MetricDataQuery
This structure is used in both GetMetricData and PutMetricAlarm. The supported use of this structure is different for those two operations.
When used in GetMetricData, it indicates the metric data to return, and whether this call is just retrieving a batch set of data for one metric, or is performing a Metrics Insights query or a math expression. A single GetMetricData call can include up to 500 MetricDataQuery structures.
When used in PutMetricAlarm, it enables you to create an alarm based on a metric math expression. Each MetricDataQuery in the array specifies either a metric to retrieve, or a math expression to be performed on retrieved metrics. A single PutMetricAlarm call can include up to 20 MetricDataQuery structures in the array. The 20 structures can include as many as 10 structures that contain a MetricStat parameter to retrieve a metric, and as many as 10 structures that contain the Expression parameter to perform a math expression. Of those Expression structures, one must have true as the value for ReturnData. The result of this expression is the value the alarm watches.
Any expression used in a PutMetricAlarm operation must return a single time series. For more information, see Metric Math Syntax and Functions in the Amazon CloudWatch User Guide.
Some of the parameters of this structure also have different uses whether you are using this structure in a GetMetricData operation or a PutMetricAlarm operation. These differences are explained in the following parameter list.
Types
Properties
This field can contain either a Metrics Insights query, or a metric math expression to be performed on the returned data. For more information about Metrics Insights queries, see Metrics Insights query components and syntax in the Amazon CloudWatch User Guide.
A short name used to tie this object to the results in the response. This name must be unique within a single call to GetMetricData. If you are performing math expressions on this set of data, this name represents that data and can serve as a variable in the mathematical expression. The valid characters are letters, numbers, and underscore. The first character must be a lowercase letter.
A human-readable label for this metric or expression. This is especially useful if this is an expression, so that you know what the value represents. If the metric or expression is shown in a CloudWatch dashboard widget, the label is shown. If Label is omitted, CloudWatch generates a default.
The metric to be returned, along with statistics, period, and units. Use this parameter only if this object is retrieving a metric and not performing a math expression on returned data.
The granularity, in seconds, of the returned data points. For metrics with regular resolution, a period can be as short as one minute (60 seconds) and must be a multiple of 60. For high-resolution metrics that are collected at intervals of less than one minute, the period can be 1, 5, 10, 30, 60, or any multiple of 60. High-resolution metrics are those metrics stored by a PutMetricData operation that includes a StorageResolution of 1 second.
When used in GetMetricData, this option indicates whether to return the timestamps and raw data values of this metric. If you are performing this call just to do math expressions and do not also need the raw data returned, you can specify false. If you omit this, the default of true is used.