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K8SPS-508 Documented the cross-site replication (#212)
* K8SPS-508 Documented the cross-site replication new file: docs/clusterset-cr.md new file: docs/cr-statuses.md modified: docs/features.md modified: docs/operator.md new file: docs/replication-setup.md new file: docs/replication.md modified: docs/users.md modified: mkdocs-base.yml * Upadted after the review * Upadted after the review p2 * Documented the linitation of restoring on replica as part of CS Updated the delete replica scenario: added steps how to delete offline replica * Removed mermaid diagram, minor fixes * Added a limitation about deleting replica before deleting the CS * Updated CS conditions * Added workaround about deleting the CS finalizer, updated diagram
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‎docs/assets/diagrams/cross-site-replication-architecture.py‎

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#!/usr/bin/env python3
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"""Generate the cross-site replication architecture diagram.
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Based on the mockup in docs/assets/images/cross-site-replication-architecture.svg.
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Requires:
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pip install diagrams
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Run from repo root:
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python docs/assets/diagrams/cross-site-replication-architecture.py
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Output:
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docs/assets/images/cross-site-replication-architecture-diagrams.png
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"""
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from pathlib import Path
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from diagrams import Cluster, Diagram, Edge
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from diagrams.k8s.compute import Pod
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from diagrams.k8s.others import CRD
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from diagrams.onprem.client import Client
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from diagrams.onprem.database import MySQL
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OUTPUT = Path(__file__).resolve().parents[1] / "images" / "cross-site-replication-architecture-diagrams.png"
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# Edge styles used across the diagram
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ASYNC_EDGE = Edge(label="Async replication", color="darkgreen")
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ADMIN_API_EDGE = Edge(label="mysqlsh AdminAPI\n(MySQL protocol)")
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def innodb_cluster_nodes():
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"""Three linked MySQL instances inside an InnoDB Cluster (Group Replication)."""
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primary = MySQL("Primary\n+ PVC")
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secondary_1 = MySQL("Secondary\n+ PVC")
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secondary_2 = MySQL("Secondary\n+ PVC")
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primary - secondary_1 - secondary_2 - primary
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return primary, secondary_1, secondary_2
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def member_site(cr_label: str):
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"""Build one ClusterSet member site: Operator, CR, and InnoDB Cluster."""
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operator = Pod("PS Operator")
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ps_cr = CRD(cr_label)
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with Cluster("InnoDB Cluster"):
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primary, secondary_1, secondary_2 = innodb_cluster_nodes()
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operator >> ps_cr
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operator >> [primary, secondary_1, secondary_2]
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return operator, primary, secondary_1, secondary_2
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graph_attr = {
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"fontsize": "13",
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"bgcolor": "white",
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"pad": "0.5",
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"splines": "spline",
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"nodesep": "0.9",
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"ranksep": "1.3",
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}
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with Diagram(
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"Cross-site replication architecture",
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filename=str(OUTPUT.with_suffix("")),
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outformat="png",
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show=False,
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direction="TB",
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graph_attr=graph_attr,
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):
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app = Client("Application")
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with Cluster("InnoDB ClusterSet (PerconaServerMySQLClusterSet)"):
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# Orchestration site - pure controller; does not manage Pods in remote clusters
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with Cluster("Orchestration site (one Kubernetes namespace)"):
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clusterset_cr = CRD("PerconaServerMySQL\nClusterSet CR")
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controller = Pod("ClusterSet\ncontroller")
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runner = Pod("mysqlshell-\nrunner Pod")
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jobs = Pod("Jobs")
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clusterset_cr >> controller >> runner >> Edge(style="dashed") >> jobs
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# Member sites - independently managed PerconaServerMySQL clusters
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with Cluster("Member sites", direction="LR"):
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with Cluster("Primary site\nKubernetes cluster / region A"):
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op_primary, mysql_p_primary, _, _ = member_site(
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"PerconaServerMySQL\nCR (group-replication)",
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)
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with Cluster("Replica site\nKubernetes cluster / region B"):
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op_replica, mysql_r_primary, _, _ = member_site(
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"PerconaServerMySQL CR\nbootstrap: manual",
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)
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with Cluster("Replica site\nDifferent K8s / cloud / on-premises"):
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op_remote, mysql_o_primary, _, _ = member_site(
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"PerconaServerMySQL\nCR (group-replication)",
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)
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# mysqlsh AdminAPI reaches MySQL endpoints at every site over the network
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runner >> ADMIN_API_EDGE >> [op_primary, op_replica, op_remote]
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# Async replication channels from the primary cluster PRIMARY member
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mysql_p_primary >> ASYNC_EDGE >> mysql_r_primary
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mysql_p_primary >> ASYNC_EDGE >> mysql_o_primary
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# Application traffic
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app >> Edge(label="Writes") >> mysql_p_primary
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app >> Edge(label="Reads") >> mysql_r_primary
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app >> Edge(label="Reads") >> mysql_o_primary
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print(f"Wrote {OUTPUT}")

‎docs/assets/diagrams/cross-site-replication-clusterset.mmd‎

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%% Cross-site replication / InnoDB ClusterSet architecture
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%% Source for the diagram in docs/replication.md
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%% Percona docs palette: fill #D4EDFB, stroke #789CD6
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flowchart TB
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classDef clusterBox fill:#D4EDFB,stroke:#789CD6,stroke-width:2px,color:#1a1a1a
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classDef innerBox fill:#ffffff,stroke:#789CD6,stroke-width:1px,color:#1a1a1a
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classDef mgmtBox fill:#E8F4FC,stroke:#326690,stroke-width:2px,color:#1a1a1a
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classDef appBox fill:#ffffff,stroke:#326690,stroke-width:2px,color:#1a1a1a
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classDef dashedBox fill:#ffffff,stroke:#789CD6,stroke-width:1px,stroke-dasharray:5 5,color:#1a1a1a
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APP["Application"]:::appBox
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subgraph CS["ClusterSet"]
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direction TB
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subgraph MGMT["ClusterSet management"]
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direction LR
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CR["PerconaServerMySQLClusterSet CR<br/>(ps-clusterset)"]:::mgmtBox
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CTRL["ClusterSet controller"]:::mgmtBox
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RUNNER["mysqlshell-runner Pod"]:::mgmtBox
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CR --- CTRL
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CTRL --- RUNNER
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end
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subgraph PRIMARY["Kubernetes cluster — primary"]
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direction TB
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OP1["PS Operator"]:::innerBox
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subgraph GR1["Group Replication"]
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direction LR
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M1["MySQL Pod<br/>+ PVC"]:::innerBox
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M2["MySQL Pod<br/>+ PVC"]:::innerBox
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M3["MySQL Pod<br/>+ PVC"]:::innerBox
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end
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HA1["HAProxy"]:::innerBox
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OP1 --> GR1
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GR1 --> HA1
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end
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subgraph REPLICA["Kubernetes cluster — replica"]
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direction TB
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OP2["PS Operator"]:::innerBox
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subgraph GR2["Group Replication"]
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direction LR
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R1["MySQL Pod<br/>+ PVC"]:::innerBox
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R2["MySQL Pod<br/>+ PVC"]:::innerBox
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R3["MySQL Pod<br/>+ PVC"]:::innerBox
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end
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HA2["HAProxy"]:::dashedBox
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OP2 --> GR2
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GR2 --> HA2
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end
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subgraph ONPREM["On-premises MySQL"]
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direction TB
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subgraph NODES["MySQL nodes"]
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direction LR
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N1["MySQL node"]:::innerBox
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N2["MySQL node"]:::innerBox
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N3["MySQL node"]:::innerBox
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end
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HA3["HAProxy"]:::innerBox
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NODES --> HA3
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end
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RUNNER -->|"mysqlsh AdminAPI"| PRIMARY
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RUNNER -->|"mysqlsh AdminAPI"| REPLICA
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RUNNER -->|"mysqlsh AdminAPI"| ONPREM
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PRIMARY ==>|"Async replication"| REPLICA
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PRIMARY ==>|"Async replication"| ONPREM
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OP1 -.->|"Async replication"| OP2
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end
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APP -->|"Writes and reads"| HA1
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APP -->|"Reads"| HA2
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APP -->|"Reads"| HA3
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class CS clusterBox
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class PRIMARY,REPLICA,ONPREM clusterBox
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class MGMT clusterBox

‎docs/assets/diagrams/cross-site-replication-clusterset_bak.py‎

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#!/usr/bin/env python3
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"""Generate the cross-site replication ClusterSet architecture diagram.
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Requires: pip install diagrams
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Run from repo root:
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python docs/assets/diagrams/cross-site-replication-clusterset.py
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Output: docs/assets/images/cross-site-replication-clusterset-diagrams.png
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"""
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from pathlib import Path
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from diagrams import Cluster, Diagram, Edge
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from diagrams.k8s.compute import Pod
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from diagrams.k8s.others import CRD
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from diagrams.onprem.client import Client
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from diagrams.onprem.compute import Server
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from diagrams.onprem.database import MySQL
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from diagrams.onprem.network import HAProxy
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OUTPUT = Path(__file__).resolve().parents[1] / "images" / "cross-site-replication-clusterset-diagrams.png"
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graph_attr = {
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"fontsize": "13",
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"bgcolor": "white",
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"pad": "0.4",
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"splines": "spline",
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"nodesep": "0.8",
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"ranksep": "1.2",
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}
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with Diagram(
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"Cross-site replication ClusterSet",
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filename=str(OUTPUT.with_suffix("")),
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outformat="png",
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show=False,
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direction="LR",
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graph_attr=graph_attr,
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):
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app = Client("Application")
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grouprepl = Edge(label="Group Replication", style="dashed", color="gray")
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asyncrepl = Edge(label="async replication", style="solid", color="green")
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with Cluster("ClusterSet", direction="LR"):
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with Cluster("ClusterSet management", direction="LR"):
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clusterset_cr = CRD("PerconaServerMySQL\nClusterSet CR")
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controller = Pod("ClusterSet\ncontroller")
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runner = Pod("mysqlshell-\nrunner Pod")
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clusterset_cr << controller >> runner
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with Cluster(""):
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with Cluster("Kubernetes cluster — primary"):
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op_primary = Pod("PS Operator")
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with Cluster("MySQL Cluster primary"):
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mysql_primary1 = Pod("Primary")
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mysql_primary2 = Pod("Secondary")
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mysql_primary3 = Pod("MySQL Pod")
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mysql_primary1 - mysql_primary2 - mysql_primary3 - mysql_primary1 << grouprepl
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haproxy_primary = HAProxy("HAProxy")
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op_primary >> mysql_primary1 >> haproxy_primary
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with Cluster("Kubernetes cluster — replica"):
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op_replica = Pod("PS Operator")
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with Cluster("MySQL Cluster primary"):
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mysql_replica1 = Pod("Primary")
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mysql_replica2 = Pod("Secondary")
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mysql_replica3 = Pod("Secondary")
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mysql_replica1 - mysql_replica2 - mysql_replica3 - mysql_replica1 << grouprepl
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haproxy_replica = HAProxy("HAProxy")
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op_replica >> mysql_replica1 >> haproxy_replica
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with Cluster("On-premises MySQL"):
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mysql_nodes = Server("MySQL nodes")
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haproxy_onprem = HAProxy("HAProxy")
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mysql_nodes >> haproxy_onprem
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runner >> Edge(label="mysqlsh AdminAPI") >> [op_primary, op_replica, mysql_nodes]
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mysql_primary1 >> Edge(label="Async replication", color="darkgreen") >> mysql_replica1
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mysql_primary1 >> Edge(label="Async replication", color="darkgreen") >> mysql_nodes
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op_primary >> Edge(label="Async replication", style="dashed", color="gray") >> op_replica
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app >> Edge(label="Writes and reads") >> mysql_primary1
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app >> Edge(label="Reads") >> mysql_replica1
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app >> Edge(label="Reads") >> mysql_nodes
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print(f"Wrote {OUTPUT}")

‎docs/assets/images/innodb-clusterset.svg‎

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‎docs/assets/images/innodb_clusterset.png‎

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