Add validation for tagkey & tagvalue. Fix issue #268 (#280)

* Add validation for tagkey & tagvalue. Fix issue #268

* Fix formatting errors

* Log warning to screen when invalid tag has been used

* Remove unnecessary import

* Fix formatting error

* Replace long string in test case

packages/opencensus-core/src/stats/view.ts

@@ -74,7 +74,10 @@ export class BaseView implements View {
   /** An object to log information to */
   // @ts-ignore
   private logger: loggerTypes.Logger;
-
+  /**
+   * Max Length of a TagKey
+   */
+  private readonly MAX_LENGTH: number = 256;
   /**
    * Creates a new View instance. This constructor is used by Stats. User should
    * prefer using Stats.createView() instead.
@@ -152,15 +155,38 @@ export class BaseView implements View {
   }
 
   /**
-   * Checks if tag keys and values have only printable characters.
+   * Checks if tag keys and values are valid.
    * @param tags The tags to be checked
    */
   private invalidTags(tags: Tags): boolean {
+    const result: boolean =
+        this.invalidPrintableCharacters(tags) || this.invalidLength(tags);
+    if (result) {
+      this.logger.warn(
+          'Unable to create tagkey/tagvalue with the specified tags.');
+    }
+    return result;
+  }
+
+  /**
+   * Checks if tag keys and values have only printable characters.
+   * @param tags The tags to be checked
+   */
+  private invalidPrintableCharacters(tags: Tags): boolean {
     return Object.keys(tags).some(tagKey => {
       return invalidString.test(tagKey) || invalidString.test(tags[tagKey]);
     });
   }
 
+  /**
+   * Checks if length of tagkey is greater than 0 & less than 256.
+   * @param tags The tags to be checked
+   */
+  private invalidLength(tags: Tags): boolean {
+    return Object.keys(tags).some(tagKey => {
+      return tagKey.length <= 0 || tagKey.length >= this.MAX_LENGTH;
+    });
+  }
   /**
    * Creates an empty aggregation data for a given tags.
    * @param tags The tags for that aggregation data

packages/opencensus-core/test/test-view.ts

@@ -193,6 +193,30 @@ describe('BaseView', () => {
          view.recordMeasurement(measurement);
          assert.ok(!view.getSnapshot(measurement.tags));
        });
+
+    it('should not record a measurement when a tag key is longer than 255 characters',
+       () => {
+         const tagkey = 'a'.repeat(256);
+         const measurement = {
+           measure,
+           tags: {[tagkey]: 'testValue'},
+           value: 10
+         };
+         view.recordMeasurement(measurement);
+         assert.ok(!view.getSnapshot(measurement.tags));
+       });
+
+    it('should not record a measurement when tag key is 0 character long',
+       () => {
+         const tagkey = '';
+         const measurement = {
+           measure,
+           tags: {[tagkey]: 'testValue'},
+           value: 10
+         };
+         view.recordMeasurement(measurement);
+         assert.ok(!view.getSnapshot(measurement.tags));
+       });
   });
 
   describe('getMetric()', () => {