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Postgres
What is Postgres
Postgres
is a Kubernetes Custom Resource Definitions
(CRD). It provides declarative configuration for PostgreSQL in a Kubernetes native way. You only need to describe the desired database configuration in a Postgres object, and the KubeDB operator will create Kubernetes objects in the desired state for you.
Postgres Spec
As with all other Kubernetes objects, a Postgres needs apiVersion
, kind
, and metadata
fields. It also needs a .spec
section.
Below is an example Postgres object.
apiVersion: kubedb.com/v1alpha1
kind: Postgres
metadata:
name: p1
namespace: demo
spec:
version: 9.6
replicas: 2
standbyMode: hot
archiver:
storage:
storageSecretName: s3-secret
s3:
bucket: kubedb
databaseSecret:
secretName: p1-auth
storage:
storageClassName: standard
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 50Mi
nodeSelector:
disktype: ssd
init:
scriptSource:
gitRepo:
directory: "."
repository: "https://github.com/kubedb/postgres-init-scripts.git"
backupSchedule:
cronExpression: "@every 6h"
storageSecretName: gcs-secret
gcs:
bucket: kubedb
prefix: demo
doNotPause: true
monitor:
agent: prometheus.io/coreos-operator
prometheus:
namespace: demo
labels:
app: kubedb
interval: 10s
resources:
requests:
memory: "64Mi"
cpu: "250m"
limits:
memory: "128Mi"
cpu: "500m"
spec.version
spec.version
is a required field specifying the version of PostgreSQL database. Currently the supported versions are:
9.6.7
,9.6
10.2
spec.replicas
spec.replicas
specifies the total number of primary and standby nodes in Postgres database cluster configuration. One pod is selected as Primary and others are acted as standby replicas.
spec.standby
spec.standby
is an optional field that specifies standby mode (warm/hot) supported by Postgres. Hot standby can run read-only queries where Warm standby can’t accept connect and only used for replication purpose.
spec.archiver
spec.archiver
is an optional field which specifies storage information that will be used by wal-g
.
spec.archiver.storage.storageSecretName
points to the Secret containing the credentials for cloud storage destination.spec.archiver.storage.s3.bucket
points to the bucket name used to store continuous archiving data.
Continuous archiving data will be stored in a folder called {bucket}/{prefix}/kubedb/{namespace}/{postgres-name}/archive/
.
spec.databaseSecret
spec.databaseSecret
is an optional field that points to a Secret used to hold credentials for postgres
super user.
If not set, KubeDB operator creates a new Secret {postgres-name}-auth
for storing the password for postgres
superuser for each Postgres object.
If you want to use an existing secret please specify that when creating the Postgres object using spec.databaseSecret.secretName
.
This Secret contains postgres
superuser password as POSTGRES_PASSWORD
key.
spec.storage
Since 0.8.0, spec.storage
is a required field that specifies the StorageClass of PVCs dynamically allocated to store data for the database. This storage spec will be passed to the StatefulSet created by KubeDB operator to run database pods. You can specify any StorageClass available in your cluster with appropriate resource requests.
spec.storage.storageClassName
is the name of the StorageClass used to provision PVCs. PVCs don’t necessarily have to request a class. A PVC with its storageClassName set equal to "" is always interpreted to be requesting a PV with no class, so it can only be bound to PVs with no class (no annotation or one set equal to “”). A PVC with no storageClassName is not quite the same and is treated differently by the cluster depending on whether the DefaultStorageClass admission plugin is turned on.spec.storage.accessModes
uses the same conventions as Kubernetes PVCs when requesting storage with specific access modes.spec.storage.resources
can be used to request specific quantities of storage. This follows the same resource model used by PVCs.
To learn how to configure spec.storage
, please visit the links below:
spec.nodeSelector
spec.nodeSelector
is an optional field that specifies a map of key-value pairs. For the pod to be eligible to run on a node, the node must have each of the indicated key-value pairs as labels (it can have additional labels as well). To learn more, see here .
spec.init
spec.init
is an optional section that can be used to initialize a newly created Postgres database. PostgreSQL databases can be initialized in one of three ways:
Initialize via Script
To initialize a PostgreSQL database using a script (shell script, db migrator, etc.), set the spec.init.scriptSource
section when creating a Postgres object. ScriptSource must have following information:
- VolumeSource: Where your script is loaded from.
Below is an example showing how a script from a git repository can be used to initialize a PostgreSQL database.
apiVersion: kubedb.com/v1alpha1
kind: Postgres
metadata:
name: postgres-db
spec:
version: 9.6
init:
scriptSource:
gitRepo:
directory: "."
repository: "https://github.com/kubedb/postgres-init-scripts.git"
In the above example, Postgres will execute provided script once database is running. directory: .
is used to get repository contents directly in mount path.
Initialize from Snapshots
To initialize from prior Snapshot, set the spec.init.snapshotSource
section when creating a Postgres object. In this case, SnapshotSource must have following information:
name:
Name of the Snapshotnamespace:
Namespace of the Snapshot
apiVersion: kubedb.com/v1alpha1
kind: Postgres
metadata:
name: postgres-db
spec:
version: 9.6
databaseSecret:
secretName: postgres-old-auth
init:
snapshotSource:
name: "snapshot-xyz"
namespace: "demo"
In the above example, PostgreSQL database will be initialized from Snapshot snapshot-xyz
in default
namespace. Here, KubeDB operator will launch a Job to initialize PostgreSQL once StatefulSet pods are running.
When initializing from Snapshot, superuser postgres
must have to match with previous one. For example, lets say, Snapshot snapshot-xyz
is for Postgres postgres-old
. In this case, new Postgres postgres-db
should use same credential for superuser of postgres-old
. Otherwise, restoration process will fail.
Initialize from WAL archive
To initialize from WAL archive, set the spec.init.postgresWAL
section when creating a Postgres object.
Below is an example showing how to initialize a PostgreSQL database from WAL archive.
apiVersion: kubedb.com/v1alpha1
kind: Postgres
metadata:
name: postgres-db
spec:
version: 9.6
databaseSecret:
secretName: postgres-old
init:
postgresWAL:
storageSecretName: s3-secret
s3:
endpoint: 's3.amazonaws.com'
bucket: kubedb
prefix: 'kubedb/demo/old-pg/archive'
In the above example, PostgreSQL database will be initialized from WAL archive.
When initializing from WAL archive, superuser postgres
must have to match with previous one. For example, lets say, we want to initialize this
database from postgres-old
WAL archive. In this case, superuser of new Postgres should use same password as postgres-old
. Otherwise, restoration process will be failed.
spec.backupSchedule
KubeDB supports taking periodic snapshots for Postgres database. This is an optional section in .spec
. When spec.backupSchedule
section is added, KubeDB operator immediately takes a backup to validate this information. After that, at each tick kubeDB operator creates a Snapshot object. This triggers operator to create a Job to take backup. If used, set the various sub-fields accordingly.
spec.backupSchedule.cronExpression
is a required cron expression. This specifies the schedule for backup operations.spec.backupSchedule.{storage}
is a required field that is used as the destination for storing snapshot data. KubeDB supports cloud storage providers like S3, GCS, Azure and OpenStack Swift. It also supports any locally mounted Kubernetes volumes, like NFS, Ceph , etc. Only one backend can be used at a time. To learn how to configure this, please visit here.spec.backupSchedule.resources
is an optional field that can request compute resources required by Jobs used to take snapshot or initialize databases from snapshot. To learn more, visit here.
spec.doNotPause
KubeDB takes advantage of ValidationWebhook
feature in Kubernetes 1.9.0 or later clusters to implement doNotPause
feature. If admission webhook is enabled, It prevents user from deleting the database as long as the spec.doNotPause
is set true
. If not set or set to false, deleting a Postgres object put the database into a dormant state. THe StatefulSet for a DormantDatabase is deleted but the underlying PVCs are left intact. This allows user to resume the database later.
spec.monitor
PostgreSQL managed by KubeDB can be monitored with builtin-Prometheus and CoreOS-Prometheus operator out-of-the-box. To learn more,
spec.resources
spec.resources
is an optional field. This can be used to request compute resources required by the database pods. To learn more, visit here.
Next Steps
- Learn how to use KubeDB to run a PostgreSQL database here.
- See the list of supported storage providers for snapshots here.
- Wondering what features are coming next? Please visit here.
- Want to hack on KubeDB? Check our contribution guidelines.