I have a Spring Boot app deployed under a Tomcat server inside a POD with Openshift 4.19 (which uses Kubernetes 1.19). My goal is to externalize the logback configuration to a configmap, so that I can change the loglevel as needed in production without restarting the pods.
I used the following configuration:
ConfigMap
kind: ConfigMap
apiVersion: v1
metadata:
name: logback-configmap
[..]
data:
logback: |
<?xml version="1.0" encoding="UTF-8"?>
<configuration scan="true" scanPeriod="60 seconds">
[...]
Deployment Config
[...]
spec:
volumes:
- name: logback-configmap-volume
configMap:
name: logback-configmap
items:
- key: logback
path: logback.xml
defaultMode: 420
[..]
volumeMounts:
- name: logback-configmap-volume
mountPath: /deployments/zfaRouter/WEB-INF/classes/logback.xml
subPath: logback.xml
[..]The problem is, that the above config clears the complete directory structure under /deployments/zfaRouter/WEB-INF/classes/:
sh-4.4$ ls -la /deployments/zfaRouter/WEB-INF/classes/
total 4
drwxr-xr-x. 2 root root 25 May 4 16:35 .
drwxr-xr-x. 3 root root 21 May 4 16:35 ..
-rw-r--r--. 1 root 1015170000 1084 May 4 16:35 logback.xmlI tried every possible combination (eg. without subPath element, without the filename in the mountPath, without the items element in the volumes section) without any luck. From what a read here and in the official Kubernetes docs, it should work like the configuration above.
Any ideas on this problem?
The directory that is used as mount point shadows all other content, therefore it appears like overwriting what you expect to be there. Even if you want to 'just' have a single file mounted, a mount point must exist.
For your specific scenario you could either mount to a different directory, like /config and add it to the classpath, or you can use a subdirectory like /deployments/zfaRouter/WEB-INF/classes/config and add that to the classpath.
If you don't want to change the classpath you could mount the config file to, f.e. /config and change your application start script to copy it to a fitting location, for example to the tomcat shared lib folder that is picked up by the tomcat classloader.