Appendix A - Common object stores for backups

You can store the backup files in any service that is supported by the Barman Cloud infrastructure. That is:

Amazon S3
Microsoft Azure Blob Storage
Google Cloud Storage

You can also use any compatible implementation of the supported services.

The required setup depends on the chosen storage provider and is discussed in the following sections.

AWS S3

AWS Simple Storage Service (S3) is a very popular object storage service offered by Amazon.

As far as CloudNativePG backup is concerned, you can define the permissions to store backups in S3 buckets in two ways:

If CloudNativePG is running in EKS. you may want to use the IRSA authentication method
Alternatively, you can use the ACCESS_KEY_ID and ACCESS_SECRET_KEY credentials

AWS Access key

You will need the following information about your environment:

ACCESS_KEY_ID: the ID of the access key that will be used to upload files into S3
ACCESS_SECRET_KEY: the secret part of the access key mentioned above
ACCESS_SESSION_TOKEN: the optional session token, in case it is required

The access key used must have permission to upload files into the bucket. Given that, you must create a Kubernetes secret with the credentials, and you can do that with the following command:

kubectl create secret generic aws-creds \
  --from-literal=ACCESS_KEY_ID=<access key here> \
  --from-literal=ACCESS_SECRET_KEY=<secret key here>
# --from-literal=ACCESS_SESSION_TOKEN=<session token here> # if required

The credentials will be stored inside Kubernetes and will be encrypted if encryption at rest is configured in your installation.

Once that secret has been created, you can configure your cluster like in the following example:

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
[...]
spec:
  backup:
    barmanObjectStore:
      destinationPath: "<destination path here>"
      s3Credentials:
        accessKeyId:
          name: aws-creds
          key: ACCESS_KEY_ID
        secretAccessKey:
          name: aws-creds
          key: ACCESS_SECRET_KEY

The destination path can be any URL pointing to a folder where the instance can upload the WAL files, e.g. s3://BUCKET_NAME/path/to/folder.

IAM Role for Service Account (IRSA)

In order to use IRSA you need to set an annotation in the ServiceAccount of the Postgres cluster.

We can configure CloudNativePG to inject them using the serviceAccountTemplate stanza:

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
metadata:
[...]
spec:
  serviceAccountTemplate:
    metadata:
      annotations:
        eks.amazonaws.com/role-arn: arn:[...]
        [...]

S3 lifecycle policy

Barman Cloud writes objects to S3, then does not update them until they are deleted by the Barman Cloud retention policy. A recommended approach for an S3 lifecycle policy is to expire the current version of objects a few days longer than the Barman retention policy, enable object versioning, and expire non-current versions after a number of days. Such a policy protects against accidental deletion, and also allows for restricting permissions to the CloudNativePG workload so that it may delete objects from S3 without granting permissions to permanently delete objects.

Other S3-compatible Object Storages providers

In case you're using S3-compatible object storage, like MinIO or Linode Object Storage, you can specify an endpoint instead of using the default S3 one.

In this example, it will use the bucket of Linode in the region us-east1.

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
[...]
spec:
  backup:
    barmanObjectStore:
      destinationPath: "s3://bucket/"
      endpointURL: "https://us-east1.linodeobjects.com"
      s3Credentials:
        [...]

In case you're using Digital Ocean Spaces, you will have to use the Path-style syntax. In this example, it will use the bucket from Digital Ocean Spaces in the region SFO3.

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
[...]
spec:
  backup:
    barmanObjectStore:
      destinationPath: "s3://[your-bucket-name]/[your-backup-folder]/"
      endpointURL: "https://sfo3.digitaloceanspaces.com"
      s3Credentials:
        [...]

Important

Suppose you configure an Object Storage provider which uses a certificate signed with a private CA, like when using MinIO via HTTPS. In that case, you need to set the option endpointCA referring to a secret containing the CA bundle so that Barman can verify the certificate correctly.

Note

If you want ConfigMaps and Secrets to be automatically reloaded by instances, you can add a label with key cnpg.io/reload to the Secrets/ConfigMaps. Otherwise, you will have to reload the instances using the kubectl cnpg reload subcommand.

Azure Blob Storage

Azure Blob Storage is the obect storage service provided by Microsoft.

In order to access your storage account for backup and recovery of CloudNativePG managed databases, you will need one of the following combinations of credentials:

Connection String
Storage account name and Storage account access key
Storage account name and Storage account SAS Token
Storage account name and Azure AD Workload Identity properly configured.

Using Azure AD Workload Identity, you can avoid saving the credentials into a Kubernetes Secret, and have a Cluster configuration adding the inheritFromAzureAD as follows:

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
[...]
spec:
  backup:
    barmanObjectStore:
      destinationPath: "<destination path here>"
      azureCredentials:
        inheritFromAzureAD: true

On the other side, using both Storage account access key or Storage account SAS Token, the credentials need to be stored inside a Kubernetes Secret, adding data entries only when needed. The following command performs that:

kubectl create secret generic azure-creds \
  --from-literal=AZURE_STORAGE_ACCOUNT=<storage account name> \
  --from-literal=AZURE_STORAGE_KEY=<storage account key> \
  --from-literal=AZURE_STORAGE_SAS_TOKEN=<SAS token> \
  --from-literal=AZURE_STORAGE_CONNECTION_STRING=<connection string>

The credentials will be encrypted at rest, if this feature is enabled in the used Kubernetes cluster.

Given the previous secret, the provided credentials can be injected inside the cluster configuration:

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
[...]
spec:
  backup:
    barmanObjectStore:
      destinationPath: "<destination path here>"
      azureCredentials:
        connectionString:
          name: azure-creds
          key: AZURE_CONNECTION_STRING
        storageAccount:
          name: azure-creds
          key: AZURE_STORAGE_ACCOUNT
        storageKey:
          name: azure-creds
          key: AZURE_STORAGE_KEY
        storageSasToken:
          name: azure-creds
          key: AZURE_STORAGE_SAS_TOKEN

When using the Azure Blob Storage, the destinationPath fulfills the following structure:

<http|https>://<account-name>.<service-name>.core.windows.net/<resource-path>

where <resource-path> is <container>/<blob>. The account name, which is also called storage account name, is included in the used host name.

Other Azure Blob Storage compatible providers

If you are using a different implementation of the Azure Blob Storage APIs, the destinationPath will have the following structure:

<http|https>://<local-machine-address>:<port>/<account-name>/<resource-path>

In that case, <account-name> is the first component of the path.

This is required if you are testing the Azure support via the Azure Storage Emulator or Azurite.

Google Cloud Storage

Currently, the CloudNativePG operator supports two authentication methods for Google Cloud Storage:

the first one assumes that the pod is running inside a Google Kubernetes Engine cluster
the second one leverages the environment variable GOOGLE_APPLICATION_CREDENTIALS

Running inside Google Kubernetes Engine

When running inside Google Kubernetes Engine you can configure your backups to simply rely on Workload Identity, without having to set any credentials. In particular, you need to:

set .spec.backup.barmanObjectStore.googleCredentials.gkeEnvironment to true
set the iam.gke.io/gcp-service-account annotation in the serviceAccountTemplate stanza

Please use the following example as a reference:

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
[...]
spec:
  [...]
  backup:
    barmanObjectStore:
      destinationPath: "gs://<destination path here>"
      googleCredentials:
        gkeEnvironment: true

  serviceAccountTemplate:
    metadata:
      annotations:
        iam.gke.io/gcp-service-account:  [...].iam.gserviceaccount.com
        [...]

Using authentication

Following the instruction from Google you will get a JSON file that contains all the required information to authenticate.

The content of the JSON file must be provided using a Secret that can be created with the following command:

kubectl create secret generic backup-creds --from-file=gcsCredentials=gcs_credentials_file.json

This will create the Secret with the name backup-creds to be used in the yaml file like this:

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
[...]
spec:
  backup:
    barmanObjectStore:
      destinationPath: "gs://<destination path here>"
      googleCredentials:
        applicationCredentials:
          name: backup-creds
          key: gcsCredentials

Now the operator will use the credentials to authenticate against Google Cloud Storage.

Important

This way of authentication will create a JSON file inside the container with all the needed information to access your Google Cloud Storage bucket, meaning that if someone gets access to the pod will also have write permissions to the bucket.

MinIO Gateway

Optionally, you can use MinIO Gateway as a common interface which relays backup objects to other cloud storage solutions, like S3 or GCS. For more information, please refer to MinIO official documentation.

Specifically, the CloudNativePG cluster can directly point to a local MinIO Gateway as an endpoint, using previously created credentials and service.

MinIO secrets will be used by both the PostgreSQL cluster and the MinIO instance. Therefore, you must create them in the same namespace:

kubectl create secret generic minio-creds \
  --from-literal=MINIO_ACCESS_KEY=<minio access key here> \
  --from-literal=MINIO_SECRET_KEY=<minio secret key here>

Note

Cloud Object Storage credentials will be used only by MinIO Gateway in this case.

Important

In order to allow PostgreSQL to reach MinIO Gateway, it is necessary to create a ClusterIP service on port 9000 bound to the MinIO Gateway instance.

For example:

apiVersion: v1
kind: Service
metadata:
  name: minio-gateway-service
spec:
  type: ClusterIP
  ports:
    - port: 9000
      targetPort: 9000
      protocol: TCP
  selector:
    app: minio

Warning

At the time of writing this documentation, the official MinIO Operator for Kubernetes does not support the gateway feature. As such, we will use a deployment instead.

The MinIO deployment will use cloud storage credentials to upload objects to the remote bucket and relay backup files to different locations.

Here is an example using AWS S3 as Cloud Object Storage:

apiVersion: apps/v1
kind: Deployment
[...]
spec:
  containers:
  - name: minio
    image: minio/minio:RELEASE.2020-06-03T22-13-49Z
    args:
    - gateway
    - s3
    env:
    # MinIO access key and secret key
    - name: MINIO_ACCESS_KEY
      valueFrom:
        secretKeyRef:
          name: minio-creds
          key: MINIO_ACCESS_KEY
    - name: MINIO_SECRET_KEY
      valueFrom:
        secretKeyRef:
          name: minio-creds
          key: MINIO_SECRET_KEY
    # AWS credentials
    - name: AWS_ACCESS_KEY_ID
      valueFrom:
        secretKeyRef:
          name: aws-creds
          key: ACCESS_KEY_ID
    - name: AWS_SECRET_ACCESS_KEY
      valueFrom:
        secretKeyRef:
          name: aws-creds
          key: ACCESS_SECRET_KEY
# Uncomment the below section if session token is required
#   - name: AWS_SESSION_TOKEN
#     valueFrom:
#       secretKeyRef:
#         name: aws-creds
#         key: ACCESS_SESSION_TOKEN
        ports:
        - containerPort: 9000

Proceed by configuring MinIO Gateway service as the endpointURL in the Cluster definition, then choose a bucket name to replace BUCKET_NAME:

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
[...]
spec:
  backup:
    barmanObjectStore:
      destinationPath: s3://BUCKET_NAME/
      endpointURL: http://minio-gateway-service:9000
      s3Credentials:
        accessKeyId:
          name: minio-creds
          key: MINIO_ACCESS_KEY
        secretAccessKey:
          name: minio-creds
          key: MINIO_SECRET_KEY
    [...]

Verify on s3://BUCKET_NAME/ the presence of archived WAL files before proceeding with a backup.