edu.umass.cs.reconfiguration

Class AbstractReconfiguratorDB<NodeIDType>

java.lang.Object

edu.umass.cs.reconfiguration.AbstractReconfiguratorDB<NodeIDType>

Type Parameters:

NodeIDType - This class is the reconfigurator "application", essentially a database. It is Replicable and Reconfigurable and ReconfiguratorDB. SQLReconfiguratorDB is an example of a class concretizing this class. It is actually not important for this database to be persistent for safety reasons when paxos provides fault recovery, but we use the disk because all records may not fit in memory. In fact, SQLReconfiguratorDB currently uses DiskMap as the default option that asynchronously swaps to disk in the background. This class relies on reflection to automatically map incoming reconfiguration packets to their respective handlers, but it only expects to process two types of packets RCRecordRequest and StopEpoch.

All Implemented Interfaces:

Application, AppRequestParser, AppRequestParserBytes, Replicable, Reconfigurable, ReconfiguratorDB<NodeIDType>, Repliconfigurable

Direct Known Subclasses:

SQLReconfiguratorDB

public abstract class AbstractReconfiguratorDB<NodeIDType>
extends java.lang.Object
implements Repliconfigurable, ReconfiguratorDB<NodeIDType>

Author:

V. Arun

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	AbstractReconfiguratorDB.RecordNames Constant RC record name keys.

Field Summary

Fields

Modifier and Type	Field and Description
protected ConsistentReconfigurableNodeConfig<NodeIDType>	consistentNodeConfig
protected NodeIDType	myID
protected boolean	recovering
protected static boolean	TWO_PAXOS_RC

Constructor Summary

Constructors

Constructor and Description
AbstractReconfiguratorDB(NodeIDType myID, ConsistentReconfigurableNodeConfig<NodeIDType> nc)

Method Summary

Modifier and Type	Method and Description
protected java.lang.String	areRCChangesCompleteDebug()
protected static java.lang.Object	autoInvokeMethod(java.lang.Object target, BasicReconfigurationPacket<?> rcPacket, boolean recovery, Stringifiable<?> unstringer)
boolean	deleteFinalState(java.lang.String name, int epoch) Garbage-collects the final state for name, epoch.
boolean	execute(Request request)
boolean	execute(Request request, boolean doNotReplyToClient) Paxos related methods below
java.lang.Integer	getEpoch(java.lang.String name) Returns the current (unique) epoch for name.
java.lang.String	getFinalState(java.lang.String name, int epoch) Return the final checkpointed state for name, epoch.
protected java.util.Set<java.lang.String>	getMergeList(java.lang.String newRCGroupName)
protected java.util.HashMap<java.lang.String,java.util.Set<java.lang.String>>	getMergeLists()
protected ConsistentHashing<NodeIDType>	getNewConsistentHashRing()
protected java.util.Map<java.lang.String,java.util.Set<NodeIDType>>	getNewRCGroups()
protected static Request	getNoopRequest(java.lang.String stringified)
protected ConsistentHashing<NodeIDType>	getOldConsistentHashRing()
protected java.util.Map<java.lang.String,java.util.Set<NodeIDType>>	getOldRCGroups()
protected java.lang.String	getRCGroupName(NodeIDType node)
protected java.lang.String	getRCGroupName(java.lang.String name)
protected java.util.Map<java.lang.String,java.util.Set<NodeIDType>>	getRCGroups(NodeIDType rc, java.util.Set<NodeIDType> allRCs)
protected java.util.Map<java.lang.String,java.util.Set<NodeIDType>>	getRCGroups(NodeIDType rc, java.util.Set<NodeIDType> allRCs, boolean print)
ReconfigurationRecord<NodeIDType>	getReconfigurationRecord(java.lang.String name, int epoch)
Request	getRequest(java.lang.String stringified) An application must support string-to-Request conversion and back.
java.util.Set<IntegerPacketType>	getRequestTypes()
ReconfigurableRequest	getStopRequest(java.lang.String name, int epoch) Returns a stop request that when executed by the app ensures that no subsequent request after the stop is executed in that epoch.
boolean	handleDemandReport(DemandReport<NodeIDType> report, boolean recovery)
boolean	handleRCRecordRequest(RCRecordRequest<NodeIDType> rcRecReq, boolean recovery) If a reconfiguration intent is being registered, a protocol task must be started that ensures that the reconfiguration completes successfully.
protected boolean	handleRequestActiveReplicas(RequestActiveReplicas requestActives, boolean recovery)
boolean	handleStopEpoch(StopEpoch<NodeIDType> stopEpoch, boolean recovery)
protected boolean	isAffected(NodeIDType rcNode, NodeIDType addOrDelNode)
protected boolean	isRCGroupName(java.lang.String name)
void	putInitialState(java.lang.String name, int epoch, java.lang.String state) Inserts the specified state as the initial state for name, epoch.
void	setCallback(ReconfiguratorCallback callback)
protected java.util.Set<NodeIDType>	setRCEpochs(java.util.Set<NodeIDType> addNodes, java.util.Set<NodeIDType> deleteNodes)
java.lang.String	toString()
protected boolean	updateActiveDBNodeConfig(int version)
protected boolean	updateDBNodeConfig(int version)

Methods inherited from class java.lang.Object

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

Methods inherited from interface edu.umass.cs.gigapaxos.interfaces.Replicable

checkpoint, restore

Methods inherited from interface edu.umass.cs.gigapaxos.interfaces.AppRequestParser

getMutualAuthRequestTypes, getRequest, getServerAuthRequestTypes

Methods inherited from interface edu.umass.cs.reconfiguration.interfaces.ReconfiguratorDB

addActiveReplica, addReconfigurator, clearMerged, close, closeReadActiveRecords, createReconfigurationRecord, createReconfigurationRecords, delayedDeleteComplete, deleteReconfigurationRecord, fetchAndAggregateMergeeStates, garbageCollectedDeletedNode, garbageCollectOldReconfigurators, getDemandStats, getPendingReconfigurations, getRCGroupNames, getRCGroups, getReconfigurationRecord, initiateReadActiveRecords, markDeleteReconfigurationRecord, mergeIntent, mergeState, readNextActiveRecord, removePending, setRCEpochs, setState, setStateInitReconfiguration, setStateInitReconfiguration, setStateMerge, setStateMerge, updateDemandStats

Field Detail

myID

protected final NodeIDType myID

consistentNodeConfig

protected final ConsistentReconfigurableNodeConfig<NodeIDType> consistentNodeConfig

recovering

protected boolean recovering

TWO_PAXOS_RC

protected static final boolean TWO_PAXOS_RC

Constructor Detail

AbstractReconfiguratorDB

public AbstractReconfiguratorDB(NodeIDType myID,
                                ConsistentReconfigurableNodeConfig<NodeIDType> nc)

Parameters:

myID -

nc -

Method Detail

getReconfigurationRecord

public ReconfigurationRecord<NodeIDType> getReconfigurationRecord(java.lang.String name,
                                                                  int epoch)

Parameters:

name -

epoch -

Returns:

ReconfigurationRecord for name:epoch.

execute

public boolean execute(Request request,
                       boolean doNotReplyToClient)

Paxos related methods below

Specified by:

execute in interface Replicable

doNotReplyToClient - If true, the application is expected to not send a response back to the originating client (say, because this request is part of a post-crash roll-forward or only the "entry replica" that received the request from the client is expected to respond back. If false, the application is expected to either send a response (if any) back to the client via the ClientMessenger interface or delegate response messaging to paxos via the ClientRequest.getResponse() interface.

Returns:

Must return true if and only if the application handled the request successfully. For safety, executing a request must have a deterministic effect on the safety-critical state. If the request is bad and is to be discarded, the application must still return true (after "successfully" discarding it). If the application returns false, the replica coordination protocol (e.g., paxos) might try to repeatedly re-execute it until successful or kill this replica group ( request.getServiceName()) altogether after a limited number of retries, so the replica group may get stuck unless it returns true after a limited number of retries. Thus, with paxos as the replica coordination protocol, returning false is not really an option as paxos has no way to "roll back" a request whose global order has already been agreed upon.

With replica coordination protocols other than paxos, the boolean return value could be used in protocol-specific ways, e.g., a primary-backup protocol might normally execute a request at just one replica but relay the request to one or more backups if the return value of Application.execute(Request) is false.

autoInvokeMethod

protected static final java.lang.Object autoInvokeMethod(java.lang.Object target,
                                                         BasicReconfigurationPacket<?> rcPacket,
                                                         boolean recovery,
                                                         Stringifiable<?> unstringer)

handleDemandReport

public boolean handleDemandReport(DemandReport<NodeIDType> report,
                                  boolean recovery)

Parameters:

report -

Returns:

True if demand report is handled successfully. False means that it may not have been processed.

setCallback

public void setCallback(ReconfiguratorCallback callback)

Specified by:

setCallback in interface ReconfiguratorDB<NodeIDType>

handleRCRecordRequest

public boolean handleRCRecordRequest(RCRecordRequest<NodeIDType> rcRecReq,
                                     boolean recovery)

If a reconfiguration intent is being registered, a protocol task must be started that ensures that the reconfiguration completes successfully.

Parameters:

rcRecReq -

recovery -

Returns:

True if the record was handled successfully.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

execute

public boolean execute(Request request)

Specified by:

execute in interface Application

Returns:

True if the request is executed successfully.

getRequest

public Request getRequest(java.lang.String stringified)
                   throws RequestParseException

Description copied from interface: AppRequestParser

An application must support string-to-Request conversion and back. Furthermore, the conversion to a string and back must preserve the return values of all Request methods, i.e., Application.getRequest (request.toString())).equals(request) must be true.

Specified by:

getRequest in interface AppRequestParser

Returns:

Request corresponding to stringified.

Throws:

RequestParseException

getNoopRequest

protected static final Request getNoopRequest(java.lang.String stringified)

getRequestTypes

public java.util.Set<IntegerPacketType> getRequestTypes()

Specified by:

getRequestTypes in interface AppRequestParser

Returns:

The set of request types that the application expects to process.

getStopRequest

public ReconfigurableRequest getStopRequest(java.lang.String name,
                                            int epoch)

Description copied from interface: Reconfigurable

Returns a stop request that when executed by the app ensures that no subsequent request after the stop is executed in that epoch. We need the app to return a stop request as opposed to just exposing a stop() method because, in general, the stop may need to be coordinated across app replicas. If nothing special has to be done by the app upon an epoch stop, it is okay for this method to just return null or a no-op request. If an app is using PaxosReplicaCoordinator, nothing special needs to be done by the app upon an epoch stop, so it can return either null or a no-op request.

Specified by:

getStopRequest in interface Reconfigurable

Returns:

InterfaceReconfigurableRequest corresponding to the stop request for the replica group name:epoch.

getEpoch

public java.lang.Integer getEpoch(java.lang.String name)

Description copied from interface: Reconfigurable

Returns the current (unique) epoch for name. At most a single epoch can actively exist at any time at a replica. The app replica may maintain the final state for lower (inactive) epochs, but may not accept requests in any epoch other than the currently active epoch if one exists. This method should return null if no active replica for the name exists at this node.

Specified by:

getEpoch in interface Reconfigurable

Parameters:

name -

Returns:

Current epoch

getFinalState

public java.lang.String getFinalState(java.lang.String name,
                                      int epoch)

Description copied from interface: Reconfigurable

Return the final checkpointed state for name, epoch. If a checkpoint does not yet exist, it has to be created. This method should return null if the app has moved on, i.e., its current epoch number is higher than epoch and it has no final state for the requested epoch (possibly because it has been garbage-collected). This method will typically get called right after a stop request has been supplied for execution to the app, so it is a good idea for the application to create the checkpoint immediately after executing an epoch stop request.

Specified by:

getFinalState in interface Reconfigurable

Returns:

The final state, or a concise handle thereof, as a String.

putInitialState

public void putInitialState(java.lang.String name,
                            int epoch,
                            java.lang.String state)

Description copied from interface: Reconfigurable

Inserts the specified state as the initial state for name, epoch. This method marks the creation of an epoch. All lower epoch numbers must be marked as inactive at this point. After this method has been called, the app can only accept requests for "name" in the epoch "epoch".

Specified by:

putInitialState in interface Reconfigurable

deleteFinalState

public boolean deleteFinalState(java.lang.String name,
                                int epoch)

Description copied from interface: Reconfigurable

Garbage-collects the final state for name, epoch.

Specified by:

deleteFinalState in interface Reconfigurable

Returns:

True if final state for name:epoch was deleted or did not exist to begin with.

areRCChangesCompleteDebug

protected java.lang.String areRCChangesCompleteDebug()

getNewRCGroups

protected java.util.Map<java.lang.String,java.util.Set<NodeIDType>> getNewRCGroups()

getOldRCGroups

protected java.util.Map<java.lang.String,java.util.Set<NodeIDType>> getOldRCGroups()

getMergeList

protected java.util.Set<java.lang.String> getMergeList(java.lang.String newRCGroupName)

getMergeLists

protected java.util.HashMap<java.lang.String,java.util.Set<java.lang.String>> getMergeLists()

getRCGroups

protected java.util.Map<java.lang.String,java.util.Set<NodeIDType>> getRCGroups(NodeIDType rc,
                                                                                java.util.Set<NodeIDType> allRCs,
                                                                                boolean print)

getRCGroups

protected java.util.Map<java.lang.String,java.util.Set<NodeIDType>> getRCGroups(NodeIDType rc,
                                                                                java.util.Set<NodeIDType> allRCs)

handleStopEpoch

public boolean handleStopEpoch(StopEpoch<NodeIDType> stopEpoch,
                               boolean recovery)

Parameters:

stopEpoch -

recovery -

Returns:

If this stopEpoch was handled successfully.

handleRequestActiveReplicas

protected boolean handleRequestActiveReplicas(RequestActiveReplicas requestActives,
                                              boolean recovery)

Parameters:

requestActives -

recovery -

Returns:

True

getRCGroupName

protected java.lang.String getRCGroupName(NodeIDType node)

getRCGroupName

protected java.lang.String getRCGroupName(java.lang.String name)

isRCGroupName

protected boolean isRCGroupName(java.lang.String name)

updateDBNodeConfig

protected boolean updateDBNodeConfig(int version)

updateActiveDBNodeConfig

protected boolean updateActiveDBNodeConfig(int version)

setRCEpochs

protected java.util.Set<NodeIDType> setRCEpochs(java.util.Set<NodeIDType> addNodes,
                                                java.util.Set<NodeIDType> deleteNodes)

isAffected

protected boolean isAffected(NodeIDType rcNode,
                             NodeIDType addOrDelNode)

getOldConsistentHashRing

protected ConsistentHashing<NodeIDType> getOldConsistentHashRing()

getNewConsistentHashRing

protected ConsistentHashing<NodeIDType> getNewConsistentHashRing()