Quelea

Quelea is the party system for the OneLiteFeather network. Players form a party and invite each other by name. When the party leader joins a game from the lobby, the members in the lobby follow onto that exact server. The state lives in a shared Dragonfly, so parties work across several Velocity proxies and any number of service replicas.

How it works

Each Velocity proxy runs the velocity plugin. The plugin reports logins, disconnects and a heartbeat to the backend service over plain HTTP, and it keeps one Server-Sent Events (SSE) stream open to receive party events. Commands from players are sent to the service, which stores all party state in Dragonfly and publishes every change on the Redis channel quelea.events. Each replica forwards these events to its open streams.

flowchart LR
    subgraph Proxies
        V1[Velocity + quelea plugin]
        V2[Velocity + quelea plugin]
    end
    V1 <-->|HTTP commands, SSE stream| R1[Quelea replica]
    V2 <-->|HTTP commands, SSE stream| R2[Quelea replica]
    R1 <--> D[(Dragonfly<br/>state + quelea.events)]
    R2 <--> D

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Follow rule. Whenever the proxy sees the party leader move from one server to another, it asks the service to warp the party to the new server and names the server the leader left. Every proxy then moves its local members to that exact server. With the default follow mode lobby, a member follows if they were on the server the leader left (they were together) or if they are in a lobby (QUELEA_LOBBY_PATTERN); a member in another game stays where they are. So a round that ends brings the party back to the lobby with its leader, and a lobby hop drags the other lobby members along. The leader's first connection after login warps nothing.

Events are delivered at most once. A proxy that reconnects does not receive events it missed, so a warp that was lost can be repeated with /party warp.

Lonely parties. A party that still has only its creator after QUELEA_PARTY_ALONE_TIMEOUT is disbanded. QUELEA_PARTY_ALONE_WARNING before that, the service publishes party.expiring with the expiry time, and the proxy tells the leader how many minutes are left. Expired parties are disbanded with the reason expired-alone. Every party.disbanded event carries a reason: leader (the leader disbanded), last-member-left (only one member remained) or expired-alone. Clients must treat an unknown reason like leader.

Party versions and conditional requests. Every party has a version: 1 when it is created, +1 with every change. It is in the party JSON and in every event. GET /v1/parties/{id} and GET /v1/players/{id}/party send it as a strong ETag (for example "4") and answer 304 Not Modified without a body when If-None-Match names the current tag. kick, promote, disband and warp accept If-Match with one or more strong tags or *. If none matches the current version, the command changes nothing and answers 412 precondition-failed. A weak tag (W/) never matches. Without the header the command runs unconditionally.

Retries. A POST may carry an Idempotency-Key header (1 to 255 visible ASCII characters). The first request with a key runs; a 2xx response is stored for QUELEA_IDEMPOTENCY_TTL, and a repeat with the same key and the same request is answered with the stored response without running again. The key is scoped to the authenticated client. The same key with another request answers 422 idempotency-key-reused; a repeat while the first request is still running answers 409 request-in-progress with Retry-After: 1. Failed responses are not stored, so a retry after an error runs again. The key is kept for QUELEA_IDEMPOTENCY_LOCK while a request runs, so a crashed request does not block its key for longer than that.

Event streams. Each stream of GET /v1/events identifies its client with clientId (proxyId is accepted as an alias). A client that falls more than QUELEA_SSE_BUFFER events behind has its stream closed and counted in quelea.sse.disconnects{reason="overflow"}; it must reconnect and take a fresh snapshot. A stream also ends when the token it was opened with expires, so it never outlives its credentials; the client reconnects with a fresh token and takes a snapshot.

Modules

Module	Artifact / output	Purpose
backend	Docker image harbor.onelitefeather.dev/onelitefeather/quelea	Micronaut HTTP service: parties, invites, presence, events, metrics.
client	net.onelitefeather:quelea-client	Java client generated from the backend's OpenAPI document.
velocity	quelea-velocity-<version>.jar on every GitHub release	Velocity proxy plugin: commands, follow, presence reporting.

Player commands

/party has the alias /p. Running it without arguments prints the help.

Command	Who	Effect
/party create	any player	Creates a party with you as leader. Refused if you are already in one.
/party invite <player>	leader	Invites an online player. Creates a party if you are not in one. The invite expires after 60 s.
/party accept [inviter]	invited player	Joins the party. Without a name, works when exactly one invite is pending; otherwise lists the inviters.
/party deny [inviter]	invited player	Declines an invite. Same name rule as accept.
/party leave	member	Leaves the party. If the leader leaves, the longest-standing member becomes leader.
/party kick <player>	leader	Removes a member.
/party promote <player>	leader	Makes a member the leader.
/party disband	leader	Ends the party for everyone.
/party list	any member	Shows the members of your party.
/party warp	leader	Moves the party to your current server. Use it to retry a warp that did not reach the members.
/pc <message>	member	Sends a message to the party chat (1 to 256 characters).

Messages are shown in English or German, following the player's client language.

Languages and message overrides

The plugin ships English and German. A player sees the bundle for their client locale: de_DE, then de, then en. A key that is missing in the chosen bundle is shown in English, so a partial translation never shows a raw key.

To change or add messages without a new release, put a file named messages_<tag>.properties into plugins/quelea/lang/ on the proxy (for example in the proxy template, next to config.properties):

• Override single messages: messages_de.properties with only the keys to change. Every other German text stays built in.
• Add a language: messages_fr.properties translates the keys it wants; the rest of the messages are English until they are translated.
• Regional variants: messages_de_AT.properties is used for Austrian clients and falls back to de, then en.

The files are read once at proxy start-up, so restart the proxy after a change. Each value is a MiniMessage template. Copy the keys from the built-in messages_en.properties in the plugin jar (lang/), and keep the placeholders (<name>, <count>, <server> and so on) as they are. If a template does not parse, the proxy logs a warning naming the key and language, and that message is shown in English.

The colour guide at the top of messages_en.properties explains which colour means what (commands, arguments, errors, hints, the leader's star).

Configuration

Backend (environment variables)

Set these on the service. Defaults are in backend/src/main/resources/application.yml.

Variable	Default	Meaning
PORT	8080	HTTP port of the service.
REDIS_URI	redis://localhost:6379	Dragonfly (Redis protocol) that holds all state.
QUELEA_REDIS_PREFIX	quelea:	Prefix of every key, so several environments can share one Dragonfly.
QUELEA_REDIS_LOCK_TTL	3s	Lease of a party lock. A holder that stalls longer loses the lock.
QUELEA_REDIS_LOCK_WAIT	1s	How long a request waits for a busy party lock before it fails with lock-timeout.
QUELEA_PARTY_MAX_SIZE	8	Maximum members per party, counting the leader. Minimum 2.
QUELEA_INVITE_TTL	60s	How long an invite stays valid. Re-inviting refreshes it.
QUELEA_PARTY_ALONE_TIMEOUT	30m	A party that has only its creator for this long is disbanded with reason expired-alone.
QUELEA_PARTY_ALONE_WARNING	5m	party.expiring is published this long before the expiry. 0s disables the warning.
QUELEA_PARTY_EXPIRY_INTERVAL	15s	How often the expiry job runs; one replica per run, under a lock. The expiry can be this late.
QUELEA_PROXY_TIMEOUT	45s	A proxy without a heartbeat for this long is treated as dead; its players are disconnected from their parties.
QUELEA_SSE_KEEPALIVE	15s	Interval of the keep-alive comment on idle event streams.
QUELEA_SSE_BUFFER	256	Events one stream may hold unread. A stream that overflows is closed.
QUELEA_IDEMPOTENCY_TTL	24h	How long the response of a completed POST is replayed for its Idempotency-Key.
QUELEA_IDEMPOTENCY_LOCK	10s	Marker of a request in progress. A duplicate within this time answers 409 request-in-progress.
QUELEA_AUTH_ISSUER	http://localhost:18090/quelea	Token issuer (iss). Outside dev/test it must be an https URL, for example https://login.microsoftonline.com/<tenant>/v2.0.
QUELEA_AUTH_AUDIENCE	quelea-api	Token audience (aud). Outside dev/test the client id GUID of the Quelea API registration.
QUELEA_AUTH_TENANT_ID	empty	Entra tenant id; tokens of another tenant are refused. Required outside dev/test.
QUELEA_AUTH_JWKS_URL	http://localhost:18090/quelea/jwks	Where the issuer publishes its signing keys (RS256 only).
QUELEA_AUTH_CLOCK_SKEW	60s	Tolerated clock difference for exp and nbf. Between 0s and 60s; larger values stop the service.
LOG_JSON	false	true writes logs as JSON with trace_id and span_id.
OTEL_TRACES_EXPORTER	none	Set to otlp to export traces.
OTEL_EXPORTER_OTLP_ENDPOINT	http://localhost:4317	OTLP gRPC endpoint for traces.
OTEL_SERVICE_NAME	quelea	Service name on traces and metrics (read from the environment by the metrics exporter too).
QUELEA_METRICS_OTLP_ENABLED	false	true pushes metrics over OTLP/HTTP.
QUELEA_METRICS_OTLP_URL	http://localhost:4318/v1/metrics	OTLP/HTTP metrics endpoint, for example http://alloy-receiver.grafana.svc:4318/v1/metrics.
QUELEA_METRICS_OTLP_STEP	60s	Interval at which metrics are pushed.

Plugin (plugins/quelea/config.properties)

On the first start the plugin creates this file with commented defaults. Each value can also be set by the environment variable shown; the environment wins over the file.

File key	Environment variable	Default	Meaning
url	QUELEA_URL	http://localhost:8080	Base URL of the party service.
proxy-id	QUELEA_PROXY_ID	random UUID per start	Name of this proxy in the service. Set it to keep a stable identity.
lobby-pattern	QUELEA_LOBBY_PATTERN	(?i)^lobby.*	Regex for lobby server names. Moves to other servers warp the party.
follow-mode	QUELEA_FOLLOW_MODE	lobby	Which members follow a warp: lobby (only members in a lobby) or always.
tenant-id	QUELEA_TENANT_ID	none	Entra tenant (GUID or domain) of the plugin's app registration.
client-id	QUELEA_CLIENT_ID	none	Client id of the plugin's app registration.
client-secret	QUELEA_CLIENT_SECRET	none	Secret of that app registration. Prefer the environment for it.
auth-scope	QUELEA_AUTH_SCOPE	none	Token scope, api://<client id of the Quelea API>/.default.

The four credential values come from the Entra app registration of the plugin, described in docs/entra-setup.md. Without all of them the plugin sends no token, logs one warning at start-up, and only a dev party service accepts its requests.

Installing the plugin

1. Download quelea-velocity-<version>.jar from the GitHub release and put it into the Velocity proxy template, next to the other plugins.
2. Set QUELEA_URL on the proxy. In production this is https://quelea.apps.onelite.feather. The proxy must trust the internal certificate authority for that host.
3. Start the proxy. The plugin logs an error and disables itself if the configuration cannot be loaded.

The proxy keeps one SSE stream open to the service. The gateway route for the service must not apply a request timeout, or the stream is cut.

Operations

• Health: GET /health. Reports the state of the Dragonfly connection.
• Metrics: pushed over OTLP/HTTP when QUELEA_METRICS_OTLP_ENABLED=true, to QUELEA_METRICS_OTLP_URL every QUELEA_METRICS_OTLP_STEP. There is no scrape endpoint; /prometheus answers 404. Names keep their Prometheus form in Mimir, for example quelea_party_operations_total. Each replica reports its pod name (HOSTNAME) as service.instance.id.
  • quelea_party_operations_total{operation,result}: service calls by operation and result.
  • quelea_parties_active: parties currently stored.
  • quelea_parties_created_total: parties created.
  • quelea_parties_disbanded_total{reason}: parties disbanded, by reason (leader, last-member-left, expired-alone).
  • quelea_party_lifetime_seconds_*{reason}: time from creation to disband, by reason (histogram).
  • quelea_party_size_*: party size after each join, counting the leader (histogram).
  • quelea_players_online: players online on all proxies, read from the presence store.
  • quelea_sse_streams: open event streams on this replica.
  • quelea_events_published_total{type}: party events published, by type.
  • quelea_events_failed_total{type}: party events that could not be published, by type.
• Traces: OpenTelemetry over OTLP when OTEL_TRACES_EXPORTER=otlp. The trace context is carried inside each event, so a warp can be traced from the leader's request to the fan-out.
• Logs: plain text by default; JSON with LOG_JSON=true.
• Errors: every error is an RFC 9457 Problem Details document (application/problem+json) with a stable code, for example party-full or not-leader. Each code and what to do about it is documented in docs/problems.md. Quote the traceId from the response when you report a problem.

Rolling out authentication

The plugin must be rolled out before the backend enforces authentication, because the 0.1.0 plugin cannot authenticate:

1. Create the Entra app registrations (see docs/entra-setup.md).
2. Release the plugin and install it on the proxies with its client credentials (QUELEA_TENANT_ID, QUELEA_CLIENT_ID, QUELEA_CLIENT_SECRET, QUELEA_AUTH_SCOPE). The 0.1.0 backend ignores the new headers, so this step is safe.
3. Update the backend with the QUELEA_AUTH_* values (QUELEA_AUTH_ISSUER, QUELEA_AUTH_AUDIENCE, QUELEA_AUTH_TENANT_ID, QUELEA_AUTH_JWKS_URL). From this point every route except /health and the API documentation requires a token.

Development

Requirements: JDK 25 and Docker.

# Start Dragonfly on localhost:6379
docker compose -f docker/docker-compose.yml up -d

# Run the service against it
./gradlew :backend:run

# Run a local Velocity proxy with the plugin (QUELEA_URL defaults to http://localhost:8080)
./gradlew :velocity:runVelocity

# Full build
./gradlew build

# Unit tests only (no Docker needed)
./gradlew :backend:test -PexcludeTags=integration

Integration tests use Testcontainers and need a running Docker daemon. They are tagged integration.

Specifications and the change history live in openspec/.

CI

Every pull request runs:

• Build: the shared OneLiteFeather Gradle workflow (build test, JDK 25).
• API compatibility: oasdiff compares the OpenAPI document of the base with the head and fails on breaking changes. The changelog goes to the job summary (.github/workflows/api-diff.yml).
• Coverage: JaCoCo XML and HTML reports for backend and velocity, uploaded to Codecov and as a workflow artifact. Coverage has no threshold and never fails the build (.github/workflows/build-pr.yml).

License

AGPL-3.0