Cache .narinfo lookups

Dependencies

• [2] SOB276BA Keep some statistics for the binary cache stores
• [3] MB3TISH2 Rate-limit the number of threads copying closures at the same time
• [4] 73YR46NJ hydra-queue-runner: Write directly to a binary cache
• [5] 32HHP5CW hydra-queue-runner: Support generating a signed binary cache
• [6] N2NKSKHS Refactor local binary cache code into a subclass
• [7] ENXUSMSV Make concurrency more robust
• [8] HPJKBFZ4 Handle concurrent finishing of the same build
• [*] GH4S4AWM Rename file
• [*] EOO4EFWD Use a single BinaryCacheStore for all threads
• [*] 24BMQDZA Start of single-process hydra-queue-runner

Change contents

• edit in src/hydra-queue-runner/binary-cache-store.cc at line 2
  [10.124]

  [3.1913]
  + #include "sync.hh"
• edit in src/hydra-queue-runner/binary-cache-store.cc at line 97
  [3.4304]

  [2.519]
  + {

  + auto state_(state.lock());

  + auto res = state_->narInfoCache.get(storePath);

  + if (res) {

  + stats.narInfoReadAverted++;

  + return **res;

  + }

  + }

  +
• replacement in src/hydra-queue-runner/binary-cache-store.cc at line 109
  [3.766]→[3.766:829](∅→∅),[3.829]→[3.1633:1672](∅→∅),[3.1633]→[3.1633:1672](∅→∅)
  − auto narInfo = NarInfo(getFile(narInfoFile), narInfoFile);

  − assert(narInfo.path == storePath);
  [3.766]

  [3.5476]
  + auto narInfo = make_ref<NarInfo>(getFile(narInfoFile), narInfoFile);

  + assert(narInfo->path == storePath);
• replacement in src/hydra-queue-runner/binary-cache-store.cc at line 113
  [3.1695]→[3.1695:1745](∅→∅)
  − if (!narInfo.checkSignature(*publicKeys))
  [3.1695]

  [3.1745]
  + if (!narInfo->checkSignature(*publicKeys))
• replacement in src/hydra-queue-runner/binary-cache-store.cc at line 117
  [3.5572]→[3.1841:1861](∅→∅)
  − return narInfo;
  [3.5572]

  [3.5588]
  + {

  + auto state_(state.lock());

  + state_->narInfoCache.upsert(storePath, narInfo);

  + stats.narInfoCacheSize = state_->narInfoCache.size();

  + }

  +

  + return *narInfo;
• edit in src/hydra-queue-runner/binary-cache-store.hh at line 5
  [3.9292]

  [2.657]
  +

  + #include "lru-cache.hh"

  + #include "sync.hh"
• edit in src/hydra-queue-runner/binary-cache-store.hh at line 28
  [11.423]

  [11.423]
  +

  + struct State

  + {

  + LRUCache<Path, ref<NarInfo>> narInfoCache{32 * 1024};

  + };

  +

  + Sync<State> state;
• edit in src/hydra-queue-runner/binary-cache-store.hh at line 54
  [2.747]

  [2.747]
  + std::atomic<uint64_t> narInfoReadAverted{0};
• edit in src/hydra-queue-runner/binary-cache-store.hh at line 56
  [2.794]

  [2.794]
  + std::atomic<uint64_t> narInfoCacheSize{0};
• edit in src/hydra-queue-runner/hydra-queue-runner.cc at line 594
  [2.2053]

  [2.2053]
  + nested.attr("narInfoReadAverted", stats.narInfoReadAverted);
• edit in src/hydra-queue-runner/hydra-queue-runner.cc at line 596
  [2.2114]

  [2.2114]
  + nested.attr("narInfoCacheSize", stats.narInfoCacheSize);
• file addition: lru-cache.hh (----------)
  [12.187]
  + #pragma once

  +

  + #include <map>

  + #include <list>

  +

  + /* A simple least-recently used cache. Not thread-safe. */

  + template<typename Key, typename Value>

  + class LRUCache

  + {

  + private:

  +

  + size_t maxSize;

  +

  + // Stupid wrapper to get around circular dependency between Data

  + // and LRU.

  + struct LRUIterator;

  +

  + using Data = std::map<Key, std::pair<LRUIterator, Value>>;

  + using LRU = std::list<typename Data::iterator>;

  +

  + struct LRUIterator { typename LRU::iterator it; };

  +

  + Data data;

  + LRU lru;

  +

  + public:

  +

  + LRUCache(size_t maxSize) : maxSize(maxSize) { }

  +

  + /* Insert or upsert an item in the cache. */

  + void upsert(const Key & key, const Value & value)

  + {

  + erase(key);

  +

  + if (data.size() >= maxSize) {

  + /* Retire the oldest item. */

  + auto oldest = lru.begin();

  + data.erase(*oldest);

  + lru.erase(oldest);

  + }

  +

  + auto res = data.emplace(key, std::make_pair(LRUIterator(), value));

  + assert(res.second);

  + auto & i(res.first);

  +

  + auto j = lru.insert(lru.end(), i);

  +

  + i->second.first.it = j;

  + }

  +

  + bool erase(const Key & key)

  + {

  + auto i = data.find(key);

  + if (i == data.end()) return false;

  + lru.erase(i->second.first.it);

  + data.erase(i);

  + return true;

  + }

  +

  + /* Look up an item in the cache. If it's exists, it becomes the

  + most recently used item. */

  + // FIXME: use boost::optional?

  + Value * get(const Key & key)

  + {

  + auto i = data.find(key);

  + if (i == data.end()) return 0;

  +

  + /* Move this item to the back of the LRU list. */

  + lru.erase(i->second.first.it);

  + auto j = lru.insert(lru.end(), i);

  + i->second.first.it = j;

  +

  + return &i->second.second;

  + }

  +

  + size_t size()

  + {

  + return data.size();

  + }

  + };
• replacement in src/hydra-queue-runner/sync.hh at line 23
  [3.10091]→[3.10091:10110](∅→∅)
  − template <class T>
  [3.10091]

  [3.10110]
  + template<class T>