Click here to close now.

Welcome!

Java IoT Authors: Yeshim Deniz, Elizabeth White, Michael Kanasoot, Ed Featherston, Pat Romanski

Related Topics: @MicroservicesE Blog, Java IoT, Industrial IoT, Microsoft Cloud, IoT User Interface, Agile Computing

@MicroservicesE Blog: Article

Evaluating the Performance of SPDY-Enabled Web Servers

With all the advantages of SPDY, you may be wondering if there is a price to pay on the server side

As you may already know, SPDY (pronounced "SPeeDY") is a new networking protocol introduced by Google and designed to reduce the web latency associated with HTTP. With SPDY, web pages load up to 64 percent faster than HTTP alone, according to Google. It accomplishes this by adding a session layer between HTTP and SSL that supports concurrent, interleaved streams over a single TCP connection. The initial draft of HTTP/2.0, the future of the web, is based on SPDY, which is a welcome step forward considering that HTTP/1.0 was released in 1996. SPDY holds great potential for mobile devices, for which latency is more of an issue, and the market is catching on. As evidence of this, Microsoft recently announced the next version of Internet Explorer will support the new protocol.

Today, SPDY can be deployed on Apache by installing a single module (mod-spdy, the Apache SPDY module). No changes to website content are required. SPDY is now enabled by default on many of the latest modern browsers, including Chrome, Firefox, Opera, and Android Browser. (You can check your own browser's support by visiting isspdyenabled.com.)

Simply by deploying the SPDY module on your Apache server, you can provide a large percentage of your users with better response times. More important, the response times of a website are correlated with the site's conversion rate and bounce rate - so SPDY can have a significant positive impact on your business!

With all the advantages of SPDY, you may be wondering if there is a price to pay on the server side. Moving from HTTP to SPDY adds encryption and compression overhead, which clearly requires more resources. It does, however, use fewer TCP connections. It wasn't immediately clear to me if all these changes in aggregate would cause noticeable drawbacks on the server.

To get to the bottom of this question, I thought it would be interesting to get some real-world performance metrics on SPDY, in particular its effect on the server side. To obtain this information, I used the new SPDY support in NeoLoad to run load tests of SPDY and compare its performance against HTTP and HTTPS.

Test Configuration Details
My approach was to test a server with a fairly typical configuration - not one that is finely tuned for a specific purpose. This setup provides a basis for comparing HTTP, HTTPS and SPDY. It's important to note here that changes to the application or the server configuration will produce different results - perhaps vastly different.

Test setup:
●     Server:
○     OS: Linux CentOS 6.3
○     Hardware:
■      Intel Core i3 CPU 540 @ 3.07GHz
■     4GB RAM
○     Apache
■     Version 2.2.15
■     worker MPM:
<IfModuleworker.c>
>StartServers    5
MaxClients      600
MinSpareThreads       50
MaxSpareThreads      150
ThreadsPerChild         50
MaxRequestsPerChild 0
</IfModule>

■     SPDY module (mod-spdy-beta-0.9.3.3-386.x86_64). Default SPDY optimization flags were used (uncommented suggested values):
●     SpdyMaxThreadsPerProcess 30
●     SpdyMaxStreamsPerConnection 100
●     Application:
○     1 web page: 1 HTML 9.5kB + 50 PNG icons (32x32).
○     The web page and all resources were served by the same server.
●     Load testing tool: NeoLoad 4.1.2
●     Tests:
○     Ramp-up from 1 to 1000 users for 20 minutes.
○     Scenario: 1 page call, wait for 5s, restart.
○     Chrome browser simulated, with 6 parallel connections to the server.
○     Emulated latency: 40ms in download, 45ms in upload.
○     Test HTTP, HTTPS, and SPDY under the same conditions.
○      Aggregation period of 30s for graphs. This smoothes variations to simplify comparison between several tests.

Results and Analysis
First I wanted to examine the hit rate (hits per second), average response time (duration), and number of errors as the number of concurrent users increased.

Here are the results for the HTTP test:

The plot illustrates the following:

  • At three minutes, the maximum number of page per second is reached. This maximum rate (16 pages/s or 827 request/s) is reached at 120 virtual users (VU), and the rate decreases as more concurrent users are added.
  • At the same time (the three-minute mark), response time starts to increase significantly.
  • The first errors (which investigation revealed to be timeouts) appear at 405 users.

The table below compares these metrics for HTTP, HTTPS, and SPDY:

 

HTTP

HTTPS

SPDY

Maximum pages/s

16.3 pages/s

after 3 minutes at 120 users

15.9 pages/s

after 3 minutes at 120 users

98 pages/s

after 14 minutes at 777 users

Page response time at 100 users

1.1s

1.3s

1.1s

Page response time at 120 users

1.4 s

1.5s

1.1s

Page response time at 200 users

7.1s

7.8s

1.1s

Page response time at 777 users

70.2s

72s

2.7s

First error

405 Users

225 Users

884 Users

Service-level agreement violation (< 3s page load time)

133 Users

133 Users

794 Users

 

Based on a service-level agreement (SLA) of less than 3s for page load time, my test server handled almost six times as many users with SPDY than HTTP.

More users with fewer workers
To handle incoming requests in parallel, Apache web servers use worker threads to process each request. Because each thread consumes resources and memory, Apache lets the system administrator limit thread use, which has an effect on how incoming requests are handled.

My HTTP and HTTPS results are typical of a scenario known as thread starvation.

This is confirmed by the following graph, which shows busy workers in orange, page rate in green, and user load in blue:

The number of busy Apache workers (threads) hits its maximum at the same time the page rate reaches its maximum.

In contrast to HTTP/S, SPDY uses a single connection for all requests. The principal benefit of this is the decreased latency seen by the client, resulting in reduced response times for users. There is another great benefit on the server side: SPDY clients consume one worker instead of six. As a result it takes much longer (that is, many more users) for all workers to become busy:

SPDY enables the server to handle more users with the same number of workers.

Server CPU and memory consumption
So far, I showed how SPDY affects Apache worker usage with my test configuration. Next, I wanted to see how CPU usage and memory were affected by SPDY.

Here is a plot showing system idle time (low when the CPU is used intensively) for HTTP/HTTPS/SPDY:

No surprise here - as most HTTP/HTTPS requests are waiting to be served after the thread limit is reached, they don't consume much CPU. For the SPDY tests, Apache is below the worker limit for much longer, resulting in a higher page rate and consequently more CPU used. The curve plateau is reached when all workers are busy (around 11 minutes).

To better understand the behavior before the worker limit is reached, I focused on the numbers at two minutes, 88 virtual users, and 12.5 pages/s. The CPU idle time measurements are an average of six values taken over 30 seconds:

CPU

HTTP

HTTPS

SPDY

CPU Idle time at 2 minutes

93.33%

91.5%

92%

The values are comparable; SPDY consumes slightly less CPU than HTTPS and slightly more than HTTP for this load.

On the memory side, here's the global overview:

Again, it's interesting to examine the memory used before the worker limit is reached. The numbers are an average of six measurements over 30 seconds.

System Memory

01:00

02:00

Difference = Consumed Memory

HTTP

3,357 MB

3,416 MB

59 MB

HTTPS

3,500 MB

3,579 MB

79 MB

SPDY

3,607 MB

3,631 MB

24 MB

The server consumed less memory when handling SPDY requests than when handling HTTP and HTTPS.

During this test, SPDY consumed just 41% of the memory consumed by HTTP, and just 30% of the memory consumed by HTTPS.

Conclusion
It's no surprise that SPDY improves response times on the client side; that's what it was designed to do. It turns out that SPDY also has advantages on the server side:

  • Compared to HTTPS, SPDY requests consume fewer resources (CPU and memory) on the server.
  • Compared to HTTP, SPDY requests consume less memory but a bit more CPU. This may be good, bad, or irrelevant depending on which resource (if either) is currently limiting your server.
  • Compared to HTTP/S, SPDY requires fewer Apache worker threads, which increases server capacity. As a result, the server may attract more SPDY traffic.

From these results, it's clear that Apache tuning performed for HTTP/S may not be appropriate after SPDY is enabled on the server. It's important to take the time to re-evaluate server sizing and retune the server before you start handling SPDY requests from your users.

As I mentioned earlier, the test results I've shared here are specific to my server configuration and the web page I used for the tests. It's important to understand how your server will perform under a realistic user load before you make SPDY available to the users on your site. I encourage you to test your own server and website using a load testing tool such as NeoLoad (there's a free 30-day trial if you want) to see how SPDY will affect your users' response times and your server's performance.

More Stories By Hervé Servy

Hervé Servy is a Senior Performance Engineer at Neotys. He has spent 10 years working for IBM-Rational and Microsoft pre-sales and marketing in France and the Middle East. During the past 3 years, as a personal project, Hervé founded a nonprofit organization in the health 2.0 area. If that isn’t techie enough, Hervé was also born on the very same day Apple Computer was founded.

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


@ThingsExpo Stories
Akana, a leading provider of API Management, API Security and Cloud Integration solutions, announced that it is introducing DevOps automation to the API lifecycle. New capabilities in Akana's API Management platform significantly reduce the time required to update API definitions and versions. DevOps teams will be able to work faster in designing and developing APIs, as well as managing them at runtime and publishing them to a portal.
2015 predictions circa 1970: houses anticipate our needs and adapt, city infrastructure is citizen and situation aware, office buildings identify and preprocess you. Today smart buildings have no such collective conscience, no shared set of fundamental services to identify, predict and synchronize around us. LiveSpace and M2Mi are changing that. LiveSpace Smart Environment devices deliver over the M2Mi IoT Platform real time presence, awareness and intent analytics as a service to local connected devices. In her session at @ThingsExpo, Sarah Cooper, VP Business of Development at M2Mi, will d...
DevOps Summit at Cloud Expo New York is offering a limited time FREE "Expo Plus" registration option in New York. On site registration price of $1,95 will be set to 'free' for delegates who register during special offer. To take advantage of this opportunity, attendees can use the coupon code, and secure their registration to attend all keynotes, @DevOpsSummit sessions at Cloud Expo, expo floor, and SYS-CON.tv power panels. Special FREE registration givess access to all Containers and Microservices sessions. Registration page is located at the DevOps Summit site. Your DevOps Summit registratio...
"Matrix is an ambitious open standard and implementation that's set up to break down the fragmentation problems that exist in IP messaging and VoIP communication," explained John Woolf, Technical Evangelist at Matrix, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
The only place to be Nov 3-5 is Cloud Expo | @ThingsExpo | DevOps Summit 2015 West at the Santa Clara Convention Center in Santa Clara, CA. Join us there as delegates from all over the world come to listen to and engage with speakers & sponsors from the leading Cloud Computing, IoT, Big Data and DevOps companies. Cloud Expo & @ThingsExpo are the leading events covering the booming market of Cloud Computing, IoT & Big Data for the enterprise. Speakers from all over the world will be hand-picked for their ability to explore the economic strategies that utility/cloud computing provides. Whether...
The basic integration architecture, as defined by ESBs, hasn’t changed for more than a decade. Most cloud integration providers still rely on an ESB architecture and their proprietary connectors. As a result, enterprise integration projects suffer from constraints of availability and reliability of these connectors that are not re-usable across other integration vendors. However, the rapid adoption of APIs and almost ubiquitous availability of APIs amongst most SaaS and Cloud applications are rapidly redefining traditional integration approaches and their reliance on proprietary connectors. ...
The world is at a tipping point where the technology, the device and global adoption are converging to such a point that we will see an explosion of a world where smartphone devices not only allow us to talk to each other, but allow for communication between everything – serving as a central hub from which we control our world – MediaTek is at the heart of both driving this and allowing the markets to drive this reality forward themselves. The next wave of consumer gadgets is here – smart, connected, and small. If your ambitions are big, so are ours. In his session at @ThingsExpo, Jack Hu, D...
The enterprise market will drive IoT device adoption over the next five years. In his session at @ThingsExpo, John Greenough, an analyst at BI Intelligence, division of Business Insider, will analyze how companies will adopt IoT products and the associated cost of adopting those products. John Greenough is the lead analyst covering the Internet of Things for BI Intelligence- Business Insider’s paid research service. Numerous IoT companies have cited his analysis of the IoT. Prior to joining BI Intelligence, he worked analyzing bank technology for Corporate Insight and The Clearing House Pay...
SYS-CON Events announced today that the "First Containers & Microservices Conference" will take place June 9-11, 2015, at the Javits Center in New York City. The “Second Containers & Microservices Conference” will take place November 3-5, 2015, at Santa Clara Convention Center, Santa Clara, CA. Containers and microservices have become topics of intense interest throughout the cloud developer and enterprise IT communities.
Explosive growth in connected devices. Enormous amounts of data for collection and analysis. Critical use of data for split-second decision making and actionable information. All three are factors in making the Internet of Things a reality. Yet, any one factor would have an IT organization pondering its infrastructure strategy. How should your organization enhance its IT framework to enable an Internet of Things implementation? In this session, James Kirkland, Red Hat's Chief Architect for the Internet of Things and Intelligent Systems, will describe how to revolutionize your architecture and...
All major researchers estimate there will be tens of billions devices - computers, smartphones, tablets, and sensors - connected to the Internet by 2020. This number will continue to grow at a rapid pace for the next several decades. With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo, June 9-11, 2015, at the Javits Center in New York City. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be
SYS-CON Events announced today that MetraTech, now part of Ericsson, has been named “Silver 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, NY. Ericsson is the driving force behind the Networked Society- a world leader in communications infrastructure, software and services. Some 40% of the world’s mobile traffic runs through networks Ericsson has supplied, serving more than 2.5 billion subscribers.
ThingsExpo New York is offering a limited time FREE "Expo Plus" registration option in New York. On site registration price of $1,95 will be set to 'free' for delegates who register during special offer. To take advantage of this opportunity, attendees can use the coupon code, and secure their registration to attend all keynotes, ThingsExpo sessions, expo floor, and SYS-CON.tv power panels. Special FREE registration givess access to all DevOps, Containers and Microservices sessions as well. Registration page is located at the ThingsExpo site.
"BSQUARE is in the business of selling software solutions for smart connected devices. It's obvious that IoT has moved from being a technology to being a fundamental part of business, and in the last 18 months people have said let's figure out how to do it and let's put some focus on it, " explained Dave Wagstaff, VP & Chief Architect, at BSQUARE Corporation, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Growth hacking is common for startups to make unheard-of progress in building their business. Career Hacks can help Geek Girls and those who support them (yes, that's you too, Dad!) to excel in this typically male-dominated world. Get ready to learn the facts: Is there a bias against women in the tech / developer communities? Why are women 50% of the workforce, but hold only 24% of the STEM or IT positions? Some beginnings of what to do about it!
SYS-CON Events announced today that O'Reilly Media has been named “Media 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. O'Reilly Media spreads the knowledge of innovators through its books, online services, magazines, and conferences. Since 1978, O'Reilly Media has been a chronicler and catalyst of cutting-edge development, homing in on the technology trends that really matter and spurring their adoption by amplifying "faint signals" from the alpha geeks who are creating the future. An active participa...
The Internet of Things is not only adding billions of sensors and billions of terabytes to the Internet. It is also forcing a fundamental change in the way we envision Information Technology. For the first time, more data is being created by devices at the edge of the Internet rather than from centralized systems. What does this mean for today's IT professional? In this Power Panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists will addresses this very serious issue of profound change in the industry.
We’re entering a new era of computing technology that many are calling the Internet of Things (IoT). Machine to machine, machine to infrastructure, machine to environment, the Internet of Everything, the Internet of Intelligent Things, intelligent systems – call it what you want, but it’s happening, and its potential is huge. IoT is comprised of smart machines interacting and communicating with other machines, objects, environments and infrastructures. As a result, huge volumes of data are being generated, and that data is being processed into useful actions that can “command and control” thi...
There will be 150 billion connected devices by 2020. New digital businesses have already disrupted value chains across every industry. APIs are at the center of the digital business. You need to understand what assets you have that can be exposed digitally, what their digital value chain is, and how to create an effective business model around that value chain to compete in this economy. No enterprise can be complacent and not engage in the digital economy. Learn how to be the disruptor and not the disruptee.
Thanks to widespread Internet adoption and more than 10 billion connected devices around the world, companies became more excited than ever about the Internet of Things in 2014. Add in the hype around Google Glass and the Nest Thermostat, and nearly every business, including those from traditionally low-tech industries, wanted in. But despite the buzz, some very real business questions emerged – mainly, not if a device can be connected, or even when, but why? Why does connecting to the cloud create greater value for the user? Why do connected features improve the overall experience? And why do...