Low disk space detector (#277)

* - Feature: Disk writes are now blocked early and return an insufficient storage error if free disk space falls below the `--low-diskspace-threshold` value
* Never keep an entry in m_ChunkBlocks that points to a nullptr

1 files changed, 23 insertions, 18 deletions

diff --git a/src/zenserver/cache/structuredcache.h b/src/zenserver/cache/structuredcache.h
index 8309361f4..77a0aee6a 100644
--- a/src/zenserver/cache/structuredcache.h
+++ b/src/zenserver/cache/structuredcache.h
@@ -24,6 +24,7 @@ struct PutRequestData;
 class ScrubContext;
 class UpstreamCache;
 class ZenCacheStore;
+class DiskWriteBlocker;
 enum class CachePolicy : uint32_t;
 enum class RpcAcceptOptions : uint16_t;
 
@@ -67,18 +68,18 @@ namespace cache {
 class HttpStructuredCacheService : public HttpService, public IHttpStatsProvider, public IHttpStatusProvider
 {
 public:
-	HttpStructuredCacheService(ZenCacheStore&	  InCacheStore,
-							   CidStore&		  InCidStore,
-							   HttpStatsService&  StatsService,
-							   HttpStatusService& StatusService,
-							   UpstreamCache&	  UpstreamCache);
+	HttpStructuredCacheService(ZenCacheStore&		   InCacheStore,
+							   CidStore&			   InCidStore,
+							   HttpStatsService&	   StatsService,
+							   HttpStatusService&	   StatusService,
+							   UpstreamCache&		   UpstreamCache,
+							   const DiskWriteBlocker* InDiskWriteBlocker);
 	~HttpStructuredCacheService();
 
 	virtual const char* BaseUri() const override;
 	virtual void		HandleRequest(HttpServerRequest& Request) override;
-
-	void Flush();
-	void Scrub(ScrubContext& Ctx);
+	void				Flush();
+	void				Scrub(ScrubContext& Ctx);
 
 private:
 	struct CacheRef
@@ -111,16 +112,17 @@ private:
 	void HandleRpcRequest(HttpServerRequest& Request);
 	void HandleDetailsRequest(HttpServerRequest& Request);
 
-	CbPackage HandleRpcPutCacheRecords(const CbPackage& BatchRequest);
-	CbPackage HandleRpcGetCacheRecords(CbObjectView BatchRequest);
-	CbPackage HandleRpcPutCacheValues(const CbPackage& BatchRequest);
-	CbPackage HandleRpcGetCacheValues(CbObjectView BatchRequest);
-	CbPackage HandleRpcGetCacheChunks(CbObjectView BatchRequest);
-	CbPackage HandleRpcRequest(const ZenContentType ContentType,
-							   IoBuffer&&			Body,
-							   uint32_t&			OutAcceptMagic,
-							   RpcAcceptOptions&	OutAcceptFlags,
-							   int&					OutTargetProcessId);
+	CbPackage		 HandleRpcPutCacheRecords(const CbPackage& BatchRequest);
+	CbPackage		 HandleRpcGetCacheRecords(CbObjectView BatchRequest);
+	CbPackage		 HandleRpcPutCacheValues(const CbPackage& BatchRequest);
+	CbPackage		 HandleRpcGetCacheValues(CbObjectView BatchRequest);
+	CbPackage		 HandleRpcGetCacheChunks(CbObjectView BatchRequest);
+	HttpResponseCode HandleRpcRequest(const ZenContentType ContentType,
+									  IoBuffer&&		   Body,
+									  uint32_t&			   OutAcceptMagic,
+									  RpcAcceptOptions&	   OutAcceptFlags,
+									  int&				   OutTargetProcessId,
+									  CbPackage&		   OutPackage);
 
 	void		 HandleCacheRequest(HttpServerRequest& Request);
 	void		 HandleCacheNamespaceRequest(HttpServerRequest& Request, std::string_view Namespace);
@@ -156,6 +158,8 @@ private:
 	/** HandleRpcGetCacheChunks Helper: Send response message containing all chunk results. */
 	CbPackage WriteGetCacheChunksResponse(std::string_view Namespace, std::vector<cache::detail::ChunkRequest>& Requests);
 
+	bool AreDiskWritesAllowed() const;
+
 	spdlog::logger&			 Log() { return m_Log; }
 	spdlog::logger&			 m_Log;
 	ZenCacheStore&			 m_CacheStore;
@@ -167,6 +171,7 @@ private:
 	metrics::OperationTiming m_HttpRequests;
 	metrics::OperationTiming m_UpstreamGetRequestTiming;
 	CacheStats				 m_CacheStats;
+	const DiskWriteBlocker*	 m_DiskWriteBlocker = nullptr;
 
 	void ReplayRequestRecorder(cache::IRpcRequestReplayer& Replayer, uint32_t ThreadCount);