Package cache Architecture

Compose 🐳

flowchart LR
    subgraph role [svc-cache-package]
        svc_frontend["frontend<br>nginx:1.31-alpine<br>http 80 · https 443"]
        svc_bootstrap["bootstrap<br>built here"]
    end

Swarm 🐝

flowchart LR
    svc_frontend["frontend"]
    svc_frontend --> rep_frontend["replicas: from the host group"]
    svc_frontend --> plc_frontend["node.role == manager"]:::pinned
    svc_bootstrap["bootstrap"]
    svc_bootstrap --> rep_bootstrap["replicas: 1"]
    svc_bootstrap --> plc_bootstrap["node.role == manager"]:::pinned
    classDef pinned fill:#fef7e0,stroke:#b06000,color:#3d2600;

Volumes

flowchart LR
    vol_data["package_cache_data"]
    vol_data -->|"nfs: false"| local_data["node-local on every node"]:::local
    classDef shared fill:#e6f4ea,stroke:#137333,color:#0b2e13;
    classDef local fill:#fef7e0,stroke:#b06000,color:#3d2600;

Condition	Effect
swarm, storage.backend: nfs, no nfs: false, role not pinned	shared over NFS
any one of those missing	node-local

All four conditions must hold, so pinning a role takes every one of its volumes node-local. Only the role’s primary entry counts as pinned here: a placement on any other service pins that service alone and leaves the backing of every volume unchanged. The chain is drawn rather than its result, because that coupling is what makes a placement change move data without saying so.

Dependencies

flowchart LR
    subgraph deps [Dependencies]
        dep_svc_bkp_volume_2_local["svc-bkp-volume-2-local 💻"]
        dep_svc_swarm_node["svc-swarm-node 💻"]
        dep_web_app_docs["web-app-docs 🐳🐝"]
    end
    subgraph role [svc-cache-package 🐳]
        svc_node["node"]
        svc_package["package"]
        svc_bootstrap["bootstrap"]
        svc_frontend["frontend"]
        svc_container_backup["container_backup"]
        svc_docs["docs"]
    end
    dep_svc_bkp_volume_2_local -- "1:1" --> svc_container_backup
    dep_svc_swarm_node -- "1:1" --> svc_node
    dep_web_app_docs -. "0..1" .-> svc_docs

Symbol	Meaning
1:1 solid	fixed relationship
0..1 dashed	conditional, enabled only in matching deployments
0..0 red	declared but turned off in this role
💻	deploys to the host
🐳	deploys under compose
🐝	deploys under swarm
❌	service explicitly turned off
⚙️	Ansible role dependency from meta/main.yml

Every dependency and dependent is listed; the graph is not truncated.