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Method-and-mechanism-for-guaranteeing-timeliness-of-programs

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Method and mechanism for guaranteeing timeliness of programs

Details

Inventors: Matena, Vladimir;
Assignee: Sun Microsystems, Inc. (Mountain View, CA)
Primary Examiner: Chung; Phung
Assistant Examiner: Baderman; Scott T.
Attorney, Agent or Firm: Blakely Sokoloff Taylor & Zafman

In order to prevent data corruption and inconsistency caused by incorrect assumption regarding a presumably failed node and/or program, a fail-fast timer mechanism enforces deadlines, i.e. enforces timeliness in programs. For example, given a program which needs to ensure a given code segment is executed within a specified deadline, the program arms a fail-fast timer before executing the code segment. After completing the execution of the code segment, the program disarms the fail-fast timer. If the program executes too slowly and the fail-fast timer expires before the fail-fast timer has been disarmed, the entire node is forced to stop very quickly (i.e. the node fails fast). The fail-fast timer of the present invention also triggers if the program exits before disarming a previously armed timeout.

DETAILED DESCRIPTION A method and an apparatus are disclosed for preventing data corruption in a distributed system caused by an incorrect assumption by a node or a program in the distributed system that another node or a program has crashed.
If a given node or program incorrectly assumes that another node or program has crashed, both nodes or programs (i.
e.
the node/program which has presumably "crashed" and the node/program which takes over for the presumably "crashed" node/program) may transmit data of their own without knowledge that the other is also simultaneously transmitting data.
Such data from the two nodes or programs may be inconsistent which may lead to the corruption of data.
In order to prevent data corruption and inconsistency caused by an incorrect assumption regarding a presumably failed node and/or program, a fail-fast timer mechanism of the present invention enforces program execution deadlines, i.
e.
a program must complete execution of an operation within a pre-determined time or the program is forced to fail.
For example, given a program which needs to ensure a given code segment is executed within a specified deadline, the program arms a fail-fast timer before executing the code segment.
After completing the execution of the code segment, the program may disarm the fail-fast timer.
If the program executes too slowly and the fail-fast timer expires before the fail-fast timer has been disarmed, the entire node is forced to stop very quickly (i.
e.
the node fails fast).
The fail-fast timer of the present invention also triggers if the program exits before disarming a previously armed timeout.
By ensuring that a given node or program fails fast in a specified period of time, the present invention guarantees that only one node or program will respond to requests for data by another program.
A reliable fail-fast timer of the present invention may be implemented by an operating system (OS) kernel and some hardware support.
There are many advantages of the present invention, for example, the present invention's fail-fast timer mechanism can be implemented using off the shelf hardware and operating system

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