Name server computer having a load levelling facility to spread the load from client computers across a plurality of server computers

• US 6,282,569 B1
• Filed: 06/03/1997
• Issued: 08/28/2001
• Est. Priority Date: 09/11/1993
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Stanford-Clark, Andrew James, Wallis, Graham Derek, Platt, Michael, Taylor, Michael George
• Primary Examiner(s): BANANKHAH, MAJID A
• Application Number:
  US08/868,111
• Time in Patent Office: 1,547 Days
• Field of Search: 709/201, 709/202, 709/203, 709/204, 709/217, 709/218, 709/219, 709/226, 709/227, 709/228, 709/330, 700/178, 710/100, 707/202, 707/203, 707/204, 707/205
• US Class Current: 709/224
• CPC Class Codes: G06F 9/505 considering the load
• CPC Class Codes: H04L 67/1001 for accessing one among a plurality of replicated servers
• CPC Class Codes: H04L 67/1008 based on parameters of servers, e.g. available memory or workload monitoring of computer activity G06F11/30
• CPC Class Codes: H04L 67/1017 based on a round robin mechanism
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

A name server computer and method of operating such a computer, for facilitating a connection of a program on a client computer to a server, the server consisting of a plurality of server computers with shared resources. The name server computer, the client computer, and the server computers all reside in a logical network. The name server computer receives a request from the client computer for a computer address of a server computer identified by a server computer name sent with the request, such computer address enabling a connection to be made from the client computer to that server computer via the network. A list of server computer names with their computer addresses is provided. The name server computer uses the list to convert the server computer name received from the client computer into the computer address of the server computer, and then sends the computer address to the client computer. The computer further includes decision logic for studying the server computers at predetermined intervals having regard to a predetermined test criteria, to select one of the server computers. The list is then updated by associating the computer address for the server computer selected by the decision logic with a particular server computer name contained as a generic server computer name in the list. Using this technique, when a client computer specifies the generic server computer name, it receives the computer address of the server computer identified by the decision logic.

Claims

1. A name server computer for facilitating a connection of a program on a client computer to a server computer, the name server computer, the client computer, and the server computer residing in a network, the name server computer comprising:

input means for receiving a request from the client computer for a network address of a server computer identified by a Uniform Resource Locator (URL) name sent with the request, such network address enabling a connection to be made from the client computer to that server computer via the network;

a storage device for storing a list identifying URL names with network addresses of server computers, said list including at least one URL name which is a generic URL name corresponding to a plurality of server computers residing in said network;

conversion means for using the list to convert a URL name received by the input means into a network address of a server computer;

output means for sending the network address from the conversion means to the client computer;

load levelling decision logic for studying the plurality of server computers corresponding to said generic URL name at predetermined intervals having regard to predetermined test criteria relating to the relative load conditions of said plurality of server computers, in order to select one of the plurality of server computers;

means for determining if the selected one of the plurality of server computers is the same server computer as that last selected,

writing means responsive to the determining means for updating the list by associating the network address for the server computer selected by the decision logic with said generic URL name only if the selected one of the plurality of server computers is different from the sever computer last selected;

a copier to copy the list from the storage device to a piece of memory accessible by the conversion means, and

a message passing means responsive to the updating of the list by the writing means, for sending a message to the copier requesting the copier to copy the updated list into the piece of memory,

whereby when a client computer specifies the generic URL name, it receives the network address of the server computer identified by the decision logic.

2. A name server computer as claimed in claim 1 wherein the predetermined test criteria are such that the decision logic identifies the server computer having the least number of client programs logged on to it.

3. A name server computer as claimed in claim 1 wherein the predetermined intervals are variable.

4. A name server computer as claimed in claim 1 wherein the predetermined test criteria are set by a user of the system.

5. A name server computer as claimed in claim 1, wherein the user can limit the number of server computers which the decision logic studies.

6. The name server computer as claimed in claim 1, wherein a plurality of generic URL names are included in the list, the decision logic employing different sets of predetermined test criteria for each generic URL name for analysing the relative load conditions of the respective plurality of server computers.

7. A name server computer as claimed in claim 6, wherein one or more of the server computers are associated with a plurality of the generic names.

8. A method of operating a name server computer to facilitate a connection of a program on a client computer to a server, the name server computer, the client computer, and the server computer residing in a network, the method comprising the steps of:

(a) receiving a request from the client computer for a network address of a server computer identified by a Uniform Resource Locator (URL) name sent with the request, such network address enabling a connection to be made from the client computer to that server computer via the network;

(b) storing a list identifying URL names with network addresses of server computers in a storage device, said list including at least one URL name which is a generic URL name corresponding to a plurality of server computers residing in said network;

(c) converting, with reference to the list, the URL name received at step (a) into the network address of a server computer; and

(d) sending the network address identified at step (c) to the client computer;

wherein the following steps are also performed to facilitate the performance of the above steps;

(e) employing load levelling decision logic to study the plurality of server computers corresponding to said generic URL name at predetermined intervals having regard to predetermined test criteria relating to the relative load conditions of said plurality of server computers, in order to select one of the plurality of server computers; and

(f) updating the list by associating the network address for the server computer selected by the decision logic with said generic URL name only if the selected one of the plurality of server computers at the present predetermined interval differs from the last selected one of the server computers;

copying the list from the storage device to a piece of memory accessible to the converting step only if the list is updated at step f);

whereby when a client computer specifies the generic URL name at step (a), it receives at step (d) the network address of the server computer identified by the decision logic at step (e) upon performance of the converting step (c).

9. A method as claimed in claim 8 wherein the predetermined intervals are set by a user of the system.

10. A method as claimed in claim 8 wherein the predetermined test criteria are set by a user of the system.

11. A method as claimed in claim 8 wherein the user can limit the number of server computers which the decision logic studies.

12. The method as claimed in claim 8, wherein a plurality of generic URL names are included in the list, the decision logic employing different sets of predetermined test criteria for each generic URL name for analysing the relative load conditions of the respective plurality of server computers.

13. A method as claimed in claim 12, wherein one or more of the server computers are associated with a plurality of the generic names.