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execute a command within docker swarm service

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眼角桃花
眼角桃花 2020-12-04 15:16

  1. Initialize swarm mode:

    root@ip-172-31-44-207:/home/ubuntu# docker swarm init --advertise-addr 172.31.44.207

Swarm initialized: current node (4mj61o
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  • 轮回少年
    2020-12-04 15:57

    created a small script for our docker swarm cluster. this script takes 3 params. first is the service you want to connect to second the task you want to run this can be /bin/bash or any other process you want to run. Third is optional and will fill -c option for bash or sh

    -n is optional to force it to connect to a node

    it retrieves the node that runs the service and runs the command.

    #! /bin/bash

set -e

task=${1}
service=$2
bash=$3

serviceID=$(sudo docker service ps -f name=$service -f desired-state=running $service -q --no-trunc |head -n1)
node=$(sudo docker service ps -f name=$service -f desired-state=running $service --format="{{.Node}}"| head -n1 )

sudo docker -H $node exec -it $service".1."$serviceID $bash -c "$task"

    note: this requires the docker nodes to accept tcp connections by exposing docker on port 2375 on the worker nodes

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  • 囚心锁ツ
    2020-12-04 15:58

    The simpliest command I found to docker exec into a swarm node (with a swarm manager at $SWARM_MANAGER_HOST) running the service $SERVICE_NAME (for example mystack_myservice) is the following:

    SERVICE_JSON=$(ssh $SWARM_MANAGER_HOST "docker service ps $SERVICE_NAME --no-trunc --format '{{ json . }}' -f desired-state=running")
ssh -t $(echo $SERVICE_JSON | jq -r '.Node') "docker exec -it $(echo $SERVICE_JSON | jq -r '.Name').$(echo $SERVICE_JSON | jq -r '.ID') bash"

    This asserts that you have ssh access to $SWARM_MANAGER_HOST as well as the swarm node currently running the service task.

    This also asserts that you have jq installed (apt install jq), but if you can't or don't want to install it and you have python installed you can create the following alias (based on this answer):

    alias jq="python3 -c 'import sys, json; print(json.load(sys.stdin)[sys.argv[2].partition(\".\")[-1]])'"
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  • 小鲜肉
    2020-12-04 16:00

    Take a look at my solution: https://github.com/binbrayer/swarmServiceExec.

    This approach is based on Docker Machines. I also created the prototype of the script to call containers asynchronously and as a result simultaneously.

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  • 生来不讨喜
    2020-12-04 16:04

    You can execute commands by filtering container name without needing to pass the entire swarm container hash, just by the service name. Like this:

    docker exec $(docker ps -q -f name=servicename) ls

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  • 暖寄归人
    2020-12-04 16:05

    EDIT 2017-10-06:

    Nowadays you can create the overlay network with --attachable flag to enable any container to join the network. This is great feature as it allows a lot of flexibility.

    E.g.

    $ docker network create --attachable --driver overlay my-network
$ docker service create --network my-network --name web --publish 80:80 nginx
$ docker run --network=my-network -ti alpine sh
(in alpine container) $  wget -qO- web

<!DOCTYPE html>
<html>
<head>
....

    You are right, you cannot run docker exec on docker swarm mode service. But you can still find out, which node is running the container and then run exec directly on the container. E.g.

    docker service ps miniconda3  # find out, which node is running the container
eval `docker-machine env <node name here>`
docker ps  # find out the container id of miniconda
docker exec -it <container id here> sh

    In your case you first have to find out, why service cannot get the miniconda container up. Maybe running docker service ps miniconda3 shows some helpful error messages..?

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  • 终归单人心
    2020-12-04 16:07

    For those who has multiple replicas and just want to run a command within any of them, here is another shortcut:

    docker exec -it $(docker ps -q -f name=SERVICE_NAME | head -1) bash
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