Deploy on Juju storage¶
Charmed PostgreSQL uses the Juju storage abstraction to utilise data volume provided by different clouds while keeping the same UI/UX for end users.
Charmed PostgreSQL 16 supports multiple storage types: archive, data, logs and temp.
The legacy PostgreSQL charm in track latest” does not support the Juju storage abstraction.
Check Juju storage details¶
Check the metadata.yaml for find Juju storage name and tech details:
Charmed PostgreSQL 16 storage list
storage:
archive:
type: filesystem
location: /var/snap/charmed-postgresql/common/data/archive
data:
type: filesystem
location: /var/snap/charmed-postgresql/common/var/lib/postgresql
logs:
type: filesystem
location: /var/snap/charmed-postgresql/common/data/logs
temp:
type: filesystem
location: /var/snap/charmed-postgresql/common/data/temp
Charmed PostgreSQL 16 supports multiple storage archive , data , logs and temp . See the deployment examples below.
Define storage size¶
> juju deploy postgresql --channel 16/stable --storage pgdata=10G
> juju storage
Unit Storage ID Type Pool Size Status Message
postgresql/1 pgdata/1 filesystem lxd 10 GiB attached
Define storage location¶
Juju supports wide list of different storage pools:
> juju create-storage-pool mystoragepool lxd
> juju storage-pools | grep mystoragepool
mystoragepool lxd
> juju deploy postgresql --channel 16/stable --storage pgdata=5G,mystoragepool
> juju storage
Unit Storage ID Type Pool Size Status Message
postgresql/2 pgdata/2 filesystem mystoragepool 5 GiB attached
Example: Re-deploy detached storage¶
To re-deploy the application with the old Juju storage, it is necessary to provide all charm/database credentials as Juju user secrets.
Charmed PostgreSQL 16 uses Juju user secrets to handle credentials:
# Note old passwords
> juju show-secret --reveal database-peers.postgresql.app
# Add new Juju User secret with old password values
> juju add-secret mypgpass \
monitoring-password=oQDLAVMV1AHFZq1L \
operator-password=IXarOnndC9XKoytS \
patroni-password=vWzJZIktqi0qGMCx \
raft-password=2pALATzLJsrpAf5q \
replication-password=2bcnAQhXLrX3ekVP \
rewind-password=bBqQOXiC7whSqQbR
# Find old storage id:
> juju storage
# Re-deploy new app re-using old storage and old credentials
> juju deploy postgresql \
--channel 16/stable \
--attach-storage pgdata/5 \
--config system-users=newsecret54321id
# Grant access to new secrets for re-deployed application
> juju grant-secret mypgpass postgresql
Example: Complete old storage re-deployment
Prepare the test data to restore later:
# Add a new model
> juju add-model teststorage
# Deploy the new postgresql to dump storage with credentials
> juju deploy postgresql --channel 16/stable --storage pgdata=5Gcompleted
Deployed "postgresql" from charm-hub charm "postgresql", revision 613 in channel 16/stable on [email protected]/stable
# Wait for deployment completed:
> juju status
...
Unit Workload Agent Machine Public address Ports Message
postgresql/0* active idle 0 10.189.210.99 5432/tcp Primary
# Reveal the Juju secrets for the simpliest DB access:
> juju show-secret --reveal database-peers.postgresql.app
d09v83poie738j7af4n0:
revision: 2
checksum: 9e28910800d4dd94cd655d5d5f49a9bb7e4b7fbf6dde232328e4f6734c7bdf84
owner: postgresql
label: database-peers.postgresql.app
created: 2025-05-01T22:22:07Z
updated: 2025-05-01T22:22:10Z
content:
monitoring-password: 6inFApK8IyJuJ6LG
operator-password: I8mkza6vIhD2w1Rh
patroni-password: JAYSlB3mQXi9g4fc
raft-password: eFWUOCYb1lIOpGuM
replication-password: SFBx8OL9XxXiWwcC
rewind-password: 92xT4yTniiG7OEch
# Create a test data
> PGPASSWORD=I8mkza6vIhD2w1Rh psql -h 10.189.210.99 -U operator -d postgres -c "create table a (id int);"
CREATE TABLE
> PGPASSWORD=I8mkza6vIhD2w1Rh psql -h 10.189.210.99 -U operator -d postgres -c "\d"
List of relations
Schema | Name | Type | Owner
--------+------+-------+----------
public | a | table | operator
(1 row)
# Check the storage status
> juju storage
Unit Storage ID Type Pool Size Status Message
postgresql/0 pgdata/0 filesystem lxd 5.0 GiB attached
# Remove the old application keeping the storage:
> juju remove-application postgresql --destroy-storage=false
WARNING This command will perform the following actions:
will remove application postgresql
- will remove unit postgresql/0
- will detach storage pgdata/0
Continue [y/N]? y
# Check the status (app and secrets are gone, but storage stays):
> juju status
Model Controller Cloud/Region Version SLA Timestamp
teststorage lxd localhost/localhost 3.6.5 unsupported 00:28:44+02:00
Model "admin/teststorage" is empty.
> juju secrets
ID Name Owner Rotation Revision Last updated
> juju storage
Unit Storage ID Type Pool Size Status Message
pgdata/0 filesystem lxd 5.0 GiB detached
Re-deploy the postgresql application reusing storage pgdata/0 :
# Create a new Juju User secret
> juju add-secret mypgpass \
monitoring-password=6inFApK8IyJuJ6LG \
operator-password=I8mkza6vIhD2w1Rh \
patroni-password=JAYSlB3mQXi9g4fc \
raft-password=eFWUOCYb1lIOpGuM \
replication-password=SFBx8OL9XxXiWwcC \
rewind-password=92xT4yTniiG7OEch
secret:d09vcn1oie738j7af4ng
# Re-deploy app with old storage and old passwords
> juju deploy postgresql \
--channel 16/stable \
--attach-storage pgdata/0 \
--config system-users=d09vcn1oie738j7af4ng
Deployed "postgresql" from charm-hub charm "postgresql", revision 613 in channel 16/stable on [email protected]/stable
# Grant new application access to manually created Juju User secret
> juju grant-secret mypgpass postgresql
# Wait for deployment
> juju status
...
Unit Workload Agent Machine Public address Ports Message
postgresql/1* active idle 1 10.189.210.179 5432/tcp Primary# Check the old data access once deployment completed (use new App IP!):
> PGPASSWORD=I8mkza6vIhD2w1Rh psql -h 10.189.210.179 -U operator -d postgres -c "\d"
List of relations
Schema | Name | Type | Owner
--------+------+-------+----------
public | a | table | operator
(1 row)
# Old storage re-used:
> juju storage
Unit Storage ID Type Pool Size Status Message
postgresql/1 pgdata/0 filesystem lxd 5.0 GiB attached