Service Discovery and Load Balancing in Kubernetes

This article mainly introduces service discovery and how to implement service discovery in kubernetes.

What is service discovery

We talk about service discovery and service discovery all day long, but what exactly is service discovery?

Simply put, service discovery solves the problem of: "Where are you? Are you okay?". In terms of our usual services, service A needs to call service B, and service A needs to know where B is, whether it can be used.

In fact, we often use some service discovery things, but we don't call it the high-level name of service discovery. See if you know any of these techniques below.

Here is another example to illustrate the concept of service discovery.

The service discovery method we used at first was purely manual. When we want to access the application or service of the opposite end, we can directly specify its IP+Port (as shown in the first case on the right side of the figure above). When there are multiple applications or services in the backend, it is also possible to configure the IP:Port of these applications into the configuration file or to rotate the access in the program (as shown in the second case on the right side of the figure above). But what if one or more of the nodes are down? Do we still need to manually change the configuration, which is very troublesome and inefficient. In order to solve this problem, programmers want to automate this process through programs, and they have produced service discovery technologies such as DNS, LVS, Nginx, etc., which largely replace the hands of operation and maintenance personnel and improve the Efficiency (as shown in the third case on the right side of the figure above).

The above are the service discovery methods that we often use at present, so how does the kubernetes platform provide a service discovery mechanism?

service discovery in kubernetes

In order to better understand the service discovery mechanism in kubernetes, let's briefly describe the currently commonly used kubernetes network deployment methods.

The basis of service discovery is that the upper-layer service discovery and load balancing strategies corresponding to different network and network solutions may be different

Today we describe the service discovery and load balancing in kubernetes based on the large layer 2 network implemented by the Flannel component. The Flannel network model is as follows: