Click here to close now.

Welcome!

MICROSERVICES Authors: Liz McMillan, Elizabeth White, Michael Kanasoot, XebiaLabs Blog, Carmen Gonzalez

Related Topics: Java, MICROSERVICES, Virtualization, AJAX & REA

Java: Article

Why Response Times Are Often Measured Incorrectly

Response time measurements and how to interpret them

Response times are in many – if not in most – cases the basis for performance analysis. When they are within expected boundaries everything is ok. When they get to high we start optimizing our applications.

So response times play a central role in performance monitoring and analysis. In virtualized and cloud environments they are the most accurate performance metric you can get. Very often, however, people measure and interpret response times the wrong way. This is more than reason enough to discuss the topic of response time measurements and how to interpret them. Therefore I will discuss typical measurement approaches, the related misunderstandings and how to improve measurement approaches.

Averaging information away
When measuring response times, we cannot look at each and every single measurement. Even in very small production systems the number of transactions is unmanageable. Therefore measurements are aggregated for a certain timeframe. Depending on the monitoring configuration this might be seconds, minutes or even hours.

While this aggregation helps us to easily understand response times in large volume systems, it also means that we are losing information. The most common approach to measurement aggregation is using averages. This means the collected measurements are averaged and we are working with the average instead of the real values.

The problem with averages is that they in many cases do not reflect what is happening in the real world. There are two main reasons why working with averages leads to wrong or misleading results.

In the case of measurements that are highly volatile in their value, the average is not representative for actually measured response times. If our measurements range from 1 to 4 seconds the average might be around 2 seconds which certainly does not represent what many of our users perceive.

So averages only provide little insight into real world performance. Instead of working with averages you should use percentiles. If you talk to people who have been working in the performance space for some time, they will tell you that the only reliable metrics to work with are percentiles. In contrast to averages, percentiles define how many users perceived response times slower than a certain threshold. If the 50th percentile for example is 2.5 seconds this means that the response times for 50 percent of your users were less or equal to 2.5 seconds. As you can see this approach is by far closer to reality than using averages

Percentiles and Average of a Measurement Series

Percentiles and Average of a Measurement Series

The only potential downside with percentiles is that they require more data to be stored than averages do. While average calculation only requires the sum and count of all measurements, percentiles require a whole range of measurement values as their calculation is more complex. This is also the reason why not all performance management tools support them.

Putting all in a box
Another important question when aggregating data is which data you use as the basis of your aggregations. If you mix together data for different transaction types like the start page, a search and a credit card validation the results will only be of little value as the base data is kind of apple and oranges. So in addition to ensuring that you are working with percentiles it is necessary to also split transaction types properly so that the data that is the basis for your calculations fits together

The concept of splitting transactions by their business function is often referred to as business transaction management. While the field of BTM is wide, the basic idea is to distinguish transactions in an application by logical parameters like what they do or where they come from. An example would be a “put into cart” transaction or the requests of a certain user.

Only a combination of both approaches ensures that the response times you measure are a solid basis for performance analysis.

Far from the real world
Another point to consider with response times is where they are measured. Most people measure response times at the server-side and implicitly assume that they represent what real users see. While server-side response times are down to 500 milliseconds and everyone thinks everything is fine, users might experience response times of several seconds.

The reason is that server-side response times don’t take a lot of factors influencing end-user response times into account. First of all server-side measurements neglect network transfer time to the end users. This easily adds half a second or more to your response times.

Server vs. Client Response Time

Server vs. Client Response Time

At the same time server-side response times often only measure the initial document sent to the user. All images, JavaScript and CSS files that are required to render a paper properly are not included in this calculation at all. Experts like Steve Souders even say that only 10 percent of the overall response time is influenced by the server side. Even if we consider this an extreme scenario it is obvious that basing performance management solely on server-side metrics does not provide a solid basis for understanding end-user performance.

The situation gets even worse with JavaScript-heavy Web 2.0 applications where a great portion of the application logic is executed within the browser. In this case server-side metrics cannot be taken as representative for end-user performance at all.

Not measuring what you want to know
A common approach to solve this problem is to use synthetic transaction monitoring. This approach often claims to be “close to the end-user”. Commercial providers offer a huge number of locations around the world from where you can test the performance of pre-defined transactions. While this provides better insight into what the perceived performance of end-users is, it is not the full truth.

The most important thing to understand is how these measurements are collected. There are two approaches to collect this data: via emulators or real browsers. From my very personal perspective any approach that does not use real browsers should be avoided as real browsers are also what your users use. They are the only way to get accurate measurements.

The issue with using synthetic transactions for performance measurement is that it is not about real users. Your synthetic transactions might run pretty fast, but that guy with a slow internet connection who just wants to book a $5,000 holiday (ok, a rare case) still sees 10 second response times. Is it the fault of your application? No. Do you care? Yes, because this is your business. Additionally synthetic transaction monitoring cannot monitor all of your transactions. You cannot really book a holiday every couple of minutes, so you at the end only get a portion of your transactions covered by your monitoring.

This does not mean that there is no value in using synthetic transactions. They are great to be informed about availability or network problems that might affect your users, but they do not represent what your users actually see. As a consequence, they do not serve as a solid basis for performance improvements

Measuring at the End-User Level
The only way to get real user performance metrics is to measure from within the users’ browser. There are two approaches to do this. You can user a tool like the free dynaTrace Ajax Edition which uses a browser plug-in to collect performance data or inject JavaScript code to get performance metrics. The W3C now also has a number of standardization activities for browser performance APIs. The Navigation Timing Specification is already supported by recent browsers and the Resource Timing Specification. Open-source implementations like Boomerang provide a convenient way to access performance data within the browser. Products like dynaTrace UEM go further by providing a highly scalable backend and full integration into your server-side systems.

The main idea is to inject custom JavaScript code which captures timing information like the beginning of a request, DOM ready and fully loaded. While these events are sufficient for “classic” web applications they are not enough for Web 2.0 applications which execute a lot of client-side code. In this case the JavaScript code has to be instrumented as well.

Is it enough to measure on the client-side?
The question now is whether it is enough to measure performance from the end-user perspective. If we know how our web application performs for each user we have enough information to see whether an application is slow or fast. If we then combine this data with information like geo location, browser and connection speed we know for which users a problem exists. So from a pure monitoring perspective this is enough.

In case of problems, however, we want to go beyond monitoring. Monitoring only tells us that we have a problem but does not help in finding the cause of the problem. Especially when we measure end-user performance our information is less rich compared to development-centric approaches. We could still use a development-focused tool like dynaTrace Ajax Edition for production troubleshooting. This however requires installing custom software on an end user’s machine. While this might be an option for SaaS environments this is not the case in a typical eCommerce scenario.

The only way to gain this level of insight for diagnostics purposes is to collect information from the browser as well as the server side to have a holistic view on application performance. As discussed using averaged metrics is not enough in this case. Using aggregated data does not provide the insight we need. So instead of aggregated information we require the possibility to identify and relate the requests of a user’s browser to server-side requests.

Client/Server Drill Down of Pages and Actions

Client/Server Drill Down of Pages and Actions

The figure below shows an architecture based (and abstracted) from dynaTrace UEM which provides this functionality. It shows the combination of browser and server-side data capturing on a transactional basis and a centralized performance repository for analysis.

 

Architecture for End-To-End User Experience Monitoring

Architecture for End-To-End User Experience Monitoring

Conclusion
There are many ways where and how to measure response times. Depending on what we want to achieve each one of them provides more or less accurate data. For the analysis of server-side problems measuring at the server-side is enough. We however have to be aware that this does not reflect the response times of our end users. It is a purely technical metric for optimizing the way we create content and service requests. The prerequisite to meaningful measurements is that we separate different transaction types properly.

Measurements from anything but the end-user’s perspective can only be used to optimize your technical infrastructure and only indirectly the performance of end users. Only performance measurements in the browser enable you to understand and optimize user-perceived performance.

Related reading:

  1. Antivirus Add-On for IE to cause 5 times slower page load times The dynaTrace AJAX Community has been really active lately –...
  2. Troubleshooting response time problems – why you cannot trust your system metrics // Production Monitoring is about ensuring the stability and health...
  3. Why you can’t compare cross browser execution times of Selenium Tests // I am currently working on a blog where I...
  4. Application Performance Monitoring in production – A Step-by-Step Guide – Part 1 // Setting up Application Performance Monitoring is a big task,...
  5. Week 9 – How to Measure Application Performance Measurement is the most central concept in any performance-related activity....

More Stories By Alois Reitbauer

Alois Reitbauer works as a Technology Strategist for dynaTrace Software where he is leading the Methods and Technology team. As part of the R&D team he influences the dynaTrace product strategy and works closely with key customers in implementing performance management solution for the entire lifecylce. Alois has 10 years experience as architect and developer in the Java and .NET space. He is a frequent speaker at technology conferences on performance and architecture related topics and regularly publishes articles blogs on blog.dynatrace.com

@MicroservicesExpo Stories
SYS-CON Events announced today that Cisco, the worldwide leader in IT that transforms how people connect, communicate and collaborate, has been named “Gold Sponsor” of SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Cisco makes amazing things happen by connecting the unconnected. Cisco has shaped the future of the Internet by becoming the worldwide leader in transforming how people connect, communicate and collaborat...
Hosted PaaS providers have given independent developers and startups huge advantages in efficiency and reduced time-to-market over their more process-bound counterparts in enterprises. Software frameworks are now available that allow enterprise IT departments to provide these same advantages for developers in their own organization. In his workshop session at DevOps Summit, Troy Topnik, ActiveState’s Technical Product Manager, will show how on-prem or cloud-hosted Private PaaS can enable organ...
SYS-CON Events announced today that MangoApps will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY., and the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. MangoApps provides private all-in-one social intranets allowing workers to securely collaborate from anywhere in the world and from any device. Social, mobile, and eas...
SYS-CON Events announced today that Solgenia will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY, and the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Solgenia is the global market leader in Cloud Collaboration and Cloud Infrastructure software solutions. Designed to “Bridge the Gap” between Personal and Professional S...
When it comes to microservices there are myths and uncertainty about the journey ahead. Deploying a “Hello World” app on Docker is a long way from making microservices work in real enterprises with large applications, complex environments and existing organizational structures. February 19, 2015 10:00am PT / 1:00pm ET → 45 Minutes Join our four experts: Special host Gene Kim, Gary Gruver, Randy Shoup and XebiaLabs’ Andrew Phillips as they explore the realities of microservices in today’s IT worl...
OmniTI has expanded its services to help customers automate their processes to deliver high quality applications to market faster. Consistent with its focus on IT agility and quality, OmniTI operates under DevOps principles, exploring the flow of value through the IT delivery process, identifying opportunities to eliminate waste, realign misaligned incentives, and open bottlenecks. OmniTI takes a unique, value-centric approach by plotting each opportunity in an effort-payoff quadrant, then work...
Cloud computing is changing the way we look at IT costs, according to industry experts on a recent Cloud Luminary Fireside Chat panel discussion. Enterprise IT, traditionally viewed as a cost center, now plays a central role in the delivery of software-driven goods and services. Therefore, companies need to understand their cloud utilization and resulting costs in order to ensure profitability on their business offerings. Led by Bernard Golden, this fireside chat offers valuable insights on ho...
The world's leading Cloud event, Cloud Expo has launched Microservices Journal on the SYS-CON.com portal, featuring over 19,000 original articles, news stories, features, and blog entries. DevOps Journal is focused on this critical enterprise IT topic in the world of cloud computing. Microservices Journal offers top articles, news stories, and blog posts from the world's well-known experts and guarantees better exposure for its authors than any other publication. Follow new article posts on T...
Modern Systems announced completion of a successful project with its new Rapid Program Modernization (eavRPMa"c) software. The eavRPMa"c technology architecturally transforms legacy applications, enabling faster feature development and reducing time-to-market for critical software updates. Working with Modern Systems, the University of California at Santa Barbara (UCSB) leveraged eavRPMa"c to transform its Student Information System from Software AG's Natural syntax to a modern application lev...
For those of us that have been practicing SOA for over a decade, it's surprising that there's so much interest in microservices. In fairness microservices don't look like the vendor play that was early SOA in the early noughties. But experienced SOA practitioners everywhere will be wondering if microservices is actually a good thing. You see microservices is basically an SOA pattern that inherits all the well-known SOA principles and adds characteristics that address the use of SOA for distribut...
Microservice architectures are the new hotness, even though they aren't really all that different (in principle) from the paradigm described by SOA (which is dead, or not dead, depending on whom you ask). One of the things this decompositional approach to application architecture does is encourage developers and operations (some might even say DevOps) to re-evaluate scaling strategies. In particular, the notion is forwarded that an application should be built to scale and then infrastructure sho...
SYS-CON Events announced today the IoT Bootcamp – Jumpstart Your IoT Strategy, being held June 9–10, 2015, in conjunction with 16th Cloud Expo and Internet of @ThingsExpo at the Javits Center in New York City. This is your chance to jumpstart your IoT strategy. Combined with real-world scenarios and use cases, the IoT Bootcamp is not just based on presentations but includes hands-on demos and walkthroughs. We will introduce you to a variety of Do-It-Yourself IoT platforms including Arduino, Ras...
Microservices are the result of decomposing applications. That may sound a lot like SOA, but SOA was based on an object-oriented (noun) premise; that is, services were built around an object - like a customer - with all the necessary operations (functions) that go along with it. SOA was also founded on a variety of standards (most of them coming out of OASIS) like SOAP, WSDL, XML and UDDI. Microservices have no standards (at least none deriving from a standards body or organization) and can be b...
Our guest on the podcast this week is Jason Bloomberg, President at Intellyx. When we build services we want them to be lightweight, stateless and scalable while doing one thing really well. In today's cloud world, we're revisiting what to takes to make a good service in the first place. Listen in to learn why following "the book" doesn't necessarily mean that you're solving key business problems.
Right off the bat, Newman advises that we should "think of microservices as a specific approach for SOA in the same way that XP or Scrum are specific approaches for Agile Software development". These analogies are very interesting because my expectation was that microservices is a pattern. So I might infer that microservices is a set of process techniques as opposed to an architectural approach. Yet in the book, Newman clearly includes some elements of concept model and architecture as well as p...
Microservices, for the uninitiated, are essentially the decomposition of applications into multiple services. This decomposition is often based on functional lines, with related functions being grouped together into a service. While this may sound a like SOA, it really isn't, especially given that SOA was an object-centered methodology that focused on creating services around "nouns" like customer and product. Microservices, while certainly capable of being noun-based, are just as likely to be v...
SYS-CON Events announced today the DevOps Foundation Certification Course, being held June ?, 2015, in conjunction with DevOps Summit and 16th Cloud Expo at the Javits Center in New York City, NY. This sixteen (16) hour course provides an introduction to DevOps – the cultural and professional movement that stresses communication, collaboration, integration and automation in order to improve the flow of work between software developers and IT operations professionals. Improved workflows will res...
Even though it’s now Microservices Journal, long-time fans of SOA World Magazine can take comfort in the fact that the URL – soa.sys-con.com – remains unchanged. And that’s no mistake, as microservices are really nothing more than a new and improved take on the Service-Oriented Architecture (SOA) best practices we struggled to hammer out over the last decade. Skeptics, however, might say that this change is nothing more than an exercise in buzzword-hopping. SOA is passé, and now that people are ...
An explosive combination of technology trends will be where ‘microservices’ and the IoT Internet of Things intersect, a concept we can describe by comparing it with a previous theme, the ‘X Internet.' The idea of using small self-contained application components has been popular since XML Web services began and a distributed computing future of smart fridges and kettles was imagined long back in the early Internet years.
SOA Software has changed its name to Akana. With roots in Web Services and SOA Governance, Akana has established itself as a leader in API Management and is expanding into cloud integration as an alternative to the traditional heavyweight enterprise service bus (ESB). The company recently announced that it achieved more than 90% year-over-year growth. As Akana, the company now addresses the evolution and diversification of SOA, unifying security, management, and DevOps across SOA, APIs, microser...