Initialize swarm mode:
root@ip-172-31-44-207:/home/ubuntu# docker swarm init --advertise-addr 172.31.44.207 Swarm initialized: current node (4mj61oxcc8ulbwd7zedxnz6ce) is now a manager. To add a worker to this swarm, run the following command:Join the second node:
docker swarm join \ --token SWMTKN-1-4xvddif3wf8tpzcg23tem3zlncth8460srbm7qtyx5qk3ton55-6g05kuek1jhs170d8fub83vs5 \ 172.31.44.207:2377
To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.
# start 2 services
docker service create continuumio/miniconda3
docker service create --name redis redis:3.0.6
root@ip-172-31-44-207:/home/ubuntu# docker service ls
ID NAME REPLICAS IMAGE COMMAND
2yc1xjmita67 miniconda3 0/1 continuumio/miniconda3
c3ptcf2q9zv2 redis 1/1 redis:3.0.6
As shown above, redis has it's replica while miniconda does not seem to be replicated.
I do usually log-in to miniconda container to type these commands:
/opt/conda/bin/conda install jupyter -y --quiet && mkdir /opt/notebooks && /opt/conda/bin/jupyter notebook --notebook-dir=/opt/notebooks --ip='*' --port=8888 --no-browser
The problem is that docker exec -it XXX bash command does not work with swarm mode.
There is one liner for accessing corresponding instance of the service for localhost:
docker exec -ti stack_myservice.1.$(docker service ps -f 'name=stack_myservice.1' stack_myservice -q --no-trunc | head -n1) /bin/bash
It is tested on PowerShell, but bash should be the same. The oneliner accesses the first instance, but replace '1' with the number of the instance you want to access in two places to get other one.
More complex example is for distributed case:
#! /bin/bash
set -e
exec_task=$1
exec_instance=$2
strindex() {
x="${1%%$2*}"
[[ "$x" = "$1" ]] && echo -1 || echo "${#x}"
}
parse_node() {
read title
id_start=0
name_start=`strindex "$title" NAME`
image_start=`strindex "$title" IMAGE`
node_start=`strindex "$title" NODE`
dstate_start=`strindex "$title" DESIRED`
id_length=name_start
name_length=`expr $image_start - $name_start`
node_length=`expr $dstate_start - $node_start`
read line
id=${line:$id_start:$id_length}
name=${line:$name_start:$name_length}
name=$(echo $name)
node=${line:$node_start:$node_length}
echo $name.$id
echo $node
}
if true; then
read fn
docker_fullname=$fn
read nn
docker_node=$nn
fi < <( docker service ps -f name=$exec_task.$exec_instance --no-trunc -f desired-state=running $exec_task | parse_node )
echo "Executing in $docker_node $docker_fullname"
eval `docker-machine env $docker_node`
docker exec -ti $docker_fullname /bin/bash
This script could be used later as:
swarm_bash stack_task 1
It just execute bash on required node.
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..?
Using the Docker API
Right now, Docker does not provide an API like docker service exec or docker stack exec for this. But regarding this, there already exists two issues dealing with this functionality:
- github.com - moby/moby - Docker service exec
- github.com - docker/swarmkit - Support for executing into a task
(Regarding the first issue, for me, it was not directly clear that this issue deals with exactly this kind of functionality. But Exec for Swarm was closed and marked as duplicate of the Docker service exec issue.)
Using Docker daemon over HTTP
As mentioned by BMitch on run docker exec from swarm manager, you could also configure the Docker daemon to use HTTP and than connect to every node without the need of ssh. But you should protect this using TLS authentication which is already integrated into Docker. Afterwards you would be able to execute the docker exec like this:
docker --tlsverify --tlscacert=ca.pem --tlscert=cert.pem --tlskey=key.pem \
-H=$HOST:2376 exec $containerId $cmd
Using skopos-plugin-swarm-exec
There exists a github project which claims to solve the problem and provide the desired functionality binding the docker daemon:
docker run -v /var/run/docker.sock:/var/run/docker.sock \
datagridsys/skopos-plugin-swarm-exec \
task-exec <taskID> <command> [<arguments>...]
As far as I can see, this works by creating another container at same node where the container reside where the docker exec should by executed on. On this node this container mounts the docker daemon socket to be able to execute docker exec there locally.
For more information have a look at: skopos-plugin-swarm-exec
Using docker swarm helpers
There is also another project called docker swarm helpers which seems to be more or less a wrapper around ssh and docker exec.
Reference:
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 $(docker ps -q -f name=servicename) ls
You can jump in a Swarm node and list the docker containers running using:
docker container ls
That will give you the container name in a format similar to: containername.1.q5k89uctyx27zmntkcfooh68f
You can then use the regular exec option to run commands on it:
docker container exec -it containername.1.q5k89uctyx27zmntkcfooh68f bash
I wrote script to exec command in docker swarm by service name. For example it can be used in cron. Also you can use bash pipelines and passes all params to docker exec command. But works only on same node where service started. I wish it could help someone
#!/bin/bash
# swarm-exec.sh
set -e
for ((i=1;i<=$#;i++)); do
val=${!i}
if [ ${val:0:1} != "-" ]; then
service_id=$(docker ps -q -f "name=$val");
if [[ $service_id == "" ]]; then
echo "Container $val not found!";
exit 1;
fi
docker exec ${@:1:$i-1} $service_id ${@:$i+1:$#};
exit 0;
fi
done
echo "Usage: $0 [OPTIONS] SERVICE_NAME COMMAND [ARG...]";
exit 1;
Example of using:
./swarm-exec.sh app_postgres pg_dump -Z 9 -F p -U postgres app > /backups/app.sql.gz
echo ls | ./swarm-exec.sh -i app /bin/bash
./swarm-exec.sh -it some_app /bin/bash
created a small script for our docker swarm cluster.
this script takes 3 params. first is the service you want to connect to second the task you want to run this can be /bin/bash or any other process you want to run. Third is optional and will fill -c option for bash or sh
-n is optional to force it to connect to a node
it retrieves the node that runs the service and runs the command.
#! /bin/bash
set -e
task=${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
来源：https://stackoverflow.com/questions/39362363/execute-a-command-within-docker-swarm-service