[PictureLoader] Schedule exponential backoff on 429 - Too many request handler and call failed on fail (#7053)

Took 16 minutes

Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>

libcockatrice_utility/libcockatrice/utility/server_rate_limiter.cpp

@@ -0,0 +1,85 @@
+#include "server_rate_limiter.h"
+
+bool ServerRateLimiter::isRateLimited(const QString &host, const QDateTime &now) const
+{
+    auto it = backoffUntil.constFind(host);
+    return it != backoffUntil.constEnd() && now < it.value();
+}
+
+int ServerRateLimiter::rounds(const QString &host) const
+{
+    return retryRounds.value(host, 0);
+}
+
+QDateTime ServerRateLimiter::deadline(const QString &host) const
+{
+    return backoffUntil.value(host);
+}
+
+QDateTime ServerRateLimiter::earliestDeadline(const QDateTime &now) const
+{
+    QDateTime earliest;
+    for (auto it = backoffUntil.cbegin(); it != backoffUntil.cend(); ++it) {
+        if (now < it.value() && (!earliest.isValid() || it.value() < earliest)) {
+            earliest = it.value();
+        }
+    }
+    return earliest;
+}
+
+QDateTime ServerRateLimiter::on429(const QString &host, const QDateTime &now, qint64 retryAfterMs)
+{
+    QDateTime existing = backoffUntil.value(host);
+    int round = retryRounds.value(host, 0);
+
+    if (!existing.isValid() || now >= existing) {
+        if (last429.value(host).isValid() && now >= last429.value(host).addMSecs(RESET_GRACE_MS)) {
+            round = 0;
+        }
+        round = qMin(round + 1, MAX_RETRIES);
+        retryRounds.insert(host, round);
+    }
+    last429.insert(host, now);
+
+    qint64 delay;
+    if (round >= MAX_RETRIES) {
+        delay = EXHAUSTED_BACKOFF_MS;
+    } else {
+        delay = qMax<qint64>(MIN_429_BACKOFF_MS, retryAfterMs);
+        delay = qMin<qint64>(delay, MAX_BACKOFF_MS);
+    }
+
+    QDateTime deadline = now.addMSecs(delay);
+    if (existing.isValid() && existing > deadline) {
+        deadline = existing; // never shorten an active backoff
+    }
+    backoffUntil.insert(host, deadline);
+
+    return deadline;
+}
+
+void ServerRateLimiter::onSuccess(const QString &host)
+{
+    backoffUntil.remove(host);
+    retryRounds.remove(host);
+    last429.remove(host);
+}
+
+void ServerRateLimiter::clearExpired(const QDateTime &now)
+{
+    auto it = backoffUntil.begin();
+    while (it != backoffUntil.end()) {
+        if (now < it.value()) {
+            ++it;
+            continue;
+        }
+
+        QString host = it.key();
+        bool budgetStillFresh = last429.value(host).isValid() && now < last429.value(host).addMSecs(RESET_GRACE_MS);
+        it = backoffUntil.erase(it);
+        if (!budgetStillFresh) {
+            retryRounds.remove(host);
+            last429.remove(host);
+        }
+    }
+}