Apache reverse proxy combined with Tomcat cluster for load balancing (I.), conceptual understanding

Good blog is generally able to do "look at the title of the text," to see the next heading to know what to say below, to write this title hesitated, would have to be the title of the Apache+tomcat to achieve load balance, but also think it seems more fuzzy. After thinking about it, I think that using Apache to do load balancing the bottom of the combination is the Tomcat cluster function. So the title was used.

First of all, the concept of cluster and load balancing, a lot of people have not understood these two concepts, do not know how to distinguish between the two concepts, and think that these two concepts as if it is a technology of two terms, in fact, the following two concepts are described below:

What is a cluster (Cluster)The so-called cluster refers to a set of independent computer systems composed of multi-processor systems, each server has an equivalent status, between them through the network to achieve inter-process communication. Applications can communicate via network shared memory and implement distributed computers. A cluster also refers to multiple computers working together to perform an application.

clusters can be divided into the following types(1) High reliability (HA). With cluster management software, when the primary server fails, the backup server can proactively take over the work of the primary server and switch the past in time. To achieve uninterrupted service to users.

(2) High Performance Computing (HP).

That is to make full use of the resources of each computer in the cluster to realize the parallel processing of complex operations, which is often used in scientific computing field.

(3) Load balancing (load Balance).

Load balancing is one of the cluster functions. That is, the load pressure is allocated to each computer in the cluster reasonably according to an algorithm to reduce the pressure on the primary server and reduce the hardware and software requirements for the primary server. Load balancing is the assignment of compute requests to a cluster to balance the compute load of computers in the cluster.

load Balancing has two implications

1: A large number of concurrent interviews or data sharing on multiple nodes of the device processing, reducing the time the user waits for a response.

2: A single heavy load operation is shared on multiple node devices to do parallel processing. After each node device processing is finished, the results are summarized, returned to the user, the system processing capacity has been greatly improved.

implementation can be divided into

(1) Server Software-based cluster load balancing.

(implemented on the server.) ）

(2) Nat cluster load balancing (on a fire wall, or on a switch). ）

(3) DNS-based cluster load balancing (implemented on DNSServer.

）

(4) It is also possible to use ISA to set the load balance of the cluster, but it is necessary to have isaserver I think the feasibility is small.

I believe you already know what a cluster is and what is load balancing. Here go to the topic of the article, online already have a lot of apache+tomcat to achieve load balance of the article, but are only limited to teach you how to do, and did not tell us why to do so, so that everyone just know it does not know why, Below I will assemble the Tomcat cluster and Apache load balancer to specifically describe.

Apache reverse proxy combined with Tomcat cluster for load balancing (I.), conceptual understanding