Keep always running Go http server app inside a Docker container - docker

I have a Docker container that runs just a Go binary I created that is a http server with Gin framework. I don't use any other Web Server, just Go's internal http server. Inside my Dockerfile at the end of file I have this:
EXPOSE 80
CMD ["/home/project/microservices/backend/engine/cmd/main"]
I use docker-compose to run the container and restart: always for each container. And it works!
But my question is that, if the http server that I created fails due to programming error or something, It will restart? how can I check this? does Docker has tools for this?
I tried go with Supervisord but it has some problems and I was not successful on running it.
I want a workaround to keep the http server inside container always running.
What can I do?

You can try killing the process from the host. Find the process id using something like
ps -aux | grep main
Then kill it using
sudo kill <process id>
Docker will then restart it. By using
docker ps
you should see that the 'status' has changed to something like Up 10 seconds.

Related

how to retrieve pid of a nginx -s reload command in alpine?

Im restarting my nginx in a docker container in a sh script and i would like to make sure i retrieve the right pid when doing so.
So nginx is already running and im doing nginx -s reload to restart the service.
If I do nginx -s reload & nginx_pid=$!, will nginx_pid indeed correspond to nginx pid ?
Thank you
Best
A Docker container only normally runs a single process, and inside the container its process ID is 1. In an nginx container I'd expect the Nginx pid to always be 1. The server won't be process 1 only if there's a separate init process (tini is a common one) or if your process is launched by a shell script without using exec; the Docker Hub nginx image does neither of these things.
In the fragment you show, nginx -s reload sends a command to the main Nginx server and exits (and it doesn't need to be run in the background). $! is the pid of that reload command and not the Nginx server.
In typical use you never need to know process IDs inside containers, manually send signals to processes, or otherwise be "inside" a container. If your application code calls fork(2) or getppid(2) it can know another process's pid but even these are somewhat unusual. If you need to restart a container process it's usually simplest to delete and recreate the entire container.

docker-compose: how to keep showing logs in 'follow' mode even when container is down?

If you run docker-compose logs -f service in one terminal and try to restart service in other, then logging will be stopped and you will need to start dkc logs again. How to keep dkc logs running?
The only solution I've found so far is to run additional noop service which will not allow dkc logs to shut down. If this is the only solution then do you have any suggestion for simplest noop service which already exists on docker hub?
My workaround:
add new noop service to the docker-compose.override.yml (I picked redis because it was already installed and is quite lightweight):
services:
noop:
image: redis:5-alpine
run docker-compose logs -f service noop instead of with just service.
run docker-compose stop/restart service. logs process will be kept alive by noop service.
Con:
extra stuff to run
cannot use dkc stop and dkc restart without specifying the service
Maybe some information about what you are logging. For example on nginx or php containers we simply move logfiles outside of container just using volume to mount them to host machine, then you can parse them as you want.
volumes:
- /var/log/mysql/error_service_xy.log:/var/log/mysql/error.log

Docker - Bind for 0.0.0.0:4000 failed: port is already allocated

I am using docker for the first time and I was trying to implement this -
https://docs.docker.com/get-started/part2/#tag-the-image
At one stage I was trying to connect with localhost by this command -
$ curl http://localhost:4000
which showed this error-
curl: (7) Failed to connect to localhost port 4000: Connection refused
However, I have solved this by following code -
$ docker-machine ip default
$ curl http://192.168.99.100:4000
After that everything was going fine, but in the last part, I was trying to run the app by using following line according to the tutorial...
$ docker run -p 4000:80 anibar/get-started:part1
But, I got this error
C:\Program Files\Docker Toolbox\docker.exe: Error response from daemon: driver failed programming external connectivity on endpoint goofy_bohr (63f5691ef18ad6d6389ef52c56198389c7a627e5fa4a79133d6bbf13953a7c98): Bind for 0.0.0.0:4000 failed: port is already allocated.
You need to make sure that the previous container you launched is killed, before launching a new one that uses the same port.
docker container ls
docker rm -f <container-name>
Paying tribute to IgorBeaz, you need to stop running the current container. For that you are going to know current CONTAINER ID:
$ docker container ls
You get something like:
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
12a32e8928ef friendlyhello "python app.py" 51 seconds ago Up 50 seconds 0.0.0.0:4000->80/tcp romantic_tesla
Then you stop the container by:
$ docker stop 12a32e8928ef
Finally you try to do what you wanted to do, for example:
$ docker run -p 4000:80 friendlyhello
I tried all the above answers, none of them worked, in my case even docker container ls doesn't show any container running. It looks like the problem is due to the fact that the docker proxy is still using ports although there are no containers running. In my case I was using ubuntu. Here's what I tried and got the problem solved, just run the following two commands:
sudo service docker stop
sudo rm -f /var/lib/docker/network/files/local-kv.db
I solved it this way:
First, I stopped all running containers:
docker-compose down
Then I executed a lsof command to find the process using the port (for me it was port 9000)
sudo lsof -i -P -n | grep 9000
Finally, I "killed" the process (in my case, it was a VSCode extension):
kill -9 <process id>
The quick fix is ​​a just restart docker:
sudo service docker stop
sudo service docker start
Above two answers are correct but didn't work for me.
I kept on seeing blank like below for docker container ls
then I tried, docker container ls -a and after that it showed all the process previously exited and running.
Then docker stop <container id> or docker container stop <container id> didn't work
then I tried docker rm -f <container id> and it worked.
Now at this I tried docker container ls -a and this process wasn't present.
When I used nginx docker image, I also got this error:
docker: Error response from daemon: driver failed programming external connectivity on endpoint recursing_knuth (9186f7d7f523732b99d3510029cde9679f3f3fe7b7eb5f612d54c4aacea58220): Bind for 0.0.0.0:8080 failed: port is already allocated.
And I solved it using following commands:
$ docker container ls
$ docker stop [CONTAINER ID]
Then, running this docker container(like this) again is ok:
$ docker run -v $PWD/vueDemo:/usr/share/nginx/html -p 8080:80 -d nginx:alpine
You just need to stop the previous docker container.
I have had same problem with docker-compose, to fix it:
Killed docker-proxy processe
Restart docker
Start docker-compose again
docker ps will reveal the list of containers running on docker. Find the one running on your needed port and note down its PID.
Stop and remove that container using following commands:
docker stop PID
docker rm PID
Now run docker-compose up and your services should run as you have freed the needed port.
on linux 'sudo systemctl restart docker' solved the issue for me
For anyone having this problem with docker-compose.
When you have more than one project (i.e. in different folders) with similar services you need to run docker-compose stop in each of your other projects.
If you are using Docker-Desktop, you can quit Docker Desktop and then restart it. It solved the problem for me.
In my case, there was no process to kill.
Updating docker fixed the problem.
It might be a conflict with the same port specified in docker-compose.yml and docker-compose.override.yml or the same port specified explicitly and using an environment variable.
I had a docker-compose.yml with ports on a container specified using environment variables, and a docker-compose.override.yml with one of the same ports specified explicitly. Apparently docker tried to open both on the same container. docker container ls -a listed neither because the container could not start and list the ports.
For me the containers where not showing up running, so NOTHING was using port 9010 (in my case) BUT Docker still complained.
I did not want to reset my Docker (for Windows) so what I did to resolve it was simply:
Remove the network (I knew that before a container was using this network with the port in question (9010) docker network ls docker network rm blabla (or id)
I actually used a new network rather than the old (buggy) one but shouldn't be needed
Restart Docker
That was the only way it worked for me. I can't explain it but somehow the "old" network was still bound to that port (9010) and Docker kept on "blocking" it (whinching about it)
FOR WINDOWS;
I killed every process that docker use and restarted the docker service on services. My containers are working now.
It is about ports that is still in use by Docker even though you are not using on that moment.
On Linux, you can run sudo netstat -tulpn to see what is currently listening on that port. You can then choose to configure either that process or your Docker container to bind to a different port to avoid the conflict.
Stopping the container didn't work for me either. I changed the port in docker-compose.yml.
For me, the problem was mapping the same port twice.
Due to a parametric docker run, it ended up being something like
docker run -p 4000:80 -p 4000:80 anibar/get-started:part1
notice double mapping on port 4000.
The log is not informative enough in this case, as it doesn't state I was the cause of the double mapping, and that the port is no longer bound after the docker run command returns with a failure.
Don't forget the easiest fix of all....
Restart your computer.
I have tried most of the above and still couldn't fix it. Then just restart my Mac and then it's all back to normal.
For anyone still looking for a solution, just make sure you have binded your port the right way round in your docker-compose.yml
It goes:
- <EXTERNAL SERVER PORT>:<INTERNAL CONTAINER PORT>
Had the same problem. Went to Docker for Mac Dashboard and clicked restart. Problem solved.
my case was dump XD I was exposing port 80 twice :D
ports:
- '${APP_PORT:-80}:80'
- '${APP_PORT:-8080}:8080'
APP_PORT is defined, thus 80 was exposed twice.
I tried almost all solutions and found out the probable/possible reason/solution. So, If you are using traefik or any other networking server, they internally facilitate proxy for load balacing. That, most use the blueprint as it, works pretty fine. It then passes the load control entirely to nginx or similiar proxy servers. So, stopping, killing(networking server) or pruning might not help.
Solution for traefik with nginx,
sudo /etc/init.d/nginx stop
# or
sudo service nginx stop
# or
sudo systemctl stop nginx
Credits
How to stop docker processes
Making Docker Stop Itself <- Safe and Fast
this is the best way to stop containers and all unstoppable processes: making docker do the job.
go to docker settings > resources. change any of the resource and click apply and restart.
docker will stop itself and its every process -- even the most stubborn ones that might not be killed by other commonly used commands such as kill or more wild commands like rm suggested by others.
i ran into a similar problem before and all the good - proper - tips from my colleagues somehow did not work out. i share this safe trick whenever someone in my team asks me about this.
Error response from daemon: driver failed programming external connectivity on endpoint foobar
Bind for 0.0.0.0:8000 failed: port is already allocated
hope this helps!
simply restart your computer, so the docker service gets restarted

Docker connection refused when started with -ti bash

I am new to docker and I tried to run the linuxconfig/lemp-php7 image. Everything worked fine and I could access the nginx web server installed on the container. To run this image I used this command:
sudo docker run linuxconfig/lemp-php7
When I tried to run the image with the following command to gain access over the container through bash I couldn't connect to nginx and I got the connection refused error message. Command: sudo docker run -ti linuxconfig/lemp-php7 bash
I tried this several times so I'm pretty sure it's not any kind of coincidence.
Why does this happen? Is this a problem specific to this particular image or is this a general problem. And how can I gain access to the shell of the container and access the web server at the same time?
I'd really like to understand this behavior to improve my general understanding of docker.
docker run runs the specified command instead of what that container would normally run. In your case, it appears to be supervisord, which presumably in turn runs the web server. So you're preventing any of that from happening.
My preferred method (except in cases where I'm trying to debug cases where the container won't even start properly) is to do the following after running the container normally:
docker exec -i -t $CONTAINER_ID /bin/bash

How to refresh a container links

I've two dockers: one is a nginx frontend and the other is an expressjs application. Nginx is the entry point and it does a proxy to expressjs.
I do:
docker run -d --name 'expressjs' geographica/expressjs
docker run -d --name 'nginx' --link expressjs nginx
After that when I update the image geographica/expressjs I need to recreated the expressjs container:
docker stop expressjs && docker rm expressjs && docker run -d --name 'expressjs' geographica/expressjs
At this point, I also need to recreate the nginx container. How can I do it without recreating the nginx container?
It's a simplification of our problem, our real server has a nginx frontend and N applications, so each time we update one of the application we need to restart the nginx and stop the service for other applications.
Please, avoid docker-compose solutions. I wouldn't like to have a unique/huge docker-compose file for all the applications.
UPDATED:
I also think that something like that would be useful. https://github.com/docker/docker/issues/7468. having a docker link command to change container links at runtime. Unfortunately, it's not still available in 1.8.2.
This was discussed in issue 6350:
If I explicitly do a docker restart the IP is correctly updated, however I was using "systemctl restart" which does a stop, kill and rm before a run
In that case ("stop - rm - run"), links are not refreshed:
docker does not assume that a container with the same name should be linked to
It doesn't always make sense to keep that "link", after all the new container could be completely unrelated.
My solution and my advice, is that:
you look into something a bit more robust like the Ambassador pattern that is just a fancy way of saying you link to a proxy that you never restart - to keep the docker links active.
(also introduced here)
Another solution is to just docker create, docker start and docker stop instead of docker rm.
Lastly, my actual solution was to use something like SkyDNS or docker-gen to keep a central DNS with all the container names. This last solution it's the best for me because it allows me to move containers between hosts and docker linking can't work like that.
With next versions of docker, libnetwork will actually the way to go.
(see "The Container Network Model (CNM)", and "Docker Online Meetup #22: Docker Networking - video")

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