API Namespace metric

原文链接：https://github.com/Microsoft/napajs/blob/master/docs/api/metric.md

Namespace metric

Table of Contents

• Introduction
• C++ API
  • Interface Metric
  • Interface MetricProvider
  • Function MetricProvider& GetMetricProvider()
• JavaScript API
  • Enum MetricType
  • Class Metric
    • set(value: number, dimensions?: string[]): void
    • increment(dimensions?: string[]): void;
    • decrement(dimensions?: string[]): void;
  • Function get(section: string, name: string, type: MetricType, dimensionNames: string[])
• Using custom metric providers
• Developing custom metric providers

介绍

与日志类似，metric是创建可监听服务的必要条件。通过Metric API，开发者在JavaScript和C++（addon）里都可以使用他们自己定义的metric系统。 一个metric有它的标识，包括如下信息：

• Section：metric的组或分类
• Name：metric的名字。在系统中Section/Name的联合使用必须是唯一的。
• Type：metric的类型，类型可以是：
  • Number（数字）：一个纯数字，例如PrivateBytes
  • Rate（频率）：带有量词的数字，例如QueryPerSecond
  • Percentile（百分比）：一个需要按百分制化简的纯数字，例如SuccessLatency
• Dimensions（维度）：一个metric有多个维度，每个维度在运行时绑定一个字符串值。例如：IncomingRequestRate 有两个维度：['client-id', 'request-type']。

Metrics是进程知晓的（process-wise）对象，能跨zone使用。

C++ API

Interface Metric （Metric 接口）

 /// <summary> Enumeration of metric type. </summary>
    enum class MetricType {
        Number = 0,
        Rate,
        Percentile,
    };

    /// <summary> Interface to represents a multi-dimensional metric with a maximum dimensionality of 64. </summary>
    class Metric {
    public:

        /// <summary> Sets a metric value with variadic dimension arguments. </summary>
        /// <param name="value"> Int64 value. </param>
        /// <param name="numberOfDimensions"> Number of dimensions being set. </param>
        /// <param name="dimensionValues"> Array of dimension value names. </param>
        /// <returns> Success/Fail. </returns>
        /// <remarks>
        ///     The number of dimension values must exactly match the number of dimensions provided when
        ///     creating this metric.
        /// </remarks>
        virtual bool Set(int64_t value, size_t numberOfDimensions, const char* dimensionValues[]) = 0;

        /// <summary>
        ///     Increments a metric value with variadic dimension arguments.
        ///     Use mainly to simplify rate counters.
        /// </summary>
        /// <param name="value"> UInt64 value to increment. </param>
        /// <param name="numberOfDimensions"> Number of dimensions being set. </param>
        /// <param name="dimensionValues"> Array of dimension value names. </param>
        /// <returns> Success/Fail. </returns>
        /// <remarks>
        ///     The number of dimension values must exactly match the number of dimensions
        ///     provided when creating this metric.
        /// </remarks>
        virtual bool Increment(uint64_t value, size_t numberOfDimensions, const char* dimensionValues[]) = 0;

        /// <summary>
        ///     Decrements metric value with variadic dimension arguments.
        ///     Use mainly to simplify rate counters.
        /// </summary>
        /// <param name="value"> UInt64 value to decrement. </param>
        /// <param name="numberOfDimensions"> Number of dimensions being set. </param>
        /// <param name="dimensionValues"> Array of dimension value names. </param>
        /// <returns> Success/Fail. </returns>
        /// <remarks>
        ///     The number of dimension values must exactly match the number of dimensions
        ///     provided when creating this metric.
        /// </remarks>
        virtual bool Decrement(uint64_t value, size_t numberOfDimensions, const char* dimensionValues[]) = 0;

        /// <summary> Explicitly destroys the Metric. </summary>
        /// <remarks>
        ///     Consumers are not required to call this.
        ///     The MetricProvider owns this class and will automatically perform cleanup on shutdown.
        /// </remarks>
        virtual void Destroy() = 0;

    protected:

        ///<summary> Prevent calling delete on the interface. Must use Destroy! </summary>
        virtual ~Metric() = default;
    };

Interface MetricProvider（MetricProvider 接口）

    /// <summary> Interface for a generic metric provider. </summary>
    /// <remarks> 
    ///     Ownership of this metric provider belongs to the shared library which created it. Hence the explicit
    ///     Destroy method in this class. To simplify memory management across multiple shared libraries, this class
    ///     can only be created via a factory method provided by the shared library. When it is no longer needed,
    ///     the caller may call Destroy() which will tell the shared library which created it to dispose of the object.
    /// </remarks>
    class MetricProvider {
    public:

        /// <summary>
        ///     Gets or creates a N-dimensional metric. Metric objects are owned and cached by this class.
        ///     Up to 64 dimensions may be used.</summary>
        /// <param name="section"> Section of the metric.</param>
        /// <param name="name"> Name of the metric.</param>
        /// <param name="type"> Type of the metric.</param>
        /// <param name="dimensions">
        ///     Number of dimensions requested for this metric.
        ///     Represents the size of the array passed in for p_dimensionNames.
        /// </param>
        /// <param name="dimensionNames"> Array of dimension names being requested for this metric.</param>
        /// <remarks>
        ///     The IMetric class returned is owned and cached by this class.
        ///     Callers are not required to call destroy() on the Metric.
        /// </remarks>
        virtual Metric* GetMetric(
            const char* section,
            const char* name,
            MetricType type,
            size_t dimensions,
            const char* dimensionNames[]) = 0;

        ///<summary> Explicitly destroys the metric provider. </summary>
        virtual void Destroy() = 0;

    protected:

        ///<summary> Prevent calling delete on the interface. Must use Destroy! </summary>
        virtual ~MetricProvider() = default;
    };

function MetricProvider& GetMetricProvider()

/// <summary> Exports a getter function for retrieves the configured metric provider. </summary>
NAPA_API MetricProvider& GetMetricProvider();

JavaScript API

enum MetricType

export enum MetricType {
    Number = 0,
    Rate,
    Percentile,

Class Metric

JavaScript中操作metric的类。

set(value: number, dimensions?: string[]): void

给被维度值限制的metric实例赋值。例如：

// Create a percentile metric to measure end-to-end latency, with 1 dimension of client-id.
// 创建百分比的metric测试端到端延迟，带有client-id维度。
latency = napa.metric.get(
    'app1',
    'end-to-end-latency',
    napa.metric.MetricType.Percentile, 
    ['client-id']);

// Set end-to-end latency of current request to 100, with client-id 'client1'.
//给client-id为client1的实例赋值当前请求的端到端的延迟为100。
latency.set(100, ['client1']);

increment(dimensions?: string[]): void

给受维度值约束的metric实例的增加值。

Example:

// Create a percentile metric to measure end-to-end latency, with 1 dimension of client-id.
latency = napa.metric.get(
    'app1',
    'qps',
    napa.metric.MetricType.Rate, 
    ['client-id']);

// Increment QPS of client-id 'client1'.
latency.increment(['client1']);

decrement(dimensions?: string[]): void

给受维度值约束的metric实例的减值。

function get(section: string, name: string, type: MetricType, dimensions: string[] = []): Metric

创建一个metric，包含section、name、type和维度。如果所给参数的metric已经存在，则其返回。

Example:

import * as napa from 'napajs';
let metric = napa.metric.get(
    'app1', 
    'counter1', 
    napa.metric.MetricType.Number, 
    []);
metric.increment([]);

Using custom metric providers

在创建zone之前，开发者可以调用如下代码来使用定义好的metric。

napa.runtime.setPlatformSettings({
    "metricProvider": "<custom-metric-provider-module-name>"
}

Developing custom metric providers

TBD