CODEWITHSUNDEEP
dockerdocker-composedocker-swarm
user3292147
user3292147

Reputation: 399

docker-compose swarm: force containers to run on specific hosts

Trying to run cluster application on different virtual machines with use of Swarm stand alone and docker-compose version '2'. Overlay network is set. But want to force certain containers to run on specific hosts.

In documentation there is following advice, but with this parameter I was not able to start any container at all:

environment:
  - "constraint:node==node-1"

ERROR: for elasticsearch1  Cannot create container for service elasticsearch1: Unable to find a node that satisfies the following conditions
[available container slots]
[node==node-1]

Should we register hosts as node-1 node-2... or it is done by default.

[root@ux-test14 ~]# docker node ls
Error response from daemon: 404 page not found
[root@ux-test14 ~]# docker run swarm list
[root@ux-test14 ~]#  

[root@ux-test14 ~]# docker info
Containers: 8
 Running: 6
 Paused: 0
 Stopped: 2
Images: 8
Server Version: swarm/1.2.5
Role: primary
Strategy: spread
Filters: health, port, containerslots, dependency, affinity, constraint
Nodes: 2
 ux-test16.rs: 10.212.212.2:2375
  â ID: JQPG:GKFF:KJZJ:AY3N:NHPZ:HD6J:SH36:KEZR:2SSH:XF65:YW3N:W4DG
  â Status: Healthy
  â Containers: 4 (4 Running, 0 Paused, 0 Stopped)
  â Reserved CPUs: 0 / 2
  â Reserved Memory: 0 B / 3.888 GiB
  â Labels: kernelversion=3.10.0-327.28.3.el7.x86_64, operatingsystem=CentOS Linux 7 (Core), storagedriver=devicemapper
  â UpdatedAt: 2016-09-05T11:11:31Z
  â ServerVersion: 1.12.1
 ux-test17.rs: 10.212.212.3:2375
  â ID: Z27V:T5NU:QKSH:DLNK:JA4M:V7UX:XYGH:UIL6:WFQU:FB5U:J426:7XIR
  â Status: Healthy
  â Containers: 4 (2 Running, 0 Paused, 2 Stopped)
  â Reserved CPUs: 0 / 2
  â Reserved Memory: 0 B / 3.888 GiB
  â Labels: kernelversion=3.10.0-327.28.3.el7.x86_64, operatingsystem=CentOS Linux 7 (Core), storagedriver=devicemapper
  â UpdatedAt: 2016-09-05T11:11:17Z
  â ServerVersion: 1.12.1
Plugins:
 Volume:
 Network:
Swarm:
 NodeID:
 Is Manager: false
 Node Address:
Security Options:
Kernel Version: 3.10.0-327.28.3.el7.x86_64
Operating System: linux
Architecture: amd64
CPUs: 4
Total Memory: 7.775 GiB
Name: 858ac2fdd225
Docker Root Dir:
Debug Mode (client): false
Debug Mode (server): false
WARNING: No kernel memory limit support

Upvotes: 9

Views: 18295

Answers (3)

jrbe228
jrbe228

Reputation: 578

Related issue - I had a recent Swarm project with a mixture of worker nodes (3 x Linux + 4 x Windows). My containers needed to run on a specific OS, but not on any specific node. Swarm mode now supports specifying an OS under "constraints" in docker-compose files. No need to create labels for each node:

version: '3'  
services:  
    service_1:  
        restart: on-failure  
        image: 'service_1'  
        deploy:  
            placement:  
                constraints:  
                    - node.platform.os == windows  
    junittestsuite:  
        restart: on-failure  
        image: 'junit_test_suite:1.0'  
        command: ant test ...  
        deploy:  
            placement:  
                constraints:  
                    - node.platform.os == linux

Upvotes: 0

Bernard
Bernard

Reputation: 17261

The environment variable constraint is only valid for the legacy (stand alone) version of Swarm. The newer "Swarm Mode" uses either mode or constraints options (not environment variables).

To enforce one and only one task (container) per node, use mode=global.

docker service create --name proxy --mode global nginx

The default mode is replicated which means that the swarm manager will create tasks (containers) across all available nodes to meet the number specified in the --replicas option. Eg:

docker service create --name proxy --replicas 5 nginx

To enforce other constraints based on hostname (node), label, role, id's use the --constraint option. Eg:

docker service create --name proxy --constraint "node.hostname!=node01" nginx

See https://docs.docker.com/engine/reference/commandline/service_create/#/specify-service-constraints

EDIT sept 2016:

Something else. docker-compose is not currently supported in "swarm mode". Swarm mode understands the new dab format instead. There is a way to convert docker-compose files to dab but it's experimental and not to be relied on at this point. It's better to create a bash script that calls all the docker service create ... directly.

EDIT March 2017:

As of docker 1.13 (17.03), docker-compose can now be used to provision swarm environments directly without having to deal with the dab step.

Upvotes: 6

Bernard
Bernard

Reputation: 17261

My first answer is about "swarm mode". You'd since clarified that you're using legacy Swarm and added more info, so here:

The constraint you list assumes that you have a host named node-1. Your hosts are named ux-test16.rs and ux-test17.rs. Just use that instead of node-1 in your constraint. Eg:

environment:
  - "constraint:node==ux-test16.rs"

Upvotes: 10

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