Haproxy runs on current hardware and can support tens of thousands of concurrent connections. And its operation mode makes it easy and safe to integrate into your current architecture, while protecting your web server from being exposed to the network. Multi process or multi thread model is limited by memory, system scheduler and ubiquitous lock, so it can rarely handle thousands of concurrent connections.
The event driven model does not have these problems because it implements all these tasks in the user space with better resource and time management. The disadvantage of this model is that these programs usually have poor scalability on multi-core systems. This has been developed and saved for a website caught in a small DDoS attack Many sites, this advantage is also other load balancer does not have. This feature can only be used after Linux 2.
This feature also makes it possible to handle some traffic for a special server without modifying the server address. The single process and event driven models significantly reduce the overhead and memory consumption of context switching. Under any available condition, the single buffering mechanism can complete the read and write operations without copying any data, which will save a lot of CPU clock cycles and memory bandwidth; 4.
With the help of the split system call on Linux 2. The memory allocator can realize real-time memory allocation in a fixed size memory pool, which can significantly reduce the duration of creating a session; 6. Tree storage: it focuses on the use of the elastic binary tree developed by the author many years ago.
It realizes keeping timer commands, keeping running queue commands, managing polling and least connection queues with low overhead of O log n ; 7. The expensive system calls are carefully reduced, and most of the work is done in user space, such as time reading, buffer aggregation and file descriptor enabling and disabling; All these fine points of optimization realize that there is still a very low CPU load on the medium-sized load.
Therefore, it is very important to tune the OS performance. Therefore, the 7-layer performance of haproxy on high-end systems can easily exceed that of hardware load balancing devices. In the production environment, the use of haproxy as an expensive high-end hardware load balancing device fault emergency solution is also visible in the production environment.
Moreover, they do not buffer any data, so they have a longer response time. Correspondingly, the software load balancing device uses TCP buffer, which can create extremely long requests and has a large response time.
Haproxy currently has three versions: 1. The RPM package of centos 6. Install haproxy. Explain the configuration file in detail The configuration file of haproxy consists of two parts: global setting and proxy setting.
It is divided into five sections: global, defaults, frontend, backend and listen. These values are usually in milliseconds, but other time unit suffixes can also be used. Us: microseconds, i. By default, only one process is started.
This option is used to set the maximum number of pipes allowed for each process. Each pipe will open two file descriptors. The same memory condition is small. A smaller value enables haproxy to accept more concurrent connections. A larger value allows some applications to use larger cookie information.
The default value is , which can be modified at compile time. However, it is strongly recommended to use the default value; — tune. A larger value can bring a larger throughput. The default value is in single process mode and 8 in multi process mode. Setting it to — 1 can prohibit this limit. Generally, it is not recommended to modify it; — tune. The default value depends on the OS.
When the value is less than , the bandwidth can be saved, but the network delay will be slightly increased. If the value is greater than , the delay will be reduced, but the network bandwidth usage will be slightly increased; — tune. It is recommended to use about When more space is needed, haproxy will automatically increase its value; — tune. If it is too short, it will lead to misjudgment and long resource consumption Maxconn: the maximum number of connections per server HTTP server close: when using a long connection, this function can make the server close the long connection in order to avoid the client timeout and not close the long connection Redispatch: when using cookie based redirection, once a backend server goes down, the session will be redirected to an upstream server.
In addition, ACL names are case sensitive. It is used to select a server in a load balancing scenario. It is only applied when persistent information is not available or when a connection needs to be redistributed to another server. The supported algorithms are: 3. This algorithm is dynamic, which means that its weight can be adjusted at runtime, but in design, each back-end server can only accept connections at most, and supports slow start.
Adjusting the server weight at run time will not take effect. However, there is no limit on the number of connections to the back-end server. Can this solution be used to support failover for non-http processes? A very simplistic failover. The app uses a network drive to store its configuration files ,etc. Any ideas? If you are thinking about that you add 2 hosts but only one host serve requests continuously and second host keep as spare.
In any case first host goes down, then second take place of them. How would you configure this, if you need the ability to failover from A to B, then after repairing A, A should then become the backup for B.
To put this a different way, A is primary, and B is failover. But, after failing over to B, B then becomes primary, and A then becomes failover. It is no longer on EPEL. You will find it in the base repo, or on your DVD if you have 6. This blog looks just like my old one!
Outstanding choice of colors! Save my name, email, and website in this browser for the next time I comment. Facebook Twitter Instagram. TecAdmin Home Ubuntu Related Posts. Hi Rahul, I have installed haproxy as root and created a non root user lbAdmin in my rhel 7. Muhamed Hussain on August 7, pm. The higher you are on the network stack layer, the faster you will be able to process requests. The caveat is that the extra performance gain comes at the cost of feature and ability loss.
This approach is accomplished by using very little processing. The biggest downside to this method of balancing is your nodes must host every component of your application PHP, Java, CSS, Javscript, IMGs, etc , and the application files on each node must be the exact same versions.
Layer 7 balancing may require more horsepower to process, but what it offers in return for large and complex websites is worth the extra CPU time. Another benefit is being able to move heavily accessed areas of your website onto separate servers. Given enough popularity, the forum may cause other areas of your website to be sluggish or become inaccessible. Using layer 7, you could separate your forum onto its own server or server group to allow you to scale it out. Layer 7 works by analyzing the application request part of every packet, and then matching it against a set of policies or rules.
In order for us to be able to install it, we need to either compile it from source preferred or add the EPEL repository to our server and install it using Yum.
This method is best for optimizing the binaries for your hardware. There are a few base configuration that should be set before we move into creating load balance clusters. If you installed HAProxy using Yum, a lot the defaults are preset.
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