Home > Articles

General-Purpose Methods and Practices

Professor and author Diomidis Spinellis outlines 13 methods that can help you debug diverse software and systems failures including automation, specialized monitoring, housecleaning, and more.

This chapter is from the book

The way you debug a failure often depends on the underlying technology and development platform. Yet, there are methods that you can use on a wide variety of cases.

Item 9: Set Yourself Up for Debugging Success

Software is often extremely complex. The movement of a mechanical watch comprises just over a hundred parts; the wiring of your entire home can have a few times as many simple components. Compare that with typical software systems, which easily consist of tens of thousands of complex statements. At the high end, consider the 9 million lines of code in the Linux kernel against the 4 million physical components in an A380 airliner. Your mind needs all the help it can get to conquer this complexity.

First you need to believe that the problem can be found and fixed. Your state of mind affects your debugging performance; this is what the experts call a match between perceived challenges and skills. If you don’t believe you can conquer the problem, your mind will wander around or give up. In such a case, you may also end up harming the code by patching the symptom, instead of the problem. Here is what you should keep in mind.

If a problem is reproducible, then make no mistake, you can fix it! (Often by following the advice in this book.) If it’s not reproducible, there are ways to make it so. In debugging you typically have two important allies: access to all the data you may require and powerful computers to process it. You can examine the problem manifestation, logs, source code, even machine instructions. You can also add detailed log statements (or at least monitoring probes) in any place of the software stack you want, and then use tools or short scripts to sift through volumes of data to locate the culprit. It is this combined ability to cast a wide net and dive arbitrarily deep when needed that makes debugging possible and, also, a uniquely satisfying experience.

To be effective in debugging you also need to set aside ample time. Debugging is a very demanding activity, more complex than programming, because it requires you to maintain in your brain both the program’s logic and its underlying effects—often at a low level. It also requires you to set up your environment, breakpoints, logging, windows, and test cases exactly right if the problem is to be reproduced in a productive fashion. Don’t squander all your invested time by stopping before you’ve squashed the bug, or at least until you’ve understood precisely what you need to do.

The complexity of debugging also requires you to work without distractions. Your brain needs time to enter a state called flow in which you become fully immersed and involved in an activity. According to Mihály Csíkszentmihályi, who termed it, in the state of flow you align your emotions with the task you perform. Flow can boost your persistence and performance through a sense of accomplishment. These are critical success factors for dealing with the immense difficulty of debugging complex systems. Distractions, such as a popup message, a phone call, a running chat, rolling social network updates, or a colleague asking for help will drag you out of the flow state, depriving you of its benefits. Avoid them! Quit unneeded applications, enable your phone’s silent mode, and hang a do not disturb sign on your monitor (or your office door, should you be so lucky as to have one).

Another helpful strategy is to sleep on a difficult problem. Researchers have found that during sleep our neurons make connections that generalize across seemingly unrelated paths. This can be a great help during debugging. You can often escape from what appears to be a dead end by trying an outside-the-box debugging strategy. Sleep is exactly the process needed to make this new connection. However, for this to work, you need to do it properly. Work hard on the problem before going to sleep to give your mind all the necessary data needed in order to find a novel solution to the problem. Giving up and going for a beer and then to bed at the first difficulty won’t help you a lot. Also, get plenty of sleep so that on the next day the conscious part of your brain can work effectively with the recommendations of its subconscious sibling.

Nobody said that debugging is easy, so to be effective in it you must persist. At the lowest level computers are deterministic, so they allow you to dig down until you isolate the error. At higher levels, nondeterminism (apparent randomness) is introduced to increase expressiveness and efficiency (think of threads). For nondeterministic errors, you can use the fact that computers are fast and programmable to run zillions of cases until you isolate the error. Therefore, debugging dead ends are mostly due to a lack of persistence: a missing test case, an ignored log file, or an unexplored angle of attack.

Finally, as an effective debug engineer, you must continuously invest in your environment, tools, and knowledge. Only in this way will you be able to keep your edge over the ever-increasing complexity of the technology stack you’re working on. In retrospect, my most common debugging mistake is insufficient investment in setting up my debugging infrastructure. This may involve failing to do any of the following:

  • Prepare a robust minimal test case (see Item 10: “Enable the Efficient Reproduction of the Problem”)

  • Automate the bug’s reproduction

  • Script a log file’s analysis

  • Learn how an API or language feature really works

Once I summon the energy to invest in what’s needed, my debugging productivity receives a large boost. From that point onward, I can often pinpoint the bug in minutes.

Things to Remember

  • Believe that the problem can be traced and fixed.

  • Set aside sufficient time for your debugging task.

  • Arrange to work without distractions.

  • Sleep on a difficult problem.

  • Don’t give up.

  • Invest in your environment, tools, and knowledge.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020