Mastodon Architecture

Compose 🐳

flowchart LR
    none["web-app-mastodon declares no service"]

Swarm 🐝

flowchart LR
    none["web-app-mastodon declares no service"]

Volumes

flowchart LR
    vol_data["mastodon_data"]
    vol_data -->|"swarm + storage.backend nfs"| nfs_data["shared over NFS"]:::shared
    vol_data -->|"compose, or backend local"| cl_data["node-local"]:::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_db_postgres["svc-db-postgres 🐳🐝"]
        dep_svc_db_redis["svc-db-redis 🐳🐝"]
        dep_svc_net_tor["svc-net-tor 🐳🐝"]
        dep_web_app_dashboard["web-app-dashboard 🐳🐝"]
        dep_web_app_docs["web-app-docs 🐳🐝"]
        dep_web_app_keycloak["web-app-keycloak 🐳🐝"]
        dep_web_app_matomo["web-app-matomo 🐳🐝"]
        dep_web_app_prometheus["web-app-prometheus 🐳🐝"]
        dep_web_app_stalwart["web-app-stalwart 🐳🐝"]
        dep_web_svc_design["web-svc-design 💻"]
        dep_web_svc_logout["web-svc-logout 🐳🐝"]
        dep_web_svc_seaweedfs["web-svc-seaweedfs 🐳🐝"]
    end
    subgraph role [web-app-mastodon 🐳🐝]
        svc_sso["sso"]
        svc_logout["logout"]
        svc_dashboard["dashboard"]
        svc_matomo["matomo"]
        svc_email["email"]
        svc_redis["redis"]
        svc_postgres["postgres"]
        svc_mastodon["mastodon"]
        svc_streaming["streaming"]
        svc_sidekiq["sidekiq"]
        svc_migrate["migrate"]
        svc_minio["minio ❌"]
        svc_seaweedfs["seaweedfs"]
        svc_design["design"]
        svc_prometheus["prometheus"]
        svc_tor["tor"]
        svc_container_backup["container_backup"]
        svc_docs["docs"]
    end
    subgraph dependents [Dependents]
        dpt_web_app_discourse["web-app-discourse 🐳🐝"]
        dpt_web_app_fediwall["web-app-fediwall 🐳🐝"]
        dpt_web_app_nextcloud["web-app-nextcloud 🐳🐝"]
    end
    dep_svc_bkp_volume_2_local -. "0..1" .-> svc_container_backup
    dep_svc_db_postgres -. "0..1" .-> svc_postgres
    dep_svc_db_redis -. "0..1" .-> svc_redis
    dep_svc_net_tor -. "0..1" .-> svc_tor
    dep_web_app_dashboard -. "0..1" .-> svc_dashboard
    dep_web_app_docs -. "0..1" .-> svc_docs
    dep_web_app_keycloak -. "0..1" .-> svc_sso
    dep_web_app_matomo -. "0..1" .-> svc_matomo
    dep_web_app_prometheus -. "0..1" .-> svc_prometheus
    dep_web_app_stalwart -. "0..1" .-> svc_email
    dep_web_svc_design -. "0..1" .-> svc_design
    dep_web_svc_logout -. "0..1" .-> svc_logout
    dep_web_svc_seaweedfs -. "0..1" .-> svc_seaweedfs
    svc_sso -. "0..1" .-> dpt_web_app_discourse
    svc_sso -. "0..1" .-> dpt_web_app_fediwall
    svc_sso -. "0..1" .-> dpt_web_app_nextcloud

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.