File 0003-Add-conditional-cache-preference-to-http-r... of Package knewstuff.17405

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File 0003-Add-conditional-cache-preference-to-http-requests.patch of Package knewstuff.17405

From 3d1c6074ce6f9379bbfb70b5d264f8d49fedd9e0 Mon Sep 17 00:00:00 2001
From: Dan Leinir Turthra Jensen <admin@leinir.dk>
Date: Wed, 9 Feb 2022 16:17:58 +0000
Subject: [PATCH 3/3] Add conditional cache preference to http requests

If we have a cache that's older than 7 days, assume that it's out of
date and actually try again. If it's younger than that, assume that it's
just the same, and prefer our cached version, if we have one.

The logic here is an attempt at striking a balance between using our cache
to its fullest potential (as in, reducing server-side load and network
roundtrips in general) while also handling the situation where the
information that we are fed about the cache is not entirely correct (such
as the case where we're told there's no expiration date, but the data in
fact does change). 7 days seems a sensible sort of deadline for that,
though we could change that later if we need to.

This was born out of a discussion on another kns review[1]

Assume that no cache expiration time will be longer than 7 days, but otherwise prefer the cache
This is mildly hacky, but if we don't do this, we end up with infinite cache expirations in some
cases, which of course isn't really acceptable... See ed62ee20 for a situation where that happened.

[1] https://invent.kde.org/frameworks/knewstuff/-/merge_requests/166#note_394067

(cherry picked from commit e1c6f2bf383876a31cd3e3f9e6edcaa19dc0a7dd)
---
 src/core/jobs/httpworker.cpp | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/core/jobs/httpworker.cpp b/src/core/jobs/httpworker.cpp
index 00e14522..21db43fe 100644
--- a/src/core/jobs/httpworker.cpp
+++ b/src/core/jobs/httpworker.cpp
@@ -40,7 +40,6 @@ public:
         return nam.get(request);
     }
 
-private:
     QNetworkDiskCache cache;
 };
 
@@ -100,6 +99,17 @@ static void addUserAgent(QNetworkRequest &request)
         agentHeader += QStringLiteral("-%1/%2").arg(QCoreApplication::instance()->applicationName(), QCoreApplication::instance()->applicationVersion());
     }
     request.setHeader(QNetworkRequest::UserAgentHeader, agentHeader);
+
+    // Assume that no cache expiration time will be longer than a week, but otherwise prefer the cache
+    // This is mildly hacky, but if we don't do this, we end up with infinite cache expirations in some
+    // cases, which of course isn't really acceptable... See ed62ee20 for a situation where that happened.
+    QNetworkCacheMetaData cacheMeta{s_httpWorkerNAM->cache.metaData(request.url())};
+    if (cacheMeta.isValid()) {
+        const QDateTime nextWeek{QDateTime::currentDateTime().addDays(7)};
+        if (cacheMeta.expirationDate().isValid() && cacheMeta.expirationDate() < nextWeek) {
+            request.setAttribute(QNetworkRequest::CacheLoadControlAttribute, QNetworkRequest::PreferCache);
+        }
+    }
 }
 
 void HTTPWorker::startRequest()
-- 
2.33.1

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