execute a command within docker swarm service

Question

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         
   
   
           

Answer 1

See addendum 2...

Example of a oneliner for entering the database my_db on node master:

DB_NODE_ID=master && docker exec -it $(docker ps -q -f name=$DB_NODE_ID) mysql my_db

In case you want to configure, say max_connections:

DB_NODE_ID=master && $(docker exec -it $(docker ps -q -f name=$DB_NODE_ID) mysql -e "SET GLOBAL max_connections = 1000") && docker exec -it $(docker ps -q -f name=$DB_NODE_ID) mysql my_db

This approach allows to enter all database nodes (e.g. slaves) just by setting the DB_NODE_ID variable accordingly.

Example for slave s2:

DB_NODE_ID=s2 && docker exec -it $(docker ps -q -f name=$DB_NODE_ID) mysql my_db

or

DB_NODE_ID=s2 && $(docker exec -it $(docker ps -q -f name=$DB_NODE_ID) mysql -e "SET GLOBAL max_connections = 1000") && docker exec -it $(docker ps -q -f name=$DB_NODE_ID) mysql my_db

Put this into your KiTTY or PuTTY configuration for master / s2 under Data/Command and you are set.

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As an addendum:

The old, non swarm mode version reads simply

docker exec -it master mysql my_db

resp.

DB_ID=master && $(docker exec -it $DB_ID mysql -e "SET GLOBAL max_connections = 1000") && docker exec -it $DB_ID mysql tmp

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Addendum 2:

As it turned out by example, the term docker ps -q -f name=$DB_NODE_ID may return wrong values under certain conditions.

The following approach works correctily:

docker ps -a  | grep "_$DB_NODE_ID." | awk '{print $1}'

You may substitute the examples above accordingly.

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Addendum 3:

Well, these terms look awful and they certainly are painful to type, so you may want to ease your work. On Linux, everybody knows how to do this. On Windws, you may want to use AHK.

This is the AHK term I use:

:*:ii::DB_NODE_ID=$(docker ps -a  | grep "_." | awk '{{}print $1{}}') && docker exec -it $id ash{Left 49} 

So when I type ii -- which is as simple as it can get -- I get the desired term with the cursor in place and just have to fill in the container name.