|By Hovhannes Avoyan||
|October 25, 2012 08:55 AM EDT||
There are a variety of ways to implement proxying capabilities for web servers. As Apache is the most popular web server, we will try to implement proxying on it. Everyone who knows Apache well, probably knows that Apache implements proxying capability for AJP13 , FTP, CONNECT , HTTP/1.x.
The choice of reverse proxy server is fully dependent on what is actually trying to be hidden behind it. Each proxy mechanism has its own benefits and bottlenecks. Only for Apache, there are several ways to hide application servers (mod_proxy, mod_passenger, mod_wsgi, mod_jk). While mod_passenger and mod_wsgi are good for ruby and python servers respectively, these are a little bit outside the proxying idea. In this article I would like to discuss mod_proxy and mod_jk.
Now let’s think about what we have and what we want to put under proxy. The most common case is to put a pool of Tomcat servers behind Apache. Tomcat servers by default listen to 8080 for HTTP and 8009 for AJP. Now, we want to have Apache listen to 80 for incoming HTTP requests and 443 for HTTPS. People who have configured Tomcat for SSL will undoubtedly agree with me that SSL on Tomcat is quite annoying, so it’s better to implement SSL on the Apache side rather than playing with Tomcat’s keystores.
Okay, now we have two Tomcat servers on 2 different servers with our application installed, and both are on 8080 and an 8009 HTTP/AJP respectively. And one Apache on a third which will do HTTP on 80 , HTTPS on 443 for us and process requests to downstream Tomcat servers.
Situation 1 with mod_proxy and mod_proxy_http:
OK, here’s what this means:
User opens http://www.yourdomain.com in their browser
- Request comes to Apache
- Apache proxies it via HTTP to downstream Tomcat to port 8080
- Tomcat sends response to Apache via HTTP
- Apache delivers content to User’s browser
Well, so what are the pros and cons of this situation? We will provide some comparison tables below, but in general:
- Easy and quick to configure
- Works for all downstream application servers
- We do not have sticky sessions: if a user logs in to Tomcat1 and sends another request it will most likely go to Tomcat2 and the user will get a session expired error.
- mod_proxy does not support failover detection, so it will continue to send requests to downstream Tomcat even if it is down.
- Some Java applications exhibit unpredictable behavior when they are under a proxy environment. (From my experience, Atlassian Bamboo and Fisheye server’s progress bars stalled on several pages, but this was corrected by moving to JK; I have heard about other strange problems as well. )
Now let’s see Situation 2, where we use JK for downstream servers:
A REAL LIFE EXAMPLE
At first sight we can see that nothing has been changed, but this is only at first sight. The main difference here is that now Apache is talking to the Tomcats via AJP 13 and not HTTP protocol. So the process of opening the web site is the following:
- User opens http://www.yourdomain.com in their browser
- Request comes to Apache
- Apache proxies it via AJP 13 to downstream Tomcat to the port 8009
- Tomcat sends response to Apache via AJP
- Apache receives AJP and delivers content to Users browser via HTTP
It seems there is a little overhead with jumping around on HTTP and AJP, but there are benefits as well. Let’s see the Good and Bad sides of JK balancing:
- After a little tweaking we can have sticky sessions just by adding sticky_session=True on Apache and jvmRoute=”NODENAME” on the Tomcat sides. After this, users who are logged in to Tomcat1 will never be dropped to Tomcat2 until Tomcat1 is alive. (Actually you can Use Membase or Memcached as session store so users will never lose their session until it expires normally)
- We have node failure detection, so if Tomcat1 fails, Apache will not send requests to it until it detects that it is back.
- JK configuration is much more advanced than that of mod_proxy and allows lots of tweaking, which will result in better performance and make the environment work just as you need it to.
- JK has a web admin tool that allows you to decommission, suspend and play with the LB factor in real time.
- So far I have found only one bad thing: it is a little harder to configure, so it required some administrator skills.
At this moment you may be asking “Why do I need this? I have a single Tomcat server and it’s working fine”. As a matter of fact, you need to build a network which can handle your current load, be scalable and which will not affect the normal behavior of your websites. From this point of view, the choice of reverse proxy solution is quite reasonable.
Here is a real life example of one of our client server architectures, which I think is a good one
In general, the process is as follows:
- User does DNS request, gets ip address of one of the Varnish servers and the Static content server/s (NGINX).
- NGINX delivers content directly.
- Varnish caches whatever needs to be cached and sends request downstream to one of the Apaches.
- Apache gets JSESSIONID and forwards request via JK to the required Tomcat server or does balance if user does not have cookie.
- Tomcat servers keep sessions in local RAM and copy in Membase cluster (so even if one Tomcat fails another can retrieve its session from Membase ). Membase is clustered memcache so it is fault tolerant by nature (we will have a closer look at Membase in another article).
- Tomcat does needed application logic, (retrieves information from Hadoop/HBase database, etc.) and responds to Apache.
- Apache sends response back to Varnish.
- Varnish updates cache if needed and does delivery to client.
This is a real live working scenario, and it proved itself to be fault tolerant and extremely fast.
I know that after reading this article a lot of people will ask, “why is Apache needed when Varnish can do session stickiness, etc. …”
But the idea here is to use the best possible software for each particular role, software which has real and approved redundancy and reasonable layers of architecture which can help us to easily and quickly detect problems and fix them as they appear. Also, if we keep in mind that the client uses not only HTTP, but also HTTPS, I did not see any webserver which worked with SSL as smoothly as Apache did. Even if we do not have SSL initially, we will have it soon, and I do not believe that any web project can go far without SSL.
Following is a little comparison of JK and mod_proxy, so you can see more closely what these tools are.
|Node failure detection||mod_proxy_balancer has to be present in the server||7||Advanced||10|
|Backend SSL||supported (mod_ssl required)||5||not supported||0|
|Session stickiness||not supported||0||Supported via JVM Route||10|
|Protocols||HTTP, HTTPS||10||AJP 13||8|
|Node decommissioning||Manual needs Apache reload||3||Online via web admin||10|
|Web admin interface||Not present||0||Advanced with RO and RW support||10|
|Large AJP packet sizes||8K||5||Larger than 8K||10|
|Compatibility with other app. servers||Works with all HTTP application servers||10||AJP Compatible (Tomcat, Glassfish, etc. …)||5|
|Configuration||Compatible with Apache Httpd configuration file||10||Need separate JK Workers file in .properties format||8|
So now let’s do some stress tests on both mod_jk and mod_proxy. The Installation schema is as described above (one load balancer, two application servers.) On both Apache server hosts, monitoring software from Monitis.com is installed which will check the servers’ health in real time.
We have used Amazon EC2 medium instances for this test. Here are the load test results in both graphical and plain text mode.
Monitoring is implemented using Monitis M3 monitors.
There are 2 monitors used:
apache_monitor – used for apache server’s health check.
http_load monitor - used to check the load time difference during Apache benchmarking.
The mentioned monitors provide useful information which helps to find relationships between various metrics.
The graphic below depicts Apache worker’s status while busy (upper line) and idle (lower line) while benchmarking using
This graph shows Apache busy and idle worker processes on the Apache web server, so we can see that of 150 enabled processes, almost all are busy during the stress test.
Http content load time (time connect, time transfer, time total)
Following is data provided by siege after benchmarking 7 times (using mod_proxy), each time increasing the concurrent users’ number by 100:
|Concurrent conns.||Trans||Elap Time||Data Trans||Resp Time||Trans Rate||Throughput||Concurrent||Failed|
The graphic below represents Apache worker’s busy (upper line) and idle (lower line) status while benchmarking using
This graph shows Apache busy and idle worker processes on the Apache webserver, so we can see that of 150 enabled processes, almost all are busy during the stress test.
Http content load time (time connect, time transfer, time total)
Following is data provided by siege after benchmarking 7 times (using mod_jk), each time increasing the concurrent users number by 100:
|Concurrent conns.||Trans||Elap time||Data Trans||Resp Time||Trans time||Throughput||Concurrent||Failed|
Both mentioned modules, mod_proxy and mod_jk, are used as balancers for backend application servers such as Tomcat and GlassFish. What are the most important features in load balancing? I assumed node failure detection at first, and ease of session stability and load balancing configuration, without requiring any other extra tools or packages. Do not forget about performance, as well.
So what do we have? The resulting tables show that when advanced load balancing or node failure detection is needed, mod_jk is preferable. However, it cannot provide flexibility such as mod_proxy does when configuring (mod_proxy configuration is as easy as Apache configuration and there is no need for separate files like workers.properties) nor for compatibility needs with servers, other than AJP compatibility.
Now a little bit about performance. While the concurrent users count is not so high (in our case: 400), both servers’ behavior is similar, and it seems mod_proxy is able to provide better performance, but things changed as the number of concurrent users grew.
Take a look at this table:
|Concurrent users||Failed requests(10 Seconds Timeout)|
As you see, with an almost equal number of connections, mod_proxy fails approximately 59% more often.
If you have a small project, or need to hide a variety of application servers (Tomcat+Rails+Django), and if you need an easily configurable and fast SSL solution and your server load is not heavy, then use mod_proxy.
But if your goal is to loadbalance Java applications servers, then JK is definitely the better solution.Share Now:
Disruptive macro trends in technology are impacting and dramatically changing the "art of the possible" relative to supply chain management practices through the innovative use of IoT, cloud, machine learning and Big Data to enable connected ecosystems of engagement. Enterprise informatics can now move beyond point solutions that merely monitor the past and implement integrated enterprise fabrics that enable end-to-end supply chain visibility to improve customer service delivery and optimize supplier management. Learn about enterprise architecture strategies for designing connected systems tha...
May. 25, 2015 05:00 AM EDT Reads: 6,000
Cloud is not a commodity. And no matter what you call it, computing doesn’t come out of the sky. It comes from physical hardware inside brick and mortar facilities connected by hundreds of miles of networking cable. And no two clouds are built the same way. SoftLayer gives you the highest performing cloud infrastructure available. One platform that takes data centers around the world that are full of the widest range of cloud computing options, and then integrates and automates everything. Join SoftLayer on June 9 at 16th Cloud Expo to learn about IBM Cloud's SoftLayer platform, explore se...
May. 25, 2015 04:45 AM EDT Reads: 3,195
SYS-CON Media announced today that 9 out of 10 " most read" DevOps articles are published by @DevOpsSummit Blog. Launched in October 2014, @DevOpsSummit Blog 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. 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 for long development cycles that produce softw...
May. 25, 2015 04:15 AM EDT Reads: 4,188
With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo in Silicon Valley. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be! Internet of @ThingsExpo, taking place Nov 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 17th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal an...
May. 25, 2015 04:00 AM EDT Reads: 2,862
15th Cloud Expo, which took place Nov. 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA, expanded the conference content of @ThingsExpo, Big Data Expo, and DevOps Summit to include two developer events. IBM held a Bluemix Developer Playground on November 5 and ElasticBox held a Hackathon on November 6. Both events took place on the expo floor. The Bluemix Developer Playground, for developers of all levels, highlighted the ease of use of Bluemix, its services and functionality and provide short-term introductory projects that developers can complete between sessions.
May. 25, 2015 04:00 AM EDT Reads: 6,360
From telemedicine to smart cars, digital homes and industrial monitoring, the explosive growth of IoT has created exciting new business opportunities for real time calls and messaging. In his session at @ThingsExpo, Ivelin Ivanov, CEO and Co-Founder of Telestax, shared some of the new revenue sources that IoT created for Restcomm – the open source telephony platform from Telestax. Ivelin Ivanov is a technology entrepreneur who founded Mobicents, an Open Source VoIP Platform, to help create, deploy, and manage applications integrating voice, video and data. He is the co-founder of TeleStax, a...
May. 25, 2015 04:00 AM EDT Reads: 6,455
The Internet of Things (IoT) promises to evolve the way the world does business; however, understanding how to apply it to your company can be a mystery. Most people struggle with understanding the potential business uses or tend to get caught up in the technology, resulting in solutions that fail to meet even minimum business goals. In his session at @ThingsExpo, Jesse Shiah, CEO / President / Co-Founder of AgilePoint Inc., showed what is needed to leverage the IoT to transform your business. He discussed opportunities and challenges ahead for the IoT from a market and technical point of vie...
May. 25, 2015 04:00 AM EDT Reads: 6,847
The 3rd International @ThingsExpo, co-located with the 16th International Cloud Expo – to be held June 9-11, 2015, at the Javits Center in New York City, NY – is now accepting Hackathon proposals. Hackathon sponsorship benefits include general brand exposure and increasing engagement with the developer ecosystem. At Cloud Expo 2014 Silicon Valley, IBM held the Bluemix Developer Playground on November 5 and ElasticBox held the DevOps Hackathon on November 6. Both events took place on the expo floor. The Bluemix Developer Playground, for developers of all levels, highlighted the ease of use of...
May. 25, 2015 03:00 AM EDT Reads: 3,498
Grow your business with enterprise wearable apps using SAP Platforms and Google Glass. SAP and Google just launched the SAP and Google Glass Challenge, an opportunity for you to innovate and develop the best Enterprise Wearable App using SAP Platforms and Google Glass and gain valuable market exposure. In his session at @ThingsExpo, Brian McPhail, Senior Director of Business Development, ISVs & Digital Commerce at SAP, outlined the timeline of the SAP Google Glass Challenge and the opportunity for developers, start-ups, and companies of all sizes to engage with SAP today.
May. 25, 2015 03:00 AM EDT Reads: 5,077
Enthusiasm for the Internet of Things has reached an all-time high. In 2013 alone, venture capitalists spent more than $1 billion dollars investing in the IoT space. With "smart" appliances and devices, IoT covers wearable smart devices, cloud services to hardware companies. Nest, a Google company, detects temperatures inside homes and automatically adjusts it by tracking its user's habit. These technologies are quickly developing and with it come challenges such as bridging infrastructure gaps, abiding by privacy concerns and making the concept a reality. These challenges can't be addressed w...
May. 25, 2015 02:45 AM EDT Reads: 6,802
The industrial software market has treated data with the mentality of “collect everything now, worry about how to use it later.” We now find ourselves buried in data, with the pervasive connectivity of the (Industrial) Internet of Things only piling on more numbers. There’s too much data and not enough information. In his session at @ThingsExpo, Bob Gates, Global Marketing Director, GE’s Intelligent Platforms business, to discuss how realizing the power of IoT, software developers are now focused on understanding how industrial data can create intelligence for industrial operations. Imagine ...
May. 25, 2015 02:00 AM EDT Reads: 5,322
SYS-CON Events announced today that Liaison Technologies, a leading provider of data management and integration cloud services and solutions, 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. Liaison Technologies is a recognized market leader in providing cloud-enabled data integration and data management solutions to break down complex information barriers, enabling enterprises to make smarter decisions, faster.
May. 25, 2015 01:30 AM EDT Reads: 5,423
The 17th International Cloud Expo has announced that its Call for Papers is open. 17th International Cloud Expo, to be held November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, APM, APIs, Microservices, Security, Big Data, Internet of Things, DevOps 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 business opportunity. Submit your speaking proposal today!
May. 25, 2015 01:15 AM EDT Reads: 4,523
Hadoop as a Service (as offered by handful of niche vendors now) is a cloud computing solution that makes medium and large-scale data processing accessible, easy, fast and inexpensive. In his session at Big Data Expo, Kumar Ramamurthy, Vice President and Chief Technologist, EIM & Big Data, at Virtusa, will discuss how this is achieved by eliminating the operational challenges of running Hadoop, so one can focus on business growth. The fragmented Hadoop distribution world and various PaaS solutions that provide a Hadoop flavor either make choices for customers very flexible in the name of opti...
May. 25, 2015 12:30 AM EDT Reads: 3,992
Cultural, regulatory, environmental, political and economic (CREPE) conditions over the past decade are creating cross-industry solution spaces that require processes and technologies from both the Internet of Things (IoT), and Data Management and Analytics (DMA). These solution spaces are evolving into Sensor Analytics Ecosystems (SAE) that represent significant new opportunities for organizations of all types. Public Utilities throughout the world, providing electricity, natural gas and water, are pursuing SmartGrid initiatives that represent one of the more mature examples of SAE. We have s...
May. 24, 2015 11:00 PM EDT Reads: 6,123
The Internet of Things will put IT to its ultimate test by creating infinite new opportunities to digitize products and services, generate and analyze new data to improve customer satisfaction, and discover new ways to gain a competitive advantage across nearly every industry. In order to help corporate business units to capitalize on the rapidly evolving IoT opportunities, IT must stand up to a new set of challenges. In his session at @ThingsExpo, Jeff Kaplan, Managing Director of THINKstrategies, will examine why IT must finally fulfill its role in support of its SBUs or face a new round of...
May. 24, 2015 10:00 PM EDT Reads: 5,491
One of the biggest challenges when developing connected devices is identifying user value and delivering it through successful user experiences. In his session at Internet of @ThingsExpo, Mike Kuniavsky, Principal Scientist, Innovation Services at PARC, described an IoT-specific approach to user experience design that combines approaches from interaction design, industrial design and service design to create experiences that go beyond simple connected gadgets to create lasting, multi-device experiences grounded in people's real needs and desires.
May. 24, 2015 09:00 PM EDT Reads: 6,143
The 4th International Internet of @ThingsExpo, co-located with the 17th International Cloud Expo - to be held November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA - announces that its Call for Papers is open. The Internet of Things (IoT) is the biggest idea since the creation of the Worldwide Web more than 20 years ago.
May. 24, 2015 09:00 PM EDT Reads: 1,951
Wearable devices have come of age. The primary applications of wearables so far have been "the Quantified Self" or the tracking of one's fitness and health status. We propose the evolution of wearables into social and emotional communication devices. Our BE(tm) sensor uses light to visualize the skin conductance response. Our sensors are very inexpensive and can be massively distributed to audiences or groups of any size, in order to gauge reactions to performances, video, or any kind of presentation. In her session at @ThingsExpo, Jocelyn Scheirer, CEO & Founder of Bionolux, will discuss ho...
May. 24, 2015 09:00 PM EDT Reads: 5,286
The true value of the Internet of Things (IoT) lies not just in the data, but through the services that protect the data, perform the analysis and present findings in a usable way. With many IoT elements rooted in traditional IT components, Big Data and IoT isn’t just a play for enterprise. In fact, the IoT presents SMBs with the prospect of launching entirely new activities and exploring innovative areas. CompTIA research identifies several areas where IoT is expected to have the greatest impact.
May. 24, 2015 09:00 PM EDT Reads: 4,937