I have a bunch of docker containers running in swarm mode (services). If the whole server restarts then containers start to run one by one after server reboot. Is there a way to set an order of container creation and run?
P.S. I can't user docker-compose as these services were created dynamically through Docker Remote API.
You can try to set a shorter restart delay (with --restart-delay) to the services you want to start firstly and a bigger to next one etc..
But I am not sure that working.
Related
I'm working with a Docker container with Debian 11 inside and a server.
I need to update this server and do other things on regular manne. I've written several scripts that can do it, but I encountered serious proble.
If I want to update the server and other packages I need to reboot the container.
I'm obviously able to do so from the computer Docker is installed on (in my case Docker Desktop running with WSL2 on Windows 10), I can reboot the container easily, but I need to automate it.
The simplest way will be to add the shutdown command to the scripts I've written. I was reading about it, but found nothing. Is there any way to reboot this container from the Debian inside it? If no, how can it be achieved and how complicated is it?
I was trying to invoke standard Linux commands to shutdown or reboot system on Debian inside container.
I expect a guide if it's possible and worth efforts.
The only way to trigger a restart of a container from within the container is to first set a restart policy on the container such as --restart=on-failure and then simply stop the container, i.e., let the main process terminate itself. The Docker engine would then restart the container.
This, however, is not the way Docker is intended to be used! Docker containers are not VMs and instead are meant to be ephemeral:
By "ephemeral", we mean that the container can be stopped and destroyed, then rebuilt and replaced with an absolute minimum set up and configuration.
This means, you shouldn't be updating the server within a running container but instead should update/rebuild the image and start a new container from it!
We have a docker swarm and we normally run service container using Docker create service API. Now we are seeing after certain time interval the services are not responding ( means the application running inside container ). As of now the solution looks like restarting the service after specific time interval.And it worked when we tried it manually .
This is the top command output of Host worker node
And output of docker stats
Wanted to know what is the best approach to fix it. Also can we automate the solution.
I am using docker-compose to deploy a project which contains about 15 containers.
I would like to configure that container b must be restarted whenever container a is restarted. Is that possible to configure in docker-compose.yml? I have been going through the docs, but I cannot find anything useful.
In this case, container b can be restarted whenever container a is restarted; that is, there is no need to wait for a certain health check of container a.
If this is not possible directly in docker-compose.yml, is there a useful docker project/image which can be used for this?
I am running a docker container which contains a node server. I want to attach to the container, kill the running server, and restart it (for development). However, when I kill the node server it kills the entire container (presumably because I am killing the process the container was started with).
Is this possible? This answer helped, but it doesn't explain how to kill the container's default process without killing the container (if possible).
If what I am trying to do isn't possible, what is the best way around this problem? Adding command: bash -c "while true; do echo 'Hit CTRL+C'; sleep 1; done" to each image in my docker-compose, as suggested in the comments of the linked answer, doesn't seem like the ideal solution, since it forces me to attach to my containers after they are up and run the command manually.
This is by design by Docker. Each container is supposed to be a stateless instance of a service. If that service is interrupted, the container is destroyed. If that service is requested/started, it is created. If you're using an orchestration platform like k8s, swarm, mesos, cattle, etc at least.
There are applications that exist to represent PID 1 rather than the service itself. But this goes against the design philosophy of microservices and containers. Here is an example of an init system that can run as PID 1 instead and allow you to kill and spawn processes within your container at will: https://github.com/Yelp/dumb-init
Why do you want to reboot the node server? To apply changes from a config file or something? If so, you're looking for a solution in the wrong direction. You should instead define a persistent volume so that when the container respawns the service would reread said config file.
https://docs.docker.com/engine/admin/volumes/volumes/
If you need to restart the process that's running the container, then simply run a:
docker restart $container_name_or_id
Exec'ing into a container shouldn't be needed for normal operations, consider that a debugging tool.
Rather than changing the script that gets run to automatically restart, I'd move that out to the docker engine so it's visible if your container is crashing:
docker run --restart=unless-stopped ...
When a container is run with the above option, docker will restart it for you, unless you intentionally run a docker stop on the container.
As for why killing pid 1 in the container shuts it down, it's the same as killing pid 1 on a linux server. If you kill init/systemd, the box will go down. Inside the namespace of the container, similar rules apply and cannot be changed.
I have a docker container that I want to deploy to a CoreOS cluster that has to download my app from a git repo.
Let's say the app container runs nginx / nodejs
How should I update it?
If i submit the container and start it, that works the first time. But the second time I'll have to stop/start the container with fleetctl then I'll obviously have downtime. Should I start up new containers that are derived from that container?
Here's a complete walkthrough on exactly such a scenario:
http://coreos.com/blog/zero-downtime-frontend-deploys-vulcand.html
Instead of pulling down your application from github inside your container, you should bake your application code inside your container/image. Your container should start its services within a few seconds. To achieve zero downtime you should keep the old container running until your new container has started and is ready to accept new connections. You could do this by separating nginx into its own container and keep it running all the time.