Baby Steps: Docker Swarm

Karl Bielefeldt

What Swarm Buys Us

• Docker managed overlay
• DNS
• Services
• Secrets
• Similar interface to starting bare containers

elif self.client.api_version < u'1.25':
    container = self.client.create_container(
        hostname=hostname,
        image=self.container,
        detach=True,
        stdin_open=True,
        tty=True,
        name=self.name,
        environment=environment,
        user=user_group,
        host_config=docker.types.HostConfig(version=self.client.api_version,
            binds=volumes,
            links=links,
            port_bindings=port_bindings,
            dns=dns,
            dns_search=dns_search,
            group_add=groups,
            cap_add=cap_add,
            **resource_limits
        )
    )
else:
    dns_config = docker.types.DNSConfig(nameservers=dns, search=dns_search)
    mapped_volumes = [docker.types.Mount(source=k, target=v.values()[0] if isinstance(v, dict) else v, type=v.keys()[0] if isinstance(v, dict) else "bind") for k, v in volumes.items()]
    container_spec = docker.types.ContainerSpec(
        image=self.container,
        hostname=hostname,
        user=user_group,
        mounts=mapped_volumes,
        groups=groups,
        tty=True,
        open_stdin=True,
        dns_config=dns_config,
        env=environment
    )
    task_template = docker.types.TaskTemplate(container_spec)
    int_port_bindings = {int(k): int(v) for k, v in port_bindings.items()}
    endpoint_spec = docker.types.EndpointSpec(ports=int_port_bindings)
    service = self.client.create_service(task_template, name=self.name, endpoint_spec=endpoint_spec, networks=['mcp'])

What I accomplished in a couple afternoons

• Manually upgraded docker to version 18.02.0-ce in an MCP VM
• Learned sshfs to speed up node admin and dockhand hacking on remote systems
• Modified dockhand to start services instead of bare containers
• Manually got a service working with docker's overlay network

Questions?