com.sleepycat.je.rep.impl

Class RepGroupDB

java.lang.Object

com.sleepycat.je.rep.impl.RepGroupDB

public class RepGroupDB
extends Object

This class is used to encapsulate all access to the rep group data that is present in every replicated JE environment. The rep group data exists primarily to support dynamic group membership. Both read and update access must be done through the APIs provided by this class. The database is simply a representation of the RepGroup. Each entry in the database represents a node in RepGroup; the key is the String node name, and the data is the serialized ReplicationNode. There is a special entry keyed by GROUP_KEY that holds the contents of the RepGroup (excluding the nodes) itself. The database may be modified concurrently by multiple transactions as a master processes requests to update it. It may also be accessed by multiple overlapping transactions as a Replica replays the rep stream. These updates need to be interleaved with operations like getGroup() that create copies of the RepGroup instance. To avoid deadlocks, entries in the database are accessed in order of ascending key. GROUP_KEY in particular is associated with the lowest key value so that it's locked first implicitly as part of any iteration and any other modifications to the database must first lock it before making changes to the group itself. An instance of this class is created as part of a replication node and is retained for the entire lifetime of that node.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	RepGroupDB.GroupBinding RepGroupImpl version 3: Add the minJEVersion field
static class	RepGroupDB.NodeBinding Supports the serialization/deserialization of node info into and out of the database.

Field Summary

Fields

Modifier and Type	Field and Description
static long	DB_ID
RepGroupImpl	emptyGroup
static String	GROUP_KEY
static DatabaseEntry	groupKeyEntry

Constructor Summary

Constructors

Constructor and Description
RepGroupDB(RepImpl repImpl) Create an instance.

Method Summary

Modifier and Type	Method and Description
void	addFirstNode() Ensures that information about this node, the current master, is in the member database.
void	ensureMember(Protocol.NodeGroupInfo membershipInfo) Ensures that the membership info for the replica is in the database.
RepGroupImpl	getGroup()
static RepGroupImpl	getGroup(File envDir) An internal API used to obtain group information by opening a stand alone environment handle and reading the RepGroupDB.
static RepGroupImpl	getGroup(RepImpl rImpl, String groupName) Returns all the members that are currently part of the replication group, using NO_CONSISTENCY.
void	reinitFirstNode(VLSN lastOldVLSN) Deletes all the current members from the rep group database and creates a new group, with just the member supplied via the configuration.
void	removeMember(RepNodeImpl removeNode, boolean delete) Removes a node from the replication group by marking the node's entry in the rep group db as removed, and optionally deleting the entry.
void	setMinJEVersion(JEVersion newMinJEVersion) Sets the minimum JE version required for nodes to join the replication group and refreshes the group object cached in the rep group.
boolean	updateLocalCBVLSN(NameIdPair nameIdPair, VLSN newCBVLSN, NodeType nodeType) This method is not used when the CBVLSN is defunct -- see GlobalCBVLSN.
void	updateMember(RepNodeImpl node, boolean quorumAck)

Methods inherited from class java.lang.Object

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

Field Detail

emptyGroup

public final RepGroupImpl emptyGroup

GROUP_KEY

public static final String GROUP_KEY

See Also:

Constant Field Values

groupKeyEntry

public static final DatabaseEntry groupKeyEntry

DB_ID

public static final long DB_ID

See Also:

Constant Field Values

Constructor Detail

RepGroupDB

public RepGroupDB(RepImpl repImpl)
           throws DatabaseException

Create an instance. Note that the database handle is not initialized at this time, since the state of the node master/replica is not known at the time the replication node (and consequently this instance) is created.

Throws:

DatabaseException

Method Detail

getGroup

public static RepGroupImpl getGroup(RepImpl rImpl,
                                    String groupName)
                             throws DatabaseException

Returns all the members that are currently part of the replication group, using NO_CONSISTENCY. This method can read the database directly, and can be used when the replicated environment is detached and the RepNode is null. It's for the latter reason that the method reads uncommitted data. In detached mode, there may be transactions on the database that were in progress when the node was last shutdown. These transactions may have locks which will not be released until after the node is re-attached and the replication stream is resumed. Using uncommitted reads avoids use of locks in this circumstance. It's safe to read these records, since the database will eventually be updated with these changes.

Returns:

the group object

Throws:

DatabaseException - if the object could not be obtained

getGroup

public RepGroupImpl getGroup()
                      throws DatabaseException

Throws:

DatabaseException

setMinJEVersion

public void setMinJEVersion(JEVersion newMinJEVersion)
                     throws DatabaseException,
                            MinJEVersionUnsupportedException

Sets the minimum JE version required for nodes to join the replication group and refreshes the group object cached in the rep group. Throws a MinJEVersionUnsupportedException if the requested version is not supported by current nodes.

If this method returns successfully, nodes that are running a JE version older than the one specified will not be permitted to join the replication group in the future. Use this method to implement features that require all group members to meet a minimum version requirement.

The update attempts to obtain acknowledgments from a simple majority, to make sure that future masters agree that the update has taken place, but does not require this.

Parameters:

newMinJEVersion - the new minimum JE version

Throws:

DatabaseException - if an error occurs when accessing the replication group database

MinJEVersionUnsupportedException - if the requested version is not supported

addFirstNode

public void addFirstNode()
                  throws DatabaseException

Ensures that information about this node, the current master, is in the member database. If it isn't, enter it into the database. If the database does not exist, create it as well.

Note that this overloading is only used by a node that is the master.

Throws:

DatabaseException

ensureMember

public void ensureMember(Protocol.NodeGroupInfo membershipInfo)
                  throws DatabaseException

Ensures that the membership info for the replica is in the database. A call to this method is initiated by the master as part of the feeder/replica handshake, where the replica provides membership information as part of the handshake protocol. The membership database must already exist, with the master in it, when this method is invoked.

This method should not be called for nodes with transient IDs.

Parameters:

membershipInfo - provided by the replica

Throws:

InsufficientReplicasException - upon failure of 2p member update

InsufficientAcksException - upon failure of 2p member update

DatabaseException - when the membership info could not be entered into the membership database.

removeMember

public void removeMember(RepNodeImpl removeNode,
                         boolean delete)

Removes a node from the replication group by marking the node's entry in the rep group db as removed, and optionally deleting the entry.

This method should not be called for nodes with transient IDs.

updateMember

public void updateMember(RepNodeImpl node,
                         boolean quorumAck)
                  throws DatabaseException

Throws:

DatabaseException

updateLocalCBVLSN

public boolean updateLocalCBVLSN(NameIdPair nameIdPair,
                                 VLSN newCBVLSN,
                                 NodeType nodeType)
                          throws DatabaseException

This method is not used when the CBVLSN is defunct -- see GlobalCBVLSN. This method was not moved to GlobalCBVLSN to avoid modularity problems. Updates the database entry associated with the node with the new local CBVLSN, if it can do so without encountering lock contention, and unless the node is a secondary, arbiter, or external node. Also updates the rep node's transient group information about the global CBVLSN. If it encounters contention, it returns false, and the caller must retry at some later point in time. Note that changes to the local CBVLSN do not update the group version number since they do not impact group membership.

Parameters:

nameIdPair - identifies the node being updated

newCBVLSN - the new local CBVLSN to be associated with the node.

nodeType - the node type of the RepNode

Returns:

true if the update succeeded.

Throws:

DatabaseException

getGroup

public static RepGroupImpl getGroup(File envDir)

An internal API used to obtain group information by opening a stand alone environment handle and reading the RepGroupDB. Used for debugging and utilities.

Parameters:

envDir - the directory containing the environment log files

Returns:

the group as currently defined by the environment

reinitFirstNode

public void reinitFirstNode(VLSN lastOldVLSN)

Deletes all the current members from the rep group database and creates a new group, with just the member supplied via the configuration. This method exists to support the utility DbResetRepGroup

The changes proceed in three steps: 1) Determine the node id sequence number. This is to ensure that rep node ids are not reused. Old rep node ids are present in the logs as commit records. 2) A new group object, with the node id sequence number determined in step 1), is created and all existing nodes are deleted. 3) The first node is added to the rep group.

Parameters:

lastOldVLSN - the VLSN used to associate the new barrier wrt this node.