Tap web UI: Fix latency formatting (#1429)

* Nicely format tap latencies to be more readable
* Various whitespace cleanups

web/app/js/components/ErrorBanner.jsx

@@ -50,7 +50,6 @@ class ErrorMessage extends React.Component {
             <div><b>Error:</b> {status} {statusText}</div>
             { !error ? null : <div><b>Message:</b> {error}</div> }
             <div><b>URL:</b> {url}</div>
-
           </Col>
           <Col span={4}>
             <div className="dismiss" onClick={this.hideMessage} role="presentation">Dismiss X</div>

web/app/js/components/TapEventTable.jsx

@@ -1,6 +1,6 @@
 import _ from 'lodash';
 import BaseTable from './BaseTable.jsx';
-import { formatLatency } from './util/Utils.js';
+import { formatLatencySec } from './util/Utils.js';
 import React from 'react';
 import { Col, Icon, Row } from 'antd';
 
@@ -157,9 +157,8 @@ let tapColumns = filterOptions => [
   }
 ];
 
-let formatTapLatency = str => {
-  let millis = parseFloat(str.replace("s", "")) * 1000;
-  return formatLatency(millis);
+const formatTapLatency = str => {
+  return formatLatencySec(str.replace("s", ""));
 };
 
 // hide verbose information

web/app/js/components/util/ApiHelpers.jsx

@@ -5,7 +5,9 @@ import React from 'react';
 import 'whatwg-fetch';
 
 const checkFetchOk = resp => {
-  if (resp.ok) { return resp; }
+  if (resp.ok) {
+    return resp;
+  }
 
   return resp.json().then(error => {
     throw {
@@ -15,7 +17,6 @@ const checkFetchOk = resp => {
       error: error.error
     };
   });
-
 };
 
 // makeCancelable from @istarkov
@@ -115,7 +116,6 @@ const ApiHelpers = (pathPrefix, defaultMetricsWindow = '1m') => {
     });
   };
 
-
   // prefix all links in the app with `pathPrefix`
   class PrefixedLink extends React.Component {
     static defaultProps = {

web/app/js/components/util/Utils.js

@@ -11,23 +11,37 @@ export const rowGutter = 3 * baseWidth;
 * Number formatters
 */
 const successRateFormatter = d3.format(".2%");
-const latencySecFormatter = d3.format(".3f");
 const latencyFormatter = d3.format(",");
 
-export const formatLatency = m => {
+export const formatLatencyMs = m => {
   if (_.isNil(m)) {
     return "---";
-  } else if (m < 1000) {
-    return `${latencyFormatter(m)} ms`;
   } else {
-    return `${latencySecFormatter(m / 1000)} s`;
+    return `${formatLatencySec(m / 1000)}`;
+  }
+};
+
+const niceLatency = l => latencyFormatter(Math.round(l));
+
+export const formatLatencySec = latency => {
+  let s = parseFloat(latency);
+  if (_.isNil(s)) {
+    return "---";
+  } else if (s === parseFloat(0.0)) {
+    return "0 s";
+  } else if (s < 0.001) {
+    return `${niceLatency(s * 1000 * 1000)} µs`;
+  } else if (s < 1.0) {
+    return `${niceLatency(s * 1000)} ms`;
+  } else {
+    return `${niceLatency(s)} s`;
   }
 };
 
 export const metricToFormatter = {
   "REQUEST_RATE": m => _.isNil(m) ? "---" : styleNum(m, " RPS", true),
   "SUCCESS_RATE": m => _.isNil(m) ? "---" : successRateFormatter(m),
-  "LATENCY": formatLatency,
+  "LATENCY": formatLatencyMs,
   "UNTRUNCATED": m => styleNum(m, "", false)
 };
 

web/app/test/UtilsTest.js

@@ -1,5 +1,10 @@
 import { expect } from 'chai';
-import { metricToFormatter, styleNum, toClassName } from '../js/components/util/Utils.js';
+import {
+  formatLatencySec,
+  metricToFormatter,
+  styleNum,
+  toClassName
+} from '../js/components/util/Utils.js';
 
 // introduce some binary floating point rounding errors, like ya do
 function float(num) {
@@ -74,9 +79,9 @@ describe('Utils', () => {
     });
 
     it('formats latency greater than 1s as s', () => {
-      expect(metricToFormatter["LATENCY"](1000)).to.equal('1.000 s');
-      expect(metricToFormatter["LATENCY"](9999)).to.equal('9.999 s');
-      expect(metricToFormatter["LATENCY"](99999)).to.equal('99.999 s');
+      expect(metricToFormatter["LATENCY"](1000)).to.equal('1 s');
+      expect(metricToFormatter["LATENCY"](9999)).to.equal('10 s');
+      expect(metricToFormatter["LATENCY"](99999)).to.equal('100 s');
     });
 
     it('formats success rate', () => {
@@ -86,6 +91,16 @@ describe('Utils', () => {
       expect(metricToFormatter["SUCCESS_RATE"](0.9999)).to.equal('99.99%');
       expect(metricToFormatter["SUCCESS_RATE"](4)).to.equal('400.00%');
     });
+
+    it('formats latencies expressed as seconds into a more appropriate display unit', () => {
+      expect(formatLatencySec("0.002837700")).to.equal("3 ms");
+      expect(formatLatencySec("0.000")).to.equal("0 s");
+      expect(formatLatencySec("0.000000797")).to.equal("1 µs");
+      expect(formatLatencySec("0.000231910")).to.equal("232 µs");
+      expect(formatLatencySec("0.000988600")).to.equal("989 µs");
+      expect(formatLatencySec("0.005598200")).to.equal("6 ms");
+      expect(formatLatencySec("3.029409200")).to.equal("3 s");
+    });
   });
 
   describe('toClassName', () => {