src/kudu/util/cache-test.cc

// Some portions Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "kudu/util/cache.h"

#include <cstring>
#include <functional>
#include <memory>
#include <string>
#include <tuple>
#include <utility>
#include <vector>

#include <gflags/gflags.h>
#include <glog/logging.h>
#include <gtest/gtest.h>

#include "kudu/gutil/macros.h"
#include "kudu/gutil/ref_counted.h"
#include "kudu/gutil/strings/substitute.h"
#include "kudu/util/block_cache_metrics.h"
#include "kudu/util/cache_metrics.h"
#include "kudu/util/coding.h"
#include "kudu/util/env.h"
#include "kudu/util/faststring.h"
#include "kudu/util/mem_tracker.h"
#include "kudu/util/metrics.h"
#include "kudu/util/nvm_cache.h"
#include "kudu/util/slice.h"
#include "kudu/util/test_macros.h"
#include "kudu/util/test_util.h"

DECLARE_bool(cache_force_single_shard);
DECLARE_string(nvm_cache_path);

DECLARE_double(cache_memtracker_approximation_ratio);

using std::make_tuple;
using std::tuple;
using std::shared_ptr;
using std::unique_ptr;
using std::vector;
using strings::Substitute;

namespace kudu {

// Conversions between numeric keys/values and the types expected by Cache.
static std::string EncodeInt(int k) {
  faststring result;
  PutFixed32(&result, k);
  return result.ToString();
}
static int DecodeInt(const Slice& k) {
  CHECK_EQ(4, k.size());
  return DecodeFixed32(k.data());
}

// Cache sharding policy affects the composition of the cache. Some test
// scenarios assume cache is single-sharded to keep the logic simpler.
enum class ShardingPolicy {
  MultiShard,
  SingleShard,
};

class CacheBaseTest : public KuduTest,
                      public Cache::EvictionCallback {
 public:
  explicit CacheBaseTest(size_t cache_size)
      : cache_size_(cache_size) {
  }

  size_t cache_size() const {
    return cache_size_;
  }

  // Implementation of the EvictionCallback interface.
  void EvictedEntry(Slice key, Slice val) override {
    evicted_keys_.push_back(DecodeInt(key));
    evicted_values_.push_back(DecodeInt(val));
  }

  int Lookup(int key) {
    auto handle(cache_->Lookup(EncodeInt(key), Cache::EXPECT_IN_CACHE));
    return handle ? DecodeInt(cache_->Value(handle)) : -1;
  }

  void Insert(int key, int value, int charge = 1) {
    std::string key_str = EncodeInt(key);
    std::string val_str = EncodeInt(value);
    auto handle(cache_->Allocate(key_str, val_str.size(), charge));
    CHECK(handle);
    memcpy(cache_->MutableValue(&handle), val_str.data(), val_str.size());
    cache_->Insert(std::move(handle), this);
  }

  void Erase(int key) {
    cache_->Erase(EncodeInt(key));
  }

 protected:
  void SetupWithParameters(Cache::MemoryType mem_type,
                           Cache::EvictionPolicy eviction_policy,
                           ShardingPolicy sharding_policy) {
    // Disable approximate tracking of cache memory since we make specific
    // assertions on the MemTracker in this test.
    FLAGS_cache_memtracker_approximation_ratio = 0;

    // Using single shard makes the logic of scenarios simple for capacity-
    // and eviction-related behavior.
    FLAGS_cache_force_single_shard =
        (sharding_policy == ShardingPolicy::SingleShard);

    if (google::GetCommandLineFlagInfoOrDie("nvm_cache_path").is_default) {
      FLAGS_nvm_cache_path = GetTestPath("nvm-cache");
      ASSERT_OK(Env::Default()->CreateDir(FLAGS_nvm_cache_path));
    }

    switch (eviction_policy) {
      case Cache::EvictionPolicy::FIFO:
        if (mem_type != Cache::MemoryType::DRAM) {
          FAIL() << "FIFO cache can only be of DRAM type";
        }
        cache_.reset(NewCache<Cache::EvictionPolicy::FIFO,
                              Cache::MemoryType::DRAM>(cache_size(),
                                                       "cache_test"));
        MemTracker::FindTracker("cache_test-sharded_fifo_cache", &mem_tracker_);
        break;
      case Cache::EvictionPolicy::LRU:
        switch (mem_type) {
          case Cache::MemoryType::DRAM:
            cache_.reset(NewCache<Cache::EvictionPolicy::LRU,
                                  Cache::MemoryType::DRAM>(cache_size(),
                                                           "cache_test"));
            break;
          case Cache::MemoryType::NVM:
            if (CanUseNVMCacheForTests()) {
              cache_.reset(NewCache<Cache::EvictionPolicy::LRU,
                                    Cache::MemoryType::NVM>(cache_size(),
                                                            "cache_test"));
            }
            break;
          default:
            FAIL() << mem_type << ": unrecognized cache memory type";
            break;
        }
        MemTracker::FindTracker("cache_test-sharded_lru_cache", &mem_tracker_);
        break;
      default:
        FAIL() << "unrecognized cache eviction policy";
        break;
    }

    // Since nvm cache does not have memtracker due to the use of
    // tcmalloc for this we only check for it in the DRAM case.
    if (mem_type == Cache::MemoryType::DRAM) {
      ASSERT_TRUE(mem_tracker_.get());
    }

    // cache_ will be null if we're trying to set up a test for the NVM cache
    // and were unable to do so.
    if (cache_) {
      scoped_refptr<MetricEntity> entity = METRIC_ENTITY_server.Instantiate(
          &metric_registry_, "test");
      unique_ptr<BlockCacheMetrics> metrics(new BlockCacheMetrics(entity));
      cache_->SetMetrics(std::move(metrics), Cache::ExistingMetricsPolicy::kKeep);
    }
  }

  const size_t cache_size_;
  vector<int> evicted_keys_;
  vector<int> evicted_values_;
  shared_ptr<MemTracker> mem_tracker_;
  unique_ptr<Cache> cache_;
  MetricRegistry metric_registry_;
};

class CacheTest :
    public CacheBaseTest,
    public ::testing::WithParamInterface<tuple<Cache::MemoryType,
                                               Cache::EvictionPolicy,
                                               ShardingPolicy>> {
 public:
  CacheTest()
      : CacheBaseTest(16 * 1024 * 1024) {
  }

  void SetUp() override {
    const auto& param = GetParam();
    SetupWithParameters(std::get<0>(param),
                        std::get<1>(param),
                        std::get<2>(param));
  }
};

INSTANTIATE_TEST_SUITE_P(
    CacheTypes, CacheTest,
    ::testing::Values(
        make_tuple(Cache::MemoryType::DRAM,
                   Cache::EvictionPolicy::FIFO,
                   ShardingPolicy::MultiShard),
        make_tuple(Cache::MemoryType::DRAM,
                   Cache::EvictionPolicy::FIFO,
                   ShardingPolicy::SingleShard),
        make_tuple(Cache::MemoryType::DRAM,
                   Cache::EvictionPolicy::LRU,
                   ShardingPolicy::MultiShard),
        make_tuple(Cache::MemoryType::DRAM,
                   Cache::EvictionPolicy::LRU,
                   ShardingPolicy::SingleShard),
        make_tuple(Cache::MemoryType::NVM,
                   Cache::EvictionPolicy::LRU,
                   ShardingPolicy::MultiShard),
        make_tuple(Cache::MemoryType::NVM,
                   Cache::EvictionPolicy::LRU,
                   ShardingPolicy::SingleShard)));

TEST_P(CacheTest, TrackMemory) {
  RETURN_IF_NO_NVM_CACHE(std::get<0>(GetParam()));
  if (mem_tracker_) {
    Insert(100, 100, 1);
    ASSERT_EQ(1, mem_tracker_->consumption());
    Erase(100);
    ASSERT_EQ(0, mem_tracker_->consumption());
    ASSERT_EQ(1, mem_tracker_->peak_consumption());
  }
}

TEST_P(CacheTest, HitAndMiss) {
  RETURN_IF_NO_NVM_CACHE(std::get<0>(GetParam()));
  ASSERT_EQ(-1, Lookup(100));

  Insert(100, 101);
  ASSERT_EQ(101, Lookup(100));
  ASSERT_EQ(-1,  Lookup(200));
  ASSERT_EQ(-1,  Lookup(300));

  Insert(200, 201);
  ASSERT_EQ(101, Lookup(100));
  ASSERT_EQ(201, Lookup(200));
  ASSERT_EQ(-1,  Lookup(300));

  Insert(100, 102);
  ASSERT_EQ(102, Lookup(100));
  ASSERT_EQ(201, Lookup(200));
  ASSERT_EQ(-1,  Lookup(300));

  ASSERT_EQ(1, evicted_keys_.size());
  ASSERT_EQ(100, evicted_keys_[0]);
  ASSERT_EQ(101, evicted_values_[0]);
}

TEST_P(CacheTest, Erase) {
  RETURN_IF_NO_NVM_CACHE(std::get<0>(GetParam()));
  Erase(200);
  ASSERT_EQ(0, evicted_keys_.size());

  Insert(100, 101);
  Insert(200, 201);
  Erase(100);
  ASSERT_EQ(-1,  Lookup(100));
  ASSERT_EQ(201, Lookup(200));
  ASSERT_EQ(1, evicted_keys_.size());
  ASSERT_EQ(100, evicted_keys_[0]);
  ASSERT_EQ(101, evicted_values_[0]);

  Erase(100);
  ASSERT_EQ(-1,  Lookup(100));
  ASSERT_EQ(201, Lookup(200));
  ASSERT_EQ(1, evicted_keys_.size());
}

TEST_P(CacheTest, EntriesArePinned) {
  RETURN_IF_NO_NVM_CACHE(std::get<0>(GetParam()));
  Insert(100, 101);
  auto h1 = cache_->Lookup(EncodeInt(100), Cache::EXPECT_IN_CACHE);
  ASSERT_EQ(101, DecodeInt(cache_->Value(h1)));

  Insert(100, 102);
  auto h2 = cache_->Lookup(EncodeInt(100), Cache::EXPECT_IN_CACHE);
  ASSERT_EQ(102, DecodeInt(cache_->Value(h2)));
  ASSERT_EQ(0, evicted_keys_.size());

  h1.reset();
  ASSERT_EQ(1, evicted_keys_.size());
  ASSERT_EQ(100, evicted_keys_[0]);
  ASSERT_EQ(101, evicted_values_[0]);

  Erase(100);
  ASSERT_EQ(-1, Lookup(100));
  ASSERT_EQ(1, evicted_keys_.size());

  h2.reset();
  ASSERT_EQ(2, evicted_keys_.size());
  ASSERT_EQ(100, evicted_keys_[1]);
  ASSERT_EQ(102, evicted_values_[1]);
}

// Add a bunch of light and heavy entries and then count the combined
// size of items still in the cache, which must be approximately the
// same as the total capacity.
TEST_P(CacheTest, HeavyEntries) {
  RETURN_IF_NO_NVM_CACHE(std::get<0>(GetParam()));
  const int kLight = cache_size() / 1000;
  const int kHeavy = cache_size() / 100;
  int added = 0;
  int index = 0;
  while (added < 2 * cache_size()) {
    const int weight = (index & 1) ? kLight : kHeavy;
    Insert(index, 1000+index, weight);
    added += weight;
    index++;
  }

  int cached_weight = 0;
  for (int i = 0; i < index; i++) {
    const int weight = (i & 1 ? kLight : kHeavy);
    int r = Lookup(i);
    if (r >= 0) {
      cached_weight += weight;
      ASSERT_EQ(1000+i, r);
    }
  }
  ASSERT_LE(cached_weight, cache_size() + cache_size() / 10);
}

TEST_P(CacheTest, InvalidateAllEntries) {
  RETURN_IF_NO_NVM_CACHE(std::get<0>(GetParam()));
  constexpr const int kEntriesNum = 1024;
  // This scenarios assumes no evictions are done at the cache capacity.
  ASSERT_LE(kEntriesNum, cache_size());

  // Running invalidation on empty cache should yield no invalidated entries.
  ASSERT_EQ(0, cache_->Invalidate({}));
  for (auto i = 0; i < kEntriesNum; ++i) {
    Insert(i, i);
  }
  // Remove a few entries from the cache (sparse pattern of keys).
  constexpr const int kSparseKeys[] = {1, 100, 101, 500, 501, 512, 999, 1001};
  for (const auto key : kSparseKeys) {
    Erase(key);
  }
  ASSERT_EQ(ARRAYSIZE(kSparseKeys), evicted_keys_.size());

  // All inserted entries, except for the removed one, should be invalidated.
  ASSERT_EQ(kEntriesNum - ARRAYSIZE(kSparseKeys), cache_->Invalidate({}));
  // In the end, no entries should be left in the cache.
  ASSERT_EQ(kEntriesNum, evicted_keys_.size());
}

TEST_P(CacheTest, InvalidateNoEntries) {
  RETURN_IF_NO_NVM_CACHE(std::get<0>(GetParam()));
  constexpr const int kEntriesNum = 10;
  // This scenarios assumes no evictions are done at the cache capacity.
  ASSERT_LE(kEntriesNum, cache_size());

  const Cache::ValidityFunc func = [](Slice /* key */, Slice /* value */) {
    return true;
  };
  // Running invalidation on empty cache should yield no invalidated entries.
  ASSERT_EQ(0, cache_->Invalidate({ func }));

  for (auto i = 0; i < kEntriesNum; ++i) {
    Insert(i, i);
  }

  // No entries should be invalidated since the validity function considers
  // all entries valid.
  ASSERT_EQ(0, cache_->Invalidate({ func }));
  ASSERT_TRUE(evicted_keys_.empty());
}

TEST_P(CacheTest, InvalidateNoEntriesNoAdvanceIterationFunctor) {
  RETURN_IF_NO_NVM_CACHE(std::get<0>(GetParam()));
  constexpr const int kEntriesNum = 256;
  // This scenarios assumes no evictions are done at the cache capacity.
  ASSERT_LE(kEntriesNum, cache_size());

  const Cache::InvalidationControl ctl = {
    Cache::kInvalidateAllEntriesFunc,
    [](size_t /* valid_entries_count */, size_t /* invalid_entries_count */) {
      // Never advance over the item list.
      return false;
    }
  };

  // Running invalidation on empty cache should yield no invalidated entries.
  ASSERT_EQ(0, cache_->Invalidate(ctl));

  for (auto i = 0; i < kEntriesNum; ++i) {
    Insert(i, i);
  }

  // No entries should be invalidated since the iteration functor doesn't
  // advance over the list of entries, even if every entry is declared invalid.
  ASSERT_EQ(0, cache_->Invalidate(ctl));
  // In the end, all entries should be in the cache.
  ASSERT_EQ(0, evicted_keys_.size());
}

TEST_P(CacheTest, InvalidateOddKeyEntries) {
  RETURN_IF_NO_NVM_CACHE(std::get<0>(GetParam()));
  constexpr const int kEntriesNum = 64;
  // This scenarios assumes no evictions are done at the cache capacity.
  ASSERT_LE(kEntriesNum, cache_size());

  const Cache::ValidityFunc func = [](Slice key, Slice /* value */) {
    return DecodeInt(key) % 2 == 0;
  };
  // Running invalidation on empty cache should yield no invalidated entries.
  ASSERT_EQ(0, cache_->Invalidate({ func }));

  for (auto i = 0; i < kEntriesNum; ++i) {
    Insert(i, i);
  }
  ASSERT_EQ(kEntriesNum / 2, cache_->Invalidate({ func }));
  ASSERT_EQ(kEntriesNum / 2, evicted_keys_.size());
  for (auto i = 0; i < kEntriesNum; ++i) {
    if (i % 2 == 0) {
      ASSERT_EQ(i,  Lookup(i));
    } else {
      ASSERT_EQ(-1,  Lookup(i));
    }
  }
}

// This class is dedicated for scenarios specific for FIFOCache.
// The scenarios use a single-shard cache for simpler logic.
class FIFOCacheTest : public CacheBaseTest {
 public:
  FIFOCacheTest()
      : CacheBaseTest(10 * 1024) {
  }

  void SetUp() override {
    SetupWithParameters(Cache::MemoryType::DRAM,
                        Cache::EvictionPolicy::FIFO,
                        ShardingPolicy::SingleShard);
  }
};

// Verify how the eviction behavior of a FIFO cache.
TEST_F(FIFOCacheTest, EvictionPolicy) {
  static constexpr int kNumElems = 20;
  const int size_per_elem = cache_size() / kNumElems;
  // First data chunk: fill the cache up to the capacity.
  int idx = 0;
  do {
    Insert(idx, idx, size_per_elem);
    // Keep looking up the very first entry: this is to make sure lookups
    // do not affect the recency criteria of the eviction policy for FIFO cache.
    Lookup(0);
    ++idx;
  } while (evicted_keys_.empty());
  ASSERT_GT(idx, 1);

  // Make sure the earliest inserted entry was evicted.
  ASSERT_EQ(-1, Lookup(0));

  // Verify that the 'empirical' capacity matches the expected capacity
  // (it's a single-shard cache).
  const int capacity = idx - 1;
  ASSERT_EQ(kNumElems, capacity);

  // Second data chunk: add (capacity / 2) more elements.
  for (int i = 1; i < capacity / 2; ++i) {
    // Earlier inserted elements should be gone one-by-one as new elements are
    // inserted, and lookups should not affect the recency criteria of the FIFO
    // eviction policy.
    ASSERT_EQ(i, Lookup(i));
    Insert(capacity + i, capacity + i, size_per_elem);
    ASSERT_EQ(capacity + i, Lookup(capacity + i));
    ASSERT_EQ(-1, Lookup(i));
  }
  ASSERT_EQ(capacity / 2, evicted_keys_.size());

  // Early inserted elements from the first chunk should be evicted
  // to accommodate the elements from the second chunk.
  for (int i = 0; i < capacity / 2; ++i) {
    SCOPED_TRACE(Substitute("early inserted elements: index $0", i));
    ASSERT_EQ(-1, Lookup(i));
  }
  // The later inserted elements from the first chunk should be still
  // in the cache.
  for (int i = capacity / 2; i < capacity; ++i) {
    SCOPED_TRACE(Substitute("late inserted elements: index $0", i));
    ASSERT_EQ(i, Lookup(i));
  }
}

class LRUCacheTest :
    public CacheBaseTest,
    public ::testing::WithParamInterface<tuple<Cache::MemoryType,
                                               ShardingPolicy>> {
 public:
  LRUCacheTest()
      : CacheBaseTest(16 * 1024 * 1024) {
  }

  void SetUp() override {
    const auto& param = GetParam();
    SetupWithParameters(std::get<0>(param),
                        Cache::EvictionPolicy::LRU,
                        std::get<1>(param));
  }
};

INSTANTIATE_TEST_SUITE_P(
    CacheTypes, LRUCacheTest,
    ::testing::Combine(::testing::Values(Cache::MemoryType::DRAM,
                                         Cache::MemoryType::NVM),
                       ::testing::Values(ShardingPolicy::MultiShard,
                                         ShardingPolicy::SingleShard)));

TEST_P(LRUCacheTest, EvictionPolicy) {
  RETURN_IF_NO_NVM_CACHE(std::get<0>(GetParam()));
  static constexpr int kNumElems = 1000;
  const int size_per_elem = cache_size() / kNumElems;

  Insert(100, 101);
  Insert(200, 201);

  // Loop adding and looking up new entries, but repeatedly accessing key 101.
  // This frequently-used entry should not be evicted.
  for (int i = 0; i < kNumElems + 1000; i++) {
    Insert(1000+i, 2000+i, size_per_elem);
    ASSERT_EQ(2000+i, Lookup(1000+i));
    ASSERT_EQ(101, Lookup(100));
  }
  ASSERT_EQ(101, Lookup(100));
  // Since '200' wasn't accessed in the loop above, it should have
  // been evicted.
  ASSERT_EQ(-1, Lookup(200));
}

}  // namespace kudu