ESProductResolver.h

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#ifndef FWCore_Framework_ESProductResolver_h
#define FWCore_Framework_ESProductResolver_h
// -*- C++ -*-
//
// Package:     Framework
// Class  :     ESProductResolver
//
//
// Author:      Chris Jones
// Created:     Thu Mar 31 12:43:01 EST 2005
//

// system include files
#include <atomic>

// user include files
#include "FWCore/Utilities/interface/thread_safety_macros.h"
#include "FWCore/Concurrency/interface/WaitingTaskHolder.h"

// forward declarations
namespace edm {
  class EventSetupImpl;
  class ServiceToken;
  class ESParentContext;

  namespace eventsetup {
    struct ComponentDescription;
    class DataKey;
    class EventSetupRecordImpl;

    class ESProductResolver {
    public:
      ESProductResolver();
      ESProductResolver(ESProductResolver const&) = delete;
      ESProductResolver const& operator=(ESProductResolver const&) = delete;
      virtual ~ESProductResolver();

      // ---------- const member functions ---------------------
      bool cacheIsValid() const { return cacheIsValid_.load(std::memory_order_acquire); }

      void prefetchAsync(WaitingTaskHolder,
                         EventSetupRecordImpl const&,
                         DataKey const&,
                         EventSetupImpl const*,
                         ServiceToken const&,
                         ESParentContext const&) const noexcept;

      void const* getAfterPrefetch(const EventSetupRecordImpl& iRecord, const DataKey& iKey, bool iTransiently) const;

      ComponentDescription const* providerDescription() const { return description_; }

      // ---------- member functions ---------------------------
      void invalidate() {
        clearCacheIsValid();
        invalidateCache();
      }

      void resetIfTransient();

      void setProviderDescription(ComponentDescription const* iDesc) { description_ = iDesc; }

      virtual void initializeForNewIOV() {}

    protected:
      virtual void prefetchAsyncImpl(WaitingTaskHolder,
                                     EventSetupRecordImpl const&,
                                     DataKey const& iKey,
                                     EventSetupImpl const*,
                                     ServiceToken const&,
                                     ESParentContext const&) noexcept = 0;

      virtual void invalidateCache() = 0;

      virtual void invalidateTransientCache();

      virtual void const* getAfterPrefetchImpl() const = 0;

      void clearCacheIsValid();

    private:
      // ---------- member data --------------------------------
      ComponentDescription const* description_;
      CMS_THREAD_SAFE mutable void const* cache_;  //protected by a global mutex
      mutable std::atomic<bool> cacheIsValid_;

      // While implementing the set of code changes that enabled support
      // for concurrent IOVs, I have gone to some effort to maintain
      // the same behavior for this variable and the things that depend on
      // it. My thinking is that we are going to revisit this and make
      // changes in the not so distant future so that the transient feature
      // works again. Alternatively, we may go through and delete it and
      // everything related to it.

      // First comment is that there is only one context in which the value
      // in nonTransientAccessRequested_ is used. This is in the resetIfTransient
      // function. This function is only called immediately after invalidate
      // was called. Therefore the value is always false and condition in
      // resetIfTransient always evaluates true. So in the current code this
      // data member does nothing and has absolutely no purpose. We should
      // delete it and the associated code if we do not modify the code to
      // actually make use of the value stored sometime soon.

      // Currently, this usage occurs is when force cache clear
      // is called from EventProcessor at beginRun (which only happens
      // when a certain configuration parameter is set) and propagates down.
      // It is also used when the looper is trying to start a new loop and
      // calls resetRecordPlusDependentRecords. It is not currently used in
      // any other context.
      //
      // One other thing to note is that the virtual invalidateTransientCache
      // function is defined in this class to just call invalidateCache.
      // Outside of unit tests, the only thing that overrides this definition
      // is in CondCore/ESSources/interface/ESProductResolver.h. So in all other cases
      // the behavior is that invalidateCache is called twice sometimes
      // instead of just once. Possibly it is important that invalidateTransientCache
      // is called in the CondCore code. I don't know.
      mutable std::atomic<bool> nonTransientAccessRequested_;
    };
  }  // namespace eventsetup
}  // namespace edm
#endif