Table of Contents

OIL2 Class Standard.ReplicaHTTPsession


class Standard . ReplicaHTTPsession {
        oid     creatorObj;
        int32   faultsToTolerate;
        string  nodeName;
        string  proxyVariableName;
        oid     replicaDir;
        string  sessionID;
        string  stateVariableName;
} inherits from Object;

DESCRIPTION

The class ReplicaHTTPsession initializes a new Byzantine fault-tolerant transaction session. Objects of this class are created as needed by the CreateReplicaHTTPsession service.

METHODS


Standard.ReplicaHTTPsession:create

ReplicaHTTPsession:create(string assignedID, oid creator, string serverPoolName, any proxyClassName, assoc queryData, array requestData, assoc options, string replyMethod, any replyDest)

Method Description

The universally unique session ID (assignedID) is computed by the local CreateReplicaHTTPsession service, whose object Id is passed as creator. When a session is deleted, the creator object must be sent a noteSessionTerminated message and passed both the object Id and session ID of the ReplicaHTTPsession object.

Application Arguments

The argument serverPoolName identifies the collection of servers that are to support the new Byzantine fault-tolerant transaction session. A CreateReplicasOnServers object is created to perform the setup. The queryData argument contains the parsed parameters from the HTTP request (processed by the parseHTTPformData() function). The requestData argument is the tokenized HTTP request. The options argument is a set of environment variables, typically used for server-side-include processing (e.g., HTTP_SSIprocessor). The resulting dynamically-generated page needs to be sent to the replyDest object by sending it a replyMethod message.

HTTP Parameters

Key elements of the request are obtained from the HTTP query data made available in the queryData argument.

type
Indicates the type of the new transaction. The specified name is used to determine the name of the implementation class and must have been previously registered by a RegisterReplicaHTTPclass object.
page
Indicates the page to which the remote client browser should be redirected.
maxFaults
optional parameter that indicate the number of simultaneous faults to be tolerated. It defaults to 1 and must be assigned a positive value. The number of servers required is 2 * maxFaults + 1.
maxInitialFaults
optional parameter which indicates the maximum number of initial faults that can be tolerated at the time the session is created. Valid values are between 0 and the value of maxFaults. It defaults to its maximum permissible value (i.e., maxFaults if minReliability is 2 or else 3 * maxFaults if minReliability is 0), which maintains the correctness guarantees asserted by Byzantine fault-tolerance or merely best-effort.
minReliability
optional parameter that permits creation of a session with limited fault-tolerance semantics. It defaults to a value of 2, which indicates Byzantine fault-tolerance. If set to 0, best-effort reliability will be performed if there are too many inital faults, which make it impossible to establish a Byzantine fault-tolerant session. In such a situation, all activity will be performed on a single server and the correctness guarantees provided by Byzantine fault-tolerance cannot be assurred. This is a significant negative, but it may outweigh the alternative of denying service in the presence of too many faults even though at least one system remains operational and capable of performing transactions.


Generated: Wed, 14 Mar 2012 02:52:23 EDT
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