PostgreSQL: Deploy into K8S
Single PostgreSQL deployment in K8S
PostgreSQL by default doesnot build for kubernetes, and a database with statefulset workload in k8s can be brutal to manage. In my lab k8s cluster, here we create namespace, secret, configuremap, PVC and statefulset to run a single PostgreSQL
# create namespace "postgresql"
[root@freeipa-server ~]# kubectl create ns postgresql
namespace/postgresql created
# create secret to store database creds
[root@freeipa-server ~]# kubectl -n postgresql create secret generic postgresql --from-literal POSTGRES_USER="postgresadmin" --from-literal POSTGRES_PASSWORD='admin123' --from-literal POSTGRES_DB="postgresdb" --from-literal REPLICATION_USER="replicationuser" --from-literal REPLICATION_PASSWORD='replicationPassword'
secret/postgresql created
# create configmap, pvc, statefulset with init container to run postgresql
[root@freeipa-server ~]# vim stateful.yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: postgres
data:
pg_hba.conf: |+
# TYPE DATABASE USER ADDRESS METHOD
host replication replicationuser 0.0.0.0/0 md5
# "local" is for Unix domain socket connections only
local all all trust
# IPv4 local connections:
host all all 127.0.0.1/32 trust
# IPv6 local connections:
host all all ::1/128 trust
# Allow replication connections from localhost, by a user with the
# replication privilege.
local replication all trust
host replication all 127.0.0.1/32 trust
host replication all ::1/128 trust
host all all all scram-sha-256
postgresql.conf: |+
data_directory = '/data/pgdata'
hba_file = '/config/pg_hba.conf'
ident_file = '/config/pg_ident.conf'
port = 5432
listen_addresses = '*'
max_connections = 100
shared_buffers = 128MB
dynamic_shared_memory_type = posix
max_wal_size = 1GB
min_wal_size = 80MB
log_timezone = 'Etc/UTC'
datestyle = 'iso, mdy'
timezone = 'Etc/UTC'
#locale settings
lc_messages = 'en_US.utf8' # locale for system error message
lc_monetary = 'en_US.utf8' # locale for monetary formatting
lc_numeric = 'en_US.utf8' # locale for number formatting
lc_time = 'en_US.utf8' # locale for time formatting
default_text_search_config = 'pg_catalog.english'
#replication
wal_level = replica
archive_mode = on
archive_command = 'test ! -f /data/archive/%f && cp %p /data/archive/%f'
max_wal_senders = 3
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: postgres
spec:
selector:
matchLabels:
app: postgres
serviceName: "postgres"
replicas: 1
template:
metadata:
labels:
app: postgres
spec:
terminationGracePeriodSeconds: 30
initContainers:
- name: init
image: postgres:15.0
command: [ "bash", "-c" ]
args:
- |
#create archive directory
mkdir -p /data/archive && chown -R 999:999 /data/archive
volumeMounts:
- name: data
mountPath: /data
readOnly: false
containers:
- name: postgres
image: postgres:15.0
args: ["-c", "config_file=/config/postgresql.conf"]
ports:
- containerPort: 5432
name: database
env:
- name: PGDATA
value: "/data/pgdata"
- name: POSTGRES_USER
valueFrom:
secretKeyRef:
name: postgresql
key: POSTGRES_USER
optional: false
- name: POSTGRES_PASSWORD
valueFrom:
secretKeyRef:
name: postgresql
key: POSTGRES_PASSWORD
optional: false
- name: POSTGRES_DB
valueFrom:
secretKeyRef:
name: postgresql
key: POSTGRES_DB
optional: false
volumeMounts:
- name: config
mountPath: /config
readOnly: false
- name: data
mountPath: /data
readOnly: false
volumes:
- name: config
configMap:
name: postgres
defaultMode: 0755
volumeClaimTemplates:
- metadata:
name: data
spec:
accessModes: [ "ReadWriteOnce" ]
storageClassName: "standard"
resources:
requests:
storage: 100Mi
---
apiVersion: v1
kind: Service
metadata:
name: postgres
labels:
app: postgres
spec:
ports:
- port: 5432
targetPort: 5432
name: postgres
clusterIP: None
selector:
app: postgres
[root@freeipa-server ~]# kubectl create -f stateful.yaml -n postgresql
configmap/postgres created
statefulset.apps/postgres created
service/postgres created
# validate for pvc, pods
[root@freeipa-server ~]# kubectl get pvc -n postgresql
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
data-postgres-0 Bound pvc-dd89fc0a-915f-40eb-b61f-917234074a61 100Mi RWO longhorn 19m
[root@freeipa-server ~]# kubectl get all -n postgresql
NAME READY STATUS RESTARTS AGE
pod/postgres-0 1/1 Running 0 6m29s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/postgres ClusterIP None <none> 5432/TCP 6m29s
NAME READY AGE
statefulset.apps/postgres 1/1 6m29s
# check container logs for database connection status
[root@freeipa-server ~]# kubectl logs -n postgresql postgres-0
Defaulted container "postgres" out of: postgres, init (init)
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 /data/pgdata ... ok
creating subdirectories ... ok
selecting dynamic shared memory implementation ... posix
selecting default max_connections ... 100
selecting default shared_buffers ... 128MB
selecting default time zone ... Etc/UTC
creating configuration files ... ok
running bootstrap script ... ok
performing post-bootstrap initialization ... ok
initdb: warning: enabling "trust" authentication for local connections
initdb: hint: You can change this by editing pg_hba.conf or using the option -A, or --auth-local and --auth-host, the next time you run initdb.
syncing data to disk ... ok
Success. You can now start the database server using:
pg_ctl -D /data/pgdata -l logfile start
waiting for server to start....2024-05-12 00:52:56.718 UTC [49] LOG: starting PostgreSQL 15.0 (Debian 15.0-1.pgdg110+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 10.2.1-6) 10.2.1 20210110, 64-bit
2024-05-12 00:52:56.719 UTC [49] LOG: listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
2024-05-12 00:52:56.730 UTC [49] LOG: could not open usermap file "/config/pg_ident.conf": No such file or directory
2024-05-12 00:52:56.733 UTC [52] LOG: database system was shut down at 2024-05-12 00:52:55 UTC
2024-05-12 00:52:56.744 UTC [49] LOG: database system is ready to accept connections
done
server started
CREATE DATABASE
/usr/local/bin/docker-entrypoint.sh: ignoring /docker-entrypoint-initdb.d/*
2024-05-12 00:52:56.957 UTC [49] LOG: received fast shutdown request
waiting for server to shut down....2024-05-12 00:52:56.961 UTC [49] LOG: aborting any active transactions
2024-05-12 00:52:56.962 UTC [49] LOG: background worker "logical replication launcher" (PID 56) exited with exit code 1
2024-05-12 00:52:56.963 UTC [50] LOG: shutting down
2024-05-12 00:52:57.042 UTC [50] LOG: checkpoint starting: shutdown immediate
..2024-05-12 00:52:59.314 UTC [50] LOG: checkpoint complete: wrote 918 buffers (5.6%); 0 WAL file(s) added, 0 removed, 1 recycled; write=0.434 s, sync=0.014 s, total=2.279 s; sync files=250, longest=0.007 s, average=0.001 s; distance=11271 kB, estimate=11271 kB
2024-05-12 00:52:59.318 UTC [49] LOG: database system is shut down
done
server stopped
PostgreSQL init process complete; ready for start up.
2024-05-12 00:52:59.385 UTC [1] LOG: starting PostgreSQL 15.0 (Debian 15.0-1.pgdg110+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 10.2.1-6) 10.2.1 20210110, 64-bit
2024-05-12 00:52:59.385 UTC [1] LOG: listening on IPv4 address "0.0.0.0", port 5432
2024-05-12 00:52:59.385 UTC [1] LOG: listening on IPv6 address "::", port 5432
2024-05-12 00:52:59.389 UTC [1] LOG: listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
2024-05-12 00:52:59.398 UTC [1] LOG: could not open usermap file "/config/pg_ident.conf": No such file or directory
2024-05-12 00:52:59.404 UTC [67] LOG: database system was shut down at 2024-05-12 00:52:59 UTC
2024-05-12 00:52:59.415 UTC [1] LOG: database system is ready to accept connectionsConclusion
Now we are able to deploy a PostgreSQL in local k8s cluster, with defined environment variables in kubernetes secret and configmap, together with init container to create data archive volume in presistent storage class, the next blog I will discover how to run PostgreSQL HA with presistent volume on kubernetes with both Helm and operater, then validate scale up and down, backup using cronjob and etc.