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* Copyright (C) 2015 Canonical Ltd.
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License version 3 as
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* published by the Free Software Foundation.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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* Authored by: Michi Henning <michi.henning@canonical.com>
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#include <core/cache_discard_policy.h>
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class PersistentStringCacheImpl;
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class PersistentStringCacheStats;
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} // namespace internal
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\brief Class that provides (read-only) access to cache statistics and settings.
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class PersistentCacheStats
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/** @name Construction, Copy and Assignment
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Copy and assignment have the usual value semantics.
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The default constructor creates an instance with
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an empty cache path, `lru_only` policy, and the
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remaining values set to zero.
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PersistentCacheStats();
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PersistentCacheStats(PersistentCacheStats const&);
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PersistentCacheStats(PersistentCacheStats&&) noexcept;
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PersistentCacheStats& operator=(PersistentCacheStats const&);
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PersistentCacheStats& operator=(PersistentCacheStats&&);
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// Accessors instead of data members for ABI stability.
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\brief Returns the path to the cache directory.
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std::string cache_path() const;
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\brief Returns the discard policy (`lru_only` or `lru_ttl`).
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CacheDiscardPolicy policy() const noexcept;
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\brief Returns the number of entries (including expired ones).
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int64_t size() const noexcept;
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\brief Returns the size of all entries (including expired ones).
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int64_t size_in_bytes() const noexcept;
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\brief Returns the maximum size of the cache.
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int64_t max_size_in_bytes() const noexcept;
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\brief Returns the number of hits since the statistics were last reset.
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int64_t hits() const noexcept;
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\brief Returns the number of misses since the statistics were last reset.
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int64_t misses() const noexcept;
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\brief Returns the number of consecutive hits since the last miss.
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int64_t hits_since_last_miss() const noexcept;
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\brief Returns the number of consecutive misses since the last hit.
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int64_t misses_since_last_hit() const noexcept;
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\brief Returns the largest number of consecutive hits.
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int64_t longest_hit_run() const noexcept;
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\brief Returns the largest number of consecutive misses.
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int64_t longest_miss_run() const noexcept;
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\brief Returns the number of entries that were evicted due to being expired.
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int64_t ttl_evictions() const noexcept;
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\brief Returns the number of entries that were evicted due to being
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int64_t lru_evictions() const noexcept;
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\brief Returns the timestamp of the most recent hit.
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std::chrono::system_clock::time_point most_recent_hit_time() const noexcept;
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\brief Returns the timestamp of the most recent miss.
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std::chrono::system_clock::time_point most_recent_miss_time() const noexcept;
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\brief Returns the time of the longest hit run.
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std::chrono::system_clock::time_point longest_hit_run_time() const noexcept;
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\brief Returns the time of the longest miss run.
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std::chrono::system_clock::time_point longest_miss_run_time() const noexcept;
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\brief Histogram of the size distribution of cache entries.
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The histogram uses a logarithmic scale and contains the number of entries in
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the cache, with entries grouped by size into a number of bins as follows:
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Index | Entry size in bytes
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----- | -------------------
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72 | 900,000,000..999,999,999
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Index 0 contains the number of entries < 10 bytes. Thereafter, the histogram
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contains 9 bins for each power of 10, plus a final bin at index 73 that contains
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the number of entries ≥ 10<sup>9</sup> bytes.
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typedef std::vector<uint32_t> Histogram;
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\brief Lower and upper bounds for the bins in the histogram.
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Each pair contains the lower and upper (inclusive) bound of
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the corresponding bin of the values returned by histogram().
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typedef std::vector<std::pair<int32_t, int32_t>> HistogramBounds;
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\brief The number of bins in a histogram.
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static constexpr unsigned NUM_BINS = 74;
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\brief Returns a histogram for the entries in the cache.
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Histogram const& histogram() const noexcept;
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\brief Returns the bounds for each bin a histogram.
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This method returns the same vector each time; it is provided
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as a convenience method to make it easier to add labels to a
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histogram for display. The returned pairs use inclusive ranges,
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that is, `pair.second` is the largest possible size of the bin.
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static HistogramBounds const& histogram_bounds() noexcept;
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PersistentCacheStats(std::shared_ptr<core::internal::PersistentStringCacheStats> const& p) noexcept;
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// We store a shared_ptr for efficiency. When the caller
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// retrieves the stats, we set p_ to point at the PersistentStringCacheStats
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// inside the cache. If the caller makes a copy or assigns,
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// We create a new instance, to provide value semantics. This means
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// that we don't have to copy all of the stats each time the caller
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std::shared_ptr<internal::PersistentStringCacheStats const> p_;
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bool internal_; // True if p_ points at the internal instance.
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friend class internal::PersistentStringCacheImpl; // For access to constructor
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removed
include/core/persistent_cache_stats.h
