Issue with Docker swarm

Users
1

Hi,

I’m deploying a new DGraph instance with Docker 18. I’ve setup a two instance swarm, both nodes are online and fully operational. When I deploy the following compose file, the services create but hang at 0/1 replicas. I’m struggling to find out what the issue is. Note that I’m using dgraph/dgraph:latest.

version: "3"
networks:
  dgraph:
services:
  zero:
    image: dgraph/dgraph:latest
    volumes:
      - data-volume:/dgraph
    ports:
      - 5080:5080
      - 6080:6080
    networks:
      - dgraph
    deploy:
      placement:
        constraints:
          - node.hostname == AP-GRAPH-1
    command: dgraph zero --my=zero:5080 --replicas 2
  server_1:
    image: dgraph/dgraph:latest
    hostname: "server_1"
    volumes:
      - data-volume:/dgraph
    ports:
      - 8080:8080
      - 9080:9080
    networks:
      - dgraph
    deploy:
      placement:
        constraints:
          - node.hostname == AP-GRAPH-1
    command: dgraph server --my=server_1:7080 --lru_mb=17192 --zero=zero:5080
  server_2:
    image: dgraph/dgraph:latest
    hostname: "server_2"
    volumes:
      - data-volume:/dgraph
    ports:
      - 8081:8081
      - 9081:9081
    networks:
      - dgraph
    deploy:
      placement:
        constraints:
          - node.hostname == AP-GRAPH-2
    command: dgraph server --my=server_2:7081 --lru_mb=17192 --zero=zero:5080 -o 1
  ratel:
    image: dgraph/dgraph:latest
    hostname: "ratel"
    ports:
      - 8000:8000
    networks:
      - dgraph
    command: dgraph-ratel
    deploy:
      placement:
        constraints:
          - node.hostname == AP-GRAPH-1
volumes:
  data-volume:

What I see when I docker service ls

ID                  NAME                MODE                REPLICAS            IMAGE                  PORTS
2va8p4ktaroj        dgraph_ratel        replicated          0/1                 dgraph/dgraph:latest   *:8000->8000/tcp
i34iuc96w94s        dgraph_server_1     replicated          0/1                 dgraph/dgraph:latest   *:8080->8080/tcp, *:9080->9080/tcp
y0kqqeptosev        dgraph_server_2     replicated          0/1                 dgraph/dgraph:latest   *:8081->8081/tcp, *:9081->9081/tcp
mw5mkat80cr2        dgraph_zero         replicated          0/1                 dgraph/dgraph:latest   *:5080->5080/tcp, *:6080->6080/tcp
2

Hmmm, I resolved the problem listed above. My hostnames weren’t setting properly – so non issue.

I did have a follow up question. Given my configuration I should have two servers deployed of which I should be able to make GRPC requests to:

AP-GRAPH-1 on 9080
AP-GRAPH-2 on 9081

If I send all my traffic through AP-GRAPH-1 do I still get the performance of the cluster or do I need to distribute my traffic to both servers (balance the load between both?). Wondering if DGraph handles it internally or if I need to send traffic accordingly.

3

Hi,

if all servers are “full replicas” (with the same data) it’s okay you do some “Balancing”, but Dgraph Zero has some level of balancing control. In special when you’re using a sharded Dgraph DB environment.

More about Zero https://docs.dgraph.io/deploy#more-about-dgraph-zero

4

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