Transaction consistency and problematic states

• US 20070072163A1
• Filed: 09/05/2006
• Published: 03/29/2007
• Est. Priority Date: 09/09/2005
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Johnson, James, Kusters, Norbert, Verma, Surendra, Groff, Dana, Kalach, Ran, Cargille, Jonathan
• Granted Patent: US 7,991,971 B2
• Time in Patent Office: Days
• US Class Current: 434/322
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 11/1474 in transactions G06F16/20 takes precedence
• CPC Class Codes: G06F 2201/82 Solving problems relating to consistency ensuring consistency in mirrored systems G06F11/2064

Abstract

Aspects of the subject matter described herein relate to transactions. In aspects, a consistency requester such as a shadow copy service requests to have a consistent view of a set of resources. In response, transactions that are in a problematic state are allowed to exit the problematic state while new and existing transactions that are not in the problematic state are allowed to perform any work except work that takes them into the problematic state. After no transactions are in the problematic state, a consistent view of the set of resources is available. This view may be used by the consistency requester as desired. Afterwards, the consistency requester may indicate that a consistent view is no longer needed. Transactions are then allowed to enter the problematic state. Transactions may also be allowed to enter the problematic state if a timeout elapses.

Claims

1. A computer-readable medium having computer-executable instructions, which when executed perform actions, comprising:

receiving a request to provide a consistent view of a set of resources, wherein a plurality of resource managers are potentially involved in a transaction affecting the set of resources;

allowing a first resource manager that is in a problematic state that makes the view inconsistent to proceed until it exits the problematic state, wherein the first resource manager is associated with a first portion of the set of resources; and

preventing a second resource manager from entering the problematic state, wherein the second resource manager is associated with a second portion of the set of resources;

indicating that the consistent view is available.

2. The computer-readable medium of claim 1, wherein a consistent view comprises a state in which no resource manager involved in the transaction is in a prepared state with respect to the transaction when another of the resource managers involved in the transaction is in a committed state with respect to the transaction.

3. The computer-readable medium of claim 1, wherein a consistent view comprises a state in which no resource manager involved in the transaction is in a prepared state with respect to the transaction when another of the resource managers involved in the transaction is in a state preceding the prepared state with respect to the transaction.

4. The computer-readable medium of claim 1, wherein the problematic state is defined by a rule that indicates a procedure to follow upon recovery.

5. The computer-readable medium of claim 4, wherein the rule indicates that any resource manager having the transaction in a prepared state rolls back the transaction during recovery.

6. The computer-readable medium of claim 5, wherein the problematic state comprises having the first resource manager in a prepare state with respect to the transaction while another of the resource managers is in a committed state with respect to the transaction.

7. The computer-readable medium of claim 4, wherein the rule indicates that any resource manager having the transaction in a prepared state commit the transaction during recovery.

8. The computer-readable medium of claim 7, wherein the problematic state comprises having the first resource manager in a state prior to the prepared state with respect to the transaction when another of the resource managers is in the prepared state with respect to the transaction.

9. The computer-readable medium of claim 1, further comprising creating a shadow copy of the set of resources after the consistent view is available.

10. The computer-readable medium of claim 9, further comprising performing a recovery on the shadow copy to rollback or commit transactions in progress when the shadow copy was created.

11. The computer-readable medium of claim 9, further comprising after creating the shadow copy allowing resource managers to enter into the problematic state with respect to transactions affecting the set of resources.

12. A method implemented at least in part by a computer, the method comprising:

requesting that resource managers be prevented from entering a problematic state with respect to transactions affecting a set of resources;

waiting until an earliest of a timeout period elasping or until all of the resource managers that are in the problematic state exit the problematic state;

if the timeout period has not elasped, receiving a notification that indicates that no resource managers are in the problematic state; and

if the timeout period has elasped, refraining from taking a shadow copy of the set of resources.

13. The method of claim 12, further comprising creating a shadow copy of the set of resources and indicating that the resource managers are allowed to enter the problematic state with respect to transactions affecting the set of resources.

14. The method of claim 12, wherein the problematic state comprises a state in which at least one of the resource managers is in a prepared state with respect to a transaction while at least one other of the resource managers is in a non-prepared state with respect to the transaction.

15. The method of claim 12, wherein the resource managers interact with transaction managers that are in a hierarchy, and further comprising notifying the transaction managers to prevent subordinate managers from entering the problematic state in an order based on the hierarchy.

16. The method of claim 15, wherein a transaction manager at the first level in the hierarchy prevents subordinate managers from entering the problematic state before the subordinate managers prevent other managers from entering the problematic state.

17. The method of claim 12, wherein a resource manager comprises a component that manages transactions for other components or a component that manages a portion of the set of resources.

18. In a computing environment, an apparatus, comprising:

a set of resource managers operable to manage a set of resources stored on a set of resource stores;

a consistency requestor operable to request a consistent view of the set of resources; and

a transaction manager operable to receive the request and in response thereto to prevent resource managers involved in transactions involving the set of resources from entering a problematic state that creates or maintains an inconsistent view of the set of resources, wherein the transaction manager is further operable to allow any resource managers involved in transactions that are in the problematic state to proceed with the transactions to exit the problematic state.

19. The apparatus of claim 18, wherein the consistency requestor is further operable to create a shadow copy of the set of resources after the consistent view is available.