[Uptime] Use manual intervals for ping histogram (#72928)

* [Uptime] Use manual intervals for ping histogram

Fixes elastic/uptime#215

Prior to this we'd get too few buckets in some ranges.

* Update test fixtures, remove overly-specific checks

* Remove unused import

Author: andrewvc

x-pack/plugins/uptime/server/lib/requests/get_ping_histogram.ts

@@ -8,6 +8,7 @@ import { UMElasticsearchQueryFn } from '../adapters';
 import { getFilterClause } from '../helper';
 import { HistogramResult, HistogramQueryResult } from '../../../common/runtime_types';
 import { QUERY } from '../../../common/constants';
+import { getHistogramInterval } from '../helper/get_histogram_interval';
 
 export interface GetPingHistogramParams {
   /** @member dateRangeStart timestamp bounds */
@@ -36,22 +37,6 @@ export const getPingHistogram: UMElasticsearchQueryFn<
   }
   const filter = getFilterClause(from, to, additionalFilters);
 
-  const seriesHistogram: any = {};
-
-  if (bucketSize) {
-    seriesHistogram.date_histogram = {
-      field: '@timestamp',
-      fixed_interval: bucketSize,
-      missing: 0,
-    };
-  } else {
-    seriesHistogram.auto_date_histogram = {
-      field: '@timestamp',
-      buckets: QUERY.DEFAULT_BUCKET_COUNT,
-      missing: 0,
-    };
-  }
-
   const params = {
     index: dynamicSettings.heartbeatIndices,
     body: {
@@ -63,7 +48,12 @@ export const getPingHistogram: UMElasticsearchQueryFn<
       size: 0,
       aggs: {
         timeseries: {
-          ...seriesHistogram,
+          date_histogram: {
+            field: '@timestamp',
+            fixed_interval:
+              bucketSize || getHistogramInterval(from, to, QUERY.DEFAULT_BUCKET_COUNT) + 'ms',
+            missing: 0,
+          },
           aggs: {
             down: {
               filter: {

x-pack/test/api_integration/apis/uptime/rest/fixtures/ping_histogram.json

@@ -1,121 +1,157 @@
 {
   "histogram": [
     {
-      "x": 1568172664000,
+      "x": 1568172657286,
       "downCount": 7,
       "upCount": 93,
       "y": 1
     },
     {
-      "x": 1568172694000,
+      "x": 1568172680087,
       "downCount": 7,
       "upCount": 93,
       "y": 1
     },
     {
-      "x": 1568172724000,
+      "x": 1568172702888,
       "downCount": 7,
       "upCount": 93,
       "y": 1
     },
     {
-      "x": 1568172754000,
+      "x": 1568172725689,
+      "downCount": 0,
+      "upCount": 0,
+      "y": 1
+    },
+    {
+      "x": 1568172748490,
       "downCount": 7,
       "upCount": 93,
       "y": 1
     },
     {
-      "x": 1568172784000,
+      "x": 1568172771291,
       "downCount": 7,
       "upCount": 93,
       "y": 1
     },
     {
-      "x": 1568172814000,
+      "x": 1568172794092,
       "downCount": 8,
       "upCount": 92,
       "y": 1
     },
     {
-      "x": 1568172844000,
+      "x": 1568172816893,
+      "downCount": 0,
+      "upCount": 0,
+      "y": 1
+    },
+    {
+      "x": 1568172839694,
       "downCount": 7,
       "upCount": 93,
       "y": 1
     },
     {
-      "x": 1568172874000,
+      "x": 1568172862495,
       "downCount": 7,
       "upCount": 93,
       "y": 1
     },
     {
-      "x": 1568172904000,
+      "x": 1568172885296,
       "downCount": 7,
       "upCount": 93,
       "y": 1
     },
     {
-      "x": 1568172934000,
+      "x": 1568172908097,
+      "downCount": 0,
+      "upCount": 0,
+      "y": 1
+    },
+    {
+      "x": 1568172930898,
       "downCount": 7,
       "upCount": 93,
       "y": 1
     },
     {
-      "x": 1568172964000,
+      "x": 1568172953699,
       "downCount": 7,
       "upCount": 93,
       "y": 1
     },
     {
-      "x": 1568172994000,
+      "x": 1568172976500,
       "downCount": 8,
       "upCount": 92,
       "y": 1
     },
     {
-      "x": 1568173024000,
+      "x": 1568172999301,
+      "downCount": 0,
+      "upCount": 0,
+      "y": 1
+    },
+    {
+      "x": 1568173022102,
       "downCount": 7,
       "upCount": 93,
       "y": 1
     },
     {
-      "x": 1568173054000,
+      "x": 1568173044903,
       "downCount": 7,
       "upCount": 93,
       "y": 1
     },
     {
-      "x": 1568173084000,
+      "x": 1568173067704,
       "downCount": 7,
       "upCount": 93,
       "y": 1
     },
     {
-      "x": 1568173114000,
+      "x": 1568173090505,
+      "downCount": 0,
+      "upCount": 0,
+      "y": 1
+    },
+    {
+      "x": 1568173113306,
       "downCount": 7,
       "upCount": 93,
       "y": 1
     },
     {
-      "x": 1568173144000,
+      "x": 1568173136107,
       "downCount": 7,
       "upCount": 93,
       "y": 1
     },
     {
-      "x": 1568173174000,
+      "x": 1568173158908,
       "downCount": 8,
       "upCount": 92,
       "y": 1
     },
     {
-      "x": 1568173204000,
+      "x": 1568173181709,
       "downCount": 7,
       "upCount": 93,
       "y": 1
     },
     {
-      "x": 1568173234000,
+      "x": 1568173204510,
+      "downCount": 0,
+      "upCount": 0,
+      "y": 1
+    },
+    {
+      "x": 1568173227311,
       "downCount": 7,
       "upCount": 93,
       "y": 1