TSVB: handle division by zero in math agg (#67111)

src/plugins/vis_type_timeseries/server/lib/vis_data/response_processors/series/math.js

@@ -91,21 +91,29 @@ export function mathAgg(resp, panel, series, meta) {
           // a safety check for the user
           const someNull = values(params).some((v) => v == null);
           if (someNull) return [ts, null];
-          // calculate the result based on the user's script and return the value
-          const result = evaluate(mathMetric.script, {
-            params: {
-              ...params,
-              _index: index,
-              _timestamp: ts,
-              _all: all,
-              _interval: split.meta.bucketSize * 1000,
-            },
-          });
-          // if the result is an object (usually when the user is working with maps and functions) flatten the results and return the last value.
-          if (typeof result === 'object') {
-            return [ts, last(flatten(result.valueOf()))];
+          try {
+            // calculate the result based on the user's script and return the value
+            const result = evaluate(mathMetric.script, {
+              params: {
+                ...params,
+                _index: index,
+                _timestamp: ts,
+                _all: all,
+                _interval: split.meta.bucketSize * 1000,
+              },
+            });
+            // if the result is an object (usually when the user is working with maps and functions) flatten the results and return the last value.
+            if (typeof result === 'object') {
+              return [ts, last(flatten(result.valueOf()))];
+            }
+            return [ts, result];
+          } catch (e) {
+            if (e.message === 'Cannot divide by 0') {
+              // Drop division by zero errors and treat as null value
+              return [ts, null];
+            }
+            throw e;
           }
-          return [ts, result];
         });
         return {
           id: split.id,

src/plugins/vis_type_timeseries/server/lib/vis_data/response_processors/series/math.test.js

@@ -0,0 +1,148 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import { mathAgg } from './math';
+import { stdMetric } from './std_metric';
+
+describe('math(resp, panel, series)', () => {
+  let panel;
+  let series;
+  let resp;
+  beforeEach(() => {
+    panel = {
+      time_field: 'timestamp',
+    };
+    series = {
+      chart_type: 'line',
+      stacked: false,
+      line_width: 1,
+      point_size: 1,
+      fill: 0,
+      id: 'test',
+      label: 'Math',
+      split_mode: 'terms',
+      split_color_mode: 'gradient',
+      color: '#F00',
+      metrics: [
+        {
+          id: 'avgcpu',
+          type: 'avg',
+          field: 'cpu',
+        },
+        {
+          id: 'mincpu',
+          type: 'min',
+          field: 'cpu',
+        },
+        {
+          id: 'mathagg',
+          type: 'math',
+          script: 'divide(params.a, params.b)',
+          variables: [
+            { name: 'a', field: 'avgcpu' },
+            { name: 'b', field: 'mincpu' },
+          ],
+        },
+      ],
+    };
+    resp = {
+      aggregations: {
+        test: {
+          meta: {
+            bucketSize: 5,
+          },
+          buckets: [
+            {
+              key: 'example-01',
+              timeseries: {
+                buckets: [
+                  {
+                    key: 1,
+                    avgcpu: { value: 0.25 },
+                    mincpu: { value: 0.125 },
+                  },
+                  {
+                    key: 2,
+                    avgcpu: { value: 0.25 },
+                    mincpu: { value: 0.25 },
+                  },
+                ],
+              },
+            },
+          ],
+        },
+      },
+    };
+  });
+
+  test('calls next when finished', () => {
+    const next = jest.fn();
+    mathAgg(resp, panel, series)(next)([]);
+    expect(next.mock.calls.length).toEqual(1);
+  });
+
+  test('creates a series', () => {
+    const next = mathAgg(resp, panel, series)((results) => results);
+    const results = stdMetric(resp, panel, series)(next)([]);
+    expect(results).toHaveLength(1);
+
+    expect(results[0]).toEqual({
+      id: 'test:example-01',
+      label: 'example-01',
+      color: 'rgb(255, 0, 0)',
+      stack: false,
+      seriesId: 'test',
+      lines: { show: true, fill: 0, lineWidth: 1, steps: false },
+      points: { show: true, radius: 1, lineWidth: 1 },
+      bars: { fill: 0, lineWidth: 1, show: false },
+      data: [
+        [1, 2],
+        [2, 1],
+      ],
+    });
+  });
+
+  test('turns division by zero into null values', () => {
+    resp.aggregations.test.buckets[0].timeseries.buckets[0].mincpu = 0;
+    const next = mathAgg(resp, panel, series)((results) => results);
+    const results = stdMetric(resp, panel, series)(next)([]);
+    expect(results).toHaveLength(1);
+
+    expect(results[0]).toEqual(
+      expect.objectContaining({
+        data: [
+          [1, null],
+          [2, 1],
+        ],
+      })
+    );
+  });
+
+  test('throws on actual tinymath expression errors', () => {
+    series.metrics[2].script = 'notExistingFn(params.a)';
+    expect(() =>
+      stdMetric(resp, panel, series)(mathAgg(resp, panel, series)((results) => results))([])
+    ).toThrow();
+
+    series.metrics[2].script = 'divide(params.a, params.b';
+    expect(() =>
+      stdMetric(resp, panel, series)(mathAgg(resp, panel, series)((results) => results))([])
+    ).toThrow();
+  });
+});