System and method for caching identification and location information in a computer network

• US 6,014,667 A
• Filed: 10/01/1997
• Issued: 01/11/2000
• Est. Priority Date: 10/01/1997
• Status: Expired due to Term

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: Novell Incorporated (Open Text Corporation)
• Inventors: Jenkins, Christopher, Childers, Randal
• Primary Examiner(s): Amsbury, Wayne
• Assistant Examiner(s): PARDO, THUY N
• Application Number:
  US08/942,165
• Time in Patent Office: 832 Days
• Field of Search: 707/8, 707/10, 707/2, 707/201, 707/203, 711/124, 711/3, 711/128, 711/118, 711/133, 395/200.31, 395/500.12
• US Class Current: 1/1
• CPC Class Codes: H04L 61/4511 using domain name system [DNS]
• CPC Class Codes: H04L 61/4517 using open systems interconnection [OSI] directories, e.g. X.500
• CPC Class Codes: H04L 61/58 Caching of addresses or names
• CPC Class Codes: H04L 67/1001 for accessing one among a plurality of replicated servers
• CPC Class Codes: H04L 67/1023 based on a hash applied to IP addresses or costs
• CPC Class Codes: H04L 67/1095 Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes
• CPC Class Codes: H04L 67/564 Enhancement of application control based on intercepted application data
• CPC Class Codes: H04L 67/5682 Policies or rules for updating, deleting or replacing the stored data
• CPC Class Codes: H04L 69/329 in the application layer [OSI layer 7]
• CPC Class Codes: Y10S 707/922 Communications
• CPC Class Codes: Y10S 707/959 Network
• CPC Class Codes: Y10S 707/972 Partitioning
• CPC Class Codes: Y10S 707/99932 Access augmentation or optimizing
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database

Abstract

Methods and systems are provided for caching information in a distributed computer system such as a directory service system. Tuples in a client cache contain component identifiers and corresponding location identifiers. Tuples may contain a list of network addresses specifying at least one server containing additional location or object information, as well as replica flags which distinguish between read-only replicas, read-write replicas, and a master replica. Requests to access an object may be serviced by using cached information rather than making one or more attempts to obtain location information from servers. Tuples may be modified or invalidated such that read operations tend to be performed using read-only replicas. Cached tuples which contain a component identifier that is no longer valid because an object was moved or renamed may be invalidated. The cache may also be modified to redirect operations from a master replica to a non-master replica.

Claims

1. A method for caching information in a computer system, comprising the computer-implemented steps of:

placing at least one tuple in a cache, each tuple containing a component identifier which identifies a cache-enabled component and a corresponding location identifier which identifies a location at which the cache-enabled component resides;

receiving an access request which identifies a requested component;

determining whether the requested component is cache-enabled;

servicing the access request by sending a corresponding request to a server computer if the requested component is not cache-enabled, and servicing the access request by using the cached location identifier if the requested component is cache-enabled;

detecting access requests that seek to modify a cache-enabled component identifier, and invalidating cache tuples which contain that identifier.

2. The method of claim 1, wherein the placing step places a location identifier that contains a list of network addresses specifying at least one server at which the corresponding cache-enabled component resides.

3. The method of claim 2, wherein the placing step places a tuple that contains a replica flag.

4. The method of claim 3, wherein the placing step places a replica flag that distinguishes between a read-only replica, a read-write replica, and a master replica.

5. The method of claim 1, wherein the placing step places a location identifier that contains a replica-wide component identifier specifying a location at which the corresponding cache-enabled component resides.

6. The method of claim 5, wherein the placing step places a tuple that contains a replica flag.

7. The method of claim 6, wherein the placing step places a replica flag that distinguishes between a read-only replica, a read-write replica, and a master replica.

8. The method of claim 1, wherein the servicing step includes sending the corresponding request to the server computer over a network communication link if the requested component is not cache-enabled.

9. The method of claim 1, further comprising the computer-implemented step of reinitializing the cache.

10. The method of claim 1, further comprising the computer-implemented steps of:

comparing a currently requested operation on a component with cached information about a previously requested operation on the component;

reading the cache to obtain information about the location of the component; and

revising the cached location information if the comparing step detects a predetermined difference between the previously requested operation and the currently requested operation.

13. The method of claim 1, wherein the placing step places a database-wide component identifier that identifies a database component.

14. The method of claim 1, wherein the receiving step receives an access request in response to a directory service request.

24. A computer storage medium having a configuration that represents data and instructions which will cause at least a portion of a computer system to perform method steps for caching tuples, the method steps comprising the steps of claim 1.

25. The storage medium of claim 24, wherein the method steps comprise the steps of claim 2.

26. The storage medium of claim 24, wherein the method steps comprise the steps of claim 4.

11. A method for caching information in a computer system, comprising the computer-implemented steps of:

placing at least one tuple in a cache, each tuple containing a component identifier which identifies a cache-enabled component and a corresponding location identifier which identifies a location at which the cache-enabled component resides;

receiving an access request which identifies a requested component;

determining whether the requested component is cache-enabled;

servicing the access request by sending a corresponding request to a server computer if the requested component is not cache-enabled, and servicing the access request by using the cached location identifier if the requested component is cache-enabled; and

identifying a requested operation to be performed on a master replica, and redirecting the operation to a non-master replica to reduce the load on the master replica.

12. The method of claim 11, wherein the redirecting step includes modifying the cache.

27. The storage medium of claim 24, wherein the method steps comprise the steps of claim 11.

15. A computer system comprising:

a client computer having a processor, a memory, and a means for receiving a component access request which identifies a requested component;

a tuple cache residing on the client computer, the tuple cache capable of holding at least one tuple, each tuple containing a component identifier which identifies a cache-enabled component and a corresponding location identifier which identifies a location at which the cache-enabled component resides;

means for placing a tuple in the tuple cache;

means for determining whether the requested component is cache-enabled;

means for servicing the access request by sending a corresponding request to a server computer if the requested component is not cache-enabled and servicing the access request by using the cached location identifier if the requested component is cache-enabled; and

means for detecting access requests that seek to modify a cache-enabled component identifier and for invalidating cache tuples which contain that identifier.

16. The system of claim 15, wherein the server computer and the client computer are separate computers connected by a network link.

17. The system of claim 15, wherein the location identifier contains a list of network addresses specifying at least one server at which the corresponding cache-enabled component resides.

18. The system of claim 15, wherein the tuple contains a replica flag.

19. The system of claim 18, wherein the replica flag distinguishes between a master replica and at least one other replica.

20. The system of claim 18, wherein the replica flag distinguishes between a read-only replica, a read-write replica, and a master replica.

21. The system of claim 15, further comprising means for reinitializing the cache.

22. The system of claim 15, further comprising means for revising the cached location information to encourage conformance with predetermined preferences that certain operations be performed using certain kinds of replicas.

23. The system of claim 15, further comprising means for modifying the cache to redirect operations from a master replica to a non-master replica.