I need to know the difference between a load balancer and load balancing.
Load balancing is the functionality provided by a Load balancer :).
In software architecture, a load balancer proxies client requests to a pool of application server, using an algorithm, with the objective of balancing the load of client requests evenly across the pool
Load balancing refers to efficiently distributing incoming network traffic across a group of backend servers, also known as a server farm or server pool.
A load balancer acts as the “traffic cop” sitting in front of your servers and routing client requests across all servers capable of fulfilling those requests in a manner that maximizes speed and capacity utilization and ensures that no one server is overworked, which could degrade performance. If a single server goes down, the load balancer redirects traffic to the remaining online servers. When a new server is added to the server group, the load balancer automatically starts to send requests to it.
refer - https://www.nginx.com/resources/glossary/load-balancing/
Load Balancing helps spread incoming request traffic across cluster of servers. If a server is not availble to take a request, load balancer passes this request to another server.
Load Balancer in turn are the ones which achieve above, they could come in between :-
User - webserver
Webserver - internal application servers
Internal servers - database servers
Application servers - cache servers
Different types of Load Balancers:
Smart Client - Adding load balance achievability by It is a client which takes a pool of service hosts and balances load across them, detects downed hosts and avoids sending requests their way.
Hardware Load Balancer - Buy your own dedicated high performance server eg. Citrix NetScaler.
Software Load Balancer - Buy a software load balancer to overcome all the pain of building your own smart client or if you not ready spending on dedicated server. Cost effective than above two is buying a software load balancer eg. VmWare, HAProxy etc
As per my knowledge both are same but you can say that the load balancer is the device used for balancing the traffic as per the availability of the server and load balancing is nothing but theoretical explanation for how to achieve this.
Please correct me if I'm wrong!
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I am trying to understand how reverse proxy and load balancing are different from each other. When its useful to use reverse proxy over load balancing.
Both promise to improve efficiency and sits in between client and server. They nearly look the same when we try to understand them, but still their functionality differs.
Load balancing: Is hardware or a software unit that distributes the total load on a website by distributing it to multiple servers.
The algorithms used by load balancing should be chosen as such it makes the best use of each servers’ capacity and can provide the result as fast as possible.
Load balancers are of three categories: DNS Round Robin, L3/L4 Load Balancer [ works on IP and TCP layer ], and L7 Load Balancer [ works on application layer].
The different kinds of algorithms used by load balancer for distributing load are IP Hash, Least connection, Round robin, Least traffic, etc.
Reverse Proxy: They act as a face of website or we can say they serve as a gateway that web traffic has to pass. The main role of a reverse proxy is:
Security: They act as a wall to your backend server. Protecting the backend from direct interactions and thus improving the security of the overall system.
Web acceleration: It also provides features like caching, SSL encryption, and Compression to reduce the time to provide responses to clients.
Flexibility: The changes in backend architecture become more flexible as the client can only access the reverse proxy.
A reverse proxy can even be relevant even when there is only one server in your system. In such cases there is no requirement of load balancers but still the reverse proxy can be useful providing security, flexibility and web acceleration.
According to this link,
A reverse proxy accepts a request from a client, forwards it to a server that can fulfill it, and returns the server’s response to the client. In other words, Reverse proxies act as such for HTTP traffic and application programming interfaces.
A load balancer distributes incoming client requests among a group of servers, in each case returning the response from the selected server to the appropriate client. Load balancers can deal with multiple protocols — HTTP as well as Domain Name System protocol, Simple Message Transfer Protocol and Internet Message Access Protocol. A load balancer receives and routes client requests for application, text, image or video data to any server in a pool that is capable of fulfilling them and then returns the server’s response to the client.
I'm totally new to clustering and load balancing.
What I'm trying to do is "Deploy Application on a Cluster which contains 2 managed servers. Now, If one of the managed server goes down, request should be redirected to another server which is Up."
For Example:
I've 2 managed servers (M1:7021 and M2:7022)
And I've a Cluster C1 having M1 and M2.
And I've an Application App1 deployed on C1 and a Data Source deployed on C1.
Application App1 is working fine.
The way through which I'm accessing application is:
http://10.184.111.11:7021/App1/
AND
http://10.184.111.11:7022/App1/
Now, Suppose if M1(7021) goes down, and request is coming like
:7021/App1/
Then, it should be redirected to :7022/App1/
Any help is highly appreciated. Thanks!
I believe you will need a load balancer (or a software equivalent) to sit above the weblogic servers and direct traffic down to those servers.
The idea being that you access your application on http://loadBalancer.com/App and then the Load Balancer forwards your request onto either one of weblogic servers. Meanwhile in the background the load balancer is continually performing health checks on the two weblogic servers to see if they are running.
In the event that one of the weblogic servers go down, the load balancer will mark it as inactive and forward all traffic to the weblogic server still running. Once the failed weblogic server has come back online the load balancer will begin routing traffic back through it.
#Garreth Well, in fact WebLogic DOES provide an internal load balancer. You are supposed to use OHS or Apache for load balancing in production environments, but for development, httpclusterservlet works great.
I am new to Google compute engine and I am try to setup network load balancing having 2 VMs for serving web pages.
For ex, I have 2 VMs - app1 and app2 - both having apache server and serves simple web page.
Both VMs are running with Red Hat Enterprise Linux Server release 7.0 (Maipo)
I am able to access both web pages through the IP in browser.
I created network load balancing setup and both apps are showing in green in target pool which means load balancer is able to connect to both VMs.
But, when I hit the IP of load balancer, it is rendering page from only one server. If I manually stop the server in the VM, load balancer IP redirects to other app. I believe load balancer is able to identify health of both VMs and able to redirect.
But it is not balancing the traffic. Can anyone help me to solve this issue?
I think that the network load balancer doesn't forward the traffic on a round-robin basis. I was able to test it with the load balancer setup that I have. As per the documentation:
By default, to distribute traffic to instances, Google Compute Engine picks an instance based on a hash of the source IP and port and the destination IP and port.
HTTP/S load balancing will proxy requests in a round-robin fashion. https://cloud.google.com/compute/docs/load-balancing/http/
We currently run a SaaS application on apache which server ecommerce websites (its a store builder). We currently host over 1000 clients on that application and are now running into scalability issues (CPU going over 90% even on a fairly large 20 core 80GB ram + all SSD disk server).
We're looking for help from an nginx expert who can:
1. Explain the difference between running nginx as a web server vs. using it like a reverse proxy. What are the benefits?
2. We also want to use nginx as a load balancer (and have that already setup in testing), but we haven't enabled cacheing on the load balancer. So while its helping redirect requests, its not really serving any traffic directly and it simply passes through everything to one of the two apache servers.
The question is that we have a lot of user-generated content coming from the apache servers, how do we invalidate the cache for only certain pages that are being cached by nginx? If we setup a cron to clear this cache every 1 minute or so, it wouldn't be that useful... as cache would then be virtually non existent.
--
Also need an overall word on what is the best architecture to build for given the above scenarios.
Is it
NGINX Load Balancer + Cacheing ==> Nginx Web Server
NGINX Load Balancer ==> Nginx Web Server + Cacheing ?
NGINX Load Balancer + Cacheing ==> Apache Web Server
NGINX Load Balancer == > Apache Web Server (unlikely)
Please help!
Scaling horizontally to support more clients is a good option. Its recommended to first evaluate what is causing the bottleneck, memory within the application, long running requests etc.
Nginx Vs other web servers: Nginx is a HTTP server and not a servlet engine. Given that, you can check if it fits your needs.
It is a fast web server. You need to evaluate the benefits of using it as a single stand alone webserver against other web servers. Speed and memory could help.
Nginx as a load balancer:
You can have multiple web server instances behind nginx.
It supports load balancing algorithms like round robin, weighted etc so the load can be distributed based on the resource availability.
It helps in terminating ssl at Nginx, filter requests, modify headers,
compression, application upgrades wihtout downtime, serve cached content etc. This frees up resources on the server running the application. Also separation of concerns.
This setup is a reverse proxy and the benefits to it.
You can handle cache expiry with nginx. nginx documentaion has good details http://nginx.com/resources/admin-guide/caching/
I'm building an asynchronous RESTful web service and I'm trying to figure out what the most scalable and high performing solution is. Originally, I planned to use the FriendFeed configuration, using one machine running nginx to host static content, act as a load balancer, and act as a reverse proxy to four machines running the Tornado web server for dynamic content. It's recommended to run nginx on a quad-core machine and each Tornado server on a single core machine. Amazon Web Services (AWS) seems to be the most economical and flexible hosting provider, so here are my questions:
1a.) On AWS, I can only find c1.medium (dual core CPU and 1.7 GB memory) instance types. So does this mean I should have one nginx instance running on c1.medium and two Tornado servers on m1.small (single core CPU and 1.7 GB memory) instances?
1b.) If I needed to scale up, how would I chain these three instances to another three instances in the same configuration?
2a.) It makes more sense to host static content in an S3 bucket. Would nginx still be hosting these files?
2b.) If not, would performance suffer from not having nginx host them?
2c.) If nginx won't be hosting the static content, it's really only acting as a load balancer. There's a great paper here that compares the performance of different cloud configurations, and says this about load balancers: "Both HaProxy and Nginx forward traffic at layer 7, so they are less scalable because of SSL termination and SSL renegotiation. In comparison, Rock forwards traffic at layer 4 without the SSL processing overhead." Would you recommend replacing nginx as a load balancer by one that operates on layer 4, or is Amazon's Elastic Load Balancer sufficiently high performing?
1a) Nginx is asynchronous server (event based), with single worker itself they can handle lots of simultaneous connection (max_clients = worker_processes * worker_connections/4 ref) and still perform well. I myself tested around 20K simultaneous connection on c1.medium kind of box (not in aws). Here you set workers to two (one for each cpu) and run 4 backend (you can even test with more to see where it breaks). Only if this gives you more problem then go for one more similar setups and chain them via an elastic load balancer
1b) As said in (1a) use elastic load balancer. See somebody tested ELB for 20K reqs/sec and this is not the limit as he gave up as they lost interest.
2a) Host static content in cloudfront, its CDN and meant for exactly this (Cheaper and faster then S3, and it can pull content from s3 bucket or your own server). Its highly scalable.
2b) Obviously with nginx serving static files, it will now have to serve more requests to same number of users. Taking that load away will reduce work of accepting connections and sending the files across (less bandwidth usage).
2c). Avoiding nginx altogether looks good solution (one less middle man). Elastic Load balancer will handle SSL termination and reduce SSL load on your backend servers (This will improve performance of backends). From above experiments it showed around 20K and since its elastic it should stretch more then software LB (See this nice document on its working)