6. Runtime view

6.1 Startup of a GeoServer replica (sub-project 2)

sequenceDiagram
    participant K as Kubernetes
    participant B as bootstrap-datadir.sh
    participant DB as Database (geoserver schema)
    participant T as Tomcat
    participant GS as GeoServer (JDBCConfig, JDBCStore)
    participant I as geoserver-init
    K->>B: starts the container (env, Secrets, emptyDir)
    B->>B: variable checks
    B->>DB: SELECT to_regclass('geoserver.object'), ('geoserver.resources')
    DB-->>B: present? → initdb/import=false (otherwise true)
    B->>B: writes jdbcconfig/jdbcstore/status/controlflow .properties
    B->>T: exec startup.sh (server.xml envsubst, admin, SKIP_DEMO_DATA)
    T->>T: binds jdbc/geoserver and jdbc/meteo (pools)
    T->>GS: starts the webapp
    GS->>DB: loads catalog (object) and resources (resources, including security/)
    GS->>I: GeoServerInitializer.initialize()
    I->>GS: workspace / JNDI datastore / layer: created or verified
    GS-->>K: /geoserver/index.html 200 (probes)

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First boot: initdb/import=true, JDBCConfig and JDBCStore create their tables and import the initial data dir (including security/). Subsequent boots: everything is re-read from the database; the local data dir only contains the files regenerated by the bootstrap.

6.2 Scaling from 3 to 5 replicas (sub-project 3)

sequenceDiagram
    participant Ops as Ops (kubectl scale / k9s)
    participant K as Kubernetes
    participant DNS as Headless Service DNS
    participant N as New pod
    participant C as Hazelcast cluster (3 members)
    participant DB as Database
    Ops->>K: replicas 3 → 5
    K->>N: creates the pod (emptyDir, env)
    K->>DNS: publishes the pod IP (publishNotReadyAddresses)
    N->>DNS: resolves geoserver-hz (bootstrap, pre-check)
    N->>N: regenerates cluster/*, jdbc*/*.properties
    N->>DB: loads catalog and resources
    N->>C: joins (5701) → size=4, then 5
    N-->>K: Ready (probes) → receives traffic
    Note over C: a configuration change on one node is published to the others (event)

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Measured: 5 pods ready in 25 s, 0 errors on in-flight requests; scale-down 5 → 2 without errors (graceful shutdown, terminationGracePeriodSeconds).

6.3 Tile request (sub-project 4)

sequenceDiagram
    participant C as WMTS client
    participant P as GeoServer pod (any of them)
    participant G as GeoWebCache
    participant S3 as gwc-tiles bucket
    participant R as Rendering engine
    C->>P: GetTile (layer, gridset, z/x/y)
    P->>G: tile?
    G->>S3: GET object
    alt HIT
        S3-->>G: tile
    else MISS
        G->>R: rendering (internal WMS)
        R-->>G: image
        G->>S3: PUT object
    end
    G-->>C: tile + header geowebcache-cache-result: HIT|MISS

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The cache is shared: a tile rendered by one pod is served as a HIT by all the others, including pods created afterwards.

6.4 Arrival of a new granule (sub-project 5)

sequenceDiagram
    participant I as Ingestion service
    participant S3 as rasters bucket
    participant DB as mosaic index (PostGIS)
    participant G as GeoServer (any pod)
    participant C as Client
    I->>I: field → canonical unit → COG
    I->>S3: PUT models/…/arpege_t_isobaric85000_run_valid.tif
    I->>DB: INSERT model_granule (time, elevation, reference_time, source_unit)
    C->>G: GetCapabilities
    G->>DB: SELECT DISTINCT time, elevation… FROM mosaic.arpege_t
    G-->>C: up-to-date dimensions (new forecast validity time included)
    C->>G: GetMap TIME=… ELEVATION=…
    G->>DB: matching granules
    G->>S3: range reads of the COG
    G-->>C: image

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No restart and no notification: measured, the new forecast validity time is visible on all pods as soon as the row is inserted.