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Merged
merged 19 commits into from
Sep 23, 2025
+200 −34
Merged

[SDK] custom hash and equality for attribute processor #3643

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faccac5
[fix]: custom hash and equality for attribute processor
nikhilbhatia08 Sep 15, 2025
844f1a2
StringViewHash Fix
nikhilbhatia08 Sep 16, 2025
7a05e7f
macos copy fix
nikhilbhatia08 Sep 16, 2025
f199a59
string_view fix
nikhilbhatia08 Sep 16, 2025
a38b2d7
more fixes
nikhilbhatia08 Sep 16, 2025
121bfcf
some more fix
nikhilbhatia08 Sep 16, 2025
53012d2
cppver fix
nikhilbhatia08 Sep 16, 2025
0a81688
hash fix
nikhilbhatia08 Sep 19, 2025
98543fc
fix
nikhilbhatia08 Sep 19, 2025
63b2338
code style fix
nikhilbhatia08 Sep 20, 2025
e5ad0c9
small fix
nikhilbhatia08 Sep 22, 2025
662b23f
Merge branch 'main' into custom_hash_equality
marcalff Sep 22, 2025
a0a5540
header fix
nikhilbhatia08 Sep 23, 2025
ae5eeb9
fix in test
nikhilbhatia08 Sep 23, 2025
4991c29
iwyu fix
nikhilbhatia08 Sep 23, 2025
3e8f5c7
name and typedef fix
nikhilbhatia08 Sep 23, 2025
5c5c3cc
Attribute map name
nikhilbhatia08 Sep 23, 2025
49e8152
format fix
nikhilbhatia08 Sep 23, 2025
7320c35
iwyu fix
nikhilbhatia08 Sep 23, 2025
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109 changes: 99 additions & 10 deletions sdk/include/opentelemetry/sdk/metrics/view/attributes_processor.h
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@

#pragma once

#include <cstring>
#include <string>
#include <unordered_map>
#include <utility>
Expand All @@ -18,8 +19,91 @@ namespace sdk
{
namespace metrics
{

using MetricAttributes = opentelemetry::sdk::metrics::FilteredOrderedAttributeMap;

/**
* Hash and equality for nostd::string_view, enabling safe use in unordered_map
* without requiring null termination.
*/
struct StringViewHash
{
#if __cplusplus >= 202002L
// enable heterogenous lookup in C++20+
using is_transparent = void;
#endif

std::size_t operator()(const std::string &s) const noexcept
{
return std::hash<std::string>{}(s);
}

std::size_t operator()(opentelemetry::nostd::string_view sv) const noexcept
{
#if __cplusplus >= 202002L
return std::hash<opentelemetry::nostd::string_view>{}(
opentelemetry::nostd::string_view{sv.data(), sv.size()});
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Copilot AI Sep 19, 2025

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Creating a new string_view from an existing string_view is redundant and may not address the original issue. The problem is that string_view may not be null-terminated, but this code still uses the same data pointer. Consider using std::string construction instead: return std::hash<std::string>{}(std::string{sv.data(), sv.size()});

Suggested change
return std::hash<opentelemetry::nostd::string_view>{}(
opentelemetry::nostd::string_view{sv.data(), sv.size()});
// Materialize to std::string to ensure safe hashing (string_view may not be null-terminated)
return std::hash<std::string>{}(std::string{sv.data(), sv.size()});

Copilot uses AI. Check for mistakes.

#else
// pre-C++20 fallback: materialize to std::string
return std::hash<std::string>{}(std::string{sv.data(), sv.size()});
#endif
}
};

struct StringViewEqual
{
#if __cplusplus >= 202002L
using is_transparent = void;
#endif

bool operator()(const std::string &lhs, const std::string &rhs) const noexcept
{
return lhs == rhs;
}

bool operator()(const std::string &lhs, opentelemetry::nostd::string_view rhs) const noexcept
{
return lhs.size() == rhs.size() && std::memcmp(lhs.data(), rhs.data(), lhs.size()) == 0;
}

bool operator()(opentelemetry::nostd::string_view lhs, const std::string &rhs) const noexcept
{
return lhs.size() == rhs.size() && std::memcmp(lhs.data(), rhs.data(), lhs.size()) == 0;
}

bool operator()(opentelemetry::nostd::string_view lhs,
opentelemetry::nostd::string_view rhs) const noexcept
{
return lhs.size() == rhs.size() && std::memcmp(lhs.data(), rhs.data(), lhs.size()) == 0;
}
};

/**
* Cross-platform heterogeneous lookup wrapper.
* Falls back to std::string construction on libc++ (macOS) and pre-c++20,
* but uses direct lookup on libstdc++ (Linux).
*/
inline auto find_hetero(
const std::unordered_map<std::string, bool, StringViewHash, StringViewEqual> &map,
opentelemetry::nostd::string_view key)
{
#if defined(_LIBCPP_VERSION) || __cplusplus < 202002L
return map.find(std::string(key));
#else
return map.find(key);
#endif
}

inline auto find_hetero(std::unordered_map<std::string, bool, StringViewHash, StringViewEqual> &map,
opentelemetry::nostd::string_view key)
{
#if defined(_LIBCPP_VERSION) || __cplusplus < 202002L
return map.find(std::string(key));
#else
return map.find(key);
#endif
}

/**
* The AttributesProcessor is responsible for customizing which
* attribute(s) are to be reported as metrics dimension(s).
Expand Down Expand Up @@ -65,12 +149,15 @@ class DefaultAttributesProcessor : public AttributesProcessor
class FilteringAttributesProcessor : public AttributesProcessor
{
public:
FilteringAttributesProcessor(std::unordered_map<std::string, bool> &&allowed_attribute_keys = {})
FilteringAttributesProcessor(
std::unordered_map<std::string, bool, StringViewHash, StringViewEqual>
&&allowed_attribute_keys = {})
: allowed_attribute_keys_(std::move(allowed_attribute_keys))
{}

FilteringAttributesProcessor(
const std::unordered_map<std::string, bool> &allowed_attribute_keys = {})
const std::unordered_map<std::string, bool, StringViewHash, StringViewEqual>
&allowed_attribute_keys = {})
: allowed_attribute_keys_(allowed_attribute_keys)
{}

Expand All @@ -80,7 +167,7 @@ class FilteringAttributesProcessor : public AttributesProcessor
MetricAttributes result;
attributes.ForEachKeyValue(
[&](nostd::string_view key, opentelemetry::common::AttributeValue value) noexcept {
if (allowed_attribute_keys_.find(std::string(key)) != allowed_attribute_keys_.end())
if (find_hetero(allowed_attribute_keys_, key) != allowed_attribute_keys_.end())
{
result.SetAttribute(key, value);
return true;
Expand All @@ -94,11 +181,11 @@ class FilteringAttributesProcessor : public AttributesProcessor

bool isPresent(nostd::string_view key) const noexcept override
{
return (allowed_attribute_keys_.find(std::string(key)) != allowed_attribute_keys_.end());
return (find_hetero(allowed_attribute_keys_, key) != allowed_attribute_keys_.end());
}

private:
std::unordered_map<std::string, bool> allowed_attribute_keys_;
std::unordered_map<std::string, bool, StringViewHash, StringViewEqual> allowed_attribute_keys_;
};

/**
Expand All @@ -109,12 +196,14 @@ class FilteringAttributesProcessor : public AttributesProcessor
class FilteringExcludeAttributesProcessor : public AttributesProcessor
{
public:
FilteringExcludeAttributesProcessor(std::unordered_map<std::string, bool> &&exclude_list = {})
FilteringExcludeAttributesProcessor(
std::unordered_map<std::string, bool, StringViewHash, StringViewEqual> &&exclude_list = {})
: exclude_list_(std::move(exclude_list))
{}

FilteringExcludeAttributesProcessor(
const std::unordered_map<std::string, bool> &exclude_list = {})
const std::unordered_map<std::string, bool, StringViewHash, StringViewEqual> &exclude_list =
{})
: exclude_list_(exclude_list)
{}

Expand All @@ -124,7 +213,7 @@ class FilteringExcludeAttributesProcessor : public AttributesProcessor
MetricAttributes result;
attributes.ForEachKeyValue(
[&](nostd::string_view key, opentelemetry::common::AttributeValue value) noexcept {
if (exclude_list_.find(std::string(key)) == exclude_list_.end())
if (find_hetero(exclude_list_, key) == exclude_list_.end())
{
result.SetAttribute(key, value);
return true;
Expand All @@ -138,11 +227,11 @@ class FilteringExcludeAttributesProcessor : public AttributesProcessor

bool isPresent(nostd::string_view key) const noexcept override
{
return (exclude_list_.find(std::string(key)) == exclude_list_.end());
return (find_hetero(exclude_list_, key) == exclude_list_.end());
}

private:
std::unordered_map<std::string, bool> exclude_list_;
std::unordered_map<std::string, bool, StringViewHash, StringViewEqual> exclude_list_;
};

} // namespace metrics
Expand Down
26 changes: 16 additions & 10 deletions sdk/test/metrics/attributes_processor_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -17,9 +17,10 @@ using namespace opentelemetry::sdk::common;

TEST(AttributesProcessor, FilteringAttributesProcessor)
{
const int kNumFilterAttributes = 3;
std::unordered_map<std::string, bool> filter = {
{"attr2", true}, {"attr4", true}, {"attr6", true}};
const int kNumFilterAttributes = 3;
std::unordered_map<std::string, bool, opentelemetry::sdk::metrics::StringViewHash,
opentelemetry::sdk::metrics::StringViewEqual>
filter = {{"attr2", true}, {"attr4", true}, {"attr6", true}};
const int kNumAttributes = 6;
std::string keys[kNumAttributes] = {"attr1", "attr2", "attr3", "attr4", "attr5", "attr6"};
int values[kNumAttributes] = {10, 20, 30, 40, 50, 60};
Expand All @@ -38,9 +39,11 @@ TEST(AttributesProcessor, FilteringAttributesProcessor)

TEST(AttributesProcessor, FilteringAllAttributesProcessor)
{
const int kNumFilterAttributes = 0;
std::unordered_map<std::string, bool> filter = {};
const int kNumAttributes = 6;
const int kNumFilterAttributes = 0;
std::unordered_map<std::string, bool, opentelemetry::sdk::metrics::StringViewHash,
opentelemetry::sdk::metrics::StringViewEqual>
filter = {};
const int kNumAttributes = 6;
std::string keys[kNumAttributes] = {"attr1", "attr2", "attr3", "attr4", "attr5", "attr6"};
int values[kNumAttributes] = {10, 20, 30, 40, 50, 60};
std::map<std::string, int> attributes = {{keys[0], values[0]}, {keys[1], values[1]},
Expand All @@ -54,8 +57,9 @@ TEST(AttributesProcessor, FilteringAllAttributesProcessor)

TEST(AttributesProcessor, FilteringExcludeAttributesProcessor)
{
std::unordered_map<std::string, bool> filter = {
{"attr2", true}, {"attr4", true}, {"attr6", true}};
std::unordered_map<std::string, bool, opentelemetry::sdk::metrics::StringViewHash,
opentelemetry::sdk::metrics::StringViewEqual>
filter = {{"attr2", true}, {"attr4", true}, {"attr6", true}};
const int kNumAttributes = 7;
std::string keys[kNumAttributes] = {"attr1", "attr2", "attr3", "attr4",
"attr5", "attr6", "attr7"};
Expand All @@ -76,8 +80,10 @@ TEST(AttributesProcessor, FilteringExcludeAttributesProcessor)

TEST(AttributesProcessor, FilteringExcludeAllAttributesProcessor)
{
std::unordered_map<std::string, bool> filter = {};
const int kNumAttributes = 6;
std::unordered_map<std::string, bool, opentelemetry::sdk::metrics::StringViewHash,
opentelemetry::sdk::metrics::StringViewEqual>
filter = {};
const int kNumAttributes = 6;
std::string keys[kNumAttributes] = {"attr1", "attr2", "attr3", "attr4", "attr5", "attr6"};
int values[kNumAttributes] = {10, 20, 30, 40, 50, 60};
std::map<std::string, int> attributes = {{keys[0], values[0]}, {keys[1], values[1]},
Expand Down
16 changes: 12 additions & 4 deletions sdk/test/metrics/sum_aggregation_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -100,7 +100,9 @@ TEST(HistogramToSumFilterAttributes, Double)
std::string instrument_name = "histogram1";
std::string instrument_desc = "histogram metrics";

std::unordered_map<std::string, bool> allowedattr;
std::unordered_map<std::string, bool, opentelemetry::sdk::metrics::StringViewHash,
opentelemetry::sdk::metrics::StringViewEqual>
allowedattr;
allowedattr["attr1"] = true;
std::unique_ptr<opentelemetry::sdk::metrics::AttributesProcessor> attrproc{
new opentelemetry::sdk::metrics::FilteringAttributesProcessor(allowedattr)};
Expand Down Expand Up @@ -154,7 +156,9 @@ TEST(HistogramToSumFilterAttributesWithCardinalityLimit, Double)
std::string instrument_desc = "histogram metrics";
size_t cardinality_limit = 10000;

std::unordered_map<std::string, bool> allowedattr;
std::unordered_map<std::string, bool, opentelemetry::sdk::metrics::StringViewHash,
opentelemetry::sdk::metrics::StringViewEqual>
allowedattr;
allowedattr["attr1"] = true;
std::unique_ptr<opentelemetry::sdk::metrics::AttributesProcessor> attrproc{
new opentelemetry::sdk::metrics::FilteringAttributesProcessor(allowedattr)};
Expand Down Expand Up @@ -281,7 +285,9 @@ TEST(CounterToSumFilterAttributes, Double)
std::string instrument_name = "counter1";
std::string instrument_desc = "counter metrics";

std::unordered_map<std::string, bool> allowedattr;
std::unordered_map<std::string, bool, opentelemetry::sdk::metrics::StringViewHash,
opentelemetry::sdk::metrics::StringViewEqual>
allowedattr;
allowedattr["attr1"] = true;
std::unique_ptr<opentelemetry::sdk::metrics::AttributesProcessor> attrproc{
new opentelemetry::sdk::metrics::FilteringAttributesProcessor(allowedattr)};
Expand Down Expand Up @@ -335,7 +341,9 @@ TEST(CounterToSumFilterAttributesWithCardinalityLimit, Double)
std::string instrument_desc = "counter metrics";
size_t cardinality_limit = 10000;

std::unordered_map<std::string, bool> allowedattr;
std::unordered_map<std::string, bool, opentelemetry::sdk::metrics::StringViewHash,
opentelemetry::sdk::metrics::StringViewEqual>
allowedattr;
allowedattr["attr1"] = true;
std::unique_ptr<opentelemetry::sdk::metrics::AttributesProcessor> attrproc{
new opentelemetry::sdk::metrics::FilteringAttributesProcessor(allowedattr)};
Expand Down
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