feat(metrics): disable metrics with POWERTOOLS_METRICS_DISABLED

packages/metrics/src/Metrics.ts

@@ -201,6 +201,11 @@ class Metrics extends Utility implements MetricsInterface {
    */
   private storedMetrics: StoredMetrics = {};
 
+  /**
+   * Whether to disable metrics
+   */
+  private disabled = false;
+
   /**
    * Custom timestamp for the metrics
    */
@@ -480,6 +485,13 @@ class Metrics extends Utility implements MetricsInterface {
     return Object.keys(this.storedMetrics).length > 0;
   }
 
+  /**
+   * Whether metrics are disabled.
+   */
+  public isDisabled(): boolean {
+    return this.disabled;
+  }
+
   /**
    * A class method decorator to automatically log metrics after the method returns or throws an error.
    *
@@ -587,8 +599,14 @@ class Metrics extends Utility implements MetricsInterface {
           'If application metrics should never be empty, consider using `throwOnEmptyMetrics`'
       );
     }
-    const emfOutput = this.serializeMetrics();
-    hasMetrics && this.console.log(JSON.stringify(emfOutput));
+
+    if (!this.disabled) {
+      const emfOutput = this.serializeMetrics();
+      hasMetrics && this.console.log(JSON.stringify(emfOutput));
+    } else {
+      // TODO log warning that metrics are disabled?
+    }
+
     this.clearMetrics();
     this.clearDimensions();
     this.clearMetadata();
@@ -921,6 +939,17 @@ class Metrics extends Utility implements MetricsInterface {
       this.getEnvVarsService().getNamespace()) as string;
   }
 
+  /**
+   * Set the disbaled flag based on the environment variables `POWERTOOLS_METRICS_DISABLED` and `POWERTOOLS_DEV`.
+   */
+  private setDisabled(): void {
+    this.disabled =
+      this.getEnvVarsService().isDevMode() ||
+      this.getEnvVarsService().getMetricsDisabled();
+
+    // TODO if POWERTOOLS_METRICS_DISABLED is set to false, and dev mode is enabled, then POWERTOOLS_METRICS_DISABLED takes precedence and the utility stays enabled.
+  }
+
   /**
    * Set the options to be used by the Metrics instance.
    *
@@ -943,6 +972,7 @@ class Metrics extends Utility implements MetricsInterface {
     this.setNamespace(namespace);
     this.setService(serviceName);
     this.setDefaultDimensions(defaultDimensions);
+    this.setDisabled();
     this.isSingleMetric = singleMetric || false;
 
     return this;

packages/metrics/src/config/EnvironmentVariablesService.ts

@@ -13,12 +13,23 @@ class EnvironmentVariablesService
 {
   private namespaceVariable = 'POWERTOOLS_METRICS_NAMESPACE';
 
+  private disabledVariable = 'POWERTOOLS_METRICS_DISABLED';
+
   /**
    * Get the value of the `POWERTOOLS_METRICS_NAMESPACE` environment variable.
    */
   public getNamespace(): string {
     return this.get(this.namespaceVariable);
   }
+
+  /**
+   * Get the value of the `POWERTOOLS_METRICS_DISABLED` environment variable.
+   */
+  public getMetricsDisabled(): boolean {
+    const value = this.get(this.disabledVariable);
+
+    return this.isValueTrue(value);
+  }
 }
 
 export { EnvironmentVariablesService };

packages/metrics/tests/unit/Metrics.test.ts

@@ -1418,6 +1418,29 @@ describe('Class: Metrics', () => {
       expect(consoleLogSpy).toBeCalledWith(JSON.stringify(mockData));
     });
 
+    test('it should not log anything if metrics are disabled', () => {
+      // Prepare
+      process.env.POWERTOOLS_METRICS_DISABLED = 'true';
+      const customLogger = {
+        log: jest.fn(),
+        warn: jest.fn(),
+        debug: jest.fn(),
+        error: jest.fn(),
+        info: jest.fn(),
+      };
+      const metrics: Metrics = new Metrics({
+        namespace: TEST_NAMESPACE,
+        logger: customLogger,
+      });
+      const consoleLogSpy = jest.spyOn(customLogger, 'log');
+
+      // Act
+      metrics.publishStoredMetrics();
+
+      // Assess
+      expect(consoleLogSpy).toHaveBeenCalledTimes(0);
+    });
+
     test('it should call clearMetrics function', () => {
       // Prepare
       const metrics: Metrics = new Metrics({ namespace: TEST_NAMESPACE });
@@ -2343,6 +2366,32 @@ describe('Class: Metrics', () => {
     });
   });
 
+  describe('Method: isDisabled', () => {
+    it('should be enabled by default', () => {
+      const metrics: Metrics = new Metrics({ namespace: TEST_NAMESPACE });
+
+      // Act & Assess
+      expect(metrics.isDisabled()).toBe(false);
+    });
+
+    it('should be disabled if POWERTOOLS_DEV is set to true', () => {
+      process.env.POWERTOOLS_DEV = 'true';
+      const metrics: Metrics = new Metrics({ namespace: TEST_NAMESPACE });
+
+      // Act & Assess
+      expect(metrics.isDisabled()).toBe(true);
+    });
+
+    it('should be disabled if POWERTOOLS_METRICS_DISABLED is set to true', () => {
+      // Prepare
+      process.env.POWERTOOLS_METRICS_DISABLED = 'true';
+      const metrics: Metrics = new Metrics({ namespace: TEST_NAMESPACE });
+
+      // Act & Assess
+      expect(metrics.isDisabled()).toBe(true);
+    });
+  });
+
   describe('Method: setTimestamp', () => {
     const testCases = [
       {