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perf: fetch the Genesis world manifest concurrently with realm /about #9540

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perf: fetch the Genesis world manifest concurrently with realm /about #9540

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c263d63
perf: fetch the Genesis world manifest concurrently with realm /about
eordano Jul 31, 2026
ee98b7a
fix: skip the Genesis manifest prefetch in local scene development
eordano Jul 31, 2026
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5 changes: 5 additions & 0 deletions Explorer/Assets/DCL/Infrastructure/Global/Dynamic/RealmController.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,11 @@ public async UniTask SetRealmAsync(URLDomain realm, CancellationToken ct)
{
serverAbout.Clear();

// Local scene development runs against a local realm and must not reach out to
// the Genesis manifest host.
if (!isLocalSceneDevelopment)
worldManifestProvider.PrefetchGenesisManifest(environment, ct);

GenericDownloadHandlerUtils.Adapter<GenericGetRequest, GenericGetArguments> genericGetRequest = webRequestController.GetAsync(new CommonArguments(url), ct, ReportCategory.REALM);
ServerAbout result = await genericGetRequest.OverwriteFromJsonAsync(serverAbout, WRJsonParser.Unity);
localSceneParcels = ParseLocalSceneParcels(result.configurations.localSceneParcels);
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12 changes: 11 additions & 1 deletion Explorer/Assets/DCL/Infrastructure/Global/Dynamic/WorldManifestProvider.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,13 @@ public class WorldManifestProvider
private const string dclWorldName = "dcl.eth";

private WorldManifest? cachedMainManifest;
private UniTask<WorldManifest>? inFlightMainManifest;

// Genesis manifest URLs are compile-time constants, so this runs concurrently with
// the realm /about request instead of waiting on realmName. Idempotent; Preserve()
// lets the Genesis branch await this same task rather than issue a second request.
Comment on lines +32 to +34

@decentraland-bot decentraland-bot Jul 31, 2026

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[P2] Comment narrates caller/external behavior (CLAUDE.md §11 anti-patterns). "runs concurrently with the realm /about request" and "lets the Genesis branch await this same task" describe what callers do, not what this method guarantees. The caller pattern can change without this code changing, silently making the comment wrong.

Suggested change
// Genesis manifest URLs are compile-time constants, so this runs concurrently with
// the realm /about request instead of waiting on realmName. Idempotent; Preserve()
// lets the Genesis branch await this same task rather than issue a second request.
// Idempotent while a fetch is pending; Preserve()d for multi-await.

public void PrefetchGenesisManifest(DecentralandEnvironment environment, CancellationToken ct) =>
inFlightMainManifest ??= FetchGenesisManifestAsync(environment, ct).Preserve();
Comment on lines +35 to +36

@decentraland-bot decentraland-bot Jul 31, 2026

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[P1] Stale task after cancellation poisons genesis manifest for the rest of the session.

??= never retries once inFlightMainManifest is set. If the CancellationToken passed to SetRealmAsync fires before the HTTP request completes, FetchGenesisManifestAsync catches OperationCanceledException and returns WorldManifest.Empty. The UniTask completes successfully (status Succeeded) with Empty, cachedMainManifest stays null, and ??= skips every subsequent call — the genesis manifest remains empty for the rest of the session with no recovery path.

This is especially insidious because PrefetchGenesisManifest is called unconditionally in SetRealmAsync (even for world realms). If a world-realm connection is cancelled, the genesis manifest prefetch is also cancelled via the shared ct, poisoning future genesis connections the user never navigated to.

Fix: Guard on cache hit and pending status instead of ??=, so a cancelled/failed fetch is retried with a fresh token.

Suggested change
public void PrefetchGenesisManifest(DecentralandEnvironment environment, CancellationToken ct) =>
inFlightMainManifest ??= FetchGenesisManifestAsync(environment, ct).Preserve();
public void PrefetchGenesisManifest(DecentralandEnvironment environment, CancellationToken ct)
{
if (cachedMainManifest.HasValue) return;
if (inFlightMainManifest.HasValue && inFlightMainManifest.Value.Status == UniTaskStatus.Pending)
return;
inFlightMainManifest = FetchGenesisManifestAsync(environment, ct).Preserve();
}


public WorldManifestProvider(IWebRequestController webRequestController)
{
Expand All @@ -38,7 +45,10 @@ public async UniTask<WorldManifest> FetchWorldManifestAsync(URLDomain assetBundl
try
{
if(MAIN_REALM_NAMES.Contains(realmName))
return await FetchGenesisManifestAsync(environment, ct);
{
PrefetchGenesisManifest(environment, ct);
return await inFlightMainManifest!.Value;

@decentraland-bot decentraland-bot Jul 31, 2026

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[P2] Null-forgiving operator ! without justifying comment (CLAUDE.md nullable reference types). The ! is correct — PrefetchGenesisManifest guarantees inFlightMainManifest is non-null on return — but the rule requires a comment when using !.

Suggested change
return await inFlightMainManifest!.Value;
return await inFlightMainManifest!.Value; // set by PrefetchGenesisManifest above

}

if(realmName.EndsWith(dclWorldName))
return await FetchNonGenesisManifestAsync(assetBundleRegistry, realmName, ct);
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