Shulou(Shulou.com)06/03 Report--

On the basis of introducing the realization of docker multi-segment communication between etcd and flannel, this paper focuses on its concrete steps, which are simple and easy to operate, and the content of the article is compact step by step. I hope you can get something according to this article.

I. brief introduction

Flannel is a third-party solution for multi-segment communication and a container network solution developed by CoreOS. Flannel assigns a subnet to each host, and the container assigns IP from this subnet. These IP can be routed between host, and the containers can communicate across hosts without NAT and port mapping. Each subnet is divided from a larger IP pool, and flannel runs an agent called flanneld on each host, which is responsible for allocating subnet from the pool. In order to share information among hosts, flannel uses etcd (key-value distributed database similar to consul) to store network configuration, allocated subnet, IP of host, and so on. How packets are forwarded between hosts is implemented by backend. Flannel provides a variety of backend, the most commonly used being vxlan and host-gw. Please refer to https://github.com/coreos/flannel for other backend. Flannel supports a variety of backend: currently, data forwarding methods such as UDP, VxLAN, AWS VPC and GCE routing are supported, and udp is used by default.

II. Preparatory work

Three VM virtual machines

One for etcd deployment

The other two are used for flannel deployment

System environment: centOS7.2

Docker version: docker-ce 19.3.5

Etcd version: etcd-3.3.11-2.el7.centos.x86_64

Flannel version: flannel-0.7.1-4.el7.x86_64

Installation, configuration and fault handling

1. Deploy etcd service

1.1 installation

[root@localhost ~] # yum install-y etcd # install etcd

1.2 modify the etcd.conf file

[root@localhost ~] # cd/ etc/etcd/

[root@localhost etcd] # cp-p etcd.conf etcd.conf.bak # back up the configuration file for fallback use.

[root@localhost etcd] # vim etcd.conf

Put the following items:

ETCD_DATA_DIR= "/ var/lib/etcd/default.etcd"

ETCD_LISTEN_CLIENT_URLS= "http://localhost:2379"

ETCD_NAME= "default"

ETCD_ADVERTISE_CLIENT_URLS= "http://localhost:2379"

Modified to:

ETCD_DATA_DIR= "/ var/lib/etcd/default.etcd"

ETCD_LISTEN_CLIENT_URLS= "http://172.16.41.251:2379"

ETCD_NAME= "default"

ETCD_ADVERTISE_CLIENT_URLS= "http://172.16.41.251:2379"

[root@localhost ~] # grep ^ [Amurz] / etc/etcd/etcd.conf # View the contents of the file

-- name: the node name that is easy to understand, defaults to default, should be unique in the cluster, and hostname can be used.

-- data-dir: the path where the service running data is saved. Default is ${name} .etcd.

-- listen-client-urls: the address where the service is provided, such as http://ip:2379,http://127.0.0.1:2379, where the client connects to interact with etcd.

-- advertise-client-urls: the publicly announced client listening address of this node, and this value will tell other nodes in the cluster.

1.3 create a new etcd.sh file and add the corresponding content

Create an etcd.sh file in the root directory

[root@localhost ~ # vim etcd.sh

Add the following to the etcd.sh file:

{"Network": "10.2.0.0 vxlan 16", "SubnetLen": 24, "Backend": {"Type": "vxlan"}}

Network: define the IP address pool of host hosts as 10.2.0.0 IP 16. Note: because etcd does not dynamically save the flannel network on host, for example, when a node is deleted, the subnet network in etcd about this node will not be deleted, so use the 10.X.X.X network to ensure that there are enough networks available

SubnetLen: specifies that the subnet size assigned to each host is 24 bits, that is, 10.2.x.0/24

Backend is vxlan, that is, hosts communicate with each other through vxlan. Backend is divided into vxlan and host-gw.

1.4 create new network/config files and add content

[root@localhost ~] # cd / usr/local/bin/

[root@localhost bin] # mkdir network

[root@localhost ~] # systemctl start etcd # start the etcd service, otherwise an error will be reported by running the following command

[root@localhost network] # etcdctl-- endpoints= http://172.16.41.251:2379 set / usr/local/bin/network/config

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