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Description:

awscdk.awscloudwatch 1.204.0

Amazon CloudWatch Construct Library
---

AWS CDK v1 has reached End-of-Support on 2023-06-01.
This package is no longer being updated, and users should migrate to AWS CDK v2.
For more information on how to migrate, see the Migrating to AWS CDK v2 guide.

Metric objects
Metric objects represent a metric that is emitted by AWS services or your own
application, such as CPUUsage, FailureCount or Bandwidth.
Metric objects can be constructed directly or are exposed by resources as
attributes. Resources that expose metrics will have functions that look
like metricXxx() which will return a Metric object, initialized with defaults
that make sense.
For example, lambda.Function objects have the fn.metricErrors() method, which
represents the amount of errors reported by that Lambda function:
# fn: lambda.Function

errors = fn.metric_errors()

Metric objects can be account and region aware. You can specify account and region as properties of the metric, or use the metric.attachTo(Construct) method. metric.attachTo() will automatically copy the region and account fields of the Construct, which can come from anywhere in the Construct tree.
You can also instantiate Metric objects to reference any
published metric
that's not exposed using a convenience method on the CDK construct.
For example:
hosted_zone = route53.HostedZone(self, "MyHostedZone", zone_name="example.org")
metric = cloudwatch.Metric(
namespace="AWS/Route53",
metric_name="DNSQueries",
dimensions_map={
"HostedZoneId": hosted_zone.hosted_zone_id
}
)

Instantiating a new Metric object
If you want to reference a metric that is not yet exposed by an existing construct,
you can instantiate a Metric object to represent it. For example:
metric = cloudwatch.Metric(
namespace="MyNamespace",
metric_name="MyMetric",
dimensions_map={
"ProcessingStep": "Download"
}
)

Metric Math
Math expressions are supported by instantiating the MathExpression class.
For example, a math expression that sums two other metrics looks like this:
# fn: lambda.Function

all_problems = cloudwatch.MathExpression(
expression="errors + throttles",
using_metrics={
"errors": fn.metric_errors(),
"faults": fn.metric_throttles()
}
)

You can use MathExpression objects like any other metric, including using
them in other math expressions:
# fn: lambda.Function
# all_problems: cloudwatch.MathExpression

problem_percentage = cloudwatch.MathExpression(
expression="(problems / invocations) * 100",
using_metrics={
"problems": all_problems,
"invocations": fn.metric_invocations()
}
)

Search Expressions
Math expressions also support search expressions. For example, the following
search expression returns all CPUUtilization metrics that it finds, with the
graph showing the Average statistic with an aggregation period of 5 minutes:
cpu_utilization = cloudwatch.MathExpression(
expression="SEARCH('{AWS/EC2,InstanceId} MetricName=\"CPUUtilization\"', 'Average', 300)",

# Specifying '' as the label suppresses the default behavior
# of using the expression as metric label. This is especially appropriate
# when using expressions that return multiple time series (like SEARCH()
# or METRICS()), to show the labels of the retrieved metrics only.
label=""
)

Cross-account and cross-region search expressions are also supported. Use
the searchAccount and searchRegion properties to specify the account
and/or region to evaluate the search expression against.
Aggregation
To graph or alarm on metrics you must aggregate them first, using a function
like Average or a percentile function like P99. By default, most Metric objects
returned by CDK libraries will be configured as Average over 300 seconds (5 minutes).
The exception is if the metric represents a count of discrete events, such as
failures. In that case, the Metric object will be configured as Sum over 300 seconds, i.e. it represents the number of times that event occurred over the
time period.
If you want to change the default aggregation of the Metric object (for example,
the function or the period), you can do so by passing additional parameters
to the metric function call:
# fn: lambda.Function

minute_error_rate = fn.metric_errors(
statistic="avg",
period=Duration.minutes(1),
label="Lambda failure rate"
)

This function also allows changing the metric label or color (which will be
useful when embedding them in graphs, see below).

Rates versus Sums
The reason for using Sum to count discrete events is that some events are
emitted as either 0 or 1 (for example Errors for a Lambda) and some are
only emitted as 1 (for example NumberOfMessagesPublished for an SNS
topic).
In case 0-metrics are emitted, it makes sense to take the Average of this
metric: the result will be the fraction of errors over all executions.
If 0-metrics are not emitted, the Average will always be equal to 1,
and not be very useful.
In order to simplify the mental model of Metric objects, we default to
aggregating using Sum, which will be the same for both metrics types. If you
happen to know the Metric you want to alarm on makes sense as a rate
(Average) you can always choose to change the statistic.

Labels
Metric labels are displayed in the legend of graphs that include the metrics.
You can use dynamic labels
to show summary information about the displayed time series
in the legend. For example, if you use:
# fn: lambda.Function

minute_error_rate = fn.metric_errors(
statistic="sum",
period=Duration.hours(1),

# Show the maximum hourly error count in the legend
label="[max: ${MAX}] Lambda failure rate"
)

As the metric label, the maximum value in the visible range will
be shown next to the time series name in the graph's legend.
If the metric is a math expression producing more than one time series, the
maximum will be individually calculated and shown for each time series produce
by the math expression.
Alarms
Alarms can be created on metrics in one of two ways. Either create an Alarm
object, passing the Metric object to set the alarm on:
# fn: lambda.Function

cloudwatch.Alarm(self, "Alarm",
metric=fn.metric_errors(),
threshold=100,
evaluation_periods=2
)

Alternatively, you can call metric.createAlarm():
# fn: lambda.Function

fn.metric_errors().create_alarm(self, "Alarm",
threshold=100,
evaluation_periods=2
)

The most important properties to set while creating an Alarms are:

threshold: the value to compare the metric against.
comparisonOperator: the comparison operation to use, defaults to metric >= threshold.
evaluationPeriods: how many consecutive periods the metric has to be
breaching the the threshold for the alarm to trigger.

To create a cross-account alarm, make sure you have enabled cross-account functionality in CloudWatch. Then, set the account property in the Metric object either manually or via the metric.attachTo() method.
Alarm Actions
To add actions to an alarm, use the integration classes from the
@aws-cdk/aws-cloudwatch-actions package. For example, to post a message to
an SNS topic when an alarm breaches, do the following:
import aws_cdk.aws_cloudwatch_actions as cw_actions
# alarm: cloudwatch.Alarm

topic = sns.Topic(self, "Topic")
alarm.add_alarm_action(cw_actions.SnsAction(topic))

Notification formats
Alarms can be created in one of two "formats":

With "top-level parameters" (these are the classic style of CloudWatch Alarms).
With a list of metrics specifications (these are the modern style of CloudWatch Alarms).

For backwards compatibility, CDK will try to create classic, top-level CloudWatch alarms
as much as possible, unless you are using features that cannot be expressed in that format.
Features that require the new-style alarm format are:

Metric math
Cross-account metrics
Labels

The difference between these two does not impact the functionality of the alarm
in any way, except that the format of the notifications the Alarm generates is
different between them. This affects both the notifications sent out over SNS,
as well as the EventBridge events generated by this Alarm. If you are writing
code to consume these notifications, be sure to handle both formats.
Composite Alarms
Composite Alarms
can be created from existing Alarm resources.
# alarm1: cloudwatch.Alarm
# alarm2: cloudwatch.Alarm
# alarm3: cloudwatch.Alarm
# alarm4: cloudwatch.Alarm

alarm_rule = cloudwatch.AlarmRule.any_of(
cloudwatch.AlarmRule.all_of(
cloudwatch.AlarmRule.any_of(alarm1,
cloudwatch.AlarmRule.from_alarm(alarm2, cloudwatch.AlarmState.OK), alarm3),
cloudwatch.AlarmRule.not(cloudwatch.AlarmRule.from_alarm(alarm4, cloudwatch.AlarmState.INSUFFICIENT_DATA))),
cloudwatch.AlarmRule.from_boolean(False))

cloudwatch.CompositeAlarm(self, "MyAwesomeCompositeAlarm",
alarm_rule=alarm_rule
)

A note on units
In CloudWatch, Metrics datums are emitted with units, such as seconds or
bytes. When Metric objects are given a unit attribute, it will be used to
filter the stream of metric datums for datums emitted using the same unit
attribute.
In particular, the unit field is not used to rescale datums or alarm threshold
values (for example, it cannot be used to specify an alarm threshold in
Megabytes if the metric stream is being emitted as bytes).
You almost certainly don't want to specify the unit property when creating
Metric objects (which will retrieve all datums regardless of their unit),
unless you have very specific requirements. Note that in any case, CloudWatch
only supports filtering by unit for Alarms, not in Dashboard graphs.
Please see the following GitHub issue for a discussion on real unit
calculations in CDK: https://github.com/aws/aws-cdk/issues/5595
Dashboards
Dashboards are set of Widgets stored server-side which can be accessed quickly
from the AWS console. Available widgets are graphs of a metric over time, the
current value of a metric, or a static piece of Markdown which explains what the
graphs mean.
The following widgets are available:

GraphWidget -- shows any number of metrics on both the left and right
vertical axes.
AlarmWidget -- shows the graph and alarm line for a single alarm.
SingleValueWidget -- shows the current value of a set of metrics.
TextWidget -- shows some static Markdown.
AlarmStatusWidget -- shows the status of your alarms in a grid view.

Graph widget
A graph widget can display any number of metrics on either the left or
right vertical axis:
# dashboard: cloudwatch.Dashboard
# execution_count_metric: cloudwatch.Metric
# error_count_metric: cloudwatch.Metric

dashboard.add_widgets(cloudwatch.GraphWidget(
title="Executions vs error rate",

left=[execution_count_metric],

right=[error_count_metric.with(
statistic="average",
label="Error rate",
color=cloudwatch.Color.GREEN
)]
))

Using the methods addLeftMetric() and addRightMetric() you can add metrics to a graph widget later on.
Graph widgets can also display annotations attached to the left or the right y-axis.
# dashboard: cloudwatch.Dashboard

dashboard.add_widgets(cloudwatch.GraphWidget(
# ...

left_annotations=[cloudwatch.HorizontalAnnotation(value=1800, label=Duration.minutes(30).to_human_string(), color=cloudwatch.Color.RED), cloudwatch.HorizontalAnnotation(value=3600, label="1 hour", color="#2ca02c")
]
))

The graph legend can be adjusted from the default position at bottom of the widget.
# dashboard: cloudwatch.Dashboard

dashboard.add_widgets(cloudwatch.GraphWidget(
# ...

legend_position=cloudwatch.LegendPosition.RIGHT
))

The graph can publish live data within the last minute that has not been fully aggregated.
# dashboard: cloudwatch.Dashboard

dashboard.add_widgets(cloudwatch.GraphWidget(
# ...

live_data=True
))

The graph view can be changed from default 'timeSeries' to 'bar' or 'pie'.
# dashboard: cloudwatch.Dashboard

dashboard.add_widgets(cloudwatch.GraphWidget(
# ...

view=cloudwatch.GraphWidgetView.BAR
))

Alarm widget
An alarm widget shows the graph and the alarm line of a single alarm:
# dashboard: cloudwatch.Dashboard
# error_alarm: cloudwatch.Alarm

dashboard.add_widgets(cloudwatch.AlarmWidget(
title="Errors",
alarm=error_alarm
))

Single value widget
A single-value widget shows the latest value of a set of metrics (as opposed
to a graph of the value over time):
# dashboard: cloudwatch.Dashboard
# visitor_count: cloudwatch.Metric
# purchase_count: cloudwatch.Metric

dashboard.add_widgets(cloudwatch.SingleValueWidget(
metrics=[visitor_count, purchase_count]
))

Show as many digits as can fit, before rounding.
# dashboard: cloudwatch.Dashboard

dashboard.add_widgets(cloudwatch.SingleValueWidget(
metrics=[],

full_precision=True
))

Text widget
A text widget shows an arbitrary piece of MarkDown. Use this to add explanations
to your dashboard:
# dashboard: cloudwatch.Dashboard

dashboard.add_widgets(cloudwatch.TextWidget(
markdown="# Key Performance Indicators"
))

Alarm Status widget
An alarm status widget displays instantly the status of any type of alarms and gives the
ability to aggregate one or more alarms together in a small surface.
# dashboard: cloudwatch.Dashboard
# error_alarm: cloudwatch.Alarm

dashboard.add_widgets(
cloudwatch.AlarmStatusWidget(
alarms=[error_alarm]
))

An alarm status widget only showing firing alarms, sorted by state and timestamp:
# dashboard: cloudwatch.Dashboard
# error_alarm: cloudwatch.Alarm

dashboard.add_widgets(cloudwatch.AlarmStatusWidget(
title="Errors",
alarms=[error_alarm],
sort_by=cloudwatch.AlarmStatusWidgetSortBy.STATE_UPDATED_TIMESTAMP,
states=[cloudwatch.AlarmState.ALARM]
))

Query results widget
A LogQueryWidget shows the results of a query from Logs Insights:
# dashboard: cloudwatch.Dashboard

dashboard.add_widgets(cloudwatch.LogQueryWidget(
log_group_names=["my-log-group"],
view=cloudwatch.LogQueryVisualizationType.TABLE,
# The lines will be automatically combined using '\n|'.
query_lines=["fields @message", "filter @message like /Error/"
]
))

Custom widget
A CustomWidget shows the result of an AWS Lambda function:
# dashboard: cloudwatch.Dashboard

# Import or create a lambda function
fn = lambda_.Function.from_function_arn(dashboard, "Function", "arn:aws:lambda:us-east-1:123456789012:function:MyFn")

dashboard.add_widgets(cloudwatch.CustomWidget(
function_arn=fn.function_arn,
title="My lambda baked widget"
))

You can learn more about custom widgets in the Amazon Cloudwatch User Guide.
Dashboard Layout
The widgets on a dashboard are visually laid out in a grid that is 24 columns
wide. Normally you specify X and Y coordinates for the widgets on a Dashboard,
but because this is inconvenient to do manually, the library contains a simple
layout system to help you lay out your dashboards the way you want them to.
Widgets have a width and height property, and they will be automatically
laid out either horizontally or vertically stacked to fill out the available
space.
Widgets are added to a Dashboard by calling add(widget1, widget2, ...).
Widgets given in the same call will be laid out horizontally. Widgets given
in different calls will be laid out vertically. To make more complex layouts,
you can use the following widgets to pack widgets together in different ways:

Column: stack two or more widgets vertically.
Row: lay out two or more widgets horizontally.
Spacer: take up empty space