Welcome!

Java IoT Authors: Jason Bloomberg, Elizabeth White, Liz McMillan, Pat Romanski, Kevin Benedict

Related Topics: Microservices Expo, Java IoT, Industrial IoT, Microsoft Cloud, Machine Learning , Agile Computing

Microservices Expo: 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
The 22nd International Cloud Expo | 1st DXWorld Expo has announced that its Call for Papers is open. Cloud Expo | DXWorld Expo, to be held June 5-7, 2018, at the Javits Center in New York, NY, brings together Cloud Computing, Digital Transformation, Big Data, Internet of Things, DevOps, Machine Learning and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding busin...
Smart cities have the potential to change our lives at so many levels for citizens: less pollution, reduced parking obstacles, better health, education and more energy savings. Real-time data streaming and the Internet of Things (IoT) possess the power to turn this vision into a reality. However, most organizations today are building their data infrastructure to focus solely on addressing immediate business needs vs. a platform capable of quickly adapting emerging technologies to address future ...
Nordstrom is transforming the way that they do business and the cloud is the key to enabling speed and hyper personalized customer experiences. In his session at 21st Cloud Expo, Ken Schow, VP of Engineering at Nordstrom, discussed some of the key learnings and common pitfalls of large enterprises moving to the cloud. This includes strategies around choosing a cloud provider(s), architecture, and lessons learned. In addition, he covered some of the best practices for structured team migration an...
No hype cycles or predictions of a gazillion things here. IoT is here. You get it. You know your business and have great ideas for a business transformation strategy. What comes next? Time to make it happen. In his session at @ThingsExpo, Jay Mason, an Associate Partner of Analytics, IoT & Cybersecurity at M&S Consulting, presented a step-by-step plan to develop your technology implementation strategy. He also discussed the evaluation of communication standards and IoT messaging protocols, data...
With tough new regulations coming to Europe on data privacy in May 2018, Calligo will explain why in reality the effect is global and transforms how you consider critical data. EU GDPR fundamentally rewrites the rules for cloud, Big Data and IoT. In his session at 21st Cloud Expo, Adam Ryan, Vice President and General Manager EMEA at Calligo, examined the regulations and provided insight on how it affects technology, challenges the established rules and will usher in new levels of diligence arou...
In his Opening Keynote at 21st Cloud Expo, John Considine, General Manager of IBM Cloud Infrastructure, led attendees through the exciting evolution of the cloud. He looked at this major disruption from the perspective of technology, business models, and what this means for enterprises of all sizes. John Considine is General Manager of Cloud Infrastructure Services at IBM. In that role he is responsible for leading IBM’s public cloud infrastructure including strategy, development, and offering m...
In his session at 21st Cloud Expo, Raju Shreewastava, founder of Big Data Trunk, provided a fun and simple way to introduce Machine Leaning to anyone and everyone. He solved a machine learning problem and demonstrated an easy way to be able to do machine learning without even coding. Raju Shreewastava is the founder of Big Data Trunk (www.BigDataTrunk.com), a Big Data Training and consulting firm with offices in the United States. He previously led the data warehouse/business intelligence and B...
Recently, REAN Cloud built a digital concierge for a North Carolina hospital that had observed that most patient call button questions were repetitive. In addition, the paper-based process used to measure patient health metrics was laborious, not in real-time and sometimes error-prone. In their session at 21st Cloud Expo, Sean Finnerty, Executive Director, Practice Lead, Health Care & Life Science at REAN Cloud, and Dr. S.P.T. Krishnan, Principal Architect at REAN Cloud, discussed how they built...
22nd International Cloud Expo, taking place June 5-7, 2018, at the Javits Center in New York City, NY, and co-located with the 1st DXWorld Expo will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud ...
22nd International Cloud Expo, taking place June 5-7, 2018, at the Javits Center in New York City, NY, and co-located with the 1st DXWorld Expo will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud ...
DevOps at Cloud Expo – being held June 5-7, 2018, at the Javits Center in New York, NY – announces that its Call for Papers is open. Born out of proven success in agile development, cloud computing, and process automation, DevOps is a macro trend you cannot afford to miss. From showcase success stories from early adopters and web-scale businesses, DevOps is expanding to organizations of all sizes, including the world's largest enterprises – and delivering real results. Among the proven benefits,...
@DevOpsSummit at Cloud Expo, taking place June 5-7, 2018, at the Javits Center in New York City, NY, is co-located with 22nd Cloud Expo | 1st DXWorld Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time to wait...
Cloud Expo | DXWorld Expo have announced the conference tracks for Cloud Expo 2018. Cloud Expo will be held June 5-7, 2018, at the Javits Center in New York City, and November 6-8, 2018, at the Santa Clara Convention Center, Santa Clara, CA. Digital Transformation (DX) is a major focus with the introduction of DX Expo within the program. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive ov...
SYS-CON Events announced today that T-Mobile exhibited at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. As America's Un-carrier, T-Mobile US, Inc., is redefining the way consumers and businesses buy wireless services through leading product and service innovation. The Company's advanced nationwide 4G LTE network delivers outstanding wireless experiences to 67.4 million customers who are unwilling to compromise on qua...
SYS-CON Events announced today that Cedexis will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 - Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Cedexis is the leader in data-driven enterprise global traffic management. Whether optimizing traffic through datacenters, clouds, CDNs, or any combination, Cedexis solutions drive quality and cost-effectiveness. For more information, please visit https://www.cedexis.com.
SYS-CON Events announced today that Google Cloud has been named “Keynote Sponsor” of SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Companies come to Google Cloud to transform their businesses. Google Cloud’s comprehensive portfolio – from infrastructure to apps to devices – helps enterprises innovate faster, scale smarter, stay secure, and do more with data than ever before.
SYS-CON Events announced today that Vivint to exhibit at SYS-CON's 21st Cloud Expo, which will take place on October 31 through November 2nd 2017 at the Santa Clara Convention Center in Santa Clara, California. As a leading smart home technology provider, Vivint offers home security, energy management, home automation, local cloud storage, and high-speed Internet solutions to more than one million customers throughout the United States and Canada. The end result is a smart home solution that sav...
SYS-CON Events announced today that Opsani will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Opsani is the leading provider of deployment automation systems for running and scaling traditional enterprise applications on container infrastructure.
SYS-CON Events announced today that Nirmata will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Nirmata provides a comprehensive platform, for deploying, operating, and optimizing containerized applications across clouds, powered by Kubernetes. Nirmata empowers enterprise DevOps teams by fully automating the complex operations and management of application containers and its underlying ...
SYS-CON Events announced today that Opsani to exhibit at SYS-CON's 21st Cloud Expo, which will take place on October 31 through November 2nd 2017 at the Santa Clara Convention Center in Santa Clara, California. Opsani is creating the next generation of automated continuous deployment tools designed specifically for containers. How is continuous deployment different from continuous integration and continuous delivery? CI/CD tools provide build and test. Continuous Deployment is the means by which...