|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:
"We're a cybersecurity firm that specializes in engineering security solutions both at the software and hardware level. Security cannot be an after-the-fact afterthought, which is what it's become," stated Richard Blech, Chief Executive Officer at Secure Channels, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 3, 2016 08:30 AM EST Reads: 440
In addition to all the benefits, IoT is also bringing new kind of customer experience challenges - cars that unlock themselves, thermostats turning houses into saunas and baby video monitors broadcasting over the internet. This list can only increase because while IoT services should be intuitive and simple to use, the delivery ecosystem is a myriad of potential problems as IoT explodes complexity. So finding a performance issue is like finding the proverbial needle in the haystack.
Dec. 3, 2016 06:30 AM EST Reads: 5,992
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life sett...
Dec. 3, 2016 05:45 AM EST Reads: 6,917
The WebRTC Summit New York, to be held June 6-8, 2017, at the Javits Center in New York City, NY, announces that its Call for Papers is now open. Topics include all aspects of improving IT delivery by eliminating waste through automated business models leveraging cloud technologies. WebRTC Summit is co-located with 20th International Cloud Expo and @ThingsExpo. WebRTC is the future of browser-to-browser communications, and continues to make inroads into the traditional, difficult, plug-in web ...
Dec. 3, 2016 05:30 AM EST Reads: 1,198
20th Cloud Expo, taking place June 6-8, 2017, at the Javits Center in New York City, NY, 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 strategy.
Dec. 3, 2016 04:15 AM EST Reads: 1,710
Internet-of-Things discussions can end up either going down the consumer gadget rabbit hole or focused on the sort of data logging that industrial manufacturers have been doing forever. However, in fact, companies today are already using IoT data both to optimize their operational technology and to improve the experience of customer interactions in novel ways. In his session at @ThingsExpo, Gordon Haff, Red Hat Technology Evangelist, will share examples from a wide range of industries – includin...
Dec. 3, 2016 02:30 AM EST Reads: 1,523
WebRTC is the future of browser-to-browser communications, and continues to make inroads into the traditional, difficult, plug-in web communications world. The 6th WebRTC Summit continues our tradition of delivering the latest and greatest presentations within the world of WebRTC. Topics include voice calling, video chat, P2P file sharing, and use cases that have already leveraged the power and convenience of WebRTC.
Dec. 3, 2016 02:15 AM EST Reads: 1,494
"We build IoT infrastructure products - when you have to integrate different devices, different systems and cloud you have to build an application to do that but we eliminate the need to build an application. Our products can integrate any device, any system, any cloud regardless of protocol," explained Peter Jung, Chief Product Officer at Pulzze Systems, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 3, 2016 01:45 AM EST Reads: 777
Data is the fuel that drives the machine learning algorithmic engines and ultimately provides the business value. In his session at 20th Cloud Expo, Ed Featherston, director/senior enterprise architect at Collaborative Consulting, will discuss the key considerations around quality, volume, timeliness, and pedigree that must be dealt with in order to properly fuel that engine.
Dec. 3, 2016 12:30 AM EST Reads: 1,520
"Once customers get a year into their IoT deployments, they start to realize that they may have been shortsighted in the ways they built out their deployment and the key thing I see a lot of people looking at is - how can I take equipment data, pull it back in an IoT solution and show it in a dashboard," stated Dave McCarthy, Director of Products at Bsquare Corporation, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 2, 2016 11:15 PM EST Reads: 911
IoT is rapidly changing the way enterprises are using data to improve business decision-making. In order to derive business value, organizations must unlock insights from the data gathered and then act on these. In their session at @ThingsExpo, Eric Hoffman, Vice President at EastBanc Technologies, and Peter Shashkin, Head of Development Department at EastBanc Technologies, discussed how one organization leveraged IoT, cloud technology and data analysis to improve customer experiences and effici...
Dec. 2, 2016 08:30 PM EST Reads: 4,981
Fact is, enterprises have significant legacy voice infrastructure that’s costly to replace with pure IP solutions. How can we bring this analog infrastructure into our shiny new cloud applications? There are proven methods to bind both legacy voice applications and traditional PSTN audio into cloud-based applications and services at a carrier scale. Some of the most successful implementations leverage WebRTC, WebSockets, SIP and other open source technologies. In his session at @ThingsExpo, Da...
Dec. 2, 2016 08:15 PM EST Reads: 1,572
"IoT is going to be a huge industry with a lot of value for end users, for industries, for consumers, for manufacturers. How can we use cloud to effectively manage IoT applications," stated Ian Khan, Innovation & Marketing Manager at Solgeniakhela, in this SYS-CON.tv interview at @ThingsExpo, held November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 2, 2016 06:45 PM EST Reads: 3,996
As data explodes in quantity, importance and from new sources, the need for managing and protecting data residing across physical, virtual, and cloud environments grow with it. Managing data includes protecting it, indexing and classifying it for true, long-term management, compliance and E-Discovery. Commvault can ensure this with a single pane of glass solution – whether in a private cloud, a Service Provider delivered public cloud or a hybrid cloud environment – across the heterogeneous enter...
Dec. 2, 2016 06:30 PM EST Reads: 1,487
The cloud promises new levels of agility and cost-savings for Big Data, data warehousing and analytics. But it’s challenging to understand all the options – from IaaS and PaaS to newer services like HaaS (Hadoop as a Service) and BDaaS (Big Data as a Service). In her session at @BigDataExpo at @ThingsExpo, Hannah Smalltree, a director at Cazena, provided an educational overview of emerging “as-a-service” options for Big Data in the cloud. This is critical background for IT and data professionals...
Dec. 2, 2016 05:00 PM EST Reads: 4,088
Today we can collect lots and lots of performance data. We build beautiful dashboards and even have fancy query languages to access and transform the data. Still performance data is a secret language only a couple of people understand. The more business becomes digital the more stakeholders are interested in this data including how it relates to business. Some of these people have never used a monitoring tool before. They have a question on their mind like “How is my application doing” but no id...
Dec. 2, 2016 04:45 PM EST Reads: 2,113
@GonzalezCarmen has been ranked the Number One Influencer and @ThingsExpo has been named the Number One Brand in the “M2M 2016: Top 100 Influencers and Brands” by Onalytica. Onalytica analyzed tweets over the last 6 months mentioning the keywords M2M OR “Machine to Machine.” They then identified the top 100 most influential brands and individuals leading the discussion on Twitter.
Dec. 2, 2016 04:45 PM EST Reads: 1,983
What happens when the different parts of a vehicle become smarter than the vehicle itself? As we move toward the era of smart everything, hundreds of entities in a vehicle that communicate with each other, the vehicle and external systems create a need for identity orchestration so that all entities work as a conglomerate. Much like an orchestra without a conductor, without the ability to secure, control, and connect the link between a vehicle’s head unit, devices, and systems and to manage the ...
Dec. 2, 2016 04:15 PM EST Reads: 428
More and more brands have jumped on the IoT bandwagon. We have an excess of wearables – activity trackers, smartwatches, smart glasses and sneakers, and more that track seemingly endless datapoints. However, most consumers have no idea what “IoT” means. Creating more wearables that track data shouldn't be the aim of brands; delivering meaningful, tangible relevance to their users should be. We're in a period in which the IoT pendulum is still swinging. Initially, it swung toward "smart for smar...
Dec. 2, 2016 04:15 PM EST Reads: 406
In an era of historic innovation fueled by unprecedented access to data and technology, the low cost and risk of entering new markets has leveled the playing field for business. Today, any ambitious innovator can easily introduce a new application or product that can reinvent business models and transform the client experience. In their Day 2 Keynote at 19th Cloud Expo, Mercer Rowe, IBM Vice President of Strategic Alliances, and Raejeanne Skillern, Intel Vice President of Data Center Group and G...
Dec. 2, 2016 04:00 PM EST Reads: 1,870