This document discusses Docker Swarm, a native clustering service for Docker that allows scheduling of container workloads across multiple hosts. It describes how to set up a Swarm cluster by labeling multiple machines and joining them to a Swarm manager node. The Swarm manager then uses scheduling options like filters and strategies to distribute containers across hosts based on constraints, affinity, ports, dependencies, health checks, and node labels. While the Swarm API is mostly compatible with Docker's API, it currently has some missing endpoints and differences related to TLS support for secure communication in the cluster.

1. Swarm – Container Cluster
System
Sriram Natarajan
T-Labs

2. Docker Platform & Related Tools
Machine
Host 1
Machine
Host 2
Machine
Host 3
Swarm / Kubernetes / CoreOS/ Marathon …
(Cluster Service)
TCP/TLS Channel
WEAVEWORKS Flannel
etcd / consul / zookeeper
(service discovery)
Deploying Apps
(Compose, fig)
Registries
(Hub, Quay)
Monitoring/Logg
ing
(seagull,
dockerana,
logjam)
UI
(DockerUI,
DockerBoard,
Kitematic)
Security
(SELinux,
Capabilities)

3. Swarm: Introduction
• Native clustering service (version: 0.2.0)
• Scheduling container workloads
• Health check & rescheduling workloads
• Supports Docker REST API

4. Swarm – Cluster Setup
docker –H --label
swarm join
Host 1
docker –H --label
swarm join
Host 2
docker –H --label
swarm join
Host 3
Swarm (Manager Node)
TCP/TLS Channel
swarm create
swarm manage
Manager Node
• Use discovery service
– Hosted (tokens)
– Etcd
– Consul
– Zookeeper
• Create a cluster
• Setup Swarm Manager to
listen for docker hosts
Host Nodes
• Start docker in n/w
interface
• Label the nodes (next
slide)
• Join the cluster
• Secure channel (if reqd..)

5. Swarm – Clustering System
docker –H --label
swarm join
Host 1
docker –H --label
swarm join
Host 2
docker –H --label
swarm join
Host 3
Swarm (Manager Node)
TCP/TLS Channel
swarm create
swarm manage
Docker CLI
Remote
APIs
Advanced Container Scheduler Options
• Filters
• Strategies

6. Scheduling Options - Filters
Filters
• Constraint
– storagedriver, executiondriver,
kernelversion,operatingsystem
– label
• Affinity
– Containers
– Images
– Other Expressions
• Port
– Nodes with available ports
• Dependency
– Co-scheduler for shared volumes
– Links, Shared network stack
– Combination of dependencies
• Health
Strategies
• Binpacking
• Random
• Spread
Label ->
service=security
FW container
Snort container
Host 1
Label ->
service=perf
Port 80
Host 2
Label ->
service=monitor
Host 3
Swarm (Manager Node)
TCP/TLS Channel
swarm create
swarm manage

7. Swarm: Remote API Support
Not Supported Yet
• Compatible with Docker remote API
• There are some missing endpoints and
few differing from docker api (75 %
coverage)
API Differences
• TLS Support
– Setup a CA
– Use CA to manage your keys and certificates for
your manager and hosts
• Setup
– Start the docker daemons in hosts with TLS
options
– Start the Swarm manager with TLS options