WO2007041764A1 - Failure resistant multiple computer system and method - Google Patents
Failure resistant multiple computer system and method Download PDFInfo
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- WO2007041764A1 WO2007041764A1 PCT/AU2006/001449 AU2006001449W WO2007041764A1 WO 2007041764 A1 WO2007041764 A1 WO 2007041764A1 AU 2006001449 W AU2006001449 W AU 2006001449W WO 2007041764 A1 WO2007041764 A1 WO 2007041764A1
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- memory locations
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L67/00—Network arrangements or protocols for supporting network services or applications
- H04L67/01—Protocols
- H04L67/10—Protocols in which an application is distributed across nodes in the network
- H04L67/1095—Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F11/00—Error detection; Error correction; Monitoring
- G06F11/07—Responding to the occurrence of a fault, e.g. fault tolerance
- G06F11/16—Error detection or correction of the data by redundancy in hardware
- G06F11/20—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements
- G06F11/202—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements where processing functionality is redundant
- G06F11/2023—Failover techniques
- G06F11/2028—Failover techniques eliminating a faulty processor or activating a spare
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F11/00—Error detection; Error correction; Monitoring
- G06F11/07—Responding to the occurrence of a fault, e.g. fault tolerance
- G06F11/16—Error detection or correction of the data by redundancy in hardware
- G06F11/1666—Error detection or correction of the data by redundancy in hardware where the redundant component is memory or memory area
Definitions
- the present invention relates to computing and, in particular, to the simultaneous operation of a plurality of computers interconnected via a communications network.
- the abovementioned patent specifications disclose that at least one application program written to be operated on only a single computer can be simultaneously operated on a number of computers each with independent local memory.
- the memory locations required for the operation of that program are replicated in the independent local memory of each computer.
- each computer has a local memory the contents of which are substantially identical to the local memory of each other computer and are updated to remain so. Since all application programs, in general, read data much more frequently than they cause new data to be written, the abovementioned arrangement enables very substantial advantages in computing speed to be achieved.
- the stratagem enables two or more commodity computers interconnected by a commodity communications network to be operated simultaneously running under the application program written to be executed on only a single computer.
- the genesis of the present invention is a desire to at least partially overcome the abovementioned difficulty.
- a failure resistant method of operating a plurality of computers each with their corresponding independent local memory, each simultaneously operating an application program, and each being connected via a communications network to permit updating of corresponding memory locations comprising the steps of: (i) categorizing the memory locations of said local memories into a first reachability category in which the local memory locations are accessible by selected ones, or all, of said computers and therefore require updating via said communications network with changes to corresponding memory locations of the other computers having access to maintain substantial memory coherence, and into a second category in which the local memory locations are accessible only by the local computer and therefore no updating is required,
- a failure resistant multiple computer system in which a plurality of computers each has a corresponding independent local memory, each simultaneously operates a corresponding portion of an application program written to be executed only on a single computer, and each is connected via a communications network to permit updating of corresponding memory locations, said system including a reachability means to categorize memory locations of said local memories into a first category in which the local memory locations are replicated in selected ones, or all, of said computers and therefore require updating via said communications network with changes to corresponding memory locations of other computers, to maintain substantial memory coherence, and into a second category in which the local memory locations are present only in the local computer and therefore no updating is required, and wherein said system further includes a failure detection means connected to each said computer to detect failure of any one of said multiple computers, and a reachability modifier connected to said failure connection means and to said reachability means to modify said reachability means by modifying said first category to remove therefrom, if present, any reference by the failed computer whereby no attempt is made
- a computer program product comprising a set of program instructions stored in a storage medium and operable to permit a plurality of computers to carry out the abovementioned method.
- a fourth aspect of the present invention there is disclosed a plurality of computers interconnected via a communications network and operable to ensure carrying out the abovementioned method.
- a single computer adapted to co-operate with at least one other computer to carry out the above method or form the above computer system.
- Fig. IA is a schematic illustration of a prior art computer arranged to operate JAVA code and thereby constitute a single JAVA virtual machine
- Fig. IB is a drawing similar to Fig. IA but illustrating the initial loading of code
- Fig. 1C illustrates the interconnection of a multiplicity of computers each being a JAVA virtual machine to form a multiple computer system
- Fig. 2 schematically illustrates "n" application running computers to which at least one additional server machine X is connected as a server
- Fig. 3 is a schematic map of the memory locations in all the multiple machines showing memory locations including classes and objects,
- Fig. 4 is a single reachability table showing the various memory locations of Fig. 3 and their ability to be reached
- Fig. 5 shows multiple reachability tables equivalent to Fig. 4,
- Fig. 6 is a map similar to Fig. 3 and showing memory location X pointing to memory location A,
- Fig. 7 is the single reachability table corresponding to Fig. 6
- Fig. 8 shows the multiple reachability tables corresponding to Fig. 6
- Fig. 9 is a flow chart showing one embodiment of the procedure to be undertaken in the event of failure of one of the n application running computers
- Fig. 10 is a flow chart of the procedures of a second embodiment
- Fig. 11 is a map similar to Fig. 6 but illustrating the situation of a break in communications with machine M2
- Fig. 12 shows the single reachability table in the circumstance of Fig. 11, and
- Fig. 13 shows the multiple reachability tables in the circumstance of Fig. 11.
- MICROSOFT.NET platform and architecture Visual Basic, Visual C, and Visual C++, and Visual C#
- FORTRAN C, C++, COBOL, BASIC and the like.
- the code and data and virtual machine configuration or arrangement of Fig IA takes the form of the application code 50 written in the JAVA language and executing within the JAVA virtual machine 61.
- the intended language of the application is the language JAVA
- a JAVA virtual machine is used which is able to operate code in JAVA irrespective of the machine manufacturer and internal details of the computer or machine.
- Fig. IA This conventional art arrangement of Fig. IA is modified in accordance with embodiments of the present invention by the provision of an additional facility which is conveniently termed a “distributed run time” or a “distributed run time system” DRT 71 and as seen in Fig. IB.
- the application code 50 is loaded onto the Java Virtual Machine(s) M 1 , M2, ... Mn in cooperation with the distributed runtime system 71 , through the loading procedure indicated by arrow 75 or 75 A or 75B.
- distributed runtime and the “distributed run time system” are essentially synonymous, and by means of illustration but not limitation are generally understood to include library code and processes which support software written in a particular language running on a particular platform. Additionally, a distributed runtime system may also include library code and processes which support software written in a particular language running within a particular distributed computing environment.
- a runtime system typically deals with the details of the interface between the program and the operating system such as system calls, program start-up and termination, and memory management.
- a conventional Distributed Computing Environment (DCE) (that does not provide the capabilities of the inventive distributed run time or distributed run time system 71 used in the preferred embodiments of the present invention) is available from the Open Software Foundation.
- This Distributed Computing Environment (DCE) performs a form of computer-to-computer communication for software running on the machines, but among its many limitations, it is not able to implement the desired modification or communication operations.
- the preferred DRT 71 coordinates the particular communications between the plurality of machines Ml, M2,...Mn.
- the preferred distributed runtime 71 comes into operation during the loading procedure indicated by arrow 75 A or 75B of the JAVA application 50 on each JAVA virtual machine 72 or machines JVM#1, JVM#2,... JVM#n of Fig. 1C. It will be appreciated in light of the description provided herein that although many examples and descriptions are provided relative to the JAVA language and JAVA virtual machines so that the reader may get the benefit of specific examples, the invention is not restricted to either the JAVA language or JAVA virtual machines, or to any other language, virtual machine, machine or operating environment.
- Fig. 1C shows in modified form the arrangement of the JAVA virtual machines, each as illustrated in Fig. IB.
- the same application code 50 is loaded onto each machine Ml , M2...Mn.
- the communications between each machine Ml, M2...Mn are as indicated by arrows 83, and although physically routed through the machine hardware, are advantageously controlled by the individual DRT's 71/1...71/n within each machine.
- this may be conceptionalised as the DRT's 71/1, ...71/n communicating with each other via the network or other communications link 53 rather than the machines Ml, M2...Mn communicating directly themselves or with each other.
- Contemplated and included are either this direct communication between machines Ml, M2...Mn or DRT's 71/1, 71/2...71/n or a combination of such communications.
- the preferred DRT 71 provides communication that is transport, protocol, and link independent.
- the one common application program or application code 50 and its executable version (with likely modification) is simultaneously or concurrently executing across the plurality of computers or machines Ml , M2...Mn.
- the application program 50 is written to execute on a single machine or computer (or to operate on the multiple computer system of the abovementioned patent applications which emulate single computer operation).
- the modified structure is to replicate an identical memory structure and contents on each of the individual machines.
- common application program is to be understood to mean an application program or application program code written to operate on a single machine, and loaded and/or executed in whole or in part on each one of the plurality of computers or machines Ml, M2...Mn, or optionally on each one of some subset of the plurality of computers or machines Ml, M2...Mn.
- application code 50 This is either a single copy or a plurality of identical copies each individually modified to generate a modified copy or version of the application program or program code. Each copy or instance is then prepared for execution on the corresponding machine. At the point after they are modified they are common in the sense that they perform similar operations and operate consistently and coherently with each other.
- a plurality of computers, machines, information appliances, or the like implementing embodiments of the invention may optionally be connected to or coupled with other computers, machines, information appliances, or the like that do not implement embodiments of the invention.
- the same application program 50 (such as for example a parallel merge sort, or a computational fluid dynamics application or a data mining application) is run on each machine, but the executable code of that application program is modified on each machine as necessary such that each executing instance (copy or replica) on each machine coordinates its local operations on that particular machine with the operations of the respective instances (or copies or replicas) on the other machines such that they function together in a consistent, coherent and coordinated manner and give the appearance of being one global instance of the application (i.e. a "meta- application").
- the copies or replicas of the same or substantially the same application codes are each loaded onto a corresponding one of the interoperating and connected machines or computers.
- the application code 50 may be modified before loading, or during the loading process, or with some disadvantages after the loading process, to provide a customization or modification of the application code on each machine.
- Some dissimilarity between the programs or application codes on the different machines may be permitted so long as the other requirements for interoperability, consistency, and coherency as described herein can be maintained.
- each of the machines Ml, M2...Mn and thus all of the machines Ml, M2...Mn have the same or substantially the same application code 50, usually with a modification that may be machine specific.
- each application code 50 is modified by a corresponding modifier 51 according to the same rules (or substantially the same rules since minor optimizing changes are permitted within each modifier 51/1, 51/2...51/n).
- Each of the machines Ml, M2...Mn operates with the same (or substantially the same or similar) modifier 51 (in some embodiments implemented as a distributed run time or DRT71 and in other embodiments implemented as an adjunct to the application code and data 50, and also able to be implemented within the JAVA virtual machine itself).
- all of the machines Ml, M2...Mn have the same (or substantially the same or similar) modifier 51 for each modification required.
- a different modification for example, may be required for memory management and replication, for initialization, for finalization, and/or for synchronization (though not all of these modification types may be required for all embodiments).
- the modifier 51 may be implemented as a component of or within the distributed run time 71, and therefore the DRT 71 may implement the functions and operations of the modifier 51.
- the function and operation of the modifier 51 may be implemented outside of the structure, software, firmware, or other means used to implement the DRT 71 such as within the code and data 50, or within the JAVA virtual machine itself.
- both the modifier 51 and DRT 71 are implemented or written in a single piece of computer program code that provides the functions of the DRT and modifier. In this case the modifier function and structure is, in practice, subsumed into the DRT.
- the modifier function and structure is responsible for modifying the executable code of the application code program
- the distributed run time function and structure is responsible for implementing communications between and among the computers or machines.
- the communications functionality in one embodiment is implemented via an intermediary protocol layer within the computer program code of the DRT on each machine.
- the DRT can, for example, implement a communications stack in the JAVA language and use the Transmission Control Protocol/Internet Protocol (TCP/IP) to provide for communications or talking between the machines.
- TCP/IP Transmission Control Protocol/Internet Protocol
- a plurality of individual computers or machines Ml, M2...Mn are provided, each of which are interconnected via a communications network 53 or other communications link.
- Each individual computer or machine is provided with a corresponding modifier 51.
- Each individual computer is also provided with a communications port which connects to the communications network.
- the communications network 53 or path can be any electronic signalling, data, or digital communications network or path and is preferably a slow speed, and thus low cost, communications path, such as a network connection over the Internet or any common networking configurations including ETHERNET or INFINIBAND and extensions and improvements, thereto.
- the computers are provided with one or more known communications ports (such as CISCO Power Connect 5224 Switches) which connect with the communications network 53.
- the size of the smallest memory of any of the machines may be used as the maximum memory capacity of the machines when such memory (or a portion thereof) is to be treated as 'common' memory (i.e. similar equivalent memory on each of the machines Ml ...Mn) or otherwise used to execute the common application code.
- each machine Ml, M2...Mn has a private (i.e. 'non-common') internal memory capability.
- the private internal memory capability of the machines Ml, M2, ..., Mn are normally approximately equal but need not be.
- each machine or computer is preferably selected to have an identical internal memory capability, but this need not be so.
- the independent local memory of each machine represents only that part of the machine's total memory which is allocated to that portion of the application program running on that machine. Thus, other memory will be occupied by the machine's operating system and other computational tasks unrelated to the application program 50.
- Non-commercial operation of a prototype multiple computer system indicates that not every machine or computer in the system utilises or needs to refer to (e.g. have a local replica of) every possible memory location.
- some or all of the plurality of individual computers or machines can be contained within a single housing or chassis (such as so-called “blade servers” manufactured by Hewlett-Packard Development Company, Intel Corporation, IBM Corporation and others) or the multiple processors (eg symmetric multiple processors or SMPs) or multiple core processors (eg dual core processors and chip multithreading processors) manufactured by Intel, AMD, or others, or implemented on a single printed circuit board or even within a single chip or chip set.
- blade servers manufactured by Hewlett-Packard Development Company, Intel Corporation, IBM Corporation and others
- the multiple processors eg symmetric multiple processors or SMPs
- multiple core processors eg dual core processors and chip multithreading processors
- computers or machines having multiple cores, multiple CPU's or other processing logic.
- the generalized platform, and/or virtual machine and/or machine and/or runtime system is able to operate application code 50 in the language(s) (possibly including for example, but not limited to any one or more of source-code languages, intermediate-code languages, object-code languages, machine-code languages, and any other code languages) of that platform and/or virtual machine and/or machine and/or runtime system environment, and utilize the platform, and/or virtual machine and/or machine and/or runtime system and/or language architecture irrespective of the machine or processor manufacturer and the internal details of the machine.
- the platform and/or runtime system can include virtual machine and non- virtual machine software and/or firmware architectures, as well as hardware and direct hardware coded applications and implementations.
- computers and/or computing machines and/or information appliances or processing systems are still applicable.
- computers and/or computing machines that do not utilize either classes and/or objects include for example, the x86 computer architecture manufactured by Intel Corporation and others, the SPARC computer architecture manufactured by Sun Microsystems, Inc and others, the Power PC computer architecture manufactured by International Business Machines Corporation and others, and the personal computer products made by Apple Computer, Inc., and others.
- primitive data types such as integer data types, floating point data types, long data types, double data types, string data types, character data types and Boolean data types
- structured data types such as arrays and records
- derived types or other code or data structures of procedural languages or other languages and environments such as functions, pointers, components, modules, structures, reference and unions.
- This analysis or scrutiny of the application code 50 can take place either prior to loading the application program code 50, or during the application program code 50 loading procedure, or even after the application program code 50 loading procedure (or some combination of these). It may be likened to an instrumentation, program transformation, translation, or compilation procedure in that the application code can be instrumented with additional instructions, and/or otherwise modified by meaning- preserving program manipulations, and/or optionally translated from an input code language to a different code language (such as for example from source-code language or intermediate-code language to object-code language or machine-code language).
- compilation normally or conventionally involves a change in code or language, for example, from source code to object code or from one language to another language.
- compilation and its grammatical equivalents
- the term "compilation” is not so restricted and can also include or embrace modifications within the same code or language.
- the compilation and its equivalents are understood to encompass both ordinary compilation (such as for example by way of illustration but not limitation, from source-code to object code), and compilation from source-code to source-code, as well as compilation from object-code to object code, and any altered combinations therein. It is also inclusive of so-called “intermediary-code languages” which are a form of "pseudo object-code”.
- the analysis or scrutiny of the application code 50 takes place during the loading of the application program code such as by the operating system reading the application code 50 from the hard disk or other storage device, medium or source and copying it into memory and preparing to begin execution of the application program code.
- the analysis or scrutiny may take place during the class loading procedure of the java.lang.ClassLoader.loadClass method (e.g. "java.lang.ClassLoader.loadClassO").
- 50 may take place even after the application program code loading procedure, such as after the operating system has loaded the application code into memory, or optionally even after execution of the relevant corresponding portion of the application program code has started, such as for example after the JAVA virtual machine has loaded the application code into the virtual machine via the "java.lang.ClassLoader.loadClass()" method and optionally commenced execution.
- One such technique is to make the modification(s) to the application code, without a preceding or consequential change of the language of the application code.
- Another such technique is to convert the original code (for example, JAVA language source-code) into an intermediate representation (or intermediate-code language, or pseudo code), such as JAVA byte code. Once this conversion takes place the modification is made to the byte code and then the conversion may be reversed. This gives the desired result of modified JAVA code.
- a further possible technique is to convert the application program to machine code, either directly from source-code or via the abovementioned intermediate language or through some other intermediate means. Then the machine code is modified before being loaded and executed.
- a still further such technique is to convert the original code to an intermediate representation, which is thus modified and subsequently converted into machine code.
- the present invention encompasses all such modification routes and also a combination of two, three or even more, of such routes.
- the DRT 71 or other code modifying means is responsible for creating or replicating a memory structure and contents on each of the individual machines Ml, M2...Mn that permits the plurality of machines to interoperate.
- this replicated memory structure will be identical. Whilst in other embodiments this memory structure will have portions that are identical and other portions that are not. In still other embodiments the memory structures are different only in format or storage conventions such as Big Endian or Little Endian formats or conventions.
- Such local memory read and write processing operation can typically be satisfied within 10 2 — 10 3 cycles of the central processing unit. Thus, in practice there is substantially less waiting for memory accesses which involves and/or writes. Also, the local memory of each machine is not able to be accessed by any other machine and can therefore be said to be independent.
- the invention is transport, network, and communications path independent, and does not depend on how the communication between machines or DRTs takes place. In one embodiment, even electronic mail (email) exchanges between machines or DRTs may suffice for the communications.
- Fig. 2 there are a number of machines Ml , M2, .... Mn, "n” being an integer greater than or equal to two, on which the application program 50 of Fig. 1 is being run substantially simultaneously.
- These machines are allocated a number 1, 2, 3, ... etc. in a hierarchical order. This order is normally looped or closed so that whilst machines 2 and 3 are hierarchically adjacent, so too are machines "n" and 1.
- the further machine X can be a low value machine, and much less expensive than the other machines which can have desirable attributes such as processor speed.
- an additional low value machine (X+l) is preferably available to provide redundancy in case machine X should fail.
- server machines X and X+l are provided, they are preferably, for reasons of simplicity, operated as dual machines in a cluster configuration.
- Machines X and X+l could be operated as a multiple computer system in accordance with the present invention, if desired. However this would result in generally undesirable complexity. If the machine X is not provided then its functions, such as housekeeping functions, are provided by one, or some, or all of the other machines.
- each of the multiple machines M 1 , M2, Mn (other than any server machine X if present) has its memory locations schematically illustrated.
- the contents of the memory location X are the same for each of the machines and each machine is able to both read from, and write to, memory location X. For this reason, the boundary of memory location X is indicated with a double line.
- the server machine X of Fig. 2 it is convenient for the server machine X of Fig. 2, to maintain a table listing each memory location and the machines which are able to access each memory location in the table.
- a table is said to be a reachability table and is illustrated in Fig. 4.
- the first row in the table of Fig. 4 deals with memory location A which is only able to be accessed by machine Mn.
- the second row in the table of Fig. 4 deals with memory location B which is only able to be accessed by machine Ml.
- object D is only able to be accessed by machine M2
- object E is only able to be accessed by machine Mn.
- the class X is able to be accessed by all of the machines Ml, M2 and Mn.
- the single reachability table of Fig. 4 is preferably located in, and maintained by, the server machine X. However, it is also possible for the computer system to be operated without a server machine X in which case it is desirable for each machine to operate its own reachability table.
- Fig. 5 illustrates individual reachability tables for the individual machines in the circumstances corresponding to Fig. 4.
- the table for machine Ml has a row for class X and a row for object B.
- the table for machine M2 has a row for class X and a row for object D.
- the table for machine Mn has three rows, one for class X, and one for each of objects A and E.
- class Xn is said to point to object A.
- object An is bounded by double lines, and is reproduced in each of the other machines as object Al, A2, etc.
- an arrow points from each corresponding class Xl, X2, etc. to the corresponding referred object Al, A2, etc.
- the first row of the reachability table of Fig. 4 is amended as illustrated in Fig. 7 so as to indicate that object A is now able to be reached by the machines Ml, M2 and Mn.
- the server machine X of Fig. 2 uses the amended reachability table of Fig. 7 to ensure that the contents of object A, if amended by one machine, are transmitted via the network 53 to all the other machines.
- the reachability data enables structures, assets or resources (ie memory locations) to be divided into two categories or classes.
- the first category consists of those locations which are able to be accessed by all machines. It is necessary that write actions carried out in respect of such memory locations be distributed to all machines so that all corresponding memory locations have the same content (except for delays due to transmission of updating data).
- write actions to these memory locations need not be distributed to all the other machines, nor need there be corresponding memory locations on the other machines. As a consequence of this categorisation, a substantial volume of data is not required to be transmitted from one machine to the others and so the volume of traffic on the network 53 is substantially reduced.
- Machine Mn can determine that object A requires replication across the other machines by consulting the table entry for class X on machine Mn. In the situation illustrated, machine Mn makes a positive determination for replication by comparing the table entries for object A and class X. If the table entry for object A includes all machines in the table entry for class X, then machine Mn can correctly determine that object A does not need to be replicated on any other machines and, additionally, no table entries need to be added to, or updated on, other machines.
- machine Mn updates the table entry for object A to include the set of machines listed in the table entry for class X, and additionally instructs all machines listed in the new table entry for object A to update their local tables for object A with the set of machines listed in the new table entry for object A on machine Mn.
- machine Mn instructs those machines (ie machines Ml and M2) to add a local table entry for object A and create local replicas in memory of object A and associated references to class X.
- the abovementioned categorization and reachability table(s) also provide an advantage in the event of failure of one of the computers. This is that the entire system does not fail. Instead the system is able to recover.
- machine M2 say, fails (for example due to failure of its power supply, CPU, failure of its link to the network 53 or similar catastrophic failure).
- This failure is able to detected by a conventional detector attached to each of the application program running machines and reporting to machine X, for example.
- a detector is commercially available as a Simple Network Management Protocol (SNMP). This is essentially a small program which operates in the background and provides a specified output signal in the event that failure is detected.
- SNMP Simple Network Management Protocol
- Such a detector is able to sense failure in a number of ways, any one, or more, of which can be used simultaneously.
- machine X can interrogate each of the other machines Ml, .... Mn in turn requesting a reply. If no reply is forthcoming after a predetermined time, or after a small number of "reminders" are sent, also without reply, the non-responding machine is pronounced "dead”.
- each of the machines Ml, .... Mn can at regular intervals, say every 30 seconds, send a predetermined message to machine X (or to all other machines in the absence of a server) to say that all is well. In the absence of such a message the machine can be presumed “dead” or can be interrogated (and if it then fails to respond) is pronounced "dead”.
- each individual machine can be "multi-peered" which means there are two or more links between the machine and the communications network 53.
- An SNMP product which provides two options in this circumstance - namely wait for both/all links to fail before signalling machine failure, or signal machine failure if any one link fails, is the 12 Port Gigabit Managed Switch GSM 7212 sold under the trade marks NETGEAR and PROSAFE.
- Step 91 in Fig. 9 is triggered by the detection of machine failure (for machine M2 in this example).
- machine X examines each record (or row) in its reachability table in turn as indicated at step 92.
- step 93 For each record the question of step 93 is asked to determine if the record in question refers to failed machine M2. If it does, at step 94 the reference to failed machine M2 is removed from the row, and then step 95 is commenced. If it does not, step 95 is commenced immediately.
- step 95 any remaining record or row in the table is then subjected to step 93 until eventually all records have been interrogated and thus no further action is required as indicated at step 96.
- each of the machines is able to detect failure of any one of the other machines (for example, by means of all machines providing a predetermined message at regular intervals).
- each of the continuing machines Ml, M3 .... Mn carries out steps 101-105 of Fig. 10 which are equivalent to steps 91-95 of Fig. 9, but in respect of its local reachability table.
- the result is that each of the local reachability tables makes no reference to machine M2 (ie has the column containing the "2's" empty - or removed).
- Fig. 11 schematically illustrates the situation where machine M2 is dead. This might be due to a power failure or, as indicated in Fig. 11, due to a break in the link between machine M2 and the communications network 53.
- the changed reachability tables (single and multiple) are respectively illustrated in Figs. 12 and 13.
- M2 is not in any way special or restricted to the second machine. That is, it could have been any one of the machines which failed. Thus, if another machine should now fail, the same procedure is carried out. Therefore successive failure of each of a number of machines in turn can be tolerated, and without loss of memory since the contents of memory locations X2 and A2 are duplicated elsewhere whilst the content of memory location D will in due course be regenerated by the re-execution of the code previously executing on machine M2, being carried out by one of the continuing machines.
- the unmodified application code may either be replaced with the modified application code in whole, corresponding to the modifications being performed, or alternatively, the unmodified application code may be replaced in part or incrementally as the modifications are performed incrementally on the executing unmodified application code. Regardless of which such modification routes are used, the modifications subsequent to being performed execute in place of the unmodified application code.
- a global identifier is as a form of 'meta-name' or
- each DRT 71 when initially recording or creating the list of all, or some subset of all objects (e.g. memory locations or fields), for each such recorded object on each machine Ml, M2...Mn there is a name or identity which is common or similar on each of the machines Ml, M2...Mn.
- the local object corresponding to a given name or identity will or may vary over time since each machine may, and generally will, store memory values or contents at different memory locations according to its own internal processes.
- the table, or list, or other data structure in each of the DRTs will have, in general, different local memory locations corresponding to a single memory name or identity, but each global
- “memory name” or identity will have the same “memory value or content” stored in the different local memory locations. So for each global name there will be a family of corresponding independent local memory locations with one family member in each of the computers. Although the local memory name may differ, the asset, object, location etc has essentially the same content or value. So the family is coherent.
- tablette or “tabulation” as used herein is intended to embrace any list or organised data structure of whatever format and within which data can be stored and read out in an ordered fashion.
- memory locations include, for example, both fields and array types.
- the above description deals with fields and the changes required for array types are essentially the same mutatis mutandis.
- the present invention is equally applicable to similar programming languages (including procedural, declarative and object orientated languages) to JAVA including Microsoft.NET platform and architecture (Visual Basic, Visual C/C ++ , and C#) FORTRAN, 0/C 4+ , COBOL, BASIC etc.
- object and class used herein are derived from the JAVA environment and are intended to embrace similar terms derived from different environments such as dynamically linked libraries (DLL), or object code packages, or function unit or memory locations.
- DLL dynamically linked libraries
- any one or each of these various means may be implemented by computer program code statements or instructions (possibly including by a plurality of computer program code statements or instructions) that execute within computer logic circuits, processors, ASICs, logic or electronic circuit hardware, microprocessors, microcontrollers or other logic to modify the operation of such logic or circuits to accomplish the recited operation or function.
- any one or each of these various means may be implemented in firmware and in other embodiments such may be implemented in hardware.
- any one or each of these various means may be implemented by a combination of computer program software, firmware, and/or hardware. Any and each of the abovedescribed methods, procedures, and/or routines may advantageously be implemented as a computer program and/or computer program product stored on any tangible media or existing in electronic, signal, or digital form.
- Such computer program or computer program products comprising instructions separately and/or organized as modules, programs, subroutines, or in any other way for execution in processing logic such as in a processor or microprocessor of a computer, computing machine, or information appliance; the computer program or computer program products modifying the operation of the computer in which it executes or on a computer coupled with, connected to, or otherwise in signal communications with the computer on which the computer program or computer program product is present or executing.
- Such a computer program or computer program product modifies the operation and architectural structure of the computer, computing machine, and/or information appliance to alter the technical operation of the computer and realize the technical effects described herein.
- the invention may therefore include a computer program product comprising a set of program instructions stored in a storage medium or existing electronically in any form and operable to permit a plurality of computers to carry out any of the methods, procedures, routines, or the like as described herein including in any of the claims.
- the invention includes (but is not limited to) a plurality of computers, or a single computer adapted to interact with a plurality of computers, interconnected via a communication network or other communications link or path and each operable to substantially simultaneously or concurrently execute the same or a different portion of an application code written to operate on only a single computer on a corresponding different one of computers.
- the computers are programmed to carry out any of the methods, procedures, or routines described in the specification or set forth in any of the claims, on being loaded with a computer program product or upon subsequent instruction.
- the invention also includes within its scope a single computer arranged to co-operate with like, or substantially similar, computers to form a multiple computer system
- the method includes the further step of;
- the method includes the further step of: (v) maintaining a single the reachability table on a server computer not forming one of the multiple computers and connected thereto via the communications network.
- the method includes the further step of:
- the method includes the further step of;
- the memory locations include an asset, structure or resource.
- a computer program product comprising a set of program instructions stored in a storage medium and operable to permit a plurality of computers to carry out the above described method(s).
- a failure resistant multiple computer system in which a plurality of computers each has a corresponding independent local memory, each simultaneously operates a corresponding portion of an application program written to be executed only on a single computer, and each is connected via a communications network to permit updating of corresponding memory locations, the system including a reachability means to categorize memory locations of the local memories into a first category in which the local memory locations are replicated in selected ones, or all, of the computers and therefore require updating via the communications network with changes to corresponding memory locations of other computers, to maintain substantial memory coherence, and into a second category in which the local memory locations are present only in the local computer and therefore no updating is required, and wherein the system further includes a failure detection means connected to each the computer to detect failure of any one of the multiple computers, and a reachability modifier connected to the failure connection means and to the reachability means to modify the reachability means by modifying the first category to remove therefrom, if present, any reference by the failed computer whereby no attempt is made to update any first category memory locations of the failed computer
- the reachability means comprises a reachability table in which is maintained data regarding the memory location classification.
- a server computer is connected to the communications network, the server computer including a single reachability table.
- each of the multiple computers includes a corresponding reachability table.
- the failure detection means is selected from the group consisting of power supply failure detectors, communication link failure detectors, interrogation response failure detectors, and regular reporting failure detectors.
- the memory locations include an asset, structure or resource.
Abstract
Description
Claims
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US20030018930A1 (en) * | 2001-07-18 | 2003-01-23 | Oscar Mora | Peer-to-peer fault detection |
WO2005103926A1 (en) * | 2004-04-22 | 2005-11-03 | Waratek Pty Limited | Modified computer architecture with coordinated objects |
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US5394542A (en) * | 1992-03-30 | 1995-02-28 | International Business Machines Corporation | Clearing data objects used to maintain state information for shared data at a local complex when at least one message path to the local complex cannot be recovered |
US20030018930A1 (en) * | 2001-07-18 | 2003-01-23 | Oscar Mora | Peer-to-peer fault detection |
WO2005103926A1 (en) * | 2004-04-22 | 2005-11-03 | Waratek Pty Limited | Modified computer architecture with coordinated objects |
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