Merge 3bd118fae9 into 3b8b1a2fb6

cockatrice/src/interface/card_picture_loader/card_picture_loader_worker.cpp

@@ -16,14 +16,15 @@
 #include <utility>
 #include <version_string.h>
 
-static constexpr int MAX_REQUESTS_PER_SEC = 10;
-static constexpr int MIN_HOST_QUOTA = 1;                ///< Floor for the per-host request allowance
+static constexpr int MAX_REQUESTS_PER_SEC = DownloadSettings::DEFAULT_HOST_REQUEST_LIMIT;
+static constexpr int MIN_HOST_QUOTA = DownloadSettings::MIN_HOST_REQUEST_LIMIT;
 static constexpr qint64 QUOTA_RECOVER_MS = 60000;       ///< Idle time before a reduced quota starts recovering
 static constexpr int DISPATCH_INTERVAL_MS = 100;        ///< Pacing between individual network requests
 static constexpr qint64 QUOTA_RESET_INTERVAL_MS = 1000; ///< Interval at which the request quota resets
 
 CardPictureLoaderWorker::CardPictureLoaderWorker()
-    : QObject(nullptr), picDownload(SettingsCache::instance().downloads().getPicDownload())
+    : QObject(nullptr), picDownload(SettingsCache::instance().downloads().getPicDownload()),
+      hostRequestLimits(SettingsCache::instance().downloads().getHostRequestLimits())
 {
     networkManager = new QNetworkAccessManager(this);
     // We need a timeout to ensure requests don't hang indefinitely in case of
@@ -73,6 +74,9 @@ CardPictureLoaderWorker::CardPictureLoaderWorker()
 
     connect(&dispatchTimer, &QTimer::timeout, this, &CardPictureLoaderWorker::dispatchQueuedRequest);
     dispatchTimer.setInterval(DISPATCH_INTERVAL_MS);
+
+    connect(&SettingsCache::instance().downloads(), &DownloadSettings::hostRequestLimitsChanged, this,
+            [this] { hostRequestLimits = SettingsCache::instance().downloads().getHostRequestLimits(); });
 }
 
 CardPictureLoaderWorker::~CardPictureLoaderWorker()
@@ -136,8 +140,21 @@ QNetworkReply *CardPictureLoaderWorker::makeRequest(const QUrl &url, CardPicture
 
     QNetworkReply *reply = networkManager->get(req);
 
-    // Connect reply handling
-    connect(reply, &QNetworkReply::finished, worker, [reply, worker] { worker->handleNetworkReply(reply); });
+    // Track in-flight replies per host so the unlocked fast path can bound how many requests it
+    // issues at once, instead of creating replies that time out before Qt opens a connection.
+    const QString host = url.host();
+    hostInFlight.insert(host, hostInFlight.value(host) + 1);
+
+    // Release the in-flight slot when the reply is destroyed, not when it emits `finished`, and use
+    // the worker (not the work object) as the context object: a reply can go away without ever
+    // finishing (aborted, or a work object deleted while a reply is still pending), and a connection
+    // bound to that work object's lifetime would then never run, permanently shrinking the fast
+    // path's concurrency until it wedges. This way the slot is released exactly once.
+    connect(reply, &QObject::destroyed, this,
+            [this, host] { hostInFlight.insert(host, qMax(0, hostInFlight.value(host) - 1)); });
+
+    // Connect reply handling; the work object is the context so its handler dies with it.
+    connect(reply, &QNetworkReply::finished, worker, [worker, reply] { worker->handleNetworkReply(reply); });
 
     return reply;
 }
@@ -145,10 +162,23 @@ QNetworkReply *CardPictureLoaderWorker::makeRequest(const QUrl &url, CardPicture
 void CardPictureLoaderWorker::resetRequestQuota()
 {
     QDateTime now = QDateTime::currentDateTime();
-    for (auto it = hostRequestQuota.begin(); it != hostRequestQuota.end(); ++it) {
+    for (auto it = hostRequestQuota.begin(); it != hostRequestQuota.end();) {
         if (!hostLast429.contains(it.key()) || now.msecsTo(hostLast429.value(it.key())) < -QUOTA_RECOVER_MS) {
-            it.value() = qMin(MAX_REQUESTS_PER_SEC, it.value() + 1);
+            if (hostAllowanceCeiling(it.key()) == DownloadSettings::UNLIMITED_HOST_QUOTA) {
+                // A developer-unlocked host that fell back after a 429 recovers towards the default
+                // allowance; once it gets there it becomes unlocked (fast-path) again.
+                if (it.value() + 1 >= DownloadSettings::DEFAULT_HOST_REQUEST_LIMIT) {
+                    it = hostRequestQuota.erase(it);
+                    continue;
+                }
+                it.value() += 1;
+            } else {
+                // Recover towards the host's effective allowance ceiling, which may be
+                // lowered by the user's per-host request limits.
+                it.value() = qMin(hostAllowanceCeiling(it.key()), it.value() + 1);
+            }
         }
+        ++it;
     }
 
     // Forget the per-second allowances; each host's allowance is re-seeded lazily from its
@@ -178,8 +208,53 @@ void CardPictureLoaderWorker::dispatchQueuedRequest()
         return;
     }
 
-    if (!processSingleRequest()) {
-        // No queued host currently has allowance left in this second; wait for the quota reset.
+    QDateTime now = QDateTime::currentDateTime();
+    bool dispatched = false;
+    // Set while an unlocked host still has queued work blocked only by the in-flight cap; the
+    // timer must keep running so it gets another try as soon as a slot frees. A host blocked by
+    // its 429 backoff instead waits for the next quota-reset tick to restart the dispatcher.
+    bool unlockedCapped = false;
+
+    // Unlocked hosts (developer cap UNLIMITED_HOST_QUOTA) skip the pacing and the per-host
+    // allowance: dispatch their queued requests back-to-back, bounded by their 429 backoff and the
+    // per-host in-flight cap so a large burst can't queue replies that time out before Qt opens a
+    // connection for them.
+    for (int i = 0; i < requestLoadQueue.size();) {
+        const auto &request = requestLoadQueue.at(i);
+        // Dispatch decisions must key on the host the request will actually go to, not the URL that
+        // merely redirects to it: a redirect learned after this URL was queued would otherwise
+        // bypass the in-flight cap and drain the whole queue onto the target host unchecked.
+        const QUrl resolvedUrl = resolveCachedRedirect(request.first);
+        const QString host = resolvedUrl.host();
+        if (isUnlockedHost(host)) {
+            if (CardPictureLoaderWorkerWork::rateLimiter().isRateLimited(host, now)) {
+                ++i;
+                continue;
+            }
+            if (hostInFlight.value(host) < MAX_IN_FLIGHT_PER_HOST) {
+                makeRequest(resolvedUrl, request.second);
+                requestLoadQueue.removeAt(i);
+                dispatched = true;
+                continue;
+            }
+            unlockedCapped = true;
+        }
+        ++i;
+    }
+
+    if (requestLoadQueue.isEmpty()) {
+        dispatchTimer.stop();
+        requestTimer.stop();
+        return;
+    }
+
+    if (processSingleRequest()) {
+        dispatched = true;
+    }
+
+    // Keep the timer running while there is progress to make or unlocked work waiting on a free
+    // in-flight slot; otherwise no host has allowance left this second, so wait for the quota reset.
+    if (!dispatched && !unlockedCapped) {
         dispatchTimer.stop();
     }
 }
@@ -222,35 +297,78 @@ bool CardPictureLoaderWorker::processSingleRequest()
 {
     QDateTime now = QDateTime::currentDateTime();
     for (int i = 0; i < requestLoadQueue.size(); ++i) {
-        const auto &request = requestLoadQueue.at(i);
-        const QString host = request.first.host();
+        // Copy the entry: takeAt(i) below erases within the list this reference points into.
+        const auto request = requestLoadQueue.at(i);
+        // Resolve cached redirects so the rate-limit and allowance arithmetic keys on the host the
+        // request will actually hit (see resolveCachedRedirect).
+        const QUrl resolvedUrl = resolveCachedRedirect(request.first);
+        const QString host = resolvedUrl.host();
         // Don't dispatch requests to a host that is currently in its 429 backoff; hand the entry
         // back to its worker so it can wait the backoff out or fall through to another source,
         // instead of leaving it parked in the queue with no reply pending.
         if (CardPictureLoaderWorkerWork::rateLimiter().isRateLimited(host, now)) {
             auto entry = requestLoadQueue.takeAt(i);
-            entry.second->startNextPicDownload();
+            if (host != entry.first.host()) {
+                // A cached redirect target is what is blocked, which the work object would not
+                // discover from its own URL; wait out that specific host (with jitter) instead.
+                entry.second->scheduleDeferredRetry(host);
+            } else {
+                entry.second->startNextPicDownload();
+            }
             return true;
         }
-        // Seed the allowance now so a host that was rate limited gets its reduced
-        // allowance instead of a fresh full quota mid-second.
+        // Unlocked hosts are handled by dispatchQueuedRequest's fast path, bounded by the in-flight
+        // cap; they must not fall through to the per-host allowance arithmetic below.
+        if (isUnlockedHost(host)) {
+            continue;
+        }
+        int ceiling = hostAllowanceCeiling(host);
+        if (ceiling == DownloadSettings::UNLIMITED_HOST_QUOTA) {
+            // A 429 dropped this unlocked host out of the fast path and installed a concrete
+            // allowance; pace it against that allowance until the recovery loop unlocks it again.
+            ceiling = hostRequestQuota.value(host, DownloadSettings::DEFAULT_HOST_REQUEST_LIMIT);
+        }
+        // Seed the allowance lazily so a host that enters the queue mid-second gets its reduced
+        // per-host allowance, clamped against the ceiling so a lowered user cap applies from this
+        // second onward.
         if (!hostQuotaRemaining.contains(host)) {
-            hostQuotaRemaining.insert(host, hostRequestQuota.value(host, MAX_REQUESTS_PER_SEC));
+            hostQuotaRemaining.insert(host, qMin(ceiling, hostRequestQuota.value(host, ceiling)));
         }
         int allowance = hostQuotaRemaining.value(host);
         if (allowance > 0) {
             hostQuotaRemaining.insert(host, allowance - 1);
             auto entry = requestLoadQueue.takeAt(i);
-            makeRequest(entry.first, entry.second);
+            makeRequest(resolvedUrl, entry.second);
             return true;
         }
     }
     return false;
 }
 
+int CardPictureLoaderWorker::hostAllowanceCeiling(const QString &host) const
+{
+    const int devCap = DownloadSettings::getDeveloperHostCaps().value(host, MAX_REQUESTS_PER_SEC);
+    if (devCap == DownloadSettings::UNLIMITED_HOST_QUOTA && !hostRequestLimits.contains(host)) {
+        return DownloadSettings::UNLIMITED_HOST_QUOTA;
+    }
+    const int requested = hostRequestLimits.value(host, devCap);
+    return SettingsCache::instance().downloads().clampHostRequestLimit(host, requested);
+}
+
+bool CardPictureLoaderWorker::isUnlockedHost(const QString &host) const
+{
+    return hostAllowanceCeiling(host) == DownloadSettings::UNLIMITED_HOST_QUOTA && !hostRequestQuota.contains(host);
+}
+
 void CardPictureLoaderWorker::onHostRateLimited(const QString &host)
 {
-    hostRequestQuota.insert(host, qMax(MIN_HOST_QUOTA, hostRequestQuota.value(host, MAX_REQUESTS_PER_SEC) / 2));
+    const int ceiling = hostAllowanceCeiling(host);
+    // An unlocked host has no per-host allowance to halve. Install one instead so it drops out of
+    // the unlocked fast path and is paced like a throttled host; the recovery loop in
+    // resetRequestQuota() then walks it back up and unlocks it again.
+    const int base =
+        ceiling == DownloadSettings::UNLIMITED_HOST_QUOTA ? DownloadSettings::DEFAULT_HOST_REQUEST_LIMIT : ceiling;
+    hostRequestQuota.insert(host, qMax(MIN_HOST_QUOTA, hostRequestQuota.value(host, base) / 2));
     hostLast429.insert(host, QDateTime::currentDateTime());
 }
 
@@ -308,6 +426,22 @@ QUrl CardPictureLoaderWorker::getCachedRedirect(const QUrl &originalUrl) const
     return {};
 }
 
+QUrl CardPictureLoaderWorker::resolveCachedRedirect(const QUrl &url) const
+{
+    // Follow the whole cached-redirect chain so dispatch keys on the host that is really hit. The
+    // depth bound keeps a corrupt or self-referencing cache entry from spinning us forever.
+    QUrl resolved = url;
+    int depth = 0;
+    while (depth++ < MAX_REDIRECT_CHAIN_DEPTH) {
+        QUrl target = getCachedRedirect(resolved);
+        if (target.isEmpty() || target == resolved) {
+            break;
+        }
+        resolved = target;
+    }
+    return resolved;
+}
+
 void CardPictureLoaderWorker::loadRedirectCache()
 {
     QSettings settings(cacheFilePath, QSettings::IniFormat);

cockatrice/src/interface/card_picture_loader/card_picture_loader_worker.h

@@ -124,15 +124,49 @@ private:
     QTimer requestTimer;                    ///< Timer to reset the request quota
     QTimer dispatchTimer;                   ///< Timer pacing individual network requests
     QHash<QString, int> hostRequestQuota;   ///< Sustained per-host request allowance
+    QHash<QString, int> hostRequestLimits;  ///< User-set per-host request allowances
     QHash<QString, int> hostQuotaRemaining; ///< Per-host allowance left in the current second
     QHash<QString, QDateTime> hostLast429;  ///< When each host was last rate limited
+    QHash<QString, int> hostInFlight;       ///< Network replies currently in flight, per host
+
+    /** @brief Maximum concurrent in-flight network replies per host. */
+    static constexpr int MAX_IN_FLIGHT_PER_HOST = 6;
+
+    /** @brief Bound on how many cached-redirect hops dispatch resolution will follow. */
+    static constexpr int MAX_REDIRECT_CHAIN_DEPTH = 10;
 
     CardPictureLoaderLocal *localLoader; ///< Loader for local images
     QSet<QString> currentlyLoading;      ///< Deduplication: contains pixmapCacheKey currently being loaded
 
+    /**
+     * @brief Effective per-host allowance ceiling for a host.
+     * @param host The host to look up
+     * @return The allowance ceiling in requests/second, or DownloadSettings::UNLIMITED_HOST_QUOTA
+     *         when the developer unlocked the host and no user limit is set for it.
+     */
+    [[nodiscard]] int hostAllowanceCeiling(const QString &host) const;
+
+    /**
+     * @brief Whether a host may skip dispatch pacing and per-host allowance entirely.
+     *
+     * A host is unlocked while it has no user limit and no reduced allowance installed by a 429.
+     * A 429 drops it out of the fast path until resetRequestQuota() walks the allowance back up.
+     */
+    [[nodiscard]] bool isUnlockedHost(const QString &host) const;
+
     /** @brief Returns cached redirect URL for the given original URL, if available. */
     [[nodiscard]] QUrl getCachedRedirect(const QUrl &originalUrl) const;
 
+    /**
+     * @brief Follows the cached-redirect chain to the URL that will actually be requested.
+     * @param url The URL to resolve
+     * @return The final URL after chasing cached redirects, or @p url itself if none lead elsewhere
+     *
+     * Dispatch decisions (unlocked-host fast path, 429 backoff, in-flight cap) must key on the host
+     * a request really goes to, not the URL that merely redirects to it.
+     */
+    [[nodiscard]] QUrl resolveCachedRedirect(const QUrl &url) const;
+
     /** @brief Loads redirect cache from disk. */
     void loadRedirectCache();
 

cockatrice/src/interface/widgets/settings_page/deck_editor_settings_page.cpp

@@ -10,7 +10,9 @@
 #include <QInputDialog>
 #include <QLineEdit>
 #include <QMessageBox>
+#include <QSet>
 #include <QToolBar>
+#include <QUrl>
 #include <libcockatrice/settings/download_settings.h>
 #include <libcockatrice/settings/paths_settings.h>
 #include <libcockatrice/settings/personal_settings.h>
@@ -51,7 +53,9 @@ DeckEditorSettingsPage::DeckEditorSettingsPage()
     urlList->setDragDropMode(QAbstractItemView::InternalMove);
     connect(urlList->model(), &QAbstractItemModel::rowsMoved, this, &DeckEditorSettingsPage::urlListChanged);
 
-    urlList->addItems(SettingsCache::instance().downloads().getAllURLs());
+    for (const QString &url : SettingsCache::instance().downloads().getAllURLs()) {
+        addUrlItem(url);
+    }
 
     aAdd = new QAction(this);
     aAdd->setIcon(themePixmap(QStringLiteral("icons/increment")));
@@ -65,11 +69,16 @@ DeckEditorSettingsPage::DeckEditorSettingsPage()
     aRemove->setIcon(themePixmap(QStringLiteral("icons/decrement")));
     connect(aRemove, &QAction::triggered, this, &DeckEditorSettingsPage::actRemoveURL);
 
+    aRateLimit = new QAction(this);
+    aRateLimit->setIcon(themePixmap(QStringLiteral("icons/cogwheel")));
+    connect(aRateLimit, &QAction::triggered, this, &DeckEditorSettingsPage::actAdjustRateLimit);
+
     auto *urlToolBar = new QToolBar;
     urlToolBar->setOrientation(Qt::Vertical);
     urlToolBar->addAction(aAdd);
     urlToolBar->addAction(aRemove);
     urlToolBar->addAction(aEdit);
+    urlToolBar->addAction(aRateLimit);
     urlToolBar->setSizePolicy(QSizePolicy::Preferred, QSizePolicy::MinimumExpanding);
 
     auto *urlListLayout = new QHBoxLayout;
@@ -117,7 +126,9 @@ void DeckEditorSettingsPage::resetDownloadedURLsButtonClicked()
 {
     SettingsCache::instance().downloads().resetToDefaultURLs();
     urlList->clear();
-    urlList->addItems(SettingsCache::instance().downloads().getAllURLs());
+    for (const QString &url : SettingsCache::instance().downloads().getAllURLs()) {
+        addUrlItem(url);
+    }
     QMessageBox::information(this, tr("Success"), tr("Download URLs have been reset."));
 }
 
@@ -126,7 +137,7 @@ void DeckEditorSettingsPage::actAddURL()
     bool ok;
     QString msg = QInputDialog::getText(this, tr("Add URL"), tr("URL:"), QLineEdit::Normal, QString(), &ok);
     if (ok) {
-        urlList->addItem(msg);
+        addUrlItem(msg);
         storeSettings();
     }
 }
@@ -141,12 +152,14 @@ void DeckEditorSettingsPage::actRemoveURL()
 
 void DeckEditorSettingsPage::actEditURL()
 {
-    if (urlList->currentItem()) {
-        QString oldText = urlList->currentItem()->text();
+    QListWidgetItem *item = urlList->currentItem();
+    if (item) {
+        const QString oldText = urlForItem(item);
         bool ok;
         QString msg = QInputDialog::getText(this, tr("Edit URL"), tr("URL:"), QLineEdit::Normal, oldText, &ok);
         if (ok) {
-            urlList->currentItem()->setText(msg);
+            item->setData(Qt::UserRole, msg);
+            item->setText(urlLabel(msg));
             storeSettings();
         }
     }
@@ -158,10 +171,133 @@ void DeckEditorSettingsPage::storeSettings()
 
     QStringList downloadUrls;
     for (int i = 0; i < urlList->count(); i++) {
-        qInfo() << "Priority" << i << ":" << urlList->item(i)->text();
-        downloadUrls << urlList->item(i)->text();
+        const QString url = urlForItem(urlList->item(i));
+        qInfo() << "Priority" << i << ":" << url;
+        downloadUrls << url;
     }
     SettingsCache::instance().downloads().setDownloadUrls(downloadUrls);
+
+    // Drop per-host limits whose host is no longer referenced by any configured URL, so removing
+    // a URL doesn't leave a stale throttle behind that reactivates if the host is re-added.
+    QSet<QString> usedHosts;
+    for (const QString &url : downloadUrls) {
+        const QString host = QUrl(url).host();
+        if (!host.isEmpty()) {
+            usedHosts.insert(host);
+        }
+    }
+    QHash<QString, int> limits = SettingsCache::instance().downloads().getHostRequestLimits();
+    bool limitsChanged = false;
+    for (auto it = limits.begin(); it != limits.end();) {
+        // Prune only limits for hosts that are neither referenced by a configured URL nor carry a
+        // developer cap. Capped hosts are often redirect targets (e.g. api.scryfall.com redirects
+        // to cards.scryfall.io) that never appear in the URL list, yet they are exactly the hosts
+        // the throttle applies to, so dropping them when a URL is removed would silently re-enable
+        // free-running traffic to a rate-sensitive server.
+        if (!usedHosts.contains(it.key()) && !DownloadSettings::getDeveloperHostCaps().contains(it.key())) {
+            it = limits.erase(it);
+            limitsChanged = true;
+        } else {
+            ++it;
+        }
+    }
+    if (limitsChanged) {
+        SettingsCache::instance().downloads().setHostRequestLimits(limits);
+    }
+
+    refreshUrlItems();
+}
+
+QListWidgetItem *DeckEditorSettingsPage::addUrlItem(const QString &url)
+{
+    auto *item = new QListWidgetItem(urlLabel(url));
+    item->setData(Qt::UserRole, url);
+    urlList->addItem(item);
+    return item;
+}
+
+QString DeckEditorSettingsPage::urlForItem(const QListWidgetItem *item) const
+{
+    return item->data(Qt::UserRole).toString();
+}
+
+QString DeckEditorSettingsPage::urlLabel(const QString &url) const
+{
+    const QString host = QUrl(url).host();
+    if (host.isEmpty()) {
+        return url;
+    }
+
+    const QHash<QString, int> limits = SettingsCache::instance().downloads().getHostRequestLimits();
+    const int devCap =
+        DownloadSettings::getDeveloperHostCaps().value(host, DownloadSettings::DEFAULT_HOST_REQUEST_LIMIT);
+    if (devCap == DownloadSettings::UNLIMITED_HOST_QUOTA && !limits.contains(host)) {
+        return tr("%1  (unlimited)").arg(url);
+    }
+
+    const int requested = limits.value(
+        host, devCap == DownloadSettings::UNLIMITED_HOST_QUOTA ? DownloadSettings::DEFAULT_HOST_REQUEST_LIMIT : devCap);
+    const int effective = SettingsCache::instance().downloads().clampHostRequestLimit(host, requested);
+    return tr("%1  (%2/s)").arg(url).arg(effective);
+}
+
+void DeckEditorSettingsPage::refreshUrlItems()
+{
+    for (int i = 0; i < urlList->count(); ++i) {
+        QListWidgetItem *item = urlList->item(i);
+        item->setText(urlLabel(urlForItem(item)));
+    }
+}
+
+void DeckEditorSettingsPage::actAdjustRateLimit()
+{
+    if (urlList->currentItem() == nullptr) {
+        QMessageBox::information(this, tr("Adjust Rate Limit"), tr("Select a URL in the list first."));
+        return;
+    }
+
+    const QString host = QUrl(urlForItem(urlList->currentItem())).host();
+    if (host.isEmpty()) {
+        QMessageBox::information(this, tr("Adjust Rate Limit"), tr("The selected URL does not have a valid host."));
+        return;
+    }
+
+    const QHash<QString, int> &devCaps = DownloadSettings::getDeveloperHostCaps();
+    const QHash<QString, int> currentLimits = SettingsCache::instance().downloads().getHostRequestLimits();
+    const int devCap = devCaps.value(host, DownloadSettings::DEFAULT_HOST_REQUEST_LIMIT);
+    const bool unlocked = devCap == DownloadSettings::UNLIMITED_HOST_QUOTA;
+
+    bool ok = false;
+    int minimum;
+    int maximum;
+    int defaultValue;
+    QString prompt;
+    if (unlocked) {
+        minimum = 0; // 0 means "unlimited"
+        maximum = DownloadSettings::UNLOCKED_HOST_LIMIT_MAX;
+        defaultValue = currentLimits.value(host, 0);
+        prompt = tr("Requests per second (0 = unlimited, fastest; up to %1):").arg(maximum);
+    } else {
+        minimum = DownloadSettings::MIN_HOST_REQUEST_LIMIT;
+        maximum = devCap;
+        defaultValue = currentLimits.value(host, devCap);
+        prompt = tr("Requests per second (developer maximum is %1):").arg(maximum);
+    }
+
+    const int value = QInputDialog::getInt(this, tr("Adjust Rate Limit for %1").arg(host), prompt, defaultValue,
+                                           minimum, maximum, 1, &ok);
+    if (!ok) {
+        return;
+    }
+
+    QHash<QString, int> limits = currentLimits;
+    if (unlocked ? value == 0 : value == devCap) {
+        limits.remove(host);
+    } else {
+        limits.insert(host, value);
+    }
+    SettingsCache::instance().downloads().setHostRequestLimits(limits);
+    refreshUrlItems();
 }
 
 void DeckEditorSettingsPage::urlListChanged(const QModelIndex &, int, int, const QModelIndex &, int)
@@ -244,4 +380,8 @@ void DeckEditorSettingsPage::retranslateUi()
     aAdd->setText(tr("Add New URL"));
     aEdit->setText(tr("Edit URL"));
     aRemove->setText(tr("Remove URL"));
+    aRateLimit->setText(tr("Adjust Rate Limit"));
+
+    // The per-URL rate limit suffixes are translated, so refresh them when the language changes.
+    refreshUrlItems();
 }

cockatrice/src/interface/widgets/settings_page/deck_editor_settings_page.h

@@ -27,6 +27,7 @@ private slots:
     void actAddURL();
     void actRemoveURL();
     void actEditURL();
+    void actAdjustRateLimit();
     void resetDownloadedURLsButtonClicked();
 
 private:
@@ -34,7 +35,7 @@ private:
     QLabel urlLinkLabel;
     QCheckBox picDownloadCheckBox;
     QListWidget *urlList;
-    QAction *aAdd, *aEdit, *aRemove;
+    QAction *aAdd, *aEdit, *aRemove, *aRateLimit;
     QCheckBox mcDownloadSpoilersCheckBox;
     QLabel msDownloadSpoilersLabel;
     QGroupBox *mpGeneralGroupBox;
@@ -46,6 +47,18 @@ private:
     QLabel infoOnSpoilersLabel;
     QPushButton *mpSpoilerPathButton;
     QPushButton *updateNowButton;
+
+    /** @brief Adds a list item for the given URL, storing the raw URL alongside its displayed label. */
+    QListWidgetItem *addUrlItem(const QString &url);
+
+    /** @brief Returns the raw URL stored on a list item. */
+    [[nodiscard]] QString urlForItem(const QListWidgetItem *item) const;
+
+    /** @brief Returns the display label for a URL, including its current effective rate limit. */
+    [[nodiscard]] QString urlLabel(const QString &url) const;
+
+    /** @brief Refreshes the displayed label of every URL item after limits or settings change. */
+    void refreshUrlItems();
 };
 
 #endif // COCKATRICE_DECK_EDITOR_SETTINGS_PAGE_H

libcockatrice_settings/libcockatrice/settings/download_settings.cpp

@@ -12,6 +12,22 @@ const QStringList DownloadSettings::DEFAULT_DOWNLOAD_URLS = {
 const QString DownloadSettings::SCRYFALL_NAMED_LOCALIZED_URL =
     "https://api.scryfall.com/cards/named?fuzzy=!localizedName!&lang=!sflang!&format=image&face=!prop:side!";
 
+// Developer-set ceilings for the per-host request allowance. Users may lower a host's
+// allowance via the download settings, but can never raise it above these values. Hosts
+// not listed default to DEFAULT_HOST_REQUEST_LIMIT. A cap of UNLIMITED_HOST_QUOTA marks a
+// host that is never throttled per host and skips the dispatch pacing (429 backoff still applies).
+const QHash<QString, int> DownloadSettings::DEVELOPER_HOST_CAPS = {
+    // The Scryfall API enforces 10 requests/second; stay one under so a burst can't trip 429s.
+    {"api.scryfall.com", 9},
+    // The Scryfall image CDN has no documented per-client rate limit.
+    {"cards.scryfall.io", UNLIMITED_HOST_QUOTA},
+};
+
+const QHash<QString, int> &DownloadSettings::getDeveloperHostCaps()
+{
+    return DEVELOPER_HOST_CAPS;
+}
+
 DownloadSettings::DownloadSettings(const QString &settingPath, QObject *parent = nullptr)
     : SettingsManager(settingPath + "downloads.ini", "downloads", QString(), parent)
 {
@@ -65,3 +81,57 @@ void DownloadSettings::setDownloadSpoilerStatus(bool _spoilerStatus)
     setValue(_spoilerStatus, "downloadSpoilers");
     emit downloadSpoilerStatusChanged();
 }
+
+QHash<QString, int> DownloadSettings::getHostRequestLimits() const
+{
+    auto settings = getSettings();
+    if (!defaultGroup.isEmpty()) {
+        settings.beginGroup(defaultGroup);
+    }
+    settings.beginGroup("hostRequestLimits");
+
+    QHash<QString, int> hostRequestLimits;
+    const QStringList hosts = settings.childKeys();
+    for (const QString &host : hosts) {
+        hostRequestLimits.insert(host, settings.value(host).toInt());
+    }
+
+    settings.endGroup();
+    if (!defaultGroup.isEmpty()) {
+        settings.endGroup();
+    }
+    return hostRequestLimits;
+}
+
+void DownloadSettings::setHostRequestLimits(const QHash<QString, int> &hostRequestLimits)
+{
+    auto settings = getSettings();
+    if (!defaultGroup.isEmpty()) {
+        settings.beginGroup(defaultGroup);
+    }
+
+    // Drop the legacy single-key form (an opaque @Variant blob) written by earlier builds so each
+    // host is stored as a plain, hand-editable key in its own subgroup.
+    settings.remove("hostRequestLimits");
+    settings.beginGroup("hostRequestLimits");
+    settings.remove(QString());
+    for (auto it = hostRequestLimits.cbegin(); it != hostRequestLimits.cend(); ++it) {
+        settings.setValue(it.key(), it.value());
+    }
+    settings.endGroup();
+
+    if (!defaultGroup.isEmpty()) {
+        settings.endGroup();
+    }
+    settings.sync();
+    emit hostRequestLimitsChanged();
+}
+
+int DownloadSettings::clampHostRequestLimit(const QString &host, int requested) const
+{
+    const int devCap = DEVELOPER_HOST_CAPS.value(host, DEFAULT_HOST_REQUEST_LIMIT);
+    if (devCap == UNLIMITED_HOST_QUOTA) {
+        return qMax(MIN_HOST_REQUEST_LIMIT, requested);
+    }
+    return qBound(MIN_HOST_REQUEST_LIMIT, requested, devCap);
+}

libcockatrice_settings/libcockatrice/settings/download_settings.h

@@ -9,6 +9,8 @@
 
 #include "settings_manager.h"
 
+#include <QHash>
+
 class DownloadSettings : public SettingsManager
 {
     Q_OBJECT
@@ -16,8 +18,35 @@ class DownloadSettings : public SettingsManager
 
     static const QStringList DEFAULT_DOWNLOAD_URLS;
     static const QString SCRYFALL_NAMED_LOCALIZED_URL;
+    static const QHash<QString, int> DEVELOPER_HOST_CAPS;
 
 public:
+    /** @brief Per-host request allowance (requests/second) when no developer cap applies. */
+    static constexpr int DEFAULT_HOST_REQUEST_LIMIT = 10;
+    /** @brief Floor for any per-host request allowance. */
+    static constexpr int MIN_HOST_REQUEST_LIMIT = 1;
+    /**
+     * @brief Upper bound offered to the user when lowering an unlocked host's allowance.
+     *
+     * Unlocked hosts have no developer cap, so `clampHostRequestLimit` puts no upper bound on
+     * them; this only bounds what the settings dialog offers, and matches the widest paced
+     * allowance a user is documented to be able to hand-edit in `downloads.ini`. Choosing 0
+     * below this restores the "unlimited" fast path.
+     */
+    static constexpr int UNLOCKED_HOST_LIMIT_MAX = 50;
+    /** @brief Developer cap marking a host as never throttled per host or by the dispatch pacing. */
+    static constexpr int UNLIMITED_HOST_QUOTA = -1;
+
+    /**
+     * @brief Developer-set per-host allowance ceilings (requests/second), keyed by host.
+     *
+     * Hosts not present default to DEFAULT_HOST_REQUEST_LIMIT. An entry of
+     * UNLIMITED_HOST_QUOTA marks a host that users may still lower, but that is never
+     * throttled per host by default. Users can never raise a host's allowance above its
+     * developer cap.
+     */
+    static const QHash<QString, int> &getDeveloperHostCaps();
+
     explicit DownloadSettings(const QString &, QObject *);
 
     QStringList getAllURLs() const;
@@ -29,9 +58,23 @@ public:
     [[nodiscard]] bool getDownloadSpoilersStatus() const;
     void setDownloadSpoilerStatus(bool _spoilerStatus);
 
+    /** @brief User-set per-host request allowances (requests/second). Missing hosts use the developer default. */
+    QHash<QString, int> getHostRequestLimits() const;
+    void setHostRequestLimits(const QHash<QString, int> &hostRequestLimits);
+
+    /**
+     * @brief Clamps the user's requested allowance for a host against its developer cap.
+     * @param host The host to clamp for
+     * @param requested The user-requested allowance in requests/second
+     * @return The effective allowance. Users may lower a host's allowance but never raise it
+     *         above the developer cap; hosts with UNLIMITED_HOST_QUOTA have no upper bound.
+     */
+    [[nodiscard]] int clampHostRequestLimit(const QString &host, int requested) const;
+
 signals:
     void picDownloadChanged();
     void downloadSpoilerStatusChanged();
+    void hostRequestLimitsChanged();
 };
 
 #endif // COCKATRICE_DOWNLOADSETTINGS_H

tests/settings/settings_defaults_test.cpp

@@ -334,6 +334,38 @@ TEST_F(SettingsDefaultsTest, Download_DownloadSpoilersStatus_Default)
     ASSERT_EQ(s.getDownloadSpoilersStatus(), false);
 }
 
+TEST_F(SettingsDefaultsTest, Download_HostRequestLimits_Default)
+{
+    DownloadSettings s(settingsPath, nullptr);
+    ASSERT_TRUE(s.getHostRequestLimits().isEmpty());
+}
+
+TEST_F(SettingsDefaultsTest, Download_HostRequestLimits_SetAndGet)
+{
+    DownloadSettings s(settingsPath, nullptr);
+    s.setHostRequestLimits({{"api.scryfall.com", 5}});
+    const QHash<QString, int> limits = s.getHostRequestLimits();
+    ASSERT_EQ(limits.size(), 1);
+    ASSERT_EQ(limits.value("api.scryfall.com"), 5);
+}
+
+TEST_F(SettingsDefaultsTest, Download_HostRequestLimits_StackedHostCaps)
+{
+    DownloadSettings s(settingsPath, nullptr);
+    // The developer cap for the Scryfall API lowers the ceiling to 9; a user can
+    // reduce it further but can never raise it above the cap.
+    ASSERT_EQ(s.clampHostRequestLimit("api.scryfall.com", 9), 9);
+    ASSERT_EQ(s.clampHostRequestLimit("api.scryfall.com", 20), 9);
+    ASSERT_EQ(s.clampHostRequestLimit("api.scryfall.com", 5), 5);
+    ASSERT_EQ(s.clampHostRequestLimit("api.scryfall.com", 0), 1);
+    // Hosts without a developer cap fall back to the global default ceiling.
+    ASSERT_EQ(s.clampHostRequestLimit("gatherer.wizards.com", 10), 10);
+    ASSERT_EQ(s.clampHostRequestLimit("gatherer.wizards.com", 20), 10);
+    // The Scryfall CDN is unlocked: no upper bound (values are only floored).
+    ASSERT_EQ(s.clampHostRequestLimit("cards.scryfall.io", 20), 20);
+    ASSERT_EQ(s.clampHostRequestLimit("cards.scryfall.io", 0), 1);
+}
+
 // --- AppearanceSettings ---
 
 TEST_F(SettingsDefaultsTest, Appearance_ThemeName_Default)