lb/TranslationCache: use class IntrusiveCache instead of StaticCache

The StaticCache class has a huge memory usage even when it's empty and
is badly tuned for large installations.  Let's use the new
IntrusiveCache class which allocates items dynamically, preparing for
making the cache size configurable.

debian/changelog

@@ -2,6 +2,7 @@ cm4all-beng-proxy (18.2) unstable; urgency=low
 
   * spawn: do not log "failed to kill: No such process"
   * lb/translation: store ANALYTICS_ID and GENERATOR in the cache
+  * lb/translation: dynamic cache allocation
 
  --   
 

src/lb/TranslationCache.cxx

@@ -134,8 +134,9 @@ class LbTranslationCacheKeyIterator {
 	}
 };
 
-LbTranslationCache::Item::Item(const TranslateResponse &response) noexcept
-	:status(response.status),
+LbTranslationCache::Item::Item(const char *_key, const TranslateResponse &response) noexcept
+	:key(_key),
+	 status(response.status),
 	 https_only(response.https_only)
 {
 	if (response.redirect != nullptr)
@@ -163,11 +164,7 @@ LbTranslationCache::Item::Item(const TranslateResponse &response) noexcept
 CacheStats
 LbTranslationCache::GetStats() const noexcept
 {
-	size_t size = 0;
-
-	cache.ForEach([&size](const std::string &key, const Item &item){
-		size += key.length() + item.GetAllocatedMemory();
-	});
+	const std::size_t size = cache.GetTotalSize();
 
 	stats.allocator = {
 		.brutto_size = size,
@@ -180,7 +177,7 @@ LbTranslationCache::GetStats() const noexcept
 void
 LbTranslationCache::Clear() noexcept
 {
-	cache.Clear();
+	cache.clear();
 	seen_vary.Clear();
 }
 
@@ -232,15 +229,14 @@ LbTranslationCache::Invalidate(const TranslationInvalidateRequest &request) noex
 		return;
 
 	if (request.site != nullptr)
-		per_site.remove_and_dispose_key_if(request.site, [this, &request](const Item &item){
-			const auto &key = cache.KeyOf(item);
-			return MatchKey(key.c_str(), request) && MatchItem(item, request);
+		per_site.remove_and_dispose_key_if(request.site, [&request](const Item &item){
+			return MatchKey(item.key.c_str(), request) && MatchItem(item, request);
 		}, [this](Item *item){
 			cache.RemoveItem(*item);
 		});
 	else
-		cache.RemoveIf([&request](const std::string &key, const Item &item){
-			return MatchKey(key.c_str(), request) && MatchItem(item, request);
+		cache.RemoveIf([&request](const Item &item){
+			return MatchKey(item.key.c_str(), request) && MatchItem(item, request);
 		});
 }
 
@@ -275,7 +271,7 @@ LbTranslationCache::Put(const IncomingHttpRequest &request,
 
 	const Vary vary(response);
 
-	if (!vary && !cache.IsEmpty()) {
+	if (!vary && !cache.empty()) {
 		logger(4, "VARY disappeared, clearing cache");
 		Clear();
 	}
@@ -288,7 +284,8 @@ LbTranslationCache::Put(const IncomingHttpRequest &request,
 	logger(4, "store '", key, "'");
 	++stats.stores;
 
-	auto &item = cache.PutOrReplace(std::string_view{key}, response);
-	if (!item.site.empty())
-		per_site.insert(item);
+	auto *item = new Item(key, response);
+	if (!item->site.empty())
+		per_site.insert(*item);
+	cache.Put(*item);
 }

src/lb/TranslationCache.hxx

@@ -6,7 +6,8 @@
 
 #include "stats/CacheStats.hxx"
 #include "io/Logger.hxx"
-#include "util/StaticCache.hxx"
+#include "util/DeleteDisposer.hxx"
+#include "util/IntrusiveCache.hxx"
 #include "util/IntrusiveList.hxx"
 
 #include <string>
@@ -24,28 +25,46 @@ class LbTranslationCache final {
 
 public:
 	struct Item {
+		IntrusiveCacheHook cache_hook;
 		IntrusiveHashSetHook<IntrusiveHookMode::AUTO_UNLINK> per_site_hook;
 
+		std::string key;
+
 		HttpStatus status = {};
 		uint16_t https_only = 0;
 		std::string redirect, message, pool, canonical_host, site, analytics_id, generator;
 
 		[[nodiscard]]
-		explicit Item(const TranslateResponse &response) noexcept;
+		explicit Item(const char *_key, const TranslateResponse &response) noexcept;
 
 		[[gnu::pure]]
 		size_t GetAllocatedMemory() const noexcept {
-			return sizeof(*this) + redirect.length() + message.length() +
+			return sizeof(*this) + key.length() +
+				redirect.length() + message.length() +
 				pool.length() + canonical_host.length() + site.length() +
 				analytics_id.length() + generator.length();
 		}
 
+		struct GetKey {
+			[[gnu::pure]]
+			std::string_view operator()(const Item &item) const noexcept {
+				return item.key;
+			}
+		};
+
 		struct GetSite {
 			[[gnu::pure]]
 			std::string_view operator()(const Item &item) const noexcept {
 				return item.site;
 			}
 		};
+
+		struct SizeOf {
+			[[gnu::pure]]
+			std::size_t operator()(const Item &item) const noexcept {
+				return item.GetAllocatedMemory();
+			}
+		};
 	};
 
 	struct Vary {
@@ -88,8 +107,17 @@ private:
 						   std::equal_to<std::string_view>>,
 			 IntrusiveHashSetMemberHookTraits<&Item::per_site_hook>> per_site;
 
-	using Cache = StaticCache<std::string, Item, 65536, N_BUCKETS,
-		std::hash<std::string_view>, std::equal_to<std::string_view>>;
+	using Cache =
+		IntrusiveCache<Item,
+			       N_BUCKETS,
+			       IntrusiveCacheOperators<Item,
+						       Item::GetKey,
+						       std::hash<std::string_view>,
+						       std::equal_to<std::string_view>,
+						       Item::SizeOf,
+						       DeleteDisposer>,
+			       IntrusiveCacheMemberHookTraits<&Item::cache_hook>>;
+
 	Cache cache;
 
 	Vary seen_vary;
@@ -98,8 +126,8 @@ private:
 
 public:
 	[[nodiscard]]
-	LbTranslationCache() noexcept
-		:logger("tcache") {}
+	explicit LbTranslationCache(std::size_t max_size) noexcept
+		:logger("tcache"), cache(max_size) {}
 
 	[[gnu::pure]]
 	CacheStats GetStats() const noexcept;

src/lb/TranslationHandler.cxx

@@ -154,7 +154,8 @@ LbTranslationHandler::PutCache(const IncomingHttpRequest &request,
 		return;
 
 	if (!cache)
-		cache.reset(new LbTranslationCache());
+		// TODO configurable cache size
+		cache.reset(new LbTranslationCache(256 * std::size_t{1024 * 1024}));
 
 	cache->Put(request, listener_tag, response);
 }