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Availability reading list

This page contains references to paper and books about building highly available systems.

The focus here is on practical information for building systems. It doesn't cover theoretical topics such as distributed algorithms, nor does it cover distributed databases, so don't expect to see the Paxos or Dynamo papers here.

I also maintain a systems and failure reading list, which covers systems and failure at a higher-level.

Mark McGranaghan maintains a services engineering reading list with some significant overlap.

Why Do Computers Stop and What Can Be Done About It?

Jim Gray, Tandem Computers, Technical Report 85.7 June 1985, PN87614

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Describes strategies for achieving good reliability and availability in the presence of faults.

Notable quotes:

  • System administration, which includes operator actions, system configuration, and system maintenace was the main source of failures -- 42%. p8

  • The top priority for improving system availability is to reduce administrative mistakes by making self-configured systems with minimal maintenance and minimal operator interaction. p12

  • A way to improve availability is to install proven hardware and software, and then leave it alone. p13

  • If you consider an industrial sofwtare system which has gone through structured design, design reviews, quality assurance, alpha test, beta test, and months or years of production, then most of the "hard" software bugs, ones that always fail on retry, are gone. The residual bugs are rare cases, typically related to strange hardware conditions (rare or transient device fault), limit conditions (out of storage, counter overflow, lost interrupt, etc,, or race conditions (forgetting to request a semaphore). p17-18 (emphasis mine).

  • Dealing with system configuration, operations, and maintenance remains an unsolved problem. p32

Making Reliable Distributed Systems In The Presence Of Software Errors

Joe Armstrong, PhD Dissertation, Royal Institute of Technology, Stockholm, Sweden Decmeber, 2003

pdf

Describes both Erlang and principles for using it to build reliable systems.

Release It!: Design and Deploy Production-Ready Software

Michael Nygard, Pragmatic Bookshelf, April, 2007

On Designing and Deploying Internet-Scale Services

James Hamilton, Proceedings of the 21st Large Installation System Administration Conference (LISA '07), November 11-16, 2007

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Even though this paper was written before cloud computing became widely adopted (the word "cloud" does not appear once), it feels as if it could have been written today. The only other indications of it being a little are a discussion of hardware, and a proposed deployment cycle of three months.

Web Operations: Keeping the Data on Time

John Allspaw & Jesse Robins, eds. O'Reilly Media, July 2010

A collection of essays.

Simple Testing Can Prevent Most Critical Failures: An Analysis of Production Failures in Distributed Data-Intensive Systems

Ding Yuan, Yu Luo, Xin Zhuang, Guilherme Renna Rodrigues, Xu Zhao, Yongle Zhang, Pranay U. Jain, and Michael Stumm Proceedings of the 11th USENIX Symposium on Operating Systems Design and Implementation (OSDI '14) Oct. 2014.

pdf

An empirical study that explores the reasons why distributed systems fail in production by analyzing the root causes of around 200 confirmed system failures. You can read my review of this paper at It Will Never Work In Theory.

Notes on Distributed Systems for Youngbloods

Jeff Hodges, Something Similar blog, January 14, 2013

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General advice from a Twitter engineer about the challenges of developing and debugging distributed systems. He also gave an excellent talk at RICON West 2013 entitled Practicalities of Productionizing Distributed Systems that is well worth your time.

Fault Injection in Production: Making the case for resiliency testing

John Allspaw, ACM Queue, Volume 10, issue 8, August 24, 2012

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Allspaw argues that you must observe the system tolerating failures in production in order to have confidence in the system's resiliency. He discusses fault injection in the context of GameDay exercises at Etsy. Although the essay does not mention Chaos Monkey, it provides a strong motivation for tools similar to Chaos Monkey.

The Error Model

Joe Duffy, Joe Duffy's Blog, February 7, 2016

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Duffy talks about the error model that they used in the Midori language. Interesting content about how to handle errors in code.

A New Accident Model for Engineering Safer Systems

Nancy Leveson, Safety Science, Vol. 42, No. 4, April 2004

pdf

Leveson proposes a model of accidents called STAMP: systems-theoretic accident model and processes. STAMP focuses on identifying safety constraints that were violated and determining why the controls were inadequate.

While this paper is focused on software safety, it is still relevant for availabilty, since an outage can be viewed as an accident.

Why do Internet services fail, and what can be done about it?

David Oppenheimer, Archana Ganapathi, and David A. Patterson, 4th Usenix Symposium on Internet Technologies and Systems (USITS ‘03), 2003.

pdf

Oppenheimer et al. did a case study of three Internet services to determine common causes of failures. Findings incldue:

  • Front-end machines are a significant source of failure, largely due to operator configuration errors.
  • Operator error is the leading cause of service failure in two of the three services.
  • Operator error was generally due to misconfiguration rather than procedural errors.
  • Operator error generally arose when operators were making changes to the system.
  • Networking problems were a significant cause of failure.

Networking problems are difficult to mask because:

  • networks are often a single point of failure
  • network failure modes tend to be complex

Proposed techniques for avoiding or mitigating failures, in decreasing order of impact:

  • Online correctness testing
  • Thoroughly expose and monitor for software and hardware failures
  • Redundancy
  • Config. checking
  • Online fault/load injection
  • Component isolation
  • Pre-deployment fault/load injection
  • Proactive restart
  • Pre-deployment correctness testing

I want to believe: some myths about the management of industry safety

Denis Besnard, Erik Hollnagel, Cognition, Technology and Work, Springer Verlag, 2014, 16 (1)

pdf

The authors discuss five myths about safety and propose revisions.

Human error

Myth: Human error is the largest single cause of accidents and incidents

Revision: 'Human error' is an artifact of a traditional engineering view, which treats humans as if they were (falliable) machines and overlooks how performance adjustments are used to match activities to the working conditions.

Procedure compliance

Myth: Systems will be safe if people comply with the proedures they have been given.

Revision: Actual working situations usually differ from what the procedures assume and strict compliance may be detrimental to both safety and efficinecy. Procedures should be used carefully and intelligently.

Protection and safety

Myth: Safety can be improved by barriers and protection; increasing the layers of protection leads to higher safety.

Revision: Technology is not value netural. Additional prteoction changes behaviour so that the intended safety improvements might not be obtained.

Mishaps and root causes

Myth: Root cause analysis can identify why mishaps happen in complex socio-technical systems.

Revision: Human performance cannot be described as if it was bimodal. In socio-technical systems, things that go wrong happen in the same way as things that go right.

Accident investigation

Myth: Accident investigation is the logical and rational identification of causes based on facts.

Revision: Accident investigation is a social process, where causes aer constructed rather than found.

Safety first

Myth: Safety always has the highest priority and will never be compromised.

Revision: Safety will be as high as affordable — from a financial and ethical perspective.

Hints for Computer System Design

Butler W. Lampson, ACM SIGOPS Operating Systems Review, Volume 17 Issue 5, October 1983

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General advice on building system, based on the author's experiences building several systems at Xerox PARC. It's all still relevant, but here are some quotes I found particularly notable:

Defining interfaces is the most important part of system design.

Interface design must satisfy three conflicting requirements:

  1. An interface should be simple
  2. An interface should be complete
  3. An interface sould admit a sufficiently small and fast implementation

Do one thing at a time, and do it well.

Don't generalize; generalizations are generally wrong.

Neither abstraction nor simplicity is a substitute for getting it right.

The purpose of abstractions is to conceal undesirable properties; desirable ones should not be hidden.

Use procedure arguments to provide flexibility in an interface (support functions as arguments).

Keep basic interfaces stable.

Even when an implementation is successful, it pays to revisit old decisions as the system evolves; in particular, optimizations for particular properties of the load or the environment (memory size, for example) often come to be far from optimal.

Use a good idea again instead of generalizing it.

Handle normal and worst cases separately as a rule.

In allocating resources, strive to avoid disaster rather than to attain an optimum.

We learned that the only important thing is to avoid thrashing.

The most successful schemes give a fixed share of the cycles to each job and don't allocate more than 100%.

Shed load to control demand, rather than allowing the system to become overloaded

End-to-end: Error recovery at the application level is absolutely necessary for a reliable system, and any other error detection or recovery is not logically necessary but is strictly for performance.

Two problems with the end-to-end strategy:

  1. It requires a cheap test for success
  2. It can lead to working sytems with severe performance defects that may not appear until the system behcomes operational and is placed under heavy load.

Log updates to record the truth about the state of an object.