Design overview¶
The Percona Operator for PostgreSQL automates and simplifies deploying and managing open source PostgreSQL clusters on Kubernetes. The Operator is based on CrunchyData’s PostgreSQL Operator.
PostgreSQL containers deployed with the Operator include the following components:
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The PostgreSQL database management system, including:
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pgAudit PostgreSQL auditing extension,
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The pgBackRest Backup & Restore utility,
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The pgBouncer connection pooler for PostgreSQL,
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The PostgreSQL high-availability implementation based on the Patroni template,
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the pg_stat_monitor PostgreSQL Query Performance Monitoring utility,
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LLVM (for JIT compilation).
To provide high availability the Operator involves node affinity to run PostgreSQL Cluster instances on separate worker nodes if possible. If some node fails, the Pod with it is automatically re-created on another node.
To provide data storage for stateful applications, Kubernetes uses Persistent Volumes. A PersistentVolumeClaim (PVC) is used to implement the automatic storage provisioning to pods. If a failure occurs, the Container Storage Interface (CSI) should be able to re-mount storage on a different node.
The Operator functionality extends the Kubernetes API with Custom Resources Definitions. These CRDs provide extensions to the Kubernetes API, and, in the case of the Operator, allow you to perform actions such as creating a PostgreSQL Cluster, updating PostgreSQL Cluster resource allocations, adding additional utilities to a PostgreSQL cluster, e.g. pgBouncer for connection pooling and more.
When a new Custom Resource is created or an existing one undergoes some changes or deletion, the Operator automatically creates/changes/deletes all needed Kubernetes objects with the appropriate settings to provide a proper Percona PostgreSQL Cluster operation.
Following CRDs are created while the Operator installation:
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pgclustersstores information required to manage a PostgreSQL cluster. This includes things like the cluster name, what storage and resource classes to use, which version of PostgreSQL to run, information about how to maintain a high-availability cluster, etc. -
pgreplicasstores information required to manage the replicas within a PostgreSQL cluster. This includes things like the number of replicas, what storage and resource classes to use, special affinity rules, etc. -
pgtasksis a general purpose CRD that accepts a type of task that is needed to run against a cluster (e.g. take a backup) and tracks the state of said task through its workflow.
