[K8S series] In-depth analysis of k8s network plug-ins—Weave Net

 

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Kubernetes (k8s) is a container orchestration platform that allows applications and services to be run in containers. Learn about k8s network plug-in-Weave Net today

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Kubernetes is a distributed system capable of managing and orchestrating containerized applications. Among them, monitoring is a very important aspect, which can help users understand the health status, performance and availability of the cluster.

In this article, we will introduce the Weave Net plugin in the Kubernetes network plugin in detail.

1 Basic introduction 

In Kubernetes, network plug-ins are also called container network interface (Container Network Interface, CNI) plug-ins, which are used to implement communication and network connections between containers. Here are some common Kubernetes networking plugins:

1. Flannel : Flannel is a popular CNI plugin that uses a virtual overlay network to connect containers on different nodes. Flannel supports a variety of back-end drivers, such as VXLAN, UDP, Host-GW, etc.

2. Calico : Calico is an open source networking and security solution that uses the BGP protocol for routing between containers. Calico supports flexible network policies and security rules, which can be used for large-scale deployment.

3. Weave Net : Weave Net is a lightweight CNI plugin that connects containers on different nodes by creating virtual network devices and network proxies. Weave Net supports overlay mode and direct connection mode, which is flexible.

4. Cilium : Cilium is a high-performance network and security solution for Kubernetes, using eBPF (Extended Berkeley Packet Filter) technology to provide fast inter-container communication and network policy enforcement.

5. Canal : Canal is a comprehensive CNI plugin that combines the functionality of Calico and Flannel. It can use Flannel to provide overlay networking while using Calico's network policy and security features.

6. Antrea : Antrea is an Open vSwitch-based CNI plugin designed for Kubernetes networking and security. It provides high-performance network connectivity and network policy functions.

7. kube-router : kube-router is an open source CNI plugin that combines network and service proxy functionality. It supports BGP and IPIP protocols, and has load balancing features.

These are some of the common options in Kubernetes networking plugins, each with its specific benefits and use cases. Choosing the right network plugin depends on factors such as your needs, network topology, and performance requirements.

At the same time, the Kubernetes community is constantly evolving and introducing new networking plugins to meet changing needs.

2  Weave Net

Weave Net is a commonly used container network solution in Kubernetes (K8s for short), which provides inter-container communication and cross-host network functions .

Weave Net can establish a virtual network between containers on different hosts , enabling them to communicate directly without any network configuration.

2.1 Key Features

Here are some key features of Weave Net in detail:

1. Virtual Network : Weave Net creates a virtual software-defined network (SDN), running an agent process on each node in the Kubernetes cluster. These agent processes are responsible for managing the networking of containers and establishing cross-host networking when needed.

2. Inter-container communication : Weave Net assigns each container a unique IP address and connects them through a virtual network. This way, containers can communicate with each other directly using IP addresses, as if they were running on the same host. Weave Net supports TCP, UDP and SCTP protocols, and provides high-performance data transmission.

3. Cross-host communication : Weave Net realizes cross-host communication by establishing a virtual network tunnel between hosts. These tunnels communicate through underlying network protocols such as VXLAN, IPv6, or UDP, connecting containers on different hosts together. This way, containers can transparently communicate across multiple hosts without additional network configuration.

4. Multi-cloud and hybrid cloud : Weave Net can operate in multi-cloud and hybrid cloud environments. It can be deployed on virtual machine instances of different cloud providers and provide a consistent network experience. This makes it easier to use Kubernetes in a cross-cloud environment without having to worry about differences in the underlying network.

5. Network Policy : Weave Net supports network policies, which can define access control rules for network traffic. Through network policies, communication between containers can be restricted to achieve network security isolation.

6. Simplified deployment : The deployment of Weave Net is relatively simple and can be deployed through the DaemonSet object of Kubernetes. DaemonSet will start a Weave Net agent process on each node, automatically configure the network and establish connections with other nodes.

Weave Net is a powerful container networking solution that provides flexible, high-performance and secure network communication capabilities for containers in Kubernetes clusters.

Its design makes inter-container communication and cross-host communication simple and transparent , and provides infrastructure support for building reliable distributed applications.

2.2 Advantages and disadvantages

advantage:

1. Ease of use : One of Weave Net's design goals is to simplify network configuration and management . It provides a simple command line interface and clear documentation, enabling users to easily set up and operate the network. In addition, Weave Net also supports automatic IP address management, no need to configure IP manually .

2. Fully flat network : Weave Net uses a global flat network model , which means that all containers can communicate directly, no matter which host they are on. This model eliminates subnetting and routing configurations in traditional networks, making communication between containers simpler and more efficient.

3. Dynamic network topology : Weave Net has an adaptive network topology that can automatically adjust network connections according to the start and stop of containers. When the container starts or stops, Weave Net will automatically update the network topology map to ensure that the connection between the containers is always normal.

4. Security : Weave Net offers several security features such as data encryption and access control. It uses network tunneling technology to encrypt communication between containers and allows users to configure access policies to restrict communication between containers.

5. Cross-host networking : Weave Net supports container communication across multiple hosts. It uses virtual network devices and virtual routers to connect containers on different hosts, providing a unified network layer that enables containers to communicate transparently.

shortcoming:

1. Performance overhead : Weave Net uses software-defined networking (SDN) technology to implement communication between containers, which may introduce certain performance overhead . Although Weave Net optimizes the forwarding and processing of network packets, it may cause some performance degradation compared to traditional physical network-based communications.

2. Single point of failure : There are some risks of single point of failure in Weave Net's architecture . For example, if a Weave Net's control node fails, it could cause network outages or communication problems. To mitigate this problem, it is recommended to deploy multiple Weave Net control nodes in production environments to increase reliability.

3. Learning curve : Although Weave Net provides an easy-to-use interface and documentation, it still requires users to have certain network knowledge and skills to understand and operate . For newcomers, it may take some time to become familiar with the concepts and configuration of Weave Net.

2.3 Implementation principle

The following is the implementation principle of Weave Net:

1. Virtual network device : Weave Net creates a virtual network device called Weave Bridge on each host. Each container is connected to this virtual network device and is given a unique virtual MAC address.

2. Virtual router : Weave Net creates a virtual router on each host in the cluster, called Weave Router. The virtual router is responsible for managing the routing and forwarding between containers.

3. Network tunnel : When communication between containers is required, Weave Net uses network tunnel technology to establish an encrypted communication channel between hosts. The network tunnel transmits the network data packets of the container between the hosts to ensure security and isolation.

4. Dynamic network topology : Weave Net uses gossip protocol to dynamically maintain network topology information. Each Weave Router exchanges network information through the gossip protocol, including container IP addresses, routing rules, and status information. This way, when containers start or stop, the network topology is automatically updated, ensuring proper connectivity between containers.

2.4 Usage Scenarios

Use cases for Weave Net include:

1. Multi-host container communication : Weave Net is suitable for scenarios where communication needs to be established between containers across multiple hosts. It provides an easy way to connect containers on different hosts, and provides a global flat network model so that containers can communicate directly.

2. Secure isolation and encrypted communication : Weave Net provides network tunneling and encryption to ensure that communication between containers is secure. This is useful for scenarios where you need to protect sensitive data and isolate different applications.

3. Dynamic network topology adjustment : Weave Net's dynamic network topology function makes it suitable for dynamic scheduling and scaling scenarios of containers. When the container starts or stops, Weave Net can automatically adjust the network connection and routing rules to ensure that the communication between the containers is always normal.

4. Simplify network configuration and management : One of Weave Net's design goals is to simplify network configuration and management. It provides a simple command line interface and easy-to-understand documentation, enabling users to easily set up and operate the network.

2.5 Configuration & Installation

The following are the specific steps to use Weave Net, including configuration and installation:

Configure WeaveNet:

1. Make sure you have a cluster running Kubernetes with administrator privileges.

2. Install Docker on each host running Kubernetes.

3. Install the Weave Net binaries on each host. It can be installed on Linux with the following command:

   sudo curl -L git.io/weave -o /usr/local/bin/weave
   sudo chmod +x /usr/local/bin/weave

4. Create a configuration file for Weave Net  weave.yamland copy the following content into the file:

   Here `weave-ipalloc-range` is the range used to allocate Weave Net IP addresses. Adjustments can be made as needed.

   yaml file

   apiVersion: v1
   kind: ConfigMap
   metadata:
     name: weave-net
     namespace: kube-system
     data:
       weave-ipalloc-range: "10.32.0.0/12"
   

5. Use  kubectl the command to apply the configuration file to the Kubernetes cluster:

   kubectl apply -f weave.yaml
   

Install WeaveNet:

1. Open a terminal and use SSH to connect to the master node of the Kubernetes cluster.

2. Run the following command on the master node to start Weave Net:

   sudo weave launch
   

   This will start Weave Net's control node on the master node and create a virtual network.

3. Run the following command on other nodes to join them to the Weave Net network:

   sudo weave join <主节点IP>
   

   Replace  <主节点IP> with the actual master node IP address.

4. Make sure all nodes have successfully joined Weave Net's network. The status of the nodes can be checked with the following command:

   sudo weave status
   

   If all is well, you should see a status of "ready" for all nodes.

So far, Weave Net has been successfully configured and installed. It automatically manages network communication and routing between containers. You can continue to create and manage containers in your Kubernetes cluster, and they will be able to communicate through Weave Net.

Please note that the above steps provide the basic configuration and installation methods of Weave Net, and the specific operations may vary according to your cluster environment and needs.

It is recommended to refer to the official documentation of Weave Net for more detailed configuration and installation instructions before use.

3 expansion

How to solve the single point of failure problem of Weave Net?

In order to solve the single point of failure problem of Weave Net, the following measures can be taken:

1. Deploying multiple control nodes : It is recommended to deploy multiple Weave Net control nodes in a production environment to improve reliability. Multiple control nodes can form a high-availability cluster, and a master node is selected through an election mechanism to handle network control tasks, and other nodes are used as backups. In this way, even if one of the nodes fails, other nodes can take over to ensure the normal operation of the network.

2. Load balancing and failover : In the case of deploying multiple control nodes, a load balancer can be used to distribute network traffic and implement failover. The load balancer can evenly distribute requests to multiple control nodes, thereby improving the availability and fault tolerance of the network. When a control node fails, the load balancer can automatically switch traffic to other available nodes.

3. Monitoring and Alarming : Implement a comprehensive monitoring and alarming system to detect and respond to Weave Net's single point of failure in a timely manner. The monitoring system can monitor the health status and network connection of control nodes, and trigger an alarm when abnormalities are found. This way, administrators can quickly take action to resolve problems and reduce network downtime.

4. Regular backup and recovery : Regularly back up Weave Net's configuration and status information so that it can be quickly restored in the event of a failure. Backups can include configuration files of control nodes, key data, and network topology information. If a control node fails, the backup can be used to restore the network configuration and restore the normal operation of the network.

5. Highly available infrastructure : In addition to Weave Net's own high availability measures, it should also ensure that the infrastructure itself is highly available. For example, use physical servers , network switches, and storage devices with redundancy and failover capabilities to reduce the impact of hardware failure on Weave Net.

Through the above measures, the availability and fault tolerance of Weave Net can be greatly improved, and the impact of single point failure on the network can be reduced. However, specific solutions may vary depending on the environment and needs, and it is recommended to evaluate and select the appropriate solution based on the actual situation.

4 Summary 

Overall, Weave Net is a powerful and easy-to-use Kubernetes network plug-in, which provides simple network configuration and management, and has the advantages of cross-host container communication, dynamic network topology and security. However, it also has some disadvantages of performance overhead and single point of failure, which need to be understood and weighed by users before using it.

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