Kubernetes 和 Mongo 卷

Question

I've been trying to get a sample mongo project working on Kubernetes minikube but for the life of me i can't get the volume to persist

anyone have any suggestions

kubectl create -f https://raw.githubusercontent.com/brianbruff/kubernetesPlayground/master/mongo.yaml

what i notice is that the /data folder appears to be mounted and if i create files on the node they appear in the single pod (and vice versa)

but for some reason i'm having no luck with mongo /data/db files it's as if the db subfolder of the volume is not mounted

any suggestions appreciated

Solution: ok this is embarrassing... my persistence test was create a db and then see if it was persisted

but mongo doesn't save/persist a db unless there is a collection or document in it!

yes i feel embarrassed...

Answer 1

The reason is even though you are mounting /data from host to /data in Pod, the /data/db in container is mounted from somewhere else.

As suggested on https://hub.docker.com/_/mongo/ you should mount /data on host to /data/db on container.

If you go to minikube ssh and see all the volumes mounted for mongo db docker inspect <mongo-db-container> container, you will see that two of the following Mounts (among others):

        {
            "Type": "volume",
            "Name": "af5f765585b153526dd7eab75a9ee4b62a0fb59d3482a23dc97b8fd23267557d",
            "Source": "/var/lib/docker/volumes/af5f765585b153526dd7eab75a9ee4b62a0fb59d3482a23dc97b8fd23267557d/_data",
            "Destination": "/data/db",
            "Driver": "local",
            "Mode": "",
            "RW": true,
            "Propagation": ""
        },
        {
            "Type": "bind",
            "Source": "/data",
            "Destination": "/data",
            "Mode": "rslave",
            "RW": true,
            "Propagation": "rslave"
        },

Answer 2

I also faced same issue. But after making a small change, It worked fine for me.

volumeMounts:
        - name: <pvc-name>
          mountPath: "/data/db/"