metrics.hh

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/*
 * This file is open source software, licensed to you under the terms
 * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
 * distributed with this work for additional information regarding copyright
 * ownership.  You may not use this file except in compliance with the License.
 *
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
/*
 * Copyright (C) 2016 ScyllaDB.
 */
 
#pragma once
 
#ifndef SEASTAR_MODULE
#include <functional>
#include <limits>
#include <map>
#include <type_traits>
#include <variant>
#include <fmt/format.h>
#endif
#include <seastar/core/sstring.hh>
#include <seastar/core/shared_ptr.hh>
#include <seastar/core/metrics_registration.hh>
#include <seastar/core/metrics_types.hh>
#include <seastar/util/std-compat.hh>
#include <seastar/util/bool_class.hh>
#include <seastar/util/modules.hh>
 
namespace seastar {
 
namespace metrics {
 
SEASTAR_MODULE_EXPORT_BEGIN
 
class double_registration : public std::runtime_error {
public:
    double_registration(std::string what);
};
 
using metric_type_def = sstring; 
using metric_name_type = sstring; 
using instance_id_type = sstring; 
using skip_when_empty = bool_class<class skip_when_empty_tag>;
 
class description {
public:
    description(sstring s = sstring()) : _s(std::move(s))
    {}
    const sstring& str() const {
        return _s;
    }
private:
    sstring _s;
};
 
class label_instance {
    sstring _key;
    sstring _value;
public:
    template<typename T>
    label_instance(const sstring& key, T v) : _key(key), _value(fmt::to_string(v)){}
 
    const sstring key() const {
        return _key;
    }
 
    const sstring value() const {
        return _value;
    }
    bool operator<(const label_instance&) const;
    bool operator==(const label_instance&) const;
    bool operator!=(const label_instance&) const;
};
 
 
class label {
    sstring key;
public:
    using instance = label_instance;
    explicit label(const sstring& key) : key(key) {
    }
 
    template<typename T>
    instance operator()(T value) const {
        return label_instance(key, std::forward<T>(value));
    }
 
    const sstring& name() const {
        return key;
    }
};
SEASTAR_MODULE_EXPORT_END
 
namespace impl {
 
// The value binding data types
enum class data_type : uint8_t {
    COUNTER,
    REAL_COUNTER,
    GAUGE,
    HISTOGRAM,
    SUMMARY,
};
 
template <bool callable, typename T>
struct real_counter_type_traits {
    using type = T;
};
 
template <typename T>
struct real_counter_type_traits<true, T> {
    using type = std::invoke_result_t<T>;
};
 
template <typename T>
struct counter_type_traits {
    using real_traits = real_counter_type_traits<std::is_invocable_v<T>, T>;
    static constexpr bool is_integral = std::is_integral_v<typename real_traits::type>;
    static constexpr data_type type = is_integral ? data_type::COUNTER : data_type::REAL_COUNTER;
};
 
class metric_value {
public:
    std::variant<double, histogram> u;
    data_type _type;
    data_type type() const {
        return _type;
    }
 
    double d() const {
        return std::get<double>(u);
    }
 
    uint64_t ui() const {
        auto d = std::get<double>(u);
        if (d >= 0 && d <= double(std::numeric_limits<long>::max())) {
            return lround(d);
        } else {
            // double value is out of range or NaN or Inf
            ulong_conversion_error(d);
            return 0;
        }
    }
 
    int64_t i() const {
        auto d = std::get<double>(u);
        if (d >= double(std::numeric_limits<long>::min()) && d <= double(std::numeric_limits<long>::max())) {
            return lround(d);
        } else {
            // double value is out of range or NaN or Inf
            ulong_conversion_error(d);
            return 0;
        }
    }
 
    metric_value()
            : _type(data_type::GAUGE) {
    }
 
    metric_value(histogram&& h, data_type t = data_type::HISTOGRAM) :
        u(std::move(h)), _type(t) {
    }
    metric_value(const histogram& h, data_type t = data_type::HISTOGRAM) :
        u(h), _type(t) {
    }
 
    metric_value(double d, data_type t)
            : u(d), _type(t) {
    }
 
    metric_value& operator+=(const metric_value& c) {
        *this = *this + c;
        return *this;
    }
 
    metric_value operator+(const metric_value& c);
    const histogram& get_histogram() const {
        return std::get<histogram>(u);
    }
 
    bool is_empty() const noexcept {
        return ((_type == data_type::HISTOGRAM || _type == data_type::SUMMARY) && get_histogram().sample_count == 0) ||
                ((_type == data_type::COUNTER || _type == data_type::REAL_COUNTER) && d() == 0);
    }
private:
    static void ulong_conversion_error(double d);
};
 
using metric_function = std::function<metric_value()>;
 
struct metric_type {
    data_type base_type;
    metric_type_def type_name;
};
 
struct metric_definition_impl {
    metric_name_type name;
    metric_type type;
    metric_function f;
    description d;
    bool enabled = true;
    skip_when_empty _skip_when_empty = skip_when_empty::no;
    std::vector<std::string> aggregate_labels;
    std::map<sstring, sstring> labels;
    metric_definition_impl& operator ()(bool enabled);
    metric_definition_impl& operator ()(const label_instance& label);
    metric_definition_impl& operator ()(skip_when_empty skip) noexcept;
    metric_definition_impl& aggregate(const std::vector<label>& labels) noexcept;
    metric_definition_impl& set_skip_when_empty(bool skip=true) noexcept;
    metric_definition_impl& set_type(const sstring& type_name);
    metric_definition_impl(
        metric_name_type name,
        metric_type type,
        metric_function f,
        description d,
        std::vector<label_instance> labels,
        std::vector<label> aggregate_labels = {});
};
 
class metric_groups_def {
public:
    metric_groups_def() = default;
    virtual ~metric_groups_def() = default;
    metric_groups_def(const metric_groups_def&) = delete;
    metric_groups_def(metric_groups_def&&) = default;
    virtual metric_groups_def& add_metric(group_name_type name, const metric_definition& md) = 0;
    virtual metric_groups_def& add_group(group_name_type name, const std::initializer_list<metric_definition>& l) = 0;
    virtual metric_groups_def& add_group(group_name_type name, const std::vector<metric_definition>& l) = 0;
};
 
instance_id_type shard();
 
template<typename T, typename = std::enable_if_t<std::is_invocable_v<T>>>
metric_function make_function(T val, data_type dt) {
    return [dt, val = std::move(val)] {
        return metric_value(val(), dt);
    };
}
 
template<typename T, typename = std::enable_if_t<!std::is_invocable_v<T>>>
metric_function make_function(T& val, data_type dt) {
    return [dt, &val] {
        return metric_value(val, dt);
    };
}
}
 
extern const bool metric_disabled;
 
extern label shard_label;
 
/*
 * The metrics definition are defined to be compatible with collectd metrics defintion.
 * Typically you should used gauge or derived.
 */
 
 
template<typename T>
impl::metric_definition_impl make_gauge(metric_name_type name,
        T&& val, description d = description(), std::vector<label_instance> labels = {}) {
    return {name, {impl::data_type::GAUGE, "gauge"}, make_function(std::forward<T>(val), impl::data_type::GAUGE), d, labels};
}
 
template<typename T>
impl::metric_definition_impl make_gauge(metric_name_type name,
        description d, T&& val) {
    return {name, {impl::data_type::GAUGE, "gauge"}, make_function(std::forward<T>(val), impl::data_type::GAUGE), d, {}};
}
 
template<typename T>
impl::metric_definition_impl make_gauge(metric_name_type name,
        description d, std::vector<label_instance> labels, T&& val) {
    return {name, {impl::data_type::GAUGE, "gauge"}, make_function(std::forward<T>(val), impl::data_type::GAUGE), d, labels};
}
 
 
template<typename T>
[[deprecated("Use make_counter()")]]
impl::metric_definition_impl make_derive(metric_name_type name,
        T&& val, description d = description(), std::vector<label_instance> labels = {}) {
    return make_counter(std::move(name), std::forward<T>(val), std::move(d), std::move(labels));
}
 
 
template<typename T>
[[deprecated("Use make_counter()")]]
impl::metric_definition_impl make_derive(metric_name_type name, description d,
        T&& val) {
    return make_counter(std::move(name), std::forward<T>(val), std::move(d), {});
}
 
 
template<typename T>
[[deprecated("Use make_counter()")]]
impl::metric_definition_impl make_derive(metric_name_type name, description d, std::vector<label_instance> labels,
        T&& val) {
    return make_counter(std::move(name), std::forward<T>(val), std::move(d), std::move(labels));
}
 
 
template<typename T>
impl::metric_definition_impl make_counter(metric_name_type name,
        T&& val, description d = description(), std::vector<label_instance> labels = {}) {
    auto type = impl::counter_type_traits<std::remove_reference_t<T>>::type;
    return {name, {type, "counter"}, make_function(std::forward<T>(val), type), d, labels};
}
 
template<typename T>
impl::metric_definition_impl make_counter(metric_name_type name, description d, T&& val) {
    return make_counter(std::move(name), std::forward<T>(val), std::move(d), {});
}
 
template<typename T>
impl::metric_definition_impl make_counter(metric_name_type name, description d, std::vector<label_instance> labels, T&& val) {
    return make_counter(std::move(name), std::forward<T>(val), std::move(d), std::move(labels));
}
 
template<typename T>
[[deprecated("Use make_counter()")]]
impl::metric_definition_impl make_absolute(metric_name_type name,
        T&& val, description d = description(), std::vector<label_instance> labels = {}) {
    return make_counter(std::move(name), std::forward<T>(val), std::move(d), std::move(labels));
}
 
template<typename T>
impl::metric_definition_impl make_histogram(metric_name_type name,
        T&& val, description d = description(), std::vector<label_instance> labels = {}) {
    return  {name, {impl::data_type::HISTOGRAM, "histogram"}, make_function(std::forward<T>(val), impl::data_type::HISTOGRAM), d, labels};
}
 
template<typename T>
impl::metric_definition_impl make_histogram(metric_name_type name,
        description d, std::vector<label_instance> labels, T&& val) {
    return  {name, {impl::data_type::HISTOGRAM, "histogram"}, make_function(std::forward<T>(val), impl::data_type::HISTOGRAM), d, labels};
}
 
 
template<typename T>
impl::metric_definition_impl make_histogram(metric_name_type name,
        description d, T&& val) {
    return  {name, {impl::data_type::HISTOGRAM, "histogram"}, make_function(std::forward<T>(val), impl::data_type::HISTOGRAM), d, {}};
}
 
template<typename T>
impl::metric_definition_impl make_summary(metric_name_type name,
        description d, T&& val) {
    return  {name, {impl::data_type::SUMMARY, "summary"}, make_function(std::forward<T>(val), impl::data_type::SUMMARY), d, {}};
}
 
 
template<typename T>
impl::metric_definition_impl make_total_bytes(metric_name_type name,
        T&& val, description d = description(), std::vector<label_instance> labels = {},
        instance_id_type = impl::shard()) {
    return make_counter(name, std::forward<T>(val), d, labels).set_type("total_bytes");
}
 
template<typename T>
impl::metric_definition_impl make_current_bytes(metric_name_type name,
        T&& val, description d = description(), std::vector<label_instance> labels = {},
        instance_id_type = impl::shard()) {
    return make_gauge(name, std::forward<T>(val), d, labels).set_type("bytes");
}
 
 
template<typename T>
impl::metric_definition_impl make_queue_length(metric_name_type name,
        T&& val, description d = description(), std::vector<label_instance> labels = {},
        instance_id_type = impl::shard()) {
    return make_gauge(name, std::forward<T>(val), d, labels).set_type("queue_length");
}
 
 
template<typename T>
impl::metric_definition_impl make_total_operations(metric_name_type name,
        T&& val, description d = description(), std::vector<label_instance> labels = {},
        instance_id_type = impl::shard()) {
    return make_counter(name, std::forward<T>(val), d, labels).set_type("total_operations");
}
 
}
}