I am currently trying to setup a docker container using ubuntu:14.04 as my base image, with nginx and gunicorn/django/celery running inside. I am using supervisor to start all of the processes, and have tested to make sure gunicorn is relaunched when it goes down. However, I can't figure out how to do it with nginx.
My supervisord.conf for nginx is as follows:
[program:nginx]
command=nginx
autorestart=false
I have autorestart set to false because, from what I can tell, the nginx command simply starts the master process and worker processes, and then exits with status code 0. If I have autorestart set to true, it simply keeps trying to restart that nginx command, which will fail for subsequent retries because the master/worker processes are already running and bound to the port.
On the surface, this seems okay, because if I try and kill a worker process, the master will start another worker to take it's place. But how do I ensure the master process stays running as well?
You need to append daemon off; to your nginx.conf configuration instructing nginx to run in the foreground.
Then modify your supervisor stanza to be:
[program:nginx]
command=nginx
autorestart=true
It will still spawn master/worker processes/subprocesses and can be used this way in production setups just fine. In this case it's supervisor that runs the process in the background and controls and supervises it.
See this FAQ entry
Related
I have Alpine Linux, 3.15.0 version on the server.
The installed nginx version is 1.21.6. I have performed apk update
nginx -t command successfully responds with
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful
When I type nginx -s reload server responds with
2023/02/03 10:58:00 [notice] 54#54: signal process started
but nothing actually happens. It's like the process started and that's all.
What am I missing?
According to Nginx documentation, command nginx -s reload actually sends signal to nginx master process and
once the master process receives the signal to reload configuration,
it checks the syntax validity of the new configuration file and tries
to apply the configuration provided in it. If this is a success, the
master process starts new worker processes and sends messages to old
worker processes, requesting them to shut down.
Thus, we can consider that nginx is restarted (If we disregard the fact that the master process itself continued to work).
At the same time, if you want to totally restart nginx, you can stop it with nginx -s quit command and then start again. Or that's much better use your system service manager. If I'm not mistaken, there is an open-rc in Alpine, thus command will be rc-service nginx restart.
I'm doing an internship focused on Docker and I have to load-balance an application which have a client, a server and a database. I use Nginx as a load-balancer and my goal is to dynamically scale the number of server containers according their CPU usage. For instance if the CPU usage is over 60% I want to add a new container on the fly without restarting Nginx to divide the CPU usage.
I have to modify the nginx.conf file to add a new container but I have to restart the Nginx container to apply the changes, which is very slow.
So my question is : is there a (free) way to do it dynamically ?
Tell me if you want further information and forgive my poor english.
Thanks.
EDIT : I did as #Konstantin Azizov told me :
docker cp ./new.conf $(docker ps -f "name=dockerizedrubis_nginx" -q ):/etc/nginx/nginx.conf
docker exec $(docker ps -f "name=dockerizedrubis_nginx" -q) bash -c 'kill -HUP $(cat /run/nginx.pid)'
docker exec $(docker ps -f "name=dockerizedrubis_nginx" -q) bash -c '/etc/init.d/nginx reload'
The configuration file is well pasted in the container supporting Nginx, I send the HUP signal to reconfigure the Nginx process et then I reload to apply my changes. There are no errors and the reload on-the-fly works fine but my new nodes are not taken into account by Nginx, the requests are still only directed to the first node created ...
EDIT 2 : I found the origin of the problem. It seems like in order to update the /etc/hosts of a container after a 'docker-compose scale', this container needs to be stopped, removed and restarted. In my case, I really don't want to stop the container supporting Nginx.
Question : Anyone has an idea of how to update /etc/hosts of a container after a re-scale without having to restart the container (beside a dirty script) ?
Thanks.
I used the nginx-proxy image from Json Wilder for a while to load balance between containers, and it works for more than one scalable service. It monitors the docker daemon and if an event happens it rebuilds the nginx config file adding the new container instances when you are scaling out or removing it if you are scaling in.
Since Docker 1.10 (not sure if this is the correct version) there is a internal DNS embedded into Docker daemon, so since then I am using the round robin feature from it. Now I am using the oficial nginx image to proxy pass the requests to the a domain that I define as alias into network options. I do not know if I was clear due to my poor english but I believe my Github example may help.
Unfortunately there is no easy(free) way to change configuration without restarting, the only way to achieve zero-downtime scaling it's graceful restart, when you restarting Nginx gracefully it will spawn new instance with new configuration wait until it boots up and then kill old instance with the previous configuration.
See official guide.
I am trying to access etcd from within a running Docker container. When I run
curl http://172.17.42.1:4001/v2/keys
I get
curl: (7) Failed to connect to 172.17.42.1 port 4001: Connection refused
I have four other hosts where this works fine, but every container on this machine has this problem. I'm really at a loss as to what's going on, and I don't know how to debug it.
My etcd environment variables are
ETCD_ADVERTISE_CLIENT_URLS=http://10.242.10.2:2379
ETCD_DISCOVERY=https://discovery.etcd.io/<token_removed>
ETCD_INITIAL_ADVERTISE_PEER_URLS=http://10.242.10.2:2380
ETCD_LISTEN_CLIENT_URLS=http://10.242.10.2:2379,http://127.0.0.1:2379,http://0.0.0.0:4001
ETCD_LISTEN_PEER_URLS=http://10.242.10.2:2380
I can also access etcd from the host with
curl http://localhost:4001/v2/keys
So there seems to be some error when routing from the container out to the host. But I can't figure out what it is. Can anyone point me in the right direction?
I observed I had to use the --advertise-client-urls and --listen-client-urls. Like so:
./etcd --advertise-client-urls 'http://0.0.0.0:2379,http://0.0.0.0:4001' --listen-client-urls 'http://0.0.0.0:2379,http://0.0.0.0:4001'
Then I was able to successfully do
curl -L http://hostname:2379/version
from any machine that could reach that server and it worked.
It turns out etcd was only listening on localhost:4001 on that machine, which is why I couldn't access it from within a container. This is despite me configuring one of the listen client urls to 0.0.0.0:4001.
It turns out that I had run sudo systemctl enable etcd2, which caused it to run before the cloud-config service ran. As such, etcd started with default configuration instead of the one that I had specified in my cloud config. Running sudo systemctl disable etcd2 fixed the issue.
With some great help from another user on here I've managed to create a script which writes the necessary network configurations required to /etc/network/interfaces and allow public access to a DomU server.
I’ve placed this script in the /etc/rc.local file, and executed chmod u+x /etc/rc.local to enable it.
The server is a DomU Ubuntu server on the a host (Dom0). And rc.local doesn't seem to be executing before the network is brought up at boot/creation time.
So the configuration changes are being made to the /etc/network/interfaces file, but are not active once the boot process completes. I have to reboot once more before the changes take effect.
I've tried adding /etc/init.d/networking restart to the the end of the rc.local script (before exit 0), but with no joy.
I also tried adding the script to the S35networking file, but again without success.
Any advice or suggestions on getting this script to execute before the network device is brought up would be greatly appreciated.?
I've set up a Flask application to run on a tornado server backed by nginx. I've written a couple of bash scripts to reload server configuration when a new version is deployed, but I am unhappy with them. Basically what I have is:
to start the server (assuming in project root)
# this starts the tornado-flask wrapper
python myapp.py --port=8000 # .. some more misc settings
# this starts nginx
nginx
to stop it
pkill -f 'myapp.py'
nginx -s stop
to restart
cd $APP_ROOT
./script/stop && ./script/start
Many times these don't work smoothly and I need to manually run the commands. Also, I'm looking for a way to verify the service is alive, and start it up if it's down. Thoughts? Thanks.
Supervisor is what you are looking for.
It's what I use to manage my Tornado apps along with some other processing daemons.
It will daemonize, handle logging, pid files... Pretty much everything you need.