam

public String getConfigParam(String paramName)
                      throws IllegalArgumentException

Return the value for this parameter.

Parameters:

paramName - a valid configuration parameter, one of the String constants in this class.

Returns:

the configuration value.

Throws:

IllegalArgumentException - if the paramName is invalid.

toString

public String toString()

List the configuration parameters and values that have been set in this configuration object.

Overrides:

toString in class Object