SYSTEM AND METHOD FOR AN APPLICATION SPACE SERVER CLUSTER

• US 20030046394A1
• Filed: 06/11/2001
• Published: 03/06/2003
• Est. Priority Date: 11/03/2000
• Status: Abandoned Application

• Current Assignee: Board of Regents of the University of Nebraska
• Original Assignee: Board of Regents of the University of Nebraska
• Inventors: Goddard, Steve, Gan, Xuehong, Ramamurthy, Byravamurthy
• Application Number:
  US09/878,787
• Publication Number:
  US 20030046394A1
• Time in Patent Office: Days
• US Class Current: 709/226
• CPC Class Codes: H04L 67/1001 for accessing one among a plurality of replicated servers
• CPC Class Codes: H04L 67/10015 Access to distributed or replicated servers, e.g. using brokers
• 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 67/1023 based on a hash applied to IP addresses or costs
• CPC Class Codes: H04L 67/1029 using data related to the state of servers by a load balancer
• CPC Class Codes: H04L 67/1031 Controlling of the operation of servers by a load balancer, e.g. adding or removing servers that serve requests
• CPC Class Codes: H04L 67/1034 Reaction to server failures by a load balancer
• CPC Class Codes: H04L 67/561 Adding application-functional data or data for application control, e.g. adding metadata
• CPC Class Codes: H04L 67/563 Data redirection of data network streams
• CPC Class Codes: H04L 67/564 Enhancement of application control based on intercepted application data
• CPC Class Codes: H04L 67/5651 Reducing the amount or size of exchanged application data
• CPC Class Codes: H04L 67/568 Storing data temporarily at an intermediate stage, e.g. caching
• CPC Class Codes: H04L 67/61 taking into account QoS or priority requirements
• CPC Class Codes: H04L 69/16 Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
• CPC Class Codes: H04L 69/161 Implementation details of TCP/IP or UDP/IP stack architecture; Specification of modified or new header fields
• CPC Class Codes: H04L 69/329 in the application layer [OSI layer 7]
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

Abstract of the Disclosure

A system and method for implementing a scalable, application-space, highly-available server cluster. The system demonstrates high performance and faulttolerance using application-space software and commercial-off-the-shelf hardwareand operating systems. The system includes an application-space dispatch serverthat performs various switching methods, including L4/2 switching or L4/3switching. The system also includes state reconstruction software and token-based protocol software. The protocol software supports self-configuring,detecting and adapting to the addition or removal of network servers. The systemoffers a flexible and cost-effective alternative to kernel-space or hardware-basedclustered web servers with performance comparable to kernel-spaceimplementations.

Claims

1. A system responsive to client requests for delivering data via a network to a client, saidsystem comprising:

at least one dispatch server receiving the client requests;

a plurality of network servers;

dispatch software executing in application-space on the dispatch server to selectivelyassign the client requests to the network servers; and

protocol software, executing in application-space on the dispatch server and each of thenetwork servers, to interrelate the dispatch server and network servers as ring members of alogical, token-passing, fault-tolerant ring network, wherein the plurality of network servers areresponsive to the dispatch software and the protocol software to deliver the data to the clients inresponse to the client requests.

2. The system of claim 1, wherein the system is structured according to an Open SourceInterconnection (OSI) reference model, wherein the dispatch software performs switching of theclient requests at layer 4 of the OSI reference model and translates addresses associated the clientrequests at layer 2 of the OSI reference model, and wherein the protocol software comprisesreconstruction software to coordinate state reconstruction after fault detection.

3. The system of claim 1, wherein the protocol software comprises broadcast messagingsoftware to coordinate broadcast messaging among the ring members.

4. The system of claim 1, wherein the dispatch software executes in application-space oneach of the network servers to functionally convert one of the network servers into a newdispatch server after detecting a fault with the dispatch server.

5. The system of claim 1, wherein one of the ring members circulates a self-identifyingheartbeat message around the ring network.

6. The system of claim 1, wherein the protocol software includes out-of-band messagingsoftware for coordinating creation and transmission of tokens by the ring members.

7. The system of claim 1, wherein the system is structured according to a multi-layerreference model, wherein the protocol software communicates at any one of the layers of thereference model.

8. The system of claim 7, wherein the reference model is the Open Source Interconnection(OSI) reference model, and wherein the dispatch software performs switching of the clientrequests at layer 4 of the OSI reference model and translates addresses associated with the clientrequests at layer 2 of the OSI reference model.

9. The system of claim 7, wherein the reference model is the Open Source Interconnection(OSI) reference model, and wherein the dispatch software performs switching of the clientrequests at layer 4 of the OSI reference model and translates addresses associated with the clientrequests at layer 3 of the OSI reference model.

10. The system of claim 7, wherein the reference model is the Open Source Interconnection(OSI) reference model, and wherein the dispatch software performs switching of the clientrequests at layer 7 of the OSI reference model and then performs switching of the client requestsat layer 3 of the OSI reference model.

11. The system of claim 10, wherein the dispatch software includes caching, and whereinsaid caching is tunable to adjust the delivery of the data to the client whereby a response time tospecific client requests is reduced.

12. The system of claim 7, wherein the dispatch software executes in application-space toselectively assign a specific client request to one of the network servers based on the content ofthe specific client request.

13. The system of claim 1, further comprising packets containing messages, wherein aplurality of the packets simultaneously circulate the ring network, wherein the ring memberstransmit and receive the packets.

14. The system of claim 1 wherein the protocol software of a specific ring member includesat least one state variable.

15. The system of claim 1 wherein the faults are symmetric-omissive.

16. The system of claim 1 wherein the protocol software includes ring expansion software foradapting to the addition of a new network server to the ring network.

17. A system responsive to client requests for delivering data via a network to a client, saidsystem comprising:

at least one dispatch server receiving the client requests;

a plurality of network servers;

dispatch software executing in application-space on the dispatch server to selectivelyassign the client requests to the network servers, wherein the system is structured according to anOpen Source Interconnection (OSI) reference model, and wherein said dispatch softwareperforms switching of the client requests at layer 4 of the OSI reference model; and

protocol software, executing in application-space on the dispatch server and each of thenetwork servers, to interrelate the dispatch server and network servers as ring members of alogical, token-passing, fault-tolerant ring network, wherein the plurality of network servers areresponsive to the dispatch software and the protocol software to deliver the data to the clients inresponse to the client requests.

18. The system of claim 17, wherein the dispatch software translates addresses associatedwith the client requests at layer 2 of the OSI reference model.

19. The system of claim 17, wherein the dispatch software translates addresses associatedwith the client requests at layer 3 of the OSI reference model.

20. A system responsive to client requests for delivering data via a network to a client, saidsystem comprising:

at least one dispatch server receiving the client requests;

a plurality of network servers;

dispatch software executing in application-space on the dispatch server to selectivelyassign the client requests to the network servers, wherein the system is structured according to anOpen Source Interconnection (OSI) reference model, wherein the dispatch software performsswitching of the client requests at layer 7 of the OSI reference model and then performsswitching of the client requests at layer 3 of the OSI reference model; and

protocol software, executing in application-space on the dispatch server and each of thenetwork servers, to organize the dispatch server and network servers as ring members of alogical, token-passing, ring network, and to detect a fault of the dispatch server or the networkservers, wherein the plurality of network servers are responsive to the dispatch software and theprotocol software to deliver the data to the clients in response to the client requests.

21. A method for delivering data to a client in response to client requests for said data via anetwork having at least one dispatch server and a plurality of network servers, said methodcomprising the steps of:

receiving the client requests;

selectively assigning the client requests to the network servers after receiving the clientrequests;

delivering the data to the clients in response to the assigned client requests;

organizing the dispatch server and network servers as ring members of a logical, token-passing, ring network;

detecting a fault of the dispatch server or the network servers; and

recovering from the fault.

22. The method of claim 21, further comprising the step of coordinating broadcast messagingamong the ring members.

23. The method of claim 21, wherein the step of selectively assigning comprises the step ofswitching the client requests at layer 4 of an Open Source Interconnection (OSI) reference model.

24. The method of claim 23, further comprising the step of coordinating state reconstructionafter fault detection.

25. The method of claim 24, wherein the step of coordinating state reconstruction includesfunctionally converting one of the network servers into a new dispatch server after detecting afault with the dispatch server.

26. The method of claim 25, further comprising the step of the new dispatch server queryingthe network servers for a list of active connections and entering the list of active connections intoa connection map associated with the new dispatch server.

27. The method of claim 21, wherein the protocol software includes packets, said methodfurther comprising the steps of a specific ring member:

receiving the packets from a ring member with an address which is numerically smallerand closest to an address of the specific ring member; and

transmitting the packets to a ring member with an address which is numerically greaterand closest to the address of the specific ring member, wherein a ring member with thenumerically smallest address in the ring network receives the packets from a ring member withthe numerically greatest address in the ring network, and wherein the ring member with thenumerically greatest address in the ring network transmits the packets to the ring member withthe numerically smallest address in the ring network.

28. The method of claim 21 wherein the step of selectively assigning the client requests to thenetwork servers comprises the steps of:

routing each client request to the dispatch server;

determining whether a connection to one of the network servers exists for each clientrequest;

creating the connection to one of the network servers if the connection does not exist;

recording the connection in a map maintained by the dispatch server;

modifying each client request to include an address of the network server associated withthe created connection; and

forwarding each client request to the network server via the created connection.

29. The method of claim 21 further comprising the step of detecting and recovering from atleast one fault by one or more of the ring members.

30. The method of claim 29, wherein the step of detecting and recovering comprises the stepsof:

detecting the fault by failing to receive communications from the one or more of the ringmembers during a communications timeout interval; and

rebuilding the ring network without the one or more of the ring members.

31. The method of claim 30, wherein the one or more of the ring members includes thedispatch server, further comprising the step of identifying during a broadcast timeout interval anew dispatch server from one of the ring members in the rebuilt ring network.

32. The method of claim 31, wherein the step of selectively assigning comprises the step ofswitching the client requests at layer 4 of an Open Source Interconnection (OSI) reference model,further comprising the steps of:

broadcasting a list of connections maintained prior to the fault in response to a request;

receiving the list of connections from each ring member; and

updating a connection map maintained by the new dispatch server with the list ofconnections from each ring member.

33. The method of claim 31 wherein the step of identifying during a broadcast timeoutinterval a new dispatch server comprises the step of identifying during a broadcast timeoutinterval a new dispatch server by selecting one of the ring members in the rebuilt ring networkwith the numerically smallest address in the ring network.

34. The method of claim 21 further comprising the step of adapting to the addition of a newnetwork server to the ring network.

35. A system for delivering data to a client in response to client requests for said data via anetwork having at least one dispatch server and a plurality of network servers, said systemcomprising:

means for receiving the client requests;

means for selectively assigning the client requests to the network servers after receivingthe client requests;

means for delivering the data to the clients in response to the assigned client requests;

means for organizing the dispatch server and network servers as ring members of alogical, token-passing, ring network;

means for detecting a fault of the dispatch server or the network servers; and

means for recovering from the fault.