Nsryjdtyk

I have stack with 2 services: Spring boot application and mongo database.
I want to deploy this stack to Docker Swarm (1 node in Germany, 1 in Finland and 1 in Estonia).

Currently Swarm schedules application to Germany cluster and Database to Finland, which means that every request goes from Germany to Finland.

Is this way how to force Swarm place all pieces of stack to single node ?

P.S. sticking to hostname is not a solution, because if node dies service is down.

My Stack.yml is:

version: '3.3'

services:

app:

  image: kyberorg/boot-mongo

  networks:

  - net

  ports:

    - "8080:8080"

  depends_on:

    - mongo

labels:

  - ee.yadev.bootmongoapp

deploy:

  mode: replicated

  replicas: 1

  update_config:

    parallelism: 1

    delay: 10s

 mongo:

   image: mongo

  networks:

    - net

  volumes:

    - example-mongo:/data/db

  deploy:

    mode: replicated

    replicas: 1

    update_config:

      parallelism: 1

      delay: 10s

networks:

  net:

   driver: overlay

volumes:

  example-mongo:

    external: true

my first idea is to suggest you to use "placement constraints" and "labels":

https://docs.docker.com/engine/swarm/services/#placement-constraints
https://docs.docker.com/engine/swarm/manage-nodes/#add-or-remove-label-metadata

Thanks to them you can assign labels to nodes for each country and then modify your stack in order to force the apps to run on the same node.

docker node update --label-add country=Germany node-germany
docker node update --label-add country=Finland node-finland

--constraint node.labels.region==east

version: '3.3'
services:
app:
image: kyberorg/boot-mongo
deploy:
placement:
constraints:
- country == Germany

mongo:
image: mongo
deploy:
placement:
constraints:
- country == Germany

Other useful links:

https://semaphoreci.com/community/tutorials/scheduling-services-on-a-docker-swarm-mode-cluster
https://container-solutions.com/using-binpack-with-docker-swarm/

I hope this can help you!

What you are looking for is something like POD in kubernetes where co-location of containers is possible. AFAIK, this is currently not available on docker.

You can have a look at this repo and see if it is useful: https://github.com/rycus86/podlike

It's an attempt to bring the concept of pods to docker.

edit: On a side note, if the app and db are so tightly coupled, it makes sense that both are part of the same container.

The architecture of Swarm is one that you usually want a single swarm in the same region due to the latency of managers. Typically a swarm is "single region, multiple availability zones" (datacenters close to each other, in the same city usually.)

I also can't think of a way where you can use either constraints and/or placement preferences to have the two containers together in one datacenter, and then managers move them to the same 2nd datacenter if the first is down.

Podlike, like giabar mentioned, is an option but doesn't solve your "single swarm across multiple regions" design challenge.