# OpenTelemetry 0.7.0 格式的 CloudWatch 指标流输出
<a name="CloudWatch-metric-streams-formats-opentelemetry"></a>

OpenTelemetry 是工具、API 和软件开发工具包的集合。您可以使用它来测量、生成、收集及导出遥测数据（指标、日志和跟踪）以进行分析。OpenTelemetry 属于云原生计算基金会。有关更多信息，请参阅 [OpenTelemetry](https://opentelemetry.io/)。

有关完整 OpenTelemetry 0.7.0 规范的信息，请参阅 [v0.7.0 版本](https://github.com/open-telemetry/opentelemetry-proto/releases/tag/v0.7.0)。

一条 Kinesis 记录可以包含一个或多个 `ExportMetricsServiceRequest` OpenTelemetry 数据结构。每个数据结构都以一个带有指示记录长度（字节）的 `UnsignedVarInt32` 的标头开头。每个 `ExportMetricsServiceRequest` 可同时包含来自多个指标的数据。

以下是 `ExportMetricsServiceRequest` OpenTelemetry 数据结构形式的消息的字符串表示。OpenTelemetry 会序列化 Google Protocol Buffers 二进制协议，此协议人类不可读。

```
resource_metrics {
  resource {
    attributes {
      key: "cloud.provider"
      value {
        string_value: "aws"
      }
    }
    attributes {
      key: "cloud.account.id"
      value {
        string_value: "2345678901"
      }
    }
    attributes {
      key: "cloud.region"
      value {
        string_value: "us-east-1"
      }
    }
    attributes {
      key: "aws.exporter.arn"
      value {
        string_value: "arn:aws:cloudwatch:us-east-1:123456789012:metric-stream/MyMetricStream"
      }
    }
  }
  instrumentation_library_metrics {
    metrics {
      name: "amazonaws.com/AWS/DynamoDB/ConsumedReadCapacityUnits"
      unit: "1"
      double_summary {
        data_points {
          labels {
            key: "Namespace"
            value: "AWS/DynamoDB"
          }
          labels {
            key: "MetricName"
            value: "ConsumedReadCapacityUnits"
          }
          labels {
            key: "TableName"
            value: "MyTable"
          }
          start_time_unix_nano: 1604948400000000000
          time_unix_nano: 1604948460000000000
          count: 1
          sum: 1.0
          quantile_values {
            quantile: 0.0
            value: 1.0
          }
          quantile_values {
            quantile: 0.95
            value: 1.0
          }          
          quantile_values {
            quantile: 0.99
            value: 1.0
          }
          quantile_values {
            quantile: 1.0
            value: 1.0
          }
        }
        data_points {
          labels {
            key: "Namespace"
            value: "AWS/DynamoDB"
          }
          labels {
            key: "MetricName"
            value: "ConsumedReadCapacityUnits"
          }
          labels {
            key: "TableName"
            value: "MyTable"
          }
          start_time_unix_nano: 1604948460000000000
          time_unix_nano: 1604948520000000000
          count: 2
          sum: 5.0
          quantile_values {
            quantile: 0.0
            value: 2.0
          }
          quantile_values {
            quantile: 1.0
            value: 3.0
          }
        }
      }
    }
  }
}
```

**用于序列化 OpenTelemetry 指标数据的顶级对象**

`ExportMetricsServiceRequest` 是用于序列化 OpenTelemetry 导出器负载的顶级包装器。它包含一个或多个 `ResourceMetrics`。

```
message ExportMetricsServiceRequest {
  // An array of ResourceMetrics.
  // For data coming from a single resource this array will typically contain one
  // element. Intermediary nodes (such as OpenTelemetry Collector) that receive
  // data from multiple origins typically batch the data before forwarding further and
  // in that case this array will contain multiple elements.
  repeated opentelemetry.proto.metrics.v1.ResourceMetrics resource_metrics = 1;
}
```

`ResourceMetrics` 是表示 MetricData 对象的顶级对象。

```
// A collection of InstrumentationLibraryMetrics from a Resource.
message ResourceMetrics {
  // The resource for the metrics in this message.
  // If this field is not set then no resource info is known.
  opentelemetry.proto.resource.v1.Resource resource = 1;
  
  // A list of metrics that originate from a resource.
  repeated InstrumentationLibraryMetrics instrumentation_library_metrics = 2;
}
```

**资源对象**

`Resource` 对象是一个值对对象，其中包含有关生成指标的资源的一些信息。对于由 Amazon 创建的指标，数据结构包含与指标相关的资源的 Amazon Resource Name (ARN)，例如 EC2 实例或 S3 存储桶。

`Resource` 对象包含名为 `attributes` 的属性，其会存储键值对列表。
+ `cloud.account.id` 包含账户 ID
+ `cloud.region` 包含区域
+ `aws.exporter.arn` 包含指标流 ARN
+ `cloud.provider` 始终为 `aws`。

```
// Resource information.
message Resource {
  // Set of labels that describe the resource.
  repeated opentelemetry.proto.common.v1.KeyValue attributes = 1;
  
  // dropped_attributes_count is the number of dropped attributes. If the value is 0,
  // no attributes were dropped.
  uint32 dropped_attributes_count = 2;
}
```

**InstrumentationLibraryMetrics 对象**

将不会填写 instrumentation\$1library 字段。我们将仅填写正在导出的指标字段。

```
// A collection of Metrics produced by an InstrumentationLibrary.
message InstrumentationLibraryMetrics {
  // The instrumentation library information for the metrics in this message.
  // If this field is not set then no library info is known.
  opentelemetry.proto.common.v1.InstrumentationLibrary instrumentation_library = 1;
  // A list of metrics that originate from an instrumentation library.
  repeated Metric metrics = 2;
}
```

**指标对象**

指标对象包含一个 `DoubleSummary` 数据字段，该字段包含一个 `DoubleSummaryDataPoint` 列表。

```
message Metric {
  // name of the metric, including its DNS name prefix. It must be unique.
  string name = 1;

  // description of the metric, which can be used in documentation.
  string description = 2;

  // unit in which the metric value is reported. Follows the format
  // described by http://unitsofmeasure.org/ucum.html.
  string unit = 3;

  oneof data {
    IntGauge int_gauge = 4;
    DoubleGauge double_gauge = 5;
    IntSum int_sum = 6;
    DoubleSum double_sum = 7;
    IntHistogram int_histogram = 8;
    DoubleHistogram double_histogram = 9;
    DoubleSummary double_summary = 11;
  }
}

message DoubleSummary {
  repeated DoubleSummaryDataPoint data_points = 1;
}
```

**MetricDescriptor 对象**

MetricDescriptor 对象包含元数据。有关更多信息，请参阅 GitHub 上的 [metrics.proto](https://github.com/open-telemetry/opentelemetry-proto/blob/main/opentelemetry/proto/metrics/v1/metrics.proto#L110)。

对于指标流，MetricDescriptor 包含以下内容：
+ `name` 将为 `amazonaws.com/metric_namespace/metric_name`
+ `description` 将为空。
+ `unit` 将通过将指标基准单位映射为计量单位统一代码的变体（区分大小写）来填充。有关更多信息，请参阅 [在 CloudWatch 中转换为 OpenTelemetry 0.7.0 格式](CloudWatch-metric-streams-formats-opentelemetry-translation.md) 和[计量单位统一代码](https://ucum.org/ucum.html)。
+ `type` 将为 `SUMMARY`。

**DoubleSummaryDataPoint 对象**

DoubleSummaryDataPoint 对象包含 DoubleSummary 指标时间序列中单个数据点的值。

```
// DoubleSummaryDataPoint is a single data point in a timeseries that describes the
// time-varying values of a Summary metric.
message DoubleSummaryDataPoint {
  // The set of labels that uniquely identify this timeseries.
  repeated opentelemetry.proto.common.v1.StringKeyValue labels = 1;

  // start_time_unix_nano is the last time when the aggregation value was reset
  // to "zero". For some metric types this is ignored, see data types for more
  // details.
  //
  // The aggregation value is over the time interval (start_time_unix_nano,
  // time_unix_nano].
  //
  // Value is UNIX Epoch time in nanoseconds since 00:00:00 UTC on 1 January
  // 1970.
  //
  // Value of 0 indicates that the timestamp is unspecified. In that case the
  // timestamp may be decided by the backend.
  fixed64 start_time_unix_nano = 2;

  // time_unix_nano is the moment when this aggregation value was reported.
  //
  // Value is UNIX Epoch time in nanoseconds since 00:00:00 UTC on 1 January
  // 1970.
  fixed64 time_unix_nano = 3;

  // count is the number of values in the population. Must be non-negative.
  fixed64 count = 4;

  // sum of the values in the population. If count is zero then this field
  // must be zero.
  double sum = 5;

  // Represents the value at a given quantile of a distribution.
  //
  // To record Min and Max values following conventions are used:
  // - The 1.0 quantile is equivalent to the maximum value observed.
  // - The 0.0 quantile is equivalent to the minimum value observed.
  message ValueAtQuantile {
    // The quantile of a distribution. Must be in the interval
    // [0.0, 1.0].
    double quantile = 1;

    // The value at the given quantile of a distribution.
    double value = 2;
  }

  // (Optional) list of values at different quantiles of the distribution calculated
  // from the current snapshot. The quantiles must be strictly increasing.
  repeated ValueAtQuantile quantile_values = 6;
}
```

有关更多信息，请参阅 [在 CloudWatch 中转换为 OpenTelemetry 0.7.0 格式](CloudWatch-metric-streams-formats-opentelemetry-translation.md)。