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Pgpool

What is Pgpool

Pgpool is a Kubernetes Custom Resource Definitions (CRD). It provides declarative configuration for Pgpool in a Kubernetes native way. You only need to describe the desired configuration in a Pgpoolobject, and the KubeDB operator will create Kubernetes objects in the desired state for you.

Pgpool Spec

As with all other Kubernetes objects, a Pgpool needs apiVersion, kind, and metadata fields. It also needs a .spec section. Below is an example Pgpool object.

apiVersion: kubedb.com/v1alpha2
kind: Pgpool
metadata:
  name: pgpool
  namespace: pool
spec:
  version: "4.5.0"
  replicas: 1
  healthChecker:
    failureThreshold: 3
    periodSeconds: 20
    timeoutSeconds: 10
  authSecret:
    name: pgpool-auth
    externallyManaged: false
  postgresRef:
    name: ha-postgres
    namespace: demo
  sslMode: verify-ca
  clientAuthMode: cert
  tls:
    issuerRef:
      apiGroup: cert-manager.io
      name: pgpool-ca-issuer
      kind: Issuer
    certificates:
      - alias: server
        subject:
          organizations:
            - kubedb:server
        dnsNames:
          - localhost
        ipAddresses:
          - "127.0.0.1"
  monitor:
    agent: prometheus.io/operator
    prometheus:
      serviceMonitor:
        labels:
          release: prometheus
        interval: 10s
  configSecret:
    name: pgpool-config
  initConfig:
    pgpoolConfig:
      log_statement : on
      log_per_node_statement : on
      sr_check_period : 0
      health_check_period : 0
      backend_clustering_mode : 'streaming_replication'
      num_init_children : 5
      max_pool : 75
      child_life_time : 300
      child_max_connections : 0
      connection_life_time : 0
      client_idle_limit : 0
      connection_cache : on
      load_balance_mode : on
      ssl : on
      failover_on_backend_error : off
      log_min_messages : warning
      statement_level_load_balance: on
      memory_cache_enabled: on
  deletionPolicy: WipeOut
  syncUsers: true
  podTemplate:
    spec:
      containers:
        - name: pgpool
          resources:
            limits:
              memory: 2Gi
            requests:
              cpu: 200m
              memory: 256Mi
  serviceTemplates:
    - alias: primary
      spec:
        type: LoadBalancer
        ports:
          - name: http
            port: 9999

spec.version

spec.version is a required field specifying the name of the PgpoolVersion crd where the docker images are specified. Currently, when you install KubeDB, it creates the following PgpoolVersion resources,

• 4.4.5, 4.5.0

spec.replicas

spec.replicas the number of members in pgpool replicaset. Minimum allowed replicas is 1 and maximum is 9.

KubeDB uses PodDisruptionBudget to ensure that majority of these replicas are available during voluntary disruptions so that quorum is maintained.

spec.healthChecker

It defines the attributes for the health checker.

• spec.healthChecker.periodSeconds specifies how often to perform the health check.
• spec.healthChecker.timeoutSeconds specifies the number of seconds after which the probe times out.
• spec.healthChecker.failureThreshold specifies minimum consecutive failures for the healthChecker to be considered failed.
• spec.healthChecker.disableWriteCheck specifies whether to disable the writeCheck or not.

spec.authSecret

spec.authSecret is an optional field that points to a Secret used to hold credentials for pgpool pcp user. If not set, KubeDB operator creates a new Secret {pgpool-object-name}-auth for storing the password for pgpool pcp user for each Pgpool object.

We can use this field in 3 mode.

1. Using an external secret. In this case, You need to create an auth secret first with required fields, then specify the secret name when creating the Pgpool object using spec.authSecret.name & set spec.authSecret.externallyManaged to true.

authSecret:
  name: <your-created-auth-secret-name>
  externallyManaged: true

2. Specifying the secret name only. In this case, You need to specify the secret name when creating the Pgpool object using spec.authSecret.name. externallyManaged is by default false.

authSecret:
  name: <intended-auth-secret-name>

3. Let KubeDB do everything for you. In this case, no work for you.

AuthSecret contains a user key and a password key which contains the username and password respectively for pgpool pcp user.

Example:

$ kubectl create secret generic pgpool-auth -n demo \
--from-literal=username=jhon \
--from-literal=password=O9xE1mZZDAdBTbrV
secret "pgpool-auth" created

apiVersion: v1
data:
  password: "O9xE1mZZDAdBTbrV"
  username: "jhon"
kind: Secret
metadata:
  name: pgpool-auth
  namespace: demo
type: Opaque

Secrets provided by users are not managed by KubeDB, and therefore, won’t be modified or garbage collected by the KubeDB operator (version 0.13.0 and higher).

spec.postgresRef

spec.postgresRef is a required field that points to the appbinding associated with the backend postgres. If the postgres is KubeDB managed an appbinding will be created automatically upon creating the postgres. If the postgres is not KubeDB managed then you need to create an appbinding yourself. spec.postgresRef takes the name (spec.postgresRef.Name) of the appbinding and the namespace (spec.postgresRef.Namespace) where the appbinding is created.

spec.sslMode

Enables TLS/SSL or mixed TLS/SSL used for all network connections. The value of sslMode field can be one of the following:

The specified ssl mode will be used by health checker and exporter of Pgpool.

spec.clientAuthMode

The value of clientAuthMode field can be one of the following:

The pool_hba.conf of Pgpool will have the configuration based on the specified clientAuthMode.

spec.tls

spec.tls specifies the TLS/SSL configurations for the MongoDB. KubeDB uses cert-manager v1 api to provision and manage TLS certificates.

The following fields are configurable in the spec.tls section:

• issuerRef is a reference to the Issuer or ClusterIssuer CR of cert-manager that will be used by KubeDB to generate necessary certificates.

  • apiGroup is the group name of the resource that is being referenced. Currently, the only supported value is cert-manager.io.
  • kind is the type of resource that is being referenced. KubeDB supports both Issuer and ClusterIssuer as values for this field.
  • name is the name of the resource (Issuer or ClusterIssuer) being referenced.

• certificates (optional) are a list of certificates used to configure the server and/or client certificate. It has the following fields:

  • alias represents the identifier of the certificate. It has the following possible value:

    • server is used for server certificate identification.
    • client is used for client certificate identification.
    • metrics-exporter is used for metrics exporter certificate identification.

  • secretName (optional) specifies the k8s secret name that holds the certificates.

    This field is optional. If the user does not specify this field, the default secret name will be created in the following format: <database-name>-<cert-alias>-cert.

  • subject (optional) specifies an X.509 distinguished name. It has the following possible field,

    • organizations (optional) are the list of different organization names to be used on the Certificate.
    • organizationalUnits (optional) are the list of different organization unit name to be used on the Certificate.
    • countries (optional) are the list of country names to be used on the Certificate.
    • localities (optional) are the list of locality names to be used on the Certificate.
    • provinces (optional) are the list of province names to be used on the Certificate.
    • streetAddresses (optional) are the list of a street address to be used on the Certificate.
    • postalCodes (optional) are the list of postal code to be used on the Certificate.
    • serialNumber (optional) is a serial number to be used on the Certificate. You can find more details from Here

  • duration (optional) is the period during which the certificate is valid.

  • renewBefore (optional) is a specifiable time before expiration duration.

  • dnsNames (optional) is a list of subject alt names to be used in the Certificate.

  • ipAddresses (optional) is a list of IP addresses to be used in the Certificate.

  • uris (optional) is a list of URI Subject Alternative Names to be set in the Certificate.

  • emailAddresses (optional) is a list of email Subject Alternative Names to be set in the Certificate.

  • privateKey (optional) specifies options to control private keys used for the Certificate.

    • encoding (optional) is the private key cryptography standards (PKCS) encoding for this certificate’s private key to be encoded in. If provided, allowed values are “pkcs1” and “pkcs8” standing for PKCS#1 and PKCS#8, respectively. It defaults to PKCS#1 if not specified.

spec.monitor

Pgpool managed by KubeDB can be monitored with builtin-Prometheus and Prometheus operator out-of-the-box. To learn more,

• Monitor Pgpool with builtin Prometheus
• Monitor Pgpool with Prometheus operator

spec.configSecret

spec.configSecret is an optional field that allows users to provide custom configuration for Pgpool. You can provide the custom configuration in a secret, then you can specify the secret name spec.configSecret.name.

Please note that, the secret key needs to be pgpool.conf.

To learn more about how to use a custom configuration file see here.

NB. If spec.configSecret is set, then spec.initConfig needs to be empty.

spec.initConfig

spec.initConfig is an optional field that allows users to provide custom configuration for Pgpool while initializing.

To learn more about how to use init configuration see here.

NB. If spec.initConfig is set, then spec.configSecret needs to be empty.

spec.deletionPolicy

deletionPolicy gives flexibility whether to nullify(reject) the delete operation of Pgpool CR or which resources KubeDB should keep or delete when you delete Pgpool CR. KubeDB provides following four deletion policies:

• DoNotTerminate
• Delete (Default)
• WipeOut

When deletionPolicy is DoNotTerminate, KubeDB takes advantage of ValidationWebhook feature in Kubernetes 1.9.0 or later clusters to implement DoNotTerminate feature. If admission webhook is enabled, DoNotTerminate prevents users from deleting the database as long as the spec.deletionPolicy is set to DoNotTerminate.

Following table show what KubeDB does when you delete Pgpool CR for different deletion policies,

If you don’t specify spec.deletionPolicy KubeDB uses Delete deletion policy by default.

spec.syncUsers

spec.syncUsers is an optional field by default its value is false. If it is true, you can provide a secret with username and password as key and with some desired labels to sync PostgreSQL users to Pgpool in runtime.

The contains a user key and a password key which contains the username and password respectively.

Example:

apiVersion: v1
kind: Secret
metadata:
  labels:
    app.kubernetes.io/instance: ha-postgres
    app.kubernetes.io/name: postgreses.kubedb.com
  name: pg-user
  namespace: demo
stringData:
  password: "12345"
  username: "alice"

• app.kubernetes.io/instance should be same asappbinding name mentioned in .spec.postgresRef.name.
• app.kubernetes.io/name should be postgreses.kubedb.com.
• namespace should be same as namespace mentioned in .spec.postgresRef.namespace.

In every 10 seconds KubeDB operator will sync all the users to Pgpool.

Secrets provided by users are not managed by KubeDB, and therefore, won’t be modified or garbage collected by the KubeDB operator (version 0.13.0 and higher).

spec.podTemplate

KubeDB allows providing a template for pod through spec.podTemplate. KubeDB operator will pass the information provided in spec.podTemplate to the PetSet created for Pgpool.

KubeDB accept following fields to set in spec.podTemplate:

• metadata:
  • annotations (pod’s annotation)
  • labels (pod’s labels)
• controller:
  • annotations (statefulset’s annotation)
  • labels (statefulset’s labels)
• spec:
  • volumes
  • initContainers
  • containers
  • imagePullSecrets
  • nodeSelector
  • serviceAccountName
  • schedulerName
  • tolerations
  • priorityClassName
  • priority
  • securityContext

You can check out the full list here. Uses of some field of spec.podTemplate is described below,

spec.podTemplate.spec.nodeSelector

spec.podTemplate.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.podTemplate.spec.resources

spec.podTemplate.spec.resources is an optional field. This can be used to request compute resources required by the database pods. To learn more, visit here.

spec.serviceTemplates

You can also provide template for the services created by KubeDB operator for Kafka cluster through spec.serviceTemplates. This will allow you to set the type and other properties of the services.

KubeDB allows following fields to set in spec.serviceTemplates:

• alias represents the identifier of the service. It has the following possible value:
  • stats is used for the exporter service identification.
• metadata:
  • labels
  • annotations
• spec:
  • type
  • ports
  • clusterIP
  • externalIPs
  • loadBalancerIP
  • loadBalancerSourceRanges
  • externalTrafficPolicy
  • healthCheckNodePort
  • sessionAffinityConfig

See here to understand these fields in detail.