MathExpression

class aws_cdk.aws_cloudwatch.MathExpression(*, expression, using_metrics, color=None, label=None, period=None)

Bases: object

A math expression built with metric(s) emitted by a service.

The math expression is a combination of an expression (x+y) and metrics to apply expression on. It also contains metadata which is used only in graphs, such as color and label. It makes sense to embed this in here, so that compound constructs can attach that metadata to metrics they expose.

This class does not represent a resource, so hence is not a construct. Instead, MathExpression is an abstraction that makes it easy to specify metrics for use in both alarms and graphs.

__init__(*, expression, using_metrics, color=None, label=None, period=None)
Parameters

  • expression (str) – The expression defining the metric.

  • using_metrics (Mapping[str, IMetric]) – The metrics used in the expression, in a map. The key is the identifier that represents the given metric in the expression, and the value is the actual Metric object.

  • color (Optional[str]) – Color for this metric when added to a Graph in a Dashboard. Default: - Automatic color

  • label (Optional[str]) – Label for this metric when added to a Graph in a Dashboard. Default: - Expression value is used as label

  • period (Optional[Duration]) – The period over which the expression’s statistics are applied. This period overrides all periods in the metrics used in this math expression. Default: Duration.minutes(5)

Return type

None

Methods

create_alarm(scope, id, *, evaluation_periods, threshold, actions_enabled=None, alarm_description=None, alarm_name=None, comparison_operator=None, datapoints_to_alarm=None, evaluate_low_sample_count_percentile=None, period=None, statistic=None, treat_missing_data=None)

Make a new Alarm for this metric.

Combines both properties that may adjust the metric (aggregation) as well as alarm properties.

Parameters

  • scope (Construct) –

  • id (str) –

  • evaluation_periods (Union[int, float]) – The number of periods over which data is compared to the specified threshold.

  • threshold (Union[int, float]) – The value against which the specified statistic is compared.

  • actions_enabled (Optional[bool]) – Whether the actions for this alarm are enabled. Default: true

  • alarm_description (Optional[str]) – Description for the alarm. Default: No description

  • alarm_name (Optional[str]) – Name of the alarm. Default: Automatically generated name

  • comparison_operator (Optional[ComparisonOperator]) – Comparison to use to check if metric is breaching. Default: GreaterThanOrEqualToThreshold

  • datapoints_to_alarm (Union[int, float, None]) – The number of datapoints that must be breaching to trigger the alarm. This is used only if you are setting an “M out of N” alarm. In that case, this value is the M. For more information, see Evaluating an Alarm in the Amazon CloudWatch User Guide. Default: evaluationPeriods

  • evaluate_low_sample_count_percentile (Optional[str]) – Specifies whether to evaluate the data and potentially change the alarm state if there are too few data points to be statistically significant. Used only for alarms that are based on percentiles. Default: - Not configured.

  • period (Optional[Duration]) – The period over which the specified statistic is applied. Cannot be used with MathExpression objects. Default: - The period from the metric

  • statistic (Optional[str]) – What function to use for aggregating. Can be one of the following: - “Minimum” | “min” - “Maximum” | “max” - “Average” | “avg” - “Sum” | “sum” - “SampleCount | “n” - “pNN.NN” Cannot be used with MathExpression objects. Default: - The statistic from the metric

  • treat_missing_data (Optional[TreatMissingData]) – Sets how this alarm is to handle missing data points. Default: TreatMissingData.Missing

Return type

Alarm

to_alarm_config()

Turn this metric object into an alarm configuration.

Return type

MetricAlarmConfig

to_graph_config()

Turn this metric object into a graph configuration.

Return type

MetricGraphConfig

to_metric_config()

Inspect the details of the metric object.

Return type

MetricConfig

to_string()

Returns a string representation of an object.

Return type

str

with_(*, color=None, label=None, period=None)

Return a copy of Metric with properties changed.

All properties except namespace and metricName can be changed.

Parameters

  • color (Optional[str]) – Color for this metric when added to a Graph in a Dashboard. Default: - Automatic color

  • label (Optional[str]) – Label for this metric when added to a Graph in a Dashboard. Default: - Expression value is used as label

  • period (Optional[Duration]) – The period over which the expression’s statistics are applied. This period overrides all periods in the metrics used in this math expression. Default: Duration.minutes(5)

Return type

MathExpression

Attributes

color

The hex color code, prefixed with ‘#’ (e.g. ‘#00ff00’), to use when this metric is rendered on a graph. The Color class has a set of standard colors that can be used here.

Return type

Optional[str]

expression

The expression defining the metric.

Return type

str

label

Label for this metric when added to a Graph.

Return type

Optional[str]

period

Aggregation period of this metric.

Return type

Duration

using_metrics

The metrics used in the expression as KeyValuePair <id, metric>.

Return type

Mapping[str, IMetric]