edu.umass.cs.reconfiguration.examples

Class AppRequest

java.lang.Object

edu.umass.cs.nio.JSONPacket

edu.umass.cs.reconfiguration.examples.AppRequest

All Implemented Interfaces:

ClientRequest, Request, RequestIdentifier, ReconfigurableRequest, ReplicableRequest, Summarizable

Direct Known Subclasses:

NoopAppRequest

public class AppRequest
extends JSONPacket
implements ReconfigurableRequest, ReplicableRequest, ClientRequest

Author:

V. Arun

A class like this is necessary if the app wants to use its own packet types to send requests and responses (as opposed to just using RequestPacket. The main requirements of application requests is that they must implement at least InterfaceRequest, and must implement InterfaceReplicable, InterfaceReconfigurable, and InterfceClientRequest in order to respectively support replication, reconfiguration, and the ability to delegate client response messaging to gigapaxos.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	AppRequest.Keys These app keys by design need not be the same as those in BasicReconfigurationPacket
static class	AppRequest.PacketType Packet type class for NoopApp requests.
static class	AppRequest.ResponseCodes

Field Summary

Fields inherited from class edu.umass.cs.nio.JSONPacket

PACKET_TYPE, type

Fields inherited from interface edu.umass.cs.reconfiguration.interfaces.ReconfigurableRequest

STOP

Fields inherited from interface edu.umass.cs.gigapaxos.interfaces.Request

NO_OP

Constructor Summary

Constructors

Constructor and Description
AppRequest(org.json.JSONObject json)
AppRequest(java.lang.String value, AppRequest req)
AppRequest(java.lang.String name, int epoch, long id, java.lang.String value, IntegerPacketType type, boolean stop)
AppRequest(java.lang.String name, long id, java.lang.String value, IntegerPacketType type, boolean stop)
AppRequest(java.lang.String name, java.lang.String value, IntegerPacketType type, boolean stop)

Method Summary

Modifier and Type	Method and Description
java.net.InetSocketAddress	getClientAddress()
int	getEpochNumber()
static AppRequest	getObliviousPaxosStopRequest(java.lang.String name, int epoch) Deprecated.
long	getRequestID() The uniqueness of this identifier across all requests to a replica group is important for safety when PaxosConfig.PC.PREVENT_DOUBLE_EXECUTION is enabled as gigapaxos may otherwise assume that the duplicate request identifier corresponds to a retransmission and will send back the response if any corresponding to the first execution.
IntegerPacketType	getRequestType()
ClientRequest	getResponse()
java.net.InetSocketAddress	getSenderAddress()
java.lang.String	getServiceName()
java.lang.String	getValue()
boolean	isStop()
static void	main(java.lang.String[] args)
boolean	needsCoordination()
AppRequest	setEpoch(int epoch)
void	setNeedsCoordination(boolean b) After this method returns, ReplicableRequest.needsCoordination() should subsequently return b.
void	setResponse(java.lang.String response)
org.json.JSONObject	toJSONObjectImpl()

Methods inherited from class edu.umass.cs.nio.JSONPacket

couldBeJSON, couldBeJSON, couldBeJSON, couldBeJSONArray, couldBeJSONObject, getPacketType, putPacketType, putPacketType, toJSONObject, toString

Methods inherited from class java.lang.Object

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

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

getSummary

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

toBytes, toString

Methods inherited from interface edu.umass.cs.utils.Summarizable

getSummary

Constructor Detail

AppRequest

public AppRequest(java.lang.String name,
                  java.lang.String value,
                  IntegerPacketType type,
                  boolean stop)

Parameters:

name -

value -

type -

stop -

AppRequest

public AppRequest(java.lang.String name,
                  int epoch,
                  long id,
                  java.lang.String value,
                  IntegerPacketType type,
                  boolean stop)

Parameters:

name -

epoch -

id -

value -

type -

stop -

AppRequest

public AppRequest(java.lang.String name,
                  long id,
                  java.lang.String value,
                  IntegerPacketType type,
                  boolean stop)

Parameters:

name -

id -

value -

type -

stop -

AppRequest

public AppRequest(java.lang.String value,
                  AppRequest req)

Parameters:

value -

req -

AppRequest

public AppRequest(org.json.JSONObject json)
           throws org.json.JSONException

Parameters:

json -

Throws:

org.json.JSONException

Method Detail

getRequestType

public IntegerPacketType getRequestType()

Specified by:

getRequestType in interface Request

Returns:

The IntegerPacketType type corresponding to this request.

getServiceName

public java.lang.String getServiceName()

Specified by:

getServiceName in interface Request

Returns:

Returns the unique app-level replica-group ID.

getValue

public java.lang.String getValue()

Returns:

Request value.

getRequestID

public long getRequestID()

Description copied from interface: RequestIdentifier

The uniqueness of this identifier across all requests to a replica group is important for safety when PaxosConfig.PC.PREVENT_DOUBLE_EXECUTION is enabled as gigapaxos may otherwise assume that the duplicate request identifier corresponds to a retransmission and will send back the response if any corresponding to the first execution. With PaxosConfig.PC.PREVENT_DOUBLE_EXECUTION disabled, the uniqueness is important for liveness as duplicate request identifiers may result in the client not receiving a response for the latter request; this is because gigapaxos stores request execution callbacks indexed by the request identifier, so there must be at most one outstanding request with a given identifier for a given replica group.

Specified by:

getRequestID in interface RequestIdentifier

Returns:

Request ID.

toJSONObjectImpl

public org.json.JSONObject toJSONObjectImpl()
                                     throws org.json.JSONException

Specified by:

toJSONObjectImpl in class JSONPacket

Returns:

JSONObject corresponding to fields in classes extending this class.

Throws:

org.json.JSONException

getSenderAddress

public java.net.InetSocketAddress getSenderAddress()

Returns:

Sending client's address.

getEpochNumber

public int getEpochNumber()

Specified by:

getEpochNumber in interface ReconfigurableRequest

Returns:

The epoch number.

isStop

public boolean isStop()

Specified by:

isStop in interface ReconfigurableRequest

Returns:

True if this request is a stop request.

needsCoordination

public boolean needsCoordination()

Specified by:

needsCoordination in interface ReplicableRequest

Returns:

True if this request needs to be coordinated, false otherwise.

setNeedsCoordination

public void setNeedsCoordination(boolean b)

Description copied from interface: ReplicableRequest

After this method returns, ReplicableRequest.needsCoordination() should subsequently return b. This method is invoked by AbstractReplicaCoordinator with a false argument just before coordinating the request so that coordinated packets are not coordinated again infinitely. For example, if a replica coordinator's coordination strategy is to simply flood the request to all replicas, there needs to be a way for a recipient of a copy of this already once coordinated request to know that it should not coordinate it again. This method provides AbstractReplicaCoordinator a placeholder in the application request to prevent such infinite coordination loops.

This method is now deprecated and does not need to be overridden by implementing classes. It's original purpose was really only to be able to easily do lazy propagation replica coordination without introducing an additional type (just to distinguish between the original request at the entry replica and the replicated request so as to avoid an infinite propagation loop), but introducing an additional type is the clean way to do this. Paxos for example already has its own types, so it doesn't need this method.

Specified by:

setNeedsCoordination in interface ReplicableRequest

Parameters:

b - True if subsequent invocations of ReplicableRequest.needsCoordination() must return true, false otherwise.

getClientAddress

public java.net.InetSocketAddress getClientAddress()

Specified by:

getClientAddress in interface ClientRequest

Returns:

The socket address of the client that sent this request. This method is now deprecated and exists only for backwards compatibility, so it is okay for applications to not explicitly override the default implementation of this method (that simply returns null); AbstractReplicaCoordinator already knows the sending client's address anyway.

getResponse

public ClientRequest getResponse()

Specified by:

getResponse in interface ClientRequest

Returns:

The response to be sent back to the client that issued this request. AbstractReplicaCoordinator, e.g., PaxosManager, will invoke this method immediately after Application.execute(Request) and, if the returned response is non-null, will send it back to the client that issued that request. Applications are expected to internally implement logic that sets the response at the end of Application.execute(Request) as follows:

public boolean Replicable.execute(Request request)} {
// execute request to obtain response
request.setResponse(response);
}

setResponse

public void setResponse(java.lang.String response)

Parameters:

response -

getObliviousPaxosStopRequest

@Deprecated
public static AppRequest getObliviousPaxosStopRequest(java.lang.String name,
                                                                  int epoch)

Deprecated.

An oblivious stop request is a no-op stop request that is not actually passed to Application.execute(Request). It is generally not a good idea to use an oblivious stop request as the app won't know that the current epoch has been stopped and will not be in a position to do any garbage collection if needed right away. This method is deprecated. gigapaxos currently generates its own oblivous stop request and subsequently invokes Replicable.restore(String, String) with a null state argument to indicate to the app that the current epoch is over. For coordination protocols other than paxos, Reconfigurable.getStopRequest(String, int) suffices.

Parameters:

name -

epoch -

Returns:

Default oblivious stop request.

setEpoch

public AppRequest setEpoch(int epoch)

Parameters:

epoch -

Returns:

New AppRequest with epoch changed.

main

public static void main(java.lang.String[] args)

Parameters:

args -