Docker SWARM 备忘单

Docker Swarm 模式速查表

Docker Swarm Mode is Docker’s native clustering and orchestration solution. It allows you to manage a group of Docker nodes as a single virtual system, enabling high availability, load balancing, and simplified deployment of containerized applications.

Key features:

Built-in orchestration
Declarative service model
Rolling updates
Auto-scaling and self-healing
Secure node communication via TLS

📌 Swarm Initialization

Initialize Swarm
```
docker swarm init 
```
Join Swarm (on worker/manager node)
```
docker swarm join-token worker 
```
Leave Swarm
```
docker swarm leave 
```
Force Leave (on manager)
```
docker swarm leave --force 
```

👥 Node Management

List nodes
```
docker node ls 
```
Promote node to manager
```
docker node promote <node-name> 
```
Demote node to worker
```
docker node demote <node-name> 
```

Inspect node

docker node inspect <node-name> --pretty

Drain node (prevent scheduling)

docker node update --availability drain <node-name>

Activate node

docker node update --availability active <node-name>

🧠 Manager Nodes

Manager nodes are responsible for:

Orchestrating tasks and services
Maintaining cluster state
Handling API requests

You can have multiple managers for high availability, but only one is the leader at any time.

Check manager status
```
docker node ls 
```
View Raft consensus info
```
docker swarm inspect 
```

📦 Service Management

Create service

docker service create --name <service-name> <image>

Create service with replicas

docker service create --name <service-name> --replicas <n> <image>

List services
```
docker service ls 
```

Inspect service

docker service inspect <service-name> --pretty

Scale service

docker service scale <service-name>=<n>

Update service

docker service update --image <new-image> <service-name>

Remove service
```
docker service rm <service-name> 
```

🔁 Replicas

Replicas define how many instances of a service should run across the swarm.

Set replicas when creating a service

docker service create --replicas 5 --name myapp myimage

Scale replicas
```
docker service scale myapp=10 
```

Swarm automatically distributes replicas across available nodes and restarts them if they fail.

🐝 Task & Container Management

List tasks of a service
```
docker service ps <service-name> 
```
List all tasks
```
docker node ps <node-name> 
```
List containers
```
docker container ls 
```

Inspect container

docker container inspect <container-id>

🌐 Networking

🧠 What Is an Overlay Network?

An overlay network is a virtual network that spans across multiple Docker hosts. It allows containers running on different nodes

Commands

Create overlay network

docker network create --driver overlay <network-name>

List networks
```
docker network ls 
```

Attach service to network

docker service create --name <service-name> --network <network-name> <image>

🛠 Useful Flags

Flag	Description
`--replicas`	Number of service instances
`--publish`	Port mapping (`<host>:<container>`)
`--mount`	Volume mounting
`--constraint`	Node placement rules
`--update-delay`	Delay between updates
`--limit-cpu` / `--limit-memory`	Resource limits

📄 Example: Create a Web Service

docker service create \ --name web \ --replicas 3 \ --publish 80:80 \ --network webnet \ nginx