Convert docker-compose to Kubernetes for nginx & php-fpm containers - php

Question

I have a dockerized symfony project and I'm trying to delpoy it in GPC on Kubernetes cluster.
In development I use docker-compose and I have two sepparate containers for php-fpm and nginx.
When I run docker-compose up --build, it all works fine, but when I try to create a kubernetes cluster I get this error after I run kubectl apply -f nginx.deployment.yaml:
nginx: [emerg] host not found in upstream "php-fpm" in /etc/nginx/conf.d/default.conf:11
This is the nginx default.conf file:
server {
listen 80;
server_name localhost;
root /app/public;
location / {
try_files $uri /index.php$is_args$args;
}
location ~ ^/index\.php(/|$) {
fastcgi_pass php-fpm:9000;
fastcgi_split_path_info ^(.+\.php)(/.*)$;
include fastcgi_params;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_param DOCUMENT_ROOT $document_root;
internal;
}
location ~ \.php$ {
return 404;
}
}
Please note
fastcgi_pass php-fpm:9000;
which references the php-fpm container.
Dockerfile for nginx:
ARG VERSION
# Dev image
FROM nginx:${VERSION}-alpine as dev
# Copy nginx config
COPY ./docker/nginx/default.conf /etc/nginx/conf.d/default.conf
# Prod image
FROM dev as prod
# Copy assets
COPY ./assets /app/public
Here it is the nginx.deployment.yaml file:
apiVersion: apps/v1
kind: Deployment
metadata:
annotations:
kompose.cmd: kompose convert -f ../docker-compose.yml
kompose.version: 1.22.0 (955b78124)
creationTimestamp: null
labels:
io.kompose.service: nginx
name: nginx
spec:
replicas: 1
selector:
matchLabels:
io.kompose.service: nginx
strategy:
type: Recreate
template:
metadata:
annotations:
kompose.cmd: kompose convert -f ../docker-compose.yml
kompose.version: 1.22.0 (955b78124)
creationTimestamp: null
labels:
io.kompose.service: nginx
spec:
containers:
- image: myDockerHubRegistry/symfony-nginx:0.2
name: nginx
ports:
- containerPort: 80
resources: {}
volumeMounts:
- mountPath: /app/public
name: nginx-claim
restartPolicy: Always
volumes:
- name: nginx-claim
persistentVolumeClaim:
claimName: nginx-claim
status: {}
I also tried to put nginx and php-fpm on the same deployment, but I still get the same error.
What am I missing?

Answer 1

There are 2 issues here:
The hostname php-fpm doesn't resolve to the service's IP via DNS in k8s
nginx/openresty refuses to start if a hostname used in a proxy pass can't be resolved
nginx: [emerg] host not found in upstream "hostname"
SOLUTION:
Use a hostname that resolves correctly inside kubernetes.
The DNS scheme used by Core DNS in GKE is <service>.<namespace>.svc.cluster.local
Store the correct hostname for the php-fpm service in a variable first.
Then use this variable as the target of the the (fastcgi-)proxy pass.
This will make nginx start regardless of being able to resolve the target hostname.
Example:
set $upstream php-fpm.your-namespace.svc.cluster.local:9000;
fastcgi_pass $upstream;

Answer 2

Since nginx refuses to start if any proxy_pass service is not already available, you need to start the php-fpm service first. You haven't shared the deployment yaml for php-fpm. Along with the kubernetes deployment for php-fpm, you need to create a kubernetes service object for php-fpm with the name php-fpm within the same namespace as nginx.
You could also use the variable hack suggested by Nicolai so that you can start nginx without any dependency on php-fpm. But either case you need to create the kubernetes deployment and service objects for php-fpm for your application to actually work.