Home > Articles

  • Print
  • + Share This
This chapter is from the book

Feedback Loops: Evolving an Architecture

Feedback loops exist in all complex systems from biological systems such as the human body to electrical control systems. The simplest way to think about feedback loops is that the output of any process is fed back as an input into the same process. An extremely simplified example is an electrical system that is used to control the temperature of a room (see Figure 2.8).

Figure 2.8

Figure 2.8 Feedback loop example

In this simple example, a sensor provides a reading of the actual temperature, which allows the system to keep the actual temperature as close as possible to the desired temperature.

Let us consider software development as a process, with the output being a system that ideally meets all functional requirements and desired quality attributes. The key goal of agile and DevOps has been to achieve greater flow of change while increasing the number of feedback loops in this process and minimizing the time between change happening and feedback being received. The ability to automate development, deployment, and testing activities is a key to this success. In Continuous Architecture, we emphasize the importance of frequent and effective feedback loops. Feedback loops are the only way that we can respond to the increasing demand to deliver software solutions in a rapid manner while addressing all quality attribute requirements.

What is a feedback loop? In simple terms, a process has a feedback loop when the results of running the process are used to improve how the process itself works in the future.

The steps of implementing a continuous feedback loop can be summarized as follows and are shown in Figure 2.9:

Figure 2.9

Figure 2.9 Continuous architecture feedback loop

  1. Collect measurements: Metrics can be gathered from many sources, including fitness functions, deployment pipelines, production defects, testing results, or direct feedback from the users of the system. The key is to not start the process by implementing a complex dashboard that may take a significant amount of time and money to get up and running. The point is to collect a small number of meaningful measurements that are important for the architecture.

  2. Assess: Form a multidisciplinary team that includes developers, operations, architects, and testers. The goal of this team is to analyze the output of the feedback—for example, why a certain quality attribute is not being addressed.

  3. Schedule incrementally: Determine incremental changes to the architecture based on the analysis. These changes can be categorized as either defects or technical debt. Again, this step is a joint effort involving all the stakeholders.

  4. Implement changes: Go back to step 1 (collect measurement).

Feedback is essential for effective software delivery. Agile processes use some of the following tools to obtain feedback:

  • Pair programming

  • Unit tests

  • Continuous integration

  • Daily Scrums

  • Sprints

  • Demonstrations for product owners

From an architectural perspective, the most important feedback loop we are interested in is the ability to measure the impact of architectural decisions on the production environment. Additional measurements that will help improve the software system include the following:

  • Amount of technical debt being introduced/reduced over time or with each release

  • Number of architectural decisions being made and their impact on quality attributes

  • Adherence to existing guidelines or standards

  • Interface dependencies and coupling between components

This is not an exhaustive list, and our objective is not to develop a full set of measurements and associated feedback loops. Such an exercise would end up in a generic model that would be interesting but not useful outside of a specific context. We recommend that you think about what measurement and feedback loops you want to focus on that are important in your context. It is important to remember that a feedback loop measures some output and takes action to keep the measurement in some allowable range.

As architectural activities get closer to the development life cycle and are owned by the team rather than a separate group, it is important to think about how to integrate them as much as possible into the delivery life cycle. Linking architectural decisions and technical debt into the product backlogs, as discussed earlier, is one technique. Focus on measurement and automation of architectural decisions; quality attributes is another aspect that is worthwhile to investigate.

One way to think about architectural decisions is look at every decision as an assertion about a possible solution that needs to be tested and proved valid or rejected. The quicker we can validate the architectural decision, ideally by executing tests, the more efficient we become. This activity in its own is another feedback loop. Architectural decisions that are not validated quickly are at risk of causing challenges as the system evolves.

Fitness Functions

A key challenge for architects is an effective mechanism to provide feedback loops into the development process of how the architecture is evolving to address quality attributes. In Building Evolutionary Architectures,28 Ford, Parsons, and Kua introduced the concept of the fitness function to address this challenge. They define fitness functions as “an architectural fitness function provides an objective integrity assessment of some architectural characteristics”—where architectural characteristics are what we have defined as quality attributes of a system. These are like the architecturally significant quality attribute scenarios discussed earlier in the chapter.

In their book, they go into detail on how to define and automate fitness functions so that a continuous feedback loop regarding the architecture can be created.

The recommendation is to define the fitness functions as early as possible. Doing so enables the team to determine the quality attributes that are relevant to the software product. Building capabilities to automate and test the fitness functions also enables the team to test out different options for the architectural decisions it needs to make.

Fitness functions are inherently interlinked with the four essential activities we have discussed. They are a powerful tool that should be visible to all stakeholders involved in the software delivery life cycle.

Continuous Testing

As previously mentioned, testing and automation are key to implementing effective feedback loops. Continuous testing implements a shift-left approach, which uses automated processes to significantly improve the speed of testing. This approach integrates the quality assurance and development phases. It includes a set of automated testing activities, which can be combined with analytics and metrics to provide a clear, fact-based picture of the quality attributes of the software being delivered. This process is illustrated in Figure 2.10.

Figure 2.10

Figure 2.10 Sample automated testing process

Leveraging a continuous testing approach provides project teams with feedback loops for the quality attributes of the software that they are building. It also allows them to test earlier and with greater coverage by removing testing bottlenecks, such as access to shared testing environments and having to wait for the user interface to stabilize. Some of the benefits of continuous testing include the following:

  • Shifting performance testing activities to the “left” of the software development life cycle (SDLC) and integrating them into software development activities

  • Integrating the testing, development, and operations teams in each step of the SDLC

  • Automating quality attribute testing (e.g., for performance) as much as possible to continuously test key capabilities being delivered

  • Providing business partners with early and continuous feedback on the quality attributes of a system

  • Removing test environment availability bottlenecks so that those environments are continuously available

  • Actively and continuously managing quality attributes across the whole delivery pipeline

Some of the challenges of continuous testing include creation and maintenance of test data sets, setup and updating of environments, time taken to run the tests, and stability of results during development.

Continuous testing relies on extensive automation of the testing and deployment processes and on ensuring that every component of the software system can be tested as soon as it is developed. For example, the following tactics29 can be used by the TFX team for continuous performance testing:

  • Designing API-testable services and components. Services need to be fully tested independently of the other TFX software system components. The goal is to fully test each service as it is built, so that there are very few unpleasant surprises when the services are put together during the full system testing process. The key question for architects following the Continuous Architecture approach when creating a new service should be, “Can this service be easily and fully tested as a standalone unit?”

  • Architecting test data for continuous testing. Having a robust and fully automated test data management solution in place is a prerequisite for continuous testing. That solution needs to be properly architected as part of the Continuous Architecture approach. An effective test data management solution needs to include several key capabilities, summarized in Figure 2.11.

    Figure 2.11

    Figure 2.11 Test data management capabilities

  • Leveraging an interface-mocking approach when some of the TFX services have not been delivered yet. Using an interface-mocking tool, the TFX team can create a virtual service by analyzing its service interface definition (inbound/outbound messages) as well as its runtime behavior. Once a mock interface has been created, it can be deployed to test environments and used to test the TFX software system until the actual service becomes available.

  • + Share This
  • 🔖 Save To Your Account

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