K
Q

Kubernetes shared mount point issue

10/19/2018

I have a Pod with logrotate and nginx containers:

apiVersion: v1
kind: Pod
metadata:
  name: nginx-log
  labels:
    app: nginx-log

spec:
  containers:

  - name: logrotate
    image: path/to/logrotate:latest
    volumeMounts:
    - name: logs
      mountPath: /var/log

  - name: nginx
    image: nginx:latest
    ports:
    - containerPort: 80
    volumeMounts:
    - name: logs
      mountPath: /var/log/nginx

  volumes:
  - name: logs
    emptyDir: {}

The problem I have is whether mountPath for nginx is /var/log or /var/log/nginx, logrotate container always sees nginx logs in /var/log/ not in /var/log/nginx/. Is it possible to force nginx to create nginx/ folder in emptyDir and log there?

-- Syn Romana
kubernetes
nginx

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2 Answers

10/19/2018

Ok, I have it working:

apiVersion: v1
kind: Pod
metadata:
  name: nginx-log
  labels:
    app: nginx-log

spec:
  containers:

  - name: logrotate
    image: path/to/image/logrotate:latest
    volumeMounts:
    - name: logs
      mountPath: /var/log

  - name: nginx
    image: nginx:latest
    ports:
    - containerPort: 80
    volumeMounts:
    - name: logs
      mountPath: /var/log/nginx
      subPath: nginx

  volumes:
  - name: logs
    emptyDir: {}

Logrotate side car is taken from: https://github.com/honestbee

with small modifications in logrotate.tpl.conf:

${LOGROTATE_PATTERN1} 
${LOGROTATE_PATTERN2}
{
    rotate ${LOGROTATE_ROTATE}
    ${LOGROTATE_MODE}
    size ${LOGROTATE_SIZE}
    missingok
    nocompress
    su root root
 }

and in Dockerfile:

FROM alpine:3.8

ENV CRON_SCHEDULE='*/30 * * * *' \
    LOGROTATE_SIZE='10M' \
    LOGROTATE_MODE='copytruncate' \
    LOGROTATE_PATTERN1='/var/log/*.log' \
    LOGROTATE_PATTERN2='/var/log/*/*.log' \
    LOGROTATE_ROTATE='5'

RUN apk --no-cache add logrotate tini gettext libintl \
    && mkdir -p /var/log \
    && chmod 775 /var/log \
    && mkdir -p /etc/logrotate.d

COPY logrotate.tpl.conf /logrotate.tpl.conf
COPY entrypoint.sh /usr/local/bin/entrypoint.sh

ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]

CMD ["/usr/sbin/crond", "-f", "-L", "/dev/stdout"]
-- Syn Romana
Source: StackOverflow
10/19/2018

I think a good use here would be Init Containers, it can be used to run tasks before Pod fully deploys.

An example would look as follows:

apiVersion: v1  
kind: Pod  
metadata:  
  name: nginx-log  
spec:  
  containers:

  - name: logrotate
    image: path/to/logrotate:latest
    volumeMounts:
    - name: logs
      mountPath: /var/log

  - name: nginx  
    image: nginx:latest  
    ports:
    - containerPort: 80    
    volumeMounts:  
    - name: logs  
      mountPath: /var/log/nginx  

  initContainers:  
  - name: logs  
    image: busybox  
    command: ["mkdir","-p","/var/log/nginx"]  
    volumeMounts:  
    - name: logs  
      mountPath: /var/log/nginx 

  volumes:
  - name: logs
    emptyDir: {}

You can also read Using InitContainers to pre-populate Volume data in Kubernetes

-- Crou
Source: StackOverflow