11.swarm
Swarm集群管理
Docker是容器运行时，而Swarm是Docker公司出品的容器编排工具。
Swarm基于Docker运行时，一个swarm由多个节点组成，每个节点是在swarm模式下运行Docker Engine的物理机或虚拟机。。Docker Swarm 支持标准的Docker API，所有任何已经与Docker Engine通信的工具都可以与Swarm集成，轻松地扩展到多个主机。
节点
节点分为管理节点和工作节点。
管理节点
管理节点处理集群管理任务：
- 维护集群状态
- 调度服务
- 响应swarm模式HTTP API 端点
管理节点通过Raft实现维护整个swarm所有服务的一致内部状态。
工作节点
工作节点是Docker引擎所在的物理机或虚拟机，其唯一目的是运行容器。
工作节点不参与 Raft 分布式状态，不做调度决策。
服务
在swarm上部署服务时，swarm管理节点接受服务定义作为服务的所需状态。
然后它将集群中节点上的服务调度为一个或多个副本任务。这些任务在集群中的节点上彼此独立运行。
例如，在三个nginx实例之间进行负载平衡。
容器是一个单独的进程。在swarm模式中，每个任务只调用一个容器。任务类似于调度器放置容器的“插槽”。一旦容器处于活动状态，调度器就会识别出任务处于运行状态。如果容器未通过健康检查或终止，则任务终止。
任务调度
任务是swarm调度的原子单位。创建或更新服务声明时，调度器会通过调度任务来实现所需的状态。
例如，定义一个服务，要求调度器始终保持三个nginx实例运行。调度器将创建三个任务。每个任务都是一个插槽，调度器通过生成容器来填充插槽。
容器是任务的实例化。如果nginx实例崩溃，调度器将创建一个新的nginx副本来生成一个新的容器。
swarm模式接受服务创建请求并将任务调度到工作节点:
Swarm
docker info | grep Swarm
# docker swarm init --advertise-addr 10.0.0.215
docker swarm init
# Swarm initialized: current node (t5thzh5eplovkkup867xh6ik4) is now a manager.
#
#To add a worker to this swarm, run the following command:
#
# docker swarm join --token SWMTKN-1-03q2kxmu8mlhpsi4qgkwyfam032o4zk8ykty19tc854hmqwr43-53hjsrn5pev37z26ctzgciwk9 10.0.0.215:2377
#
# To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.
docker node ls
# ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION
# t5thzh5eplovkkup867xh6ik4 * ubuntu Ready Active Leader 20.10.21
可以看到唯一一个node是当前的Leader
serivce
docker service类似于docker run指令
创建一个服务 ping www.aws.com.cn
docker service create alpine ping 8.218.126.38
# tgbf1ac65aeismat25wfaajax
# overall progress: 1 out of 1 tasks
# 1/1: running [==================================================>]
# verify: Service converged
查看该服务：
- 当前replicas状态为1/1
- 系统分配了ID和名字
docker service ls
# ID NAME MODE REPLICAS IMAGE PORTS
# tgbf1ac65aei distracted_volhard replicated 1/1 alpine:latest
根据名字查看细节
- 当前运行的node
- 每个容器的名字，是服务名加后缀
docker service ps distracted_volhard
# ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
# xcesiihrnc21 distracted_volhard.1 alpine:latest ubuntu Running Running about a minute ago
在节点层面，查看运行中的容器
docker container ls
# CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
# a0070e666888 alpine:latest "ping 8.218.126.38" 2 minutes ago Up 2 minutes distracted_volhard.1.xcesiihrnc21vqsayq3dyyxp3
扩展服务节点
docker service update tgbf1ac65aei --replicas 3
tgbf1ac65aei
# overall progress: 3 out of 3 tasks
# 1/3: running [==================================================>]
# 2/3: running [==================================================>]
# 3/3: running [==================================================>]
# verify: Service converged
再次查看服务，replicas 3/3
docker service ls
# ID NAME MODE REPLICAS IMAGE PORTS
# tgbf1ac65aei distracted_volhard replicated 3/3 alpine:latest
根据名字查看细节
docker service ps distracted_volhard
# ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
# xcesiihrnc21 distracted_volhard.1 alpine:latest ubuntu Running Running 4 minutes ago
# 5jp0ekrthai8 distracted_volhard.2 alpine:latest ubuntu Running Running 44 seconds ago
# n7jjoxqspjko distracted_volhard.3 alpine:latest ubuntu Running Running 44 seconds ago
随便删除一个节点
docker container rm -f distracted_volhard.2
docker container ls
# CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
# 8f19c562d31b alpine:latest "ping 8.218.126.38" 3 minutes ago Up 3 minutes distracted_volhard.3.n7jjoxqspjkotvfsjx74usze9
# a0070e666888 alpine:latest "ping 8.218.126.38" 7 minutes ago Up 7 minutes distracted_volhard.1.xcesiihrnc21vqsayq3dyyxp3
查看服务，状态变为2/3
docker service ls
# ID NAME MODE REPLICAS IMAGE PORTS
# tgbf1ac65aei distracted_volhard replicated 2/3 alpine:latest
等待一会儿，状态又变成3/3
docker service ls
# ID NAME MODE REPLICAS IMAGE PORTS
# tgbf1ac65aei distracted_volhard replicated 3/3 alpine:latest
查看看服务状态，可以看到之前有一个容器被删除
docker service ps distracted_volhard
# ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
# xcesiihrnc21 distracted_volhard.1 alpine:latest ubuntu Running Running 7 minutes ago
# w68ar2z42kdy distracted_volhard.2 alpine:latest ubuntu Running Running 40 seconds ago
# sydzmsh6auzd \_ distracted_volhard.2 alpine:latest ubuntu Shutdown Failed 46 seconds ago "task: non-zero exit (137)"
# n7jjoxqspjko distracted_volhard.3 alpine:latest ubuntu Running Running 4 minutes ago
删除服务
docker service rm distracted_volhard
# distracted_volhard
快速查看容器状态，发现容器还未完全删除。说明swarm是先解除服务，再清理容器
docker container ls
# CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
# 5a01c6c6c177 alpine:latest "ping 8.218.126.38" 9 minutes ago Up 9 minutes distracted_volhard.1.bka8ah2jj4nc11m9zp2k0cht1
过一会儿再看，容器被清除
docker container ls
# CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
多节点swarm
配置一个三节点的虚拟机集群，node1/node2/node3，可相互通信
部署 https://github.com/play-with-docker/play-with-docker
docker swarm leave --force sudo apt install golang-go -y git clone https://github.com/play-with-docker/play-with-docker cd play-with-docker docker run hello-world sudo modprobe xt_ipvs docker swarm init docker pull franela/dind go mod vendor docker-compose up
在node1上
docker swarm init
# Error response from daemon: could not choose an IP address to advertise since this system has multiple addresses on different interfaces (172.18.0.81 on eth1 and 192.168.0.8 on eth0) - specify one with --advertise-addr
# 选择对外可见的IP
docker swarm init --advertise-addr 192.168.0.8
# Swarm initialized: current node (xsnu8ijh23xj5qqv1crmrmqb5) is now a manager.
#
# To add a worker to this swarm, run the following command:
#
# docker swarm join --token SWMTKN-1-0hpw0ddhbvj5e6hobki3sakfpi4pykv3c9f5juoqpfsapuelgj-4dgjf34cq6z3lltxsqe8888da 192.168.0.8:2377
#
# To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.
在node2上，加入swarm集群
docker swarm join --token SWMTKN-1-0hpw0ddhbvj5e6hobki3sakfpi4pykv3c9f5juoqpfsapuelgj-4dgjf34cq6z3lltxsqe8888da 192.168.0.8:2377
# This node joined a swarm as a worker.
此时node2 以worker节点身份加入
在node1上，查看节点
docker node ls
# ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION
# xsnu8ijh23xj5qqv1crmrmqb5 * node1 Ready Active Leader 20.10.17
# k10fphc0j8vh8u5o7j98vwdz3 node2 Ready Active 20.10.17
node2加入。当前node1 有leader状态
在node1上，修改node2的role
docker node update --role manager node2
# node2
docker node ls
# ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION
# xsnu8ijh23xj5qqv1crmrmqb5 * node1 Ready Active Leader 20.10.17
# k10fphc0j8vh8u5o7j98vwdz3 node2 Ready Active Reachable 20.10.17
此时node2出现reachable状态。
让node3 直接以管理节点身份加入。在node1上
docker swarm join-token manager
#To add a manager to this swarm, run the following command:
#
# docker swarm join --token SWMTKN-1-0hpw0ddhbvj5e6hobki3sakfpi4pykv3c9f5juoqpfsapuelgj-9rwy33fwi8xf9zpzh33muw4lf 192.168.0.8:2377
复制这段指令
在node3上
docker swarm join --token SWMTKN-1-0hpw0ddhbvj5e6hobki3sakfpi4pykv3c9f5juoqpfsapuelgj-9rwy33fwi8xf9zpzh33muw4lf 192.168.0.8:2377
# This node joined a swarm as a manager.
node3以管理节点身份加入。
在node1上查看
docker node ls
# ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION
# xsnu8ijh23xj5qqv1crmrmqb5 * node1 Ready Active Leader 20.10.17
# k10fphc0j8vh8u5o7j98vwdz3 node2 Ready Active Reachable 20.10.17
# fldbwcgpw3bhyryoqu7x7y4qb node3 Ready Active Reachable 20.10.17
此时node3出现reachable状态。
在多节点swarm上启动服务
在node1上
docker service create --replicas 3 alpine ping 8.218.126.38
# 2oe8jd4jt0cxyqf4b9kaj0hcw
# overall progress: 3 out of 3 tasks
# 1/3: running [==================================================>]
# 2/3: running [==================================================>]
# 3/3: running [==================================================>]
# verify: Service converged
# 查看服务
docker service ls
# ID NAME MODE REPLICAS IMAGE PORTS
# 2oe8jd4jt0cx agitated_kare replicated 3/3 alpine:latest
# 查看当前节点容器
docker node ps
# ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
# pqse8hj55jkt agitated_kare.2 alpine:latest node1 Running Running 16 seconds ago
# 查看node2节点容器
docker node ps node2
# ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
# 7ug7hlhv15dt agitated_kare.3 alpine:latest node2 Running Running 37 seconds ago
# 查看服务在节点容器的分布
docker service ps agitated_kare
# ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
# 5kk10j2lo2bf agitated_kare.1 alpine:latest node3 Running Running 52 seconds ago
# pqse8hj55jkt agitated_kare.2 alpine:latest node1 Running Running 51 seconds ago
# 7ug7hlhv15dt agitated_kare.3 alpine:latest node2 Running Running 51 seconds ago
docker node ls
# ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION
# xsnu8ijh23xj5qqv1crmrmqb5 * node1 Ready Active Leader 20.10.17
# k10fphc0j8vh8u5o7j98vwdz3 node2 Ready Active Reachable 20.10.17
# fldbwcgpw3bhyryoqu7x7y4qb node3 Ready Active Reachable 20.10.17
说明三个可用节点，每个分配到了一个容器