Compensator Class

Definition

Represents the base class for all Compensating Resource Manager (CRM) Compensators.

public ref class Compensator : System::EnterpriseServices::ServicedComponent
public class Compensator : System.EnterpriseServices.ServicedComponent
type Compensator = class
    inherit ServicedComponent
Public Class Compensator
Inherits ServicedComponent
Inheritance

Examples

The following code example demonstrates the use of this class.

// A CRM Compensator
public ref class AccountCompensator : public Compensator
{
private:
    bool receivedPrepareRecord;

public:
    AccountCompensator()
    {
        receivedPrepareRecord = false;
    } 

public:
    virtual void BeginPrepare() override 
    {
        // nothing to do
    }

public:
    virtual bool PrepareRecord(LogRecord^ log) override 
    {

        // Check the validity of the record.
        if (log == nullptr)
        {
            return false;
        }
        array<Object^>^ record = dynamic_cast<array<Object^>^>(log->Record);
        if (record == nullptr)
        {
            return false;
        }
        if (record->Length != 2)
        {
            return false;
        }

        // The record is valid.
        receivedPrepareRecord = true;
        return true;              
    }

public:
    virtual bool EndPrepare() override
    {
        // Allow the transaction to proceed onlyif we have received a prepare
        // record.
        if (receivedPrepareRecord)
        {
            return true;
        }
        else
        {
            return false;
        }
    }

public:
    virtual void BeginCommit(bool commit) override
    {
        // nothing to do
    }

public:
    virtual bool CommitRecord(LogRecord^ log) override
    {
        // nothing to do
        return(false);
    }

public:
    virtual void EndCommit() override
    {
        // nothing to do
    }

public:
    virtual void BeginAbort(bool abort) override
    {
        // nothing to do
    }

public:
    virtual bool AbortRecord(LogRecord^ log) override
    {

        // Check the validity of the record.
        if (log == nullptr)
        {
            return true;
        }
        array<Object^>^ record = dynamic_cast<array<Object^>^>(log->Record);
        if (record == nullptr)
        {
            return true;
        }
        if (record->Length != 2)
        {
            return true;
        }

        // Extract old account data from the record.
        String^ filename = (String^) record[0];
        int balance = (int) record[1];

        // Restore the old state of the account.
        WriteAccountBalance(filename, balance);

        return false;
    }

public:
    virtual void EndAbort() override
    {
        // nothing to do
    }    

};
// A CRM Compensator
public class AccountCompensator : Compensator
{

    private bool receivedPrepareRecord = false;

    public override void BeginPrepare ()
    {
        // nothing to do
    }

    public override bool PrepareRecord (LogRecord log)
    {

        // Check the validity of the record.
        if (log == null) return(true);
        Object[] record = log.Record as Object[];
        if (record == null) return(true);
        if (record.Length != 2) return(true);

        // The record is valid.
        receivedPrepareRecord = true;
        return(false);              
    }

    public override bool EndPrepare ()
    {
        // Allow the transaction to proceed onlyif we have received a prepare record.
        if (receivedPrepareRecord)
        {
            return(true);
        }
        else
        {
            return(false);
        }
    }

    public override void BeginCommit (bool commit)
    {
        // nothing to do
    }

    public override bool CommitRecord (LogRecord log)
    {
        // nothing to do
        return(false);
    }

    public override void EndCommit ()
    {
        // nothing to do
    }

    public override void BeginAbort (bool abort)
    {
        // nothing to do
    }

    public override bool AbortRecord (LogRecord log)
    {

        // Check the validity of the record.
        if (log == null) return(true);
        Object[] record = log.Record as Object[];
        if (record == null) return(true);
        if (record.Length != 2) return(true);

        // Extract old account data from the record.
        string filename = (string) record[0];
        int balance = (int) record[1];
 
        // Restore the old state of the account.
        AccountManager.WriteAccountBalance(filename, balance);

        return(false);
    }

    public override void EndAbort ()
    {
        // nothing to do
    }    

}
' A CRM Compensator

Public Class AccountCompensator
    Inherits Compensator
    
    Private receivedPrepareRecord As Boolean = False
    
    
    Public Overrides Sub BeginPrepare() 
    
    End Sub
    
    ' nothing to do
    Public Overrides Function PrepareRecord(ByVal log As LogRecord) As Boolean 
        
        ' Check the validity of the record.
        If log Is Nothing Then
            Return True
        End If
        Dim record As [Object]() = log.Record
        
        If record Is Nothing Then
            Return True
        End If
        If record.Length <> 2 Then
            Return True
        End If 
        ' The record is valid.
        receivedPrepareRecord = True
        Return False
    
    End Function 'PrepareRecord
    
    Public Overrides Function EndPrepare() As Boolean 
        ' Allow the transaction to proceed onlyif we have received a prepare record.
        If receivedPrepareRecord Then
            Return True
        Else
            Return False
        End If
    
    End Function 'EndPrepare
    
    Public Overrides Sub BeginCommit(ByVal commit As Boolean) 
    
    End Sub
    
    ' nothing to do
    Public Overrides Function CommitRecord(ByVal log As LogRecord) As Boolean 
        ' nothing to do
        Return False
    
    End Function 'CommitRecord
    
    Public Overrides Sub EndCommit() 
    
    End Sub
    
    ' nothing to do
    Public Overrides Sub BeginAbort(ByVal abort As Boolean) 
    
    End Sub
    
    ' nothing to do
    Public Overrides Function AbortRecord(ByVal log As LogRecord) As Boolean 
        
        ' Check the validity of the record.
        If log Is Nothing Then
            Return True
        End If
        Dim record As [Object]() = log.Record
        
        If record Is Nothing Then
            Return True
        End If
        If record.Length <> 2 Then
            Return True
        End If 
        ' Extract old account data from the record.
        Dim filename As String = CStr(record(0))
        Dim balance As Integer = Fix(record(1))
        
        ' Restore the old state of the account.
        AccountManager.WriteAccountBalance(filename, balance)
        
        Return False
    
    End Function 'AbortRecord
    
    Public Overrides Sub EndAbort() 
    
    End Sub
End Class

This compensator is used by the following worker class.

// A CRM Worker
[Transaction]
public ref class Account : public ServicedComponent
{

    // A data member for the account file name.
private:
    String^ filenameValue;

public:
    property String^ Filename
    {
        String^ get()
        {
            return filenameValue;
        }
        void set( String^ value )
        {
            filenameValue = value;
        }
    }

    // A boolean data member that determines whether to commit or abort the 
    // transaction.
private:
    bool allowCommitValue;

public:
    property bool AllowCommit
    {
        bool get()
        {
            return allowCommitValue;
        }
        void set( bool value )
        {
            allowCommitValue = value;
        }
    }

    // Debit the account, 
public:
    void DebitAccount(int amount)
    {

        // Create a new clerk using the AccountCompensator class.
        Clerk^ clerk = gcnew Clerk(AccountCompensator::typeid,
            "An account transaction compensator", CompensatorOptions::AllPhases);

        // Create a record of previous account status, and deliver it to the
        // clerk.
        int balance = ReadAccountBalance(Filename);

        array<Object^>^ record = gcnew array<Object^>(2);
        record[0] = Filename;
        record[1] = balance;

        clerk->WriteLogRecord(record);
        clerk->ForceLog();

        // Perform the transaction
        balance -= amount;

        Console::WriteLine("{0}: {1}", Filename, balance);

        WriteAccountBalance(Filename, balance);

        // Commit or abort the transaction 
        if (AllowCommit)
        {
            ContextUtil::SetComplete();
        }
        else
        {
            ContextUtil::SetAbort();
        }

    }

};
// A CRM Worker
[Transaction]
public class Account : ServicedComponent
{

    // A data member for the account file name.
    private string filename;
    
    public string Filename
    {
        get
        {
            return(filename);
        }
        set
        {
            filename = value;
        }
    }


    // A boolean data member that determines whether to commit or abort the transaction.
    private bool commit;

    public bool AllowCommit
    {
        get
        {
            return(commit);
        }
        set
        {
            commit = value;
        }
    }



    // Debit the account, 
    public void DebitAccount (int ammount)
    {

        // Create a new clerk using the AccountCompensator class.
        Clerk clerk = new Clerk(typeof(AccountCompensator),
          "An account transaction compensator", CompensatorOptions.AllPhases);

        // Create a record of previous account status, and deliver it to the clerk.
        int balance = AccountManager.ReadAccountBalance(filename);

    Object[] record = new Object[2];
    record[0] = filename;
        record[1] = balance;

        clerk.WriteLogRecord(record);
        clerk.ForceLog();

        // Perform the transaction
        balance -= ammount;
        AccountManager.WriteAccountBalance(filename, balance);

        // Commit or abort the transaction 
        if (commit)
        {
            ContextUtil.SetComplete();
        }
        else
        {
            ContextUtil.SetAbort();
        }
      
    }

}
' A CRM Worker
<Transaction()>  _
Public Class Account
    Inherits ServicedComponent
    
    ' A data member for the account file name.
    Private filename As String
    
    
    Public Property Filenam() As String
        Get
            Return Filename
        End Get
        Set(ByVal value As String)
            filename = Value
        End Set
    End Property
    
    
    ' A boolean data member that determines whether to commit or abort the transaction.
    Private commit As Boolean
    
    
    Public Property AllowCommit() As Boolean 
        Get
            Return commit
        End Get
        Set
            commit = value
        End Set
    End Property
    
    
    
    
    ' Debit the account, 
    Public Sub DebitAccount(ByVal ammount As Integer) 
        
        ' Create a new clerk using the AccountCompensator class.
        Dim clerk As New Clerk(GetType(AccountCompensator), "An account transaction compensator", CompensatorOptions.AllPhases)
        ' Create a record of previous account status, and deliver it to the clerk.
        Dim balance As Integer = AccountManager.ReadAccountBalance(Filenam)
        
        Dim record(1) As [Object]
        record(0) = filename
        record(1) = balance
        
        clerk.WriteLogRecord(record)
        clerk.ForceLog()
        ' Perform the transaction
        balance -= ammount
        AccountManager.WriteAccountBalance(filename, balance)
        
        ' Commit or abort the transaction 
        If commit Then
            ContextUtil.SetComplete()
        Else
            ContextUtil.SetAbort()
        End If
    End Sub
    
End Class

The following code example demonstrates a client that exercises this compensator and worker.

#using "System.EnterpriseServices.dll"

using namespace System;

[assembly: System::Reflection::AssemblyKeyFile("CrmServer.key")];

int main ()
{

    // Create a new account object. The object is created in a COM+ server application.
    Account^ account = gcnew Account();

    // Transactionally debit the account.
    try
    {
        account->Filename = System::IO::Path::GetFullPath("JohnDoe");
        account->AllowCommit = true;
        account->DebitAccount(3);
    }
    finally
    {
        delete account;
    }

}
using System;

public class CrmClient
{

    public static void Main ()
    {

        // Create a new account object. The object is created in a COM+ server application.
        Account account = new Account();

        // Transactionally debit the account.
        try
        {
            account.Filename = System.IO.Path.GetFullPath("JohnDoe");
            account.AllowCommit = true;
            account.DebitAccount(3);
        }
        finally
        {
            account.Dispose();
        }
          
    }

}
Public Class CrmClient
    
    
    Public Shared Sub Main() 
        
        ' Create a new account object. The object is created in a COM+ server application.
        Dim account As New Account()
        
        ' Transactionally debit the account.
        Try
            account.Filenam = System.IO.Path.GetFullPath("JohnDoe")
            account.AllowCommit = True
            account.DebitAccount(3)
        Finally
            account.Dispose()
        End Try
    
    End Sub
End Class

Remarks

The user should extend from this object in order to write a custom transaction Compensator.

A Compensator must always have a public constructor; otherwise, the recovery engine cannot create it.

For more information, see How to: Create a Compensating Resource Manager (CRM).

Constructors

Compensator()

Initializes a new instance of the Compensator class.

Properties

Clerk

Gets a value representing the Compensating Resource Manager (CRM) Clerk object.

Methods

AbortRecord(LogRecord)

Delivers a log record to the Compensating Resource Manager (CRM) Compensator during the abort phase.

Activate()

Called by the infrastructure when the object is created or allocated from a pool. Override this method to add custom initialization code to objects.

(Inherited from ServicedComponent)
BeginAbort(Boolean)

Notifies the Compensating Resource Manager (CRM) Compensator of the abort phase of the transaction completion, and the upcoming delivery of records.

BeginCommit(Boolean)

Notifies the Compensating Resource Manager (CRM) Compensator of the commit phase of the transaction completion and the upcoming delivery of records.

BeginPrepare()

Notifies the Compensating Resource Manager (CRM) Compensator of the prepare phase of the transaction completion and the upcoming delivery of records.

CanBePooled()

This method is called by the infrastructure before the object is put back into the pool. Override this method to vote on whether the object is put back into the pool.

(Inherited from ServicedComponent)
CommitRecord(LogRecord)

Delivers a log record in forward order during the commit phase.

Construct(String)

Called by the infrastructure just after the constructor is called, passing in the constructor string. Override this method to make use of the construction string value.

(Inherited from ServicedComponent)
CreateObjRef(Type)

Creates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object.

(Inherited from MarshalByRefObject)
Deactivate()

Called by the infrastructure when the object is about to be deactivated. Override this method to add custom finalization code to objects when just-in-time (JIT) compiled code or object pooling is used.

(Inherited from ServicedComponent)
Dispose()

Releases all resources used by the ServicedComponent.

(Inherited from ServicedComponent)
Dispose(Boolean)

Releases the unmanaged resources used by the ServicedComponent and optionally releases the managed resources.

(Inherited from ServicedComponent)
EndAbort()

Notifies the Compensating Resource Manager (CRM) Compensator that it has received all the log records available during the abort phase.

EndCommit()

Notifies the Compensating Resource Manager (CRM) Compensator that it has delivered all the log records available during the commit phase.

EndPrepare()

Notifies the Compensating Resource Manager (CRM) Compensator that it has had all the log records available during the prepare phase.

Equals(Object)

Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetHashCode()

Serves as the default hash function.

(Inherited from Object)
GetLifetimeService()

Retrieves the current lifetime service object that controls the lifetime policy for this instance.

(Inherited from MarshalByRefObject)
GetType()

Gets the Type of the current instance.

(Inherited from Object)
InitializeLifetimeService()

Obtains a lifetime service object to control the lifetime policy for this instance.

(Inherited from MarshalByRefObject)
MemberwiseClone()

Creates a shallow copy of the current Object.

(Inherited from Object)
MemberwiseClone(Boolean)

Creates a shallow copy of the current MarshalByRefObject object.

(Inherited from MarshalByRefObject)
PrepareRecord(LogRecord)

Delivers a log record in forward order during the prepare phase.

ToString()

Returns a string that represents the current object.

(Inherited from Object)

Explicit Interface Implementations

IRemoteDispatch.RemoteDispatchAutoDone(String)

Ensures that, in the COM+ context, the ServicedComponent class object's done bit is set to true after a remote method invocation.

(Inherited from ServicedComponent)
IRemoteDispatch.RemoteDispatchNotAutoDone(String)

Does not ensure that, in the COM+ context, the ServicedComponent class object's done bit is set to true after a remote method invocation.

(Inherited from ServicedComponent)
IServicedComponentInfo.GetComponentInfo(Int32, String[])

Obtains certain information about the ServicedComponent class instance.

(Inherited from ServicedComponent)

Applies to