# MetricFilter

A filter that extracts information from CloudWatch Logs and emits to CloudWatch Metrics.

Extends: Construct › Resource › MetricFilter
Implements: IResource, IEnvironmentAware, IConstruct, IDependable

- CloudFormation: [`AWS::Logs::MetricFilter`](https://docs.aws.amazon.com/AWSCloudFormation/latest/TemplateReference/aws-resource-logs-metricfilter.html)
- L1 type: [`CfnMetricFilter`](/cdk/api/v2/docs/aws-cdk-lib.aws_logs.CfnMetricFilter.html)
- Source: [`aws-logs/lib/metric-filter.ts`](https://github.com/aws/aws-cdk/blob/v2.275.0/packages/aws-cdk-lib/aws-logs/lib/metric-filter.ts#L25)
- Type last changed: v2.196.0 · 16 May 2025

## Example

```ts
const repository = new ecr.Repository(this, 'TestRepository');

const runtime = new agentcore.Runtime(this, 'Runtime', {
  agentRuntimeArtifact: agentcore.AgentRuntimeArtifact.fromEcrRepository(repository, 'v1.0.0'),
});

new logs.MetricFilter(this, 'ToolErrors', {
  logGroup: runtime.applicationLogGroup,
  filterPattern: logs.FilterPattern.stringValue('$.tool_status', '=', 'error'),
  metricNamespace: 'MyApp',
  metricName: 'ToolExecutionErrors',
});
```

## Initializer

```ts
new MetricFilter(scope: Construct, id: string, props: MetricFilterProps)
```

## Construct Props

- `applyOnTransformedLogs`: boolean = false — Whether the metric filter is applied on the tranformed logs.

  This parameter is valid only for log groups that have an active log transformer.
  If this value is true, the metric filter is applied on the transformed version of the log events instead of the original ingested log events.

- `defaultValue`: number — The value to emit if the pattern does not match a particular event.

  **Default:** No metric emitted.

- `dimensions`: { [key: string]: string } — The fields to use as dimensions for the metric.

  **Default:** No dimensions attached to metrics.

  One metric filter can include as many as three dimensions.

- `filterName`: string — The name of the metric filter.

  **Default:** Cloudformation generated name.

- `filterPattern`: [IFilterPattern](/cdk/api/v2/docs/aws-cdk-lib.aws_logs.IFilterPattern.html) (required) — Pattern to search for log events.

- `logGroup`: [ILogGroupRef](/cdk/api/v2/docs/aws-cdk-lib.interfaces.aws_logs.ILogGroupRef.html) (required) — The log group to create the filter on.

- `metricName`: string (required) — The name of the metric to emit.

- `metricNamespace`: string (required) — The namespace of the metric to emit.

- `metricValue`: string = "1" — The value to emit for the metric.

  Can either be a literal number (typically "1"), or the name of a field in the structure
  to take the value from the matched event. If you are using a field value, the field
  value must have been matched using the pattern.

  If you want to specify a field from a matched JSON structure, use '$.fieldName',
  and make sure the field is in the pattern (if only as '$.fieldName = *').

  If you want to specify a field from a matched space-delimited structure,
  use '$fieldName'.

- `unit`: [Unit](/cdk/api/v2/docs/aws-cdk-lib.aws_cloudwatch.Unit.html) — The unit to assign to the metric.

  **Default:** No unit attached to metrics.

## Properties

- `env`: [ResourceEnvironment](/cdk/api/v2/docs/aws-cdk-lib.interfaces.ResourceEnvironment.html) — The environment this resource belongs to.

  For resources that are created and managed in a Stack (those created by
  creating new class instances like `new Role()`, `new Bucket()`, etc.), this
  is always the same as the environment of the stack they belong to.

  For referenced resources (those obtained from referencing methods like
  `Role.fromRoleArn()`, `Bucket.fromBucketName()`, etc.), they might be
  different than the stack they were imported into.

- `node`: [Node](/cdk/api/v2/docs/constructs.Node.html) — The tree node.

- `PROPERTY_INJECTION_ID`: string (static) — Uniquely identifies this class.

- `stack`: [Stack](/cdk/api/v2/docs/aws-cdk-lib.Stack.html) — The stack in which this resource is defined.

## Methods

- `applyCrossStackReferenceStrength(strength: ReferenceStrength): void` — Override the cross-stack reference strength for this resource.

  When set, any cross-stack reference to this resource will use the specified
  mechanism instead of the global default determined by the
  `@aws-cdk/core:defaultCrossStackReferences` context key. This is useful for
  selectively weakening specific references to avoid the "deadly embrace" problem
  without changing the app-wide default.

  **Parameters**

  - `strength` — - The reference strength to use for this resource.

- `applyRemovalPolicy(policy: RemovalPolicy): void` — Apply the given removal policy to this resource.

  The Removal Policy controls what happens to this resource when it stops
  being managed by CloudFormation, either because you've removed it from the
  CDK application or because you've made a change that requires the resource
  to be replaced.

  The resource can be deleted (`RemovalPolicy.DESTROY`), or left in your AWS
  account for data recovery and cleanup later (`RemovalPolicy.RETAIN`).

- `isConstruct(x: any): boolean` (static) — Checks if `x` is a construct.

  Use this method instead of `instanceof` to properly detect `Construct`
  instances, even when the construct library is symlinked.

  Explanation: in JavaScript, multiple copies of the `constructs` library on
  disk are seen as independent, completely different libraries. As a
  consequence, the class `Construct` in each copy of the `constructs` library
  is seen as a different class, and an instance of one class will not test as
  `instanceof` the other class. `npm install` will not create installations
  like this, but users may manually symlink construct libraries together or
  use a monorepo tool: in those cases, multiple copies of the `constructs`
  library can be accidentally installed, and `instanceof` will behave
  unpredictably. It is safest to avoid using `instanceof`, and using
  this type-testing method instead.

  **Parameters**

  - `x` — Any object.

  **Returns:** true if `x` is an object created from a class which extends `Construct`.

- `isOwnedResource(construct: IConstruct): boolean` (static) — Returns true if the construct was created by CDK, and false otherwise.

- `isResource(construct: IConstruct): boolean` (static) — Check whether the given construct is a Resource.

- `metric(props?: MetricOptions): Metric` — Return the given named metric for this Metric Filter.

- `toString(): string` — Returns a string representation of this construct.

- `with(...mixins: IMixin[]): IConstruct` — Applies one or more mixins to this construct.

  Mixins are applied in order. The list of constructs is captured at the
  start of the call, so constructs added by a mixin will not be visited.
  Use multiple `with()` calls if subsequent mixins should apply to added
  constructs.