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Threading allows a separate sequence of execution for each API call that can block. This can prevent the overall application from stalling while waiting for a resource. This has the benefit that none of the information about the state of the API call is lost while other activities take place.
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Timers allow a blocked call to be interrupted. A periodic timer allows the programmer to emulate threading. Interrupts typically destroy any information related to the state of a blocked API call or intensive calculation, so the programmer must keep track of this information separately.
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Redundancy relies on replicating information on more than one computer computing device so that the recovery delay is brief. This can be achieved using continuous backup to a live system that remains inactive until needed (synchronized backup).
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As an example, the TCP call blocks until a response becomes available from a remote server. This occurs every time you perform an action with a web browser. Intensive calculations cause lengthy delays with the same effect as a blocked API call.
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Backup requires an information-restore strategy to make backup information available on a replacement system. The restore process is usually time-consuming, and information will be unavailable until the restore process is complete.
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Initialized handler functions are paired with each signal when the software starts. This causes the handler function to startup when the corresponding signal arrives. This technique can be used with timers to emulate threading.
159:. The need to control software fault is one of the most rising challenges facing software industries today. Fault tolerance must be a key consideration in the early stage of
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To make your system more fault tolerant, you should measure 99th percentile latency and keep the remaining 1% (aka tail latencies) in check through self healing mechanisms.
663:
Eckhardt, D. E., "Fundamental
Differences in the Reliability of N-Modular Redundancy and N-Version Programming", The Journal of Systems and Software, 8, 1988, pp. 313–318.
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The only thing constant is change. This is certainly more true of software systems than almost any phenomenon, not all software change in the same way so software
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Ray
Giguette and Johnette Hassell, “Toward A Resourceful Method of Software Fault Tolerance”, ACM Southeast regional conference, April, 1999.
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In-line handler functions are associated with a call using specialized syntax. The most familiar is the following used with C++ and Java.
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This can also be achieved by replicating information as it is created on multiple identical systems, which can eliminate recovery delay.
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should be combined together to make the system more fault tolerant: retry, fallback, timeout, circuit breaker, and bulkhead pattern.
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193:(API) to access shared resources, like the keyboard, mouse, screen, disk drive, network, and printer. These can fail in two ways.
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in POSIX compliant systems, and these signals originate from API calls, from the operating system, and from other applications.
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A blocked call is a request for services from the operating system that halts the computer program until results are available.
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The termination signal is the only signal that cannot be handled. All other signals can be directed to a handler function.
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Backup maintains information in the event that hardware must be replaced. This can be done in one of two ways.
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The handler is a function that is performed on-demand when the application receives a signal. This is called
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Any signal that does not have handler code becomes a fault that causes premature application termination.
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Understanding
Distributed Systems: What every developer should know about large distributed applications
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methods are designed to overcome execution errors by modifying variable values to create an acceptable
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Software fault tolerance, by Chris Inacio at
Carnegie Mellon University (1998)
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Corrupted state will occur with timers. This is avoided with the following.
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There exist different mechanisms for software fault tolerance, among which:
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to continue its normal operation despite the presence of system or
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Hardware fault tolerance for software requires the following.
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has the ability to satisfy requirements despite failures.
46:. Unsourced material may be challenged and removed.
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395:Handler functions come in two broad varieties.
216:There are two methods used to handle blocking.
575:"Portable and Fault Tolerant Software Systems"
331:Un-threaded languages include the following.
187:Computer applications make a call using the
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231:Threaded languages include the following.
467:Automatic scheduled backup using software
106:Learn how and when to remove this message
580:. Massachusetts Institute of Technology.
638:
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44:adding citations to reliable sources
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470:Manual backup on a regular schedule
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541:OpenSAF - Service Availability API
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190:application programming interface
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518:Fault-tolerant computer system
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563:. Carnegie Mellon University.
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561:"Software Fault Tolerance"
522:Immunity-aware programming
55:"Software fault tolerance"
639:Vitillo, Roberto (2021).
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526:Logic built-in self-test
183:Operating system failure
119:Software fault tolerance
503:Built-in test equipment
131:Fault-tolerant software
178:Self-checking software
706:Software architecture
531:N-version programming
513:Fault-tolerant system
508:Fault-tolerant design
375:Fault are induced by
434:signal_handler_code;
356:Track software state
161:software development
40:improve this article
643:. Roberto Vitillo.
473:Information restore
536:Safety engineering
498:Built-in self-test
387:exception handling
175:N-version software
121:is the ability of
618:. Manning. 2024.
594:. Manning. 2022.
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96:February 2011
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51:Find sources:
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147:Introduction
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38:Please help
33:verification
30:
420:API_call();
399:Initialized
286:Perl 5.8.7+
695:Categories
547:References
458:Redundancy
340:Javascript
301:Smalltalk
136:Following
66:newspapers
360:Semaphore
315:Ballerina
272:Napier 88
492:See also
365:Blocking
269:Modula 3
129:faults.
127:hardware
402:In-line
377:signals
283:pSather
278:Presto
266:Magenta
255:Erlang
220:Threads
80:scholar
647:
622:
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453:Backup
371:Faults
312:Unicon
306:Tcl/Tk
292:Python
252:Eiffel
223:Timers
200:Faults
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578:(PDF)
428:catch
240:Afnix
87:JSTOR
73:books
645:ISBN
620:ISBN
596:ISBN
337:Bash
298:Ruby
263:Lisp
260:Java
249:CILK
59:news
414:try
343:SQL
289:PHP
243:C++
237:Ada
42:by
697::
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275:Oz
246:C#
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