Electrical computers and digital processing systems: multicomput – Computer network managing – Computer network monitoring
Reexamination Certificate
1997-06-03
2001-08-28
Banankhah, Majid (Department: 2151)
Electrical computers and digital processing systems: multicomput
Computer network managing
Computer network monitoring
C709S203000, C709S223000, C709S226000, C709S205000
Reexamination Certificate
active
06282569
ABSTRACT:
The present invention relates to a data processing system for facilitating the connection of a program on a client computer to a server, the server consisting of a plurality of server computers with shared resources.
The data processing system, the client computer, and the server computers are all resident on a network. This network need not be one physical network such as a Local Area Network (LAN); for instance it may consist of a number of LANS or WANS (wide area networks) connected together (eg. via ‘bridges’) to form a single logical network. However the same network protocol will be employed throughout the network, a typical example of such a protocol being TCP/IP which will be familiar to those skilled in the art.
In many environments it is increasingly found that a number of server computers are connected together using some form of network, eg. a LAN. It is often the case that several users of client computers will be connected to one such server computer, whilst other server computers stand idle. An example of this is when such computers are situated in workers' offices, connected by, for example, a token ring LAN using the standard TCP/IP network protocol. When workers are away from their offices, their computers will usually stand idle.
In such situations it is commonly the case that a few of the computers in the network are heavily loaded, whilst other computers in the network are very lightly loaded, giving poor response and performance for the client computers using the heavily loaded server computers. Hence there is a problem of how to enable the client user load to be spread more evenly across the available computing resources of the server in a manner which is transparent to the client computer and its programs. If transparency is to be achieved, standard protocols need to be observed in order that client computers can use a variety of connection methods without modification of any programs being required.
A prior art technique which has been developed to provide some sort of load spreading is called “Static load levelling”. With this technique each application on each client computer has a designated server to which it always connects. Hence, for example, if there are 200 potential clients of a server having five server computers, a pre-specified group of, say, 40 of the clients will be told (or configured) to always connect to machine
1
, etc. On average it may be argued that this will give a reasonably even load across all of the server computers. However in practice it is often the case that, using this technique, a large number of users of client computers are connected to one server computer, while an adjacent server computer stands completely idle (eg. given the above example there could easily be 40 users on one server computer whilst the other 4 server computers stand idle). Hence in situations where the user loading changes from time to time, the prior art static load levelling technique is not particularly satisfactory. What is required in such instances is a more ‘dynamic’ technique which can respond to changing user loads, and thus direct new users to the most suitable (eg. least heavily loaded) server computers in the server.
Other prior art techniques can be found in other environments, such as those where job allocation is an issue. For instance in “batch processing”, a client computer submits an encapsulated task to a central server, which determines which one of several possible servers is quiet enough to be able to handle the task. The task is sent to that server, is processed, and the results are then sent back to the client (e.g. as a results file, or by electronic mail). With a batch processing system, there is a brief connection to the central server while the job is transferred from the client to the server allocated by the central server. After this brief connection the client disconnects, and has no more interaction with the submitted task until it has been completed, and the results have been passed back to the client by some means.
However in the situation with which we are currently concerned, the dynamic load levelling technique that is required must be able to deal with “interactive” sessions. Rather like a phone conversation, the connection between the program on the client computer and a particular server computer will persist for the duration of the “conversation” session. Hence the batch processing concept is inappropriate in the present situation.
It is possible to write some specific code within a program on a client computer which contains internal message-passing systems to route work from that client program to a corresponding server program. Such systems are dedicated only to that particular client program, and the connection and load-levelling methods are not accessible to other client-server applications. Often, such systems operate by the client connecting to a specific “host” server computer, and from there the work will be sent to another server for processing. Clearly this technique can result in large bottlenecks arising at the “host” server computer.
Hence such a technique is not suitable in the present situation since it only supports one very specific type of client-server connection, whereas we need a technique that will allow any client-server connection method using the network protocol to be connected to a quiet server in a way that is completely transparent to the client program. Further the above technique relies on an initial connection to the ‘central’ host server computer, which then passes the request on to another server computer; as described above this can potentially create a serious bottleneck.
It is an object of the present invention to provide a technique which facilitates a connection between a client program and a server computer on a server in a way that takes into account the current status of the server computers forming the server. This technique must observe standard network protocols and should operate in a manner which is transparent to the client program requesting access.
Accordingly the present invention provides a data processing system 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 data processing system, the client computer, and the server computers residing in a network, the system comprising: input means for receiving a request from the client computer for a machine address of a server computer identified by a server computer name sent with the request, such a machine 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 server computer names with machine addresses of the server computers; conversion means for using the list to convert the server computer name received by the input means into the machine address of the server computer; output means for sending the machine address from the conversion means to the client computer; the system being characterised by: decision logic for studying the server computers at predetermined intervals having regard to predetermined test criteria, in order to select one of the server computers; and writing means for updating the list by associating the machine 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; whereby when a client computer specifies the generic server computer name, it receives the machine address of the server computer identified by the decision logic.
Typically the conversion means will access the list from a local piece of storage, the data processing system having a copier to copy the list from the storage device to that piece of memory. In preferred embodiments the data processing system further comprises a messaging 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 local memor
Platt Michael
Stanford-Clark Andrew James
Taylor Michael George
Wallis Graham Derek
Banankhah Majid
Herndon Jerry W.
International Business Machines Corp.
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