Protected content

Read a published project's index and files with a short-lived read token that your game gets for its signed-in player, refreshed before it expires, retried once when the server refuses it, and paced when the server asks for fewer requests.

module: com.awakekt.awake:project module: com.awakekt.awake.project:runtime transports: com.awakekt.awake.project:transport-ktor, com.awakekt.awake.project:transport-browser Desktop · Android · iOS · Web

IndexedAssetSource reads a published project's files as its index lists them, checks each one against the index's size and SHA-256, and keeps it in a ContentCache. It sends requests through a fetch the host supplies, so com.awakekt.awake:project carries no HTTP library. When the content server wants a read token on every request, use a TokenAuthorizedFetch: your game supplies the token, and the engine attaches it, refreshes it, retries with it, and waits out a 429 or a 503 with Retry-After.

Wire a token provider

1. Pick a transport. A ContentTransport sends one GET with the headers it is given and answers the status, body and response headers. Two ready-made ones cover most games, each in its own optional module, so a game takes only the HTTP stack it uses:

Host	Module	Transport
Desktop, Android, iOS: a game with a Ktor HttpClient	com.awakekt.awake.project:transport-ktor	KtorContentTransport(client, baseUrl)
Web (wasmJs), with no HTTP library	com.awakekt.awake.project:transport-browser	BrowserContentTransport(baseUrl), over fetch()
Anything else	none	your own ContentTransport, below

With Ktor, pass the client your game already has. Its engine (OkHttp or Android, Darwin, CIO or Java, Js) and its plugins, such as HttpTimeout, are yours; the transport names no engine.

Kotlin (Ktor)

// The client your game already has, with the engine it chose: OkHttp, Darwin, CIO or Js.
val httpClient = HttpClient(engine)
val transport = KtorContentTransport(httpClient, baseUrl = "https://content.example.com/release/")
val contentFetch = TokenAuthorizedFetch(transport) {
    val grant = gameBackend.requestReadToken()
    ReadToken(grant.token, expiresIn = grant.expiresInSeconds.seconds)
}
val source = IndexedAssetSource.open(fetch = contentFetch, cache = cache)

In the browser, the transport calls fetch() itself:

Kotlin (wasmJs)

val transport = BrowserContentTransport(baseUrl = "https://content.example.com/release/")
val contentFetch = TokenAuthorizedFetch(transport) {
    val grant = gameBackend.requestReadToken()
    ReadToken(grant.token, expiresIn = grant.expiresInSeconds.seconds)
}
val source = IndexedAssetSource.open(fetch = contentFetch, cache = IndexedDbContentCache(namespace = "harbor-town"))

baseUrl is the folder the index was published to, ending in /; the index's relative URLs resolve against it the way a browser resolves a link. Without it, the Ktor transport sends each URL as it comes (for a client with its own defaultRequest URL) and the browser resolves it against the page.

To adapt another client, answer every status, 401, 403, 429 and 503 included, instead of throwing: that is how a refused token is told apart from a missing file. Pass the response headers too, so the Retry-After of a 429 or 503 is honoured.

Kotlin

val baseUrl = "https://content.example.com/release/"
val transport = ContentTransport { request ->
    // Resolve the index's relative URLs, send the headers, and answer every status, 401, 429
    // and 503 included, with the response headers, so their Retry-After is honoured.
    val (status, body, headers) = httpClient.get(baseUrl + request.url, request.headers)
    ContentResponse(status, body, headers)
}

2. Supply the token. The provider is a suspend function that answers a ReadToken: the token and how long it stays valid. Get it however your game does, typically from your own server once the player has signed in. The engine calls it on the first request and again before the token expires, never twice at once.

Kotlin

val contentFetch = TokenAuthorizedFetch(transport) {
    // The game's own server signs its player in and answers a short-lived read token.
    val grant = gameBackend.requestReadToken()
    ReadToken(grant.token, expiresIn = grant.expiresInSeconds.seconds)
}

3. Open the project through it. Passing the TokenAuthorizedFetch to IndexedAssetSource.open reads the index with the token too, then every file and content bundle.

Kotlin

val source = IndexedAssetSource.open(fetch = contentFetch, cache = cache)
source.prefetch(listOf("assets/crate.glb")) { done, total -> println("Downloaded $done of $total bytes") }
val crate = source.read(AssetPath("assets/crate.glb")).getOrThrow()

With an index you already have, pass the fetch function instead: IndexedAssetSource(index, contentFetch::fetch, cache). Bundles go through the same fetch: a whole bundle with fetch, and one member alone with fetchRange (open(..., rangeReads = true)), which adds a Range header beside the token.

A host that can't send headers

Where a request can carry only a URL, put the token in the query instead. The transport then ignores request.headers, and request.url arrives with ?access_token=<token> added (after any query the URL already has, and before any fragment).

Kotlin

val contentFetch = TokenAuthorizedFetch(
    transport = { request ->
        // This host loads through a URL alone, so the token comes in request.url.
        val (status, body) = httpClient.get("https://content.example.com/release/" + request.url, emptyMap())
        ContentResponse(status, body)
    },
    placement = ReadTokenPlacement.QueryParameter(), // ?access_token=...
) {
    val grant = gameBackend.requestReadToken()
    ReadToken(grant.token, expiresIn = grant.expiresInSeconds.seconds)
}

Host	Placement
Desktop, Android, iOS: any HTTP client that sets request headers	AuthorizationHeader, the default
Browser fetch()	AuthorizationHeader; cross-origin, see the browser and CORS
A loader that takes only a URL	QueryParameter()

A token in the URL can be recorded

Servers, proxies, CDNs and browser history may log full URLs, query included. Use QueryParameter only where the host can't send a header, and keep the token short-lived.

The browser and CORS

When the content server is on another origin than the page, its CORS answers decide what reaches the game. A browser reports a request it refused for CORS exactly as it does a network failure, so BrowserContentTransport's error message lists what the server must allow.

Response header	Value	Why
Access-Control-Allow-Origin	the game's origin	Without it, every request fails before a status arrives.
Access-Control-Allow-Headers	Authorization, Range	Authorization makes the browser send a preflight OPTIONS first; Range is for a bundle member read alone.
Access-Control-Expose-Headers	Retry-After	Otherwise the browser hides it: a 429 backs off exponentially instead, and a 503 fails at once.
Access-Control-Max-Age	e.g. 600	Lets the browser reuse a preflight answer instead of sending one per file.

No cookies are sent cross-origin (credentials: same-origin), so the read token is the only credential. With QueryParameter there is no preflight, at the cost of the token in the URL.

Rate limits

A server that answers 429 Too Many Requests, or 503 Service Unavailable with a Retry-After, is waited out and the request sent again, as RateLimitBackoff says (RFC 9110 lets a 503 say, with Retry-After, how long the service stays unavailable):

• Retry-After first. The wait is exactly what the header says: a number of seconds, or an HTTP date (Wed, 21 Oct 2026 07:28:00 GMT, or either obsolete form). A date already past sends again at once.
• Otherwise exponential, with jitter. A 429 with no Retry-After, or one that doesn't parse, waits up to initialDelay before the first retry, each later one up to twice the one before, never more than maxDelay. Each wait is drawn from between half and all of that, so players refused together don't all come back together.
• Bounded. A request is sent at most maxAttempts times while it is answered 429 or 503 with Retry-After, and one fetch waits at most maxTotalWait in all. A wait that would go past that isn't started: the fetch fails at once with a ContentFetchException whose status is 429 or 503 and whose message says why it stopped.
• A 503 only with Retry-After. A 503 without the header, or with one that doesn't parse, says nothing about when to come back and is not retried: the fetch fails at once with a ContentFetchException whose status is 503. There is no exponential fallback for a 503.
• Only 429 and 503, only reads. No other status is retried. Every content request is a GET, so sending it again changes nothing on the server.
• Never blocking. A wait suspends, so it is safe on the frame thread, and cancelling the fetch cancels it. After a wait, the token is checked again and refreshed if the wait brought it close to expiring.

Tune it, or turn it off with RateLimitBackoff.None:

Kotlin

val contentFetch = TokenAuthorizedFetch(
    transport = KtorContentTransport(HttpClient(engine), "https://content.example.com/release/"),
    // At most 3 sends of a request answered 429, and 10 seconds of waiting per fetch.
    rateLimitBackoff = RateLimitBackoff(maxAttempts = 3, maxTotalWait = 10.seconds),
) {
    val grant = gameBackend.requestReadToken()
    ReadToken(grant.token, expiresIn = grant.expiresInSeconds.seconds)
}

Property	Type	Default	What it does
maxAttempts	Int	4	Sends of one request while it is answered 429 or 503 with Retry-After, the first included. 1 never retries.
maxTotalWait	Duration	30 seconds	The longest one fetch waits in all.
initialDelay	Duration	1 second	The longest first wait when the server sends no Retry-After.
maxDelay	Duration	8 seconds	The longest any one wait grows to when the server sends no Retry-After.
clock	Clock	Clock.System	The wall clock an HTTP-date Retry-After is measured against.
random	Random	Random.Default	The jitter's source.
delay	suspend (Duration) -> Unit	kotlinx.coroutines.delay	Takes a wait; a test passes its own to record waits instead.

Don't retry a 429 twice

If your Ktor client installs HttpRequestRetry, keep 429 out of what it retries, or each wait is taken twice. Network failures and timeouts stay the client's to retry.

Properties

Property	Type	Default	What it does
transport	ContentTransport	required	Sends each request; resolves relative URLs against wherever the index came from.
placement	ReadTokenPlacement	AuthorizationHeader	Authorization: Bearer <token>, or QueryParameter(name), by default access_token.
refreshAhead	Duration	60 seconds	How long before expiry the next token is asked for. A token shorter-lived than twice this is replaced at half its lifetime.
timeSource	TimeSource	TimeSource.Monotonic	Measures a token's lifetime, unaffected by changes to the device clock.
rateLimitBackoff	RateLimitBackoff	RateLimitBackoff()	How a 429, or a 503 with Retry-After, is waited out; see Rate limits.
tokenProvider	suspend () -> ReadToken	required	Answers a current token.

ReadToken(value, expiresIn) takes the token and how long it stays valid from now: an OAuth expires_in, or a JWT's exp less the current time.

How it works

• Refresh before expiry. The token is kept until it is within refreshAhead of expiring, then the next request asks the provider for a new one before it is sent.
• One retry on refusal. A 401 or 403 gets a fresh token and the request is sent once more. A second refusal throws ContentFetchException with that status and a message saying the fresh token was refused too.
• A 429 waits, and so does a 503 with Retry-After. See Rate limits. Any other status but 2xx, a 503 without Retry-After included, throws at once, with no retry.
• One refresh for many requests. prefetch reads up to six files at once. When they need a new token at the same moment, or are all refused, they wait on a single call to the provider and share its token. If that call fails, the requests waiting on it fail with it, and the next request asks again.
• The cache never sees the token. ContentCache stores checked bytes under their SHA-256, so a new token, or a new release that lists the same files, reads them from the cache. Only the index is fetched again.
• The token stays out of messages. ContentFetchException names the URL as you passed it, before the token was added. A transport failure whose message quotes the token is reported with it replaced by <redacted>, and without that cause attached. ReadToken and ContentRequest print without it, so logging one is safe.

Keep network retries and resumes in the transport

TokenAuthorizedFetch retries only a refused token, a 429 and a 503 with Retry-After. Network retries, timeouts and resumed downloads belong to your HTTP client, behind the transport.

Play a protected project after sign-in

A routed app declares its routes before it starts, but a protected project can be read only once the player has signed in. Give its route the project as a loader with projectRoute, from com.awakekt.awake.project:runtime: the router runs the loader the first time the route is entered, off the frame thread, and shows the route's loading scene until the project arrives.

Kotlin

// Completed by the sign-in scene once the player has signed in.
val signedIn = CompletableDeferred<PlayerSession>()

val game = app {
    scenes {
        route("sign-in", label = "Sign in") {
            cameraEntity("camera") // and the game's sign-in screen
        }
        projectRoute(
            "harbor-town",
            label = "Harbor Town",
            loading = {
                ui { Text("Loading Harbor Town...") }
                update { _, _ ->
                    // Back to sign-in when the content can't be read; entering again loads again.
                    val router = requireService(SceneRouterRuntime::class)
                    if (router.activeRouteStatus is SceneRouteStatus.Failed) router.switchTo("sign-in")
                }
            },
        ) {
            // Runs off the frame thread the first time the route is entered, and waits for sign-in.
            val session = signedIn.await()
            val contentFetch = TokenAuthorizedFetch(transport) { session.readToken() }
            loadProject(IndexedAssetSource.open(fetch = contentFetch, cache = contentCache))
        }
    }
}
val router = game.requireService<SceneRouterRuntime>()

When sign-in succeeds, complete what the loader waits for and enter the route:

Kotlin

// The sign-in scene, once the game's server has signed the player in:
signedIn.complete(session)
router.switchTo("harbor-town")

Entering the route before the player has signed in is fine too: the loading scene plays until the loader returns. To start reading the project before the player enters the route, call router.preload("harbor-town") as sign-in succeeds; entering it once it has loaded plays it at once.

When	What happens
The route is entered before the project has loaded	activeSceneId names the route, its loading scene plays, and routeStatus is Loading. The project's scene takes its place at the start of the first frame after the loader returns.
The route is entered after it has loaded	The project plays at once, with no loading frame.
The loader throws, for instance when the token is refused	The route stays on its loading scene with routeStatus Failed(cause), and the failure is logged. Entering the route again with switchTo runs the loader again.
The player leaves while it loads	The load goes on, and the project waits, unplayed, for the next entry; the router never switches to the route on its own. Stopping the app cancels the load and closes a project that loaded but never played.
The player leaves the route after it played	Its scene stops and the project is closed, physics world included, because a project plays once. Entering again runs the loader again; the files it read come from the ContentCache.

A route whose scene is not a project uses deferredRoute(id) { ... }, from awake:scene:authoring, which returns a sceneApp { } instead. It keeps what it loaded for later entries unless it is given keepLoaded = false. Routes declared with route load before the app starts, as they always have.

See also

• Content bundles
• Load a scene document
• Run in the browser
• Modules