[APM] Use rounded bucket sizes for transaction distribution

x-pack/legacy/plugins/apm/index.ts

@@ -68,7 +68,7 @@ export const apm: LegacyPluginInitializer = kibana => {
 
         // buckets
         minimumBucketSize: Joi.number().default(15),
-        bucketTargetCount: Joi.number().default(27)
+        bucketTargetCount: Joi.number().default(15)
       }).default();
     },
 

x-pack/legacy/plugins/apm/server/lib/helpers/round_nice.test.ts

@@ -0,0 +1,52 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+import { roundNice } from './round_nice';
+
+describe('roundNice', () => {
+  [
+    {
+      input: 11,
+      output: 10
+    },
+    {
+      input: 45,
+      output: 50
+    },
+    {
+      input: 55,
+      output: 50
+    },
+    {
+      input: 400,
+      output: 500
+    },
+    {
+      input: 1001,
+      output: 1000
+    },
+    {
+      input: 2000,
+      output: 1000
+    },
+    {
+      input: 4000,
+      output: 5000
+    },
+    {
+      input: 20000,
+      output: 10000
+    },
+    {
+      input: 80000,
+      output: 100000
+    }
+  ].forEach(({ input, output }) => {
+    it(`should convert ${input} to ${output}`, () => {
+      expect(roundNice(input)).toBe(output);
+    });
+  });
+});

x-pack/legacy/plugins/apm/server/lib/helpers/round_nice.ts

@@ -0,0 +1,11 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+export function roundNice(v: number) {
+  const five = Math.pow(10, Math.floor(Math.log10(v))) * 5;
+  const ten = Math.pow(10, Math.round(Math.log10(v)));
+  return Math.abs(five - v) < Math.abs(ten - v) ? five : ten;
+}

x-pack/legacy/plugins/apm/server/lib/transactions/distribution/get_buckets/fetcher.ts

@@ -23,11 +23,11 @@ export function bucketFetcher(
   transactionType: string,
   transactionId: string,
   traceId: string,
+  distributionMax: number,
   bucketSize: number,
   setup: Setup
 ) {
   const { start, end, uiFiltersES, client, config } = setup;
-  const bucketTargetCount = config.get<number>('xpack.apm.bucketTargetCount');
 
   const params = {
     index: config.get<string>('apm_oss.transactionIndices'),
@@ -58,7 +58,7 @@ export function bucketFetcher(
             min_doc_count: 0,
             extended_bounds: {
               min: 0,
-              max: bucketSize * bucketTargetCount
+              max: distributionMax
             }
           },
           aggs: {

x-pack/legacy/plugins/apm/server/lib/transactions/distribution/get_buckets/index.ts

@@ -14,6 +14,7 @@ export async function getBuckets(
   transactionType: string,
   transactionId: string,
   traceId: string,
+  distributionMax: number,
   bucketSize: number,
   setup: Setup
 ) {
@@ -23,6 +24,7 @@ export async function getBuckets(
     transactionType,
     transactionId,
     traceId,
+    distributionMax,
     bucketSize,
     setup
   );

x-pack/legacy/plugins/apm/server/lib/transactions/distribution/calculate_bucket_size.ts → x-pack/legacy/plugins/apm/server/lib/transactions/distribution/get_distribution_max.ts

@@ -13,7 +13,7 @@ import {
 } from '../../../../common/elasticsearch_fieldnames';
 import { Setup } from '../../helpers/setup_request';
 
-export async function calculateBucketSize(
+export async function getDistributionMax(
   serviceName: string,
   transactionName: string,
   transactionType: string,
@@ -56,10 +56,5 @@ export async function calculateBucketSize(
   };
 
   const resp = await client.search(params);
-
-  const minBucketSize: number = config.get('xpack.apm.minimumBucketSize');
-  const bucketTargetCount: number = config.get('xpack.apm.bucketTargetCount');
-  const max = resp.aggregations.stats.max;
-  const bucketSize = Math.floor(max / bucketTargetCount);
-  return bucketSize > minBucketSize ? bucketSize : minBucketSize;
+  return resp.aggregations.stats.max;
 }

x-pack/legacy/plugins/apm/server/lib/transactions/distribution/index.ts

@@ -6,8 +6,18 @@
 
 import { PromiseReturnType } from '../../../../typings/common';
 import { Setup } from '../../helpers/setup_request';
-import { calculateBucketSize } from './calculate_bucket_size';
 import { getBuckets } from './get_buckets';
+import { getDistributionMax } from './get_distribution_max';
+import { roundNice } from '../../helpers/round_nice';
+
+function getBucketSize(max: number, { config }: Setup) {
+  const minBucketSize: number = config.get<number>(
+    'xpack.apm.minimumBucketSize'
+  );
+  const bucketTargetCount = config.get<number>('xpack.apm.bucketTargetCount');
+  const bucketSize = max / bucketTargetCount;
+  return roundNice(bucketSize > minBucketSize ? bucketSize : minBucketSize);
+}
 
 export type TransactionDistributionAPIResponse = PromiseReturnType<
   typeof getTransactionDistribution
@@ -27,19 +37,25 @@ export async function getTransactionDistribution({
   traceId: string;
   setup: Setup;
 }) {
-  const bucketSize = await calculateBucketSize(
+  const distributionMax = await getDistributionMax(
     serviceName,
     transactionName,
     transactionType,
     setup
   );
 
+  if (distributionMax == null) {
+    return { totalHits: 0, buckets: [], bucketSize: 0 };
+  }
+
+  const bucketSize = getBucketSize(distributionMax, setup);
   const { buckets, totalHits } = await getBuckets(
     serviceName,
     transactionName,
     transactionType,
     transactionId,
     traceId,
+    distributionMax,
     bucketSize,
     setup
   );

x-pack/legacy/plugins/apm/typings/elasticsearch.ts

@@ -93,16 +93,16 @@ declare module 'elasticsearch' {
         };
         extended_stats: {
           count: number;
-          min: number;
-          max: number;
-          avg: number;
+          min: number | null;
+          max: number | null;
+          avg: number | null;
           sum: number;
-          sum_of_squares: number;
-          variance: number;
-          std_deviation: number;
+          sum_of_squares: number | null;
+          variance: number | null;
+          std_deviation: number | null;
           std_deviation_bounds: {
-            upper: number;
-            lower: number;
+            upper: number | null;
+            lower: number | null;
           };
         };
       }[AggregationType & keyof AggregationOption[AggregationName]];