feat(metrics): use async local storage for metrics

Author: svozza

package-lock.json

@@ -88,7 +88,8 @@
     "url": "https://github.com/aws-powertools/powertools-lambda-typescript/issues"
   },
   "dependencies": {
-    "@aws-lambda-powertools/commons": "2.27.0"
+    "@aws-lambda-powertools/commons": "2.27.0",
+    "@aws/lambda-invoke-store": "0.1.0"
   },
   "keywords": [
     "aws",

packages/metrics/package.json

@@ -0,0 +1,91 @@
+import { InvokeStore } from '@aws/lambda-invoke-store';
+import type { Dimensions } from './types/Metrics.js';
+
+/**
+ * Manages storage of metrics dimensions with automatic context detection.
+ *
+ * This class abstracts the storage mechanism for metrics, automatically
+ * choosing between AsyncLocalStorage (when in async context) and a fallback
+ * object (when outside async context). The decision is made at runtime on
+ * every method call to support Lambda's transition to async contexts.
+ */
+class DimensionsStore {
+  readonly #dimensionsKey = Symbol('powertools.metrics.dimensions');
+  readonly #dimensionSetsKey = Symbol('powertools.metrics.dimensionSets');
+
+  #fallbackDimensions: Dimensions = {};
+  #fallbackDimensionSets: Dimensions[] = [];
+
+  #getDimensions(): Dimensions {
+    if (InvokeStore.getContext() === undefined) {
+      return this.#fallbackDimensions;
+    }
+
+    let stored = InvokeStore.get(this.#dimensionsKey) as Dimensions | undefined;
+    if (stored == null) {
+      stored = {};
+      InvokeStore.set(this.#dimensionsKey, stored);
+    }
+    return stored;
+  }
+
+  #getDimensionSets(): Dimensions[] {
+    if (InvokeStore.getContext() === undefined) {
+      return this.#fallbackDimensionSets;
+    }
+
+    let stored = InvokeStore.get(this.#dimensionSetsKey) as
+      | Dimensions[]
+      | undefined;
+    if (stored == null) {
+      stored = [];
+      InvokeStore.set(this.#dimensionSetsKey, stored);
+    }
+    return stored;
+  }
+
+  addDimension(name: string, value: string): string {
+    this.#getDimensions()[name] = value;
+    return value;
+  }
+
+  addDimensionSet(dimensionSet: Dimensions): Dimensions {
+    this.#getDimensionSets().push({ ...dimensionSet });
+    return dimensionSet;
+  }
+
+  getDimensions(): Dimensions {
+    return { ...this.#getDimensions() };
+  }
+
+  getDimensionSets(): Dimensions[] {
+    return this.#getDimensionSets().map((set) => ({ ...set }));
+  }
+
+  clear(): void {
+    if (InvokeStore.getContext() === undefined) {
+      this.#fallbackDimensions = {};
+      this.#fallbackDimensionSets = [];
+      return;
+    }
+
+    InvokeStore.set(this.#dimensionsKey, {});
+    InvokeStore.set(this.#dimensionSetsKey, []);
+  }
+
+  getDimensionCount(defaultDimensions: Dimensions): number {
+    const dimensions = this.#getDimensions();
+    const dimensionSets = this.#getDimensionSets();
+    const dimensionSetsCount = dimensionSets.reduce(
+      (total, dimensionSet) => total + Object.keys(dimensionSet).length,
+      0
+    );
+    return (
+      Object.keys(dimensions).length +
+      Object.keys(defaultDimensions).length +
+      dimensionSetsCount
+    );
+  }
+}
+
+export { DimensionsStore };

packages/metrics/src/DimensionsStore.ts

@@ -0,0 +1,50 @@
+import { InvokeStore } from '@aws/lambda-invoke-store';
+
+/**
+ * Manages storage of metrics #metadata with automatic context detection.
+ *
+ * This class abstracts the storage mechanism for metrics, automatically
+ * choosing between AsyncLocalStorage (when in async context) and a fallback
+ * object (when outside async context). The decision is made at runtime on
+ * every method call to support Lambda's transition to async contexts.
+ */
+class MetadataStore {
+  readonly #metadataKey = Symbol('powertools.metrics.metadata');
+
+  #fallbackStorage: Record<string, string> = {};
+
+  #getStorage(): Record<string, string> {
+    if (InvokeStore.getContext() === undefined) {
+      return this.#fallbackStorage;
+    }
+
+    let stored = InvokeStore.get(this.#metadataKey) as
+      | Record<string, string>
+      | undefined;
+    if (stored == null) {
+      stored = {};
+      InvokeStore.set(this.#metadataKey, stored);
+    }
+    return stored;
+  }
+
+  public set(key: string, value: string): string {
+    this.#getStorage()[key] = value;
+    return value;
+  }
+
+  public getAll(): Record<string, string> {
+    return { ...this.#getStorage() };
+  }
+
+  public clear(): void {
+    if (InvokeStore.getContext() === undefined) {
+      this.#fallbackStorage = {};
+      return;
+    }
+
+    InvokeStore.set(this.#metadataKey, {});
+  }
+}
+
+export { MetadataStore };