How to deploy Postgresql on Kubernetes with NFS volume - postgresql

Question

I'm using the below manifest to deploy postgresql on kubernetes within NFS persistent volume:
apiVersion: v1
kind: PersistentVolume
metadata:
name: nfs2
spec:
capacity:
storage: 6Gi
accessModes:
- ReadWriteMany
persistentVolumeReclaimPolicy: Retain
nfs:
server: 10.139.82.123
path: /nfsfileshare/postgres
---
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
name: nfs2
spec:
accessModes:
- ReadWriteMany
resources:
requests:
storage: 6Gi
---
apiVersion: v1
kind: Service
metadata:
name: db
labels:
app: aiflow-db
spec:
selector:
app: aiflow-db
clusterIP: None
ports:
- port: 5432
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: db
namespace: test-aiflow
labels:
app: aiflow-db
spec:
selector:
matchLabels:
app: aiflow-db
template:
metadata:
labels:
app: aiflow-db
spec:
containers:
- name: db
image: postgresql:10
ports:
- containerPort: 5432
env:
- name: PGDATA
value: /var/lib/postgresql/data/pgdata
volumeMounts:
- mountPath: /var/lib/postgresql/data/pgdata
name: nfs2
volumes:
- name: nfs2
persistentVolumeClaim:
claimName: nfs2
restartPolicy: Always
The pg data can be mounted to nfs server (/nfsfileshare/postgres *(rw,async,no_subtree_check,no_root_squash)):
total 124
drwx------ 19 999 root 4096 Aug 7 11:10 ./
drwxrwxrwx 5 root root 4096 Aug 7 10:28 ../
drwx------ 3 999 docker 4096 Aug 7 11:02 base/
drwx------ 2 999 docker 4096 Aug 7 11:10 global/
drwx------ 2 999 docker 4096 Aug 7 11:01 pg_commit_ts/
drwx------ 2 999 docker 4096 Aug 7 11:01 pg_dynshmem/
-rw------- 1 999 docker 4513 Aug 7 11:02 pg_hba.conf
-rw------- 1 999 docker 1636 Aug 7 11:02 pg_ident.conf
drwx------ 4 999 docker 4096 Aug 7 11:09 pg_logical/
drwx------ 4 999 docker 4096 Aug 7 11:01 pg_multixact/
drwx------ 2 999 docker 4096 Aug 7 11:10 pg_notify/
drwx------ 2 999 docker 4096 Aug 7 11:02 pg_replslot/
drwx------ 2 999 docker 4096 Aug 7 11:01 pg_serial/
drwx------ 2 999 docker 4096 Aug 7 11:01 pg_snapshots/
drwx------ 2 999 docker 4096 Aug 7 11:02 pg_stat/
drwx------ 2 999 docker 4096 Aug 7 11:02 pg_stat_tmp/
drwx------ 2 999 docker 4096 Aug 7 11:02 pg_subtrans/
drwx------ 2 999 docker 4096 Aug 7 11:02 pg_tblspc/
drwx------ 2 999 docker 4096 Aug 7 11:01 pg_twophase/
-rw------- 1 999 docker 3 Aug 7 11:02 PG_VERSION
drwx------ 3 999 docker 4096 Aug 7 11:02 pg_wal/
drwx------ 2 999 docker 4096 Aug 7 11:02 pg_xact/
-rw------- 1 999 docker 88 Aug 7 11:02 postgresql.auto.conf
-rw------- 1 999 docker 22729 Aug 7 11:02 postgresql.conf
-rw------- 1 999 docker 74 Aug 7 11:10 postmaster.pid
However the container is stuck with below log:
The files belonging to this database system will be owned by user
"postgres". This user must also own the server process.
The database cluster will be initialized with locale "en_US.utf8". The
default database encoding has accordingly been set to "UTF8". The
default text search configuration will be set to "english".
Data page checksums are disabled.
fixing permissions on existing directory
/var/lib/postgresql/data/pgdata ... ok creating subdirectories ... ok
selecting default max_connections ... 100 selecting default
shared_buffers ... 128MB selecting dynamic shared memory
implementation ... posix creating configuration files ... ok running
bootstrap script ... ok
Seems it stuck on post-bootstrap initialization.
It works only if I do not use nfs volume (works by using hostPath volume), why is that?

Answer 1

NFS does not support fsync kernel vfs call which is required transaction logs for ensuring the writing out the redo logs on the disk. So you should use block storage when you need to use RDBMS, such as PostgreSQL and MySQL. You might lose the data consistency althogh you can run the one on the NFS.

Answer 2

I meet the same question, When I use helm deploy the gitlab, the postgresql can't run, and errors below:
FATAL: data directory "/var/lib/postgresql/data/pgdata" has wrong ownership.
HINT: The server must be started by the user that owns the data directory.
I think it's because the postgresql run property need it's data should be own by user postgres and group postgres, but the nfs change the own user and group, makes the postgresql can't run.
Maybe change another tools like glusterfs can solve this problem, or try mysql's data mount by nfs.