From c47509fabcbe075372cf4d107604f29aedd935a0 Mon Sep 17 00:00:00 2001
From: Stanislav Chzhen <s.chzhen@adguard.com>
Date: Wed, 9 Aug 2023 14:33:52 +0300
Subject: [PATCH] Pull request 1928: 1453-stats-tests

Updates #1453.

Squashed commit of the following:

commit f08f68ef5493dad03d3eb120d886f2df1af28be6
Merge: b70b088af 54aee2272
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Tue Aug 8 19:04:06 2023 +0300

    Merge branch 'master' into 1453-stats-tests

commit b70b088af0fdc7d6d048d688160048bad1fceb12
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Thu Aug 3 19:32:04 2023 +0300

    stats: imp code

commit c341012ba61894c255c1868624be1cac0d26a6fa
Merge: a2ac8c34e 5eb3cd0f9
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Thu Aug 3 13:36:24 2023 +0300

    Merge branch 'master' into 1453-stats-tests

commit a2ac8c34ee32606ca5e259c3e2a47db0dd5858de
Author: Ildar Kamalov <ik@adguard.com>
Date:   Thu Aug 3 13:25:12 2023 +0300

    client: add top upstreams and average processing time tables

commit 11118947f9bf945be0b056f8475cf3b848c6e66e
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Tue Aug 1 17:24:57 2023 +0300

    stats: imp docs

commit 904cf81d02a1f327b9647fa7ad9e181cfabb68a4
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Mon Jul 31 17:34:06 2023 +0300

    stats: imp code

commit 34f0c96dd5865d1470385322a88842dd0b3d996d
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Mon Jul 31 15:43:46 2023 +0300

    all: imp docs

commit 2cb2d0d8bef3580f64bc25c414fe9b5ea6b9f997
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Fri Jul 28 17:24:31 2023 +0300

    all: imp code

commit 5251a899fecc21e50a0ba06042f96f5b404e196a
Merge: b6c2b12d4 300821a7f
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Thu Jul 27 20:34:39 2023 +0300

    Merge branch 'master' into 1453-stats-tests

commit b6c2b12d4425012efd73549c3a426735f3a677cd
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Thu Jul 27 20:32:18 2023 +0300

    stats: imp code

commit 5546b82a78326f9cc6d8c87df5083f8fc66a0178
Merge: 8a3d6b1b4 5f8fa006c
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Thu Jul 27 14:24:01 2023 +0300

    Merge branch 'master' into 1453-stats-tests

commit 8a3d6b1b49ce189f95adfa7406a34108e885e676
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Thu Jul 27 14:17:47 2023 +0300

    all: imp code

commit 2a48001e275e3cdcf70e13e1c9cebd4e502f3259
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Tue Jul 25 18:27:20 2023 +0300

    all: imp docs

commit 3dd21890175af32a3368378f7e013383f6d040ec
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Tue Jul 25 16:00:39 2023 +0300

    all: imp naming

commit 6124456fc3149b71f6bd58d35ecf24eb6cf40d5d
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Thu Jul 20 16:15:56 2023 +0300

    all: add upstreams avg processing time

commit 187ad0c77a81c9fd95c24e23141355db2e83e50d
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Tue Jul 18 16:42:19 2023 +0300

    all: add top upstreams
---
 CHANGELOG.md                                  |   3 +
 client/src/__locales/en.json                  |   4 +
 client/src/actions/stats.js                   |   2 +
 .../components/Dashboard/UpstreamAvgTime.js   |  79 +++++++
 .../components/Dashboard/UpstreamResponses.js |  76 +++++++
 client/src/components/Dashboard/index.js      |  97 +++++----
 client/src/components/ui/Cell.js              |  44 ++--
 client/src/reducers/stats.js                  |   4 +
 internal/dnsforward/stats.go                  |   8 +-
 internal/dnsforward/stats_test.go             |   4 +-
 internal/stats/http.go                        |   6 +
 internal/stats/stats.go                       |  30 +--
 internal/stats/stats_internal_test.go         |   4 +-
 internal/stats/stats_test.go                  |  52 +++--
 internal/stats/unit.go                        | 202 ++++++++++++++----
 internal/stats/unit_internal_test.go          | 177 +++++++++++++++
 openapi/CHANGELOG.md                          |  10 +
 openapi/openapi.yaml                          |  22 +-
 scripts/make/go-lint.sh                       |   2 +-
 19 files changed, 686 insertions(+), 140 deletions(-)
 create mode 100644 client/src/components/Dashboard/UpstreamAvgTime.js
 create mode 100644 client/src/components/Dashboard/UpstreamResponses.js
 create mode 100644 internal/stats/unit_internal_test.go

diff --git a/CHANGELOG.md b/CHANGELOG.md
index abdd864c..ba9d6854 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -25,6 +25,8 @@ NOTE: Add new changes BELOW THIS COMMENT.
 
 ### Added
 
+- Two new metrics showing total number of responses from each upstream DNS
+  server and their average processing time in the Web UI ([#1453]).
 - The ability to set the port for the `pprof` debug API, see configuration
   changes below.
 
@@ -59,6 +61,7 @@ In this release, the schema version has changed from 24 to 25.
 - Panic on shutting down while DNS requests are in process of filtering
   ([#5948]).
 
+[#1453]: https://github.com/AdguardTeam/AdGuardHome/issues/1453
 [#5948]: https://github.com/AdguardTeam/AdGuardHome/issues/5948
 
 <!--
diff --git a/client/src/__locales/en.json b/client/src/__locales/en.json
index 6b73220a..8d8ec15e 100644
--- a/client/src/__locales/en.json
+++ b/client/src/__locales/en.json
@@ -125,6 +125,8 @@
     "top_clients": "Top clients",
     "no_clients_found": "No clients found",
     "general_statistics": "General statistics",
+    "top_upstreams": "Top upstreams",
+    "no_upstreams_data_found": "No upstreams data found",
     "number_of_dns_query_days": "The number of DNS queries processed for the last {{count}} day",
     "number_of_dns_query_days_plural": "The number of DNS queries processed for the last {{count}} days",
     "number_of_dns_query_24_hours": "The number of DNS queries processed for the last 24 hours",
@@ -134,6 +136,7 @@
     "enforced_save_search": "Enforced safe search",
     "number_of_dns_query_to_safe_search": "The number of DNS requests to search engines for which Safe Search was enforced",
     "average_processing_time": "Average processing time",
+    "processing_time": "Processing time",
     "average_processing_time_hint": "Average time in milliseconds on processing a DNS request",
     "block_domain_use_filters_and_hosts": "Block domains using filters and hosts files",
     "filters_block_toggle_hint": "You can setup blocking rules in the <a>Filters</a> settings.",
@@ -158,6 +161,7 @@
     "upstream_dns_configured_in_file": "Configured in {{path}}",
     "test_upstream_btn": "Test upstreams",
     "upstreams": "Upstreams",
+    "upstream": "Upstream",
     "apply_btn": "Apply",
     "disabled_filtering_toast": "Disabled filtering",
     "enabled_filtering_toast": "Enabled filtering",
diff --git a/client/src/actions/stats.js b/client/src/actions/stats.js
index 0e5b416e..d0408b63 100644
--- a/client/src/actions/stats.js
+++ b/client/src/actions/stats.js
@@ -56,6 +56,8 @@ export const getStats = () => async (dispatch) => {
             top_clients: topClientsWithInfo,
             top_queried_domains: normalizeTopStats(stats.top_queried_domains),
             avg_processing_time: secondsToMilliseconds(stats.avg_processing_time),
+            top_upstreams_responses: normalizeTopStats(stats.top_upstreams_responses),
+            top_upstrems_avg_time: normalizeTopStats(stats.top_upstreams_avg_time),
         };
 
         dispatch(getStatsSuccess(normalizedStats));
diff --git a/client/src/components/Dashboard/UpstreamAvgTime.js b/client/src/components/Dashboard/UpstreamAvgTime.js
new file mode 100644
index 00000000..f56b5165
--- /dev/null
+++ b/client/src/components/Dashboard/UpstreamAvgTime.js
@@ -0,0 +1,79 @@
+import React from 'react';
+import ReactTable from 'react-table';
+import PropTypes from 'prop-types';
+import round from 'lodash/round';
+import { withTranslation, Trans } from 'react-i18next';
+
+import Card from '../ui/Card';
+import DomainCell from './DomainCell';
+
+const TimeCell = ({ value }) => {
+    if (!value) {
+        return '–';
+    }
+
+    const valueInMilliseconds = round(value * 1000);
+
+    return (
+        <div className="logs__row o-hidden">
+            <span className="logs__text logs__text--full" title={valueInMilliseconds}>
+                {valueInMilliseconds}&nbsp;ms
+            </span>
+        </div>
+    );
+};
+
+TimeCell.propTypes = {
+    value: PropTypes.oneOfType([
+        PropTypes.string,
+        PropTypes.number,
+    ]),
+};
+
+const UpstreamAvgTime = ({
+    t,
+    refreshButton,
+    topUpstreamsAvgTime,
+    subtitle,
+}) => (
+    <Card
+        title={t('average_processing_time')}
+        subtitle={subtitle}
+        bodyType="card-table"
+        refresh={refreshButton}
+    >
+        <ReactTable
+            data={topUpstreamsAvgTime.map(({ name: domain, count }) => ({
+                domain,
+                count,
+            }))}
+            columns={[
+                {
+                    Header: <Trans>upstream</Trans>,
+                    accessor: 'domain',
+                    Cell: DomainCell,
+                },
+                {
+                    Header: <Trans>processing_time</Trans>,
+                    accessor: 'count',
+                    maxWidth: 190,
+                    Cell: TimeCell,
+                },
+            ]}
+            showPagination={false}
+            noDataText={t('no_upstreams_data_found')}
+            minRows={6}
+            defaultPageSize={100}
+            className="-highlight card-table-overflow--limited stats__table"
+        />
+    </Card>
+);
+
+UpstreamAvgTime.propTypes = {
+    topUpstreamsAvgTime: PropTypes.array.isRequired,
+    refreshButton: PropTypes.node.isRequired,
+    subtitle: PropTypes.string.isRequired,
+    t: PropTypes.func.isRequired,
+};
+
+export default withTranslation()(UpstreamAvgTime);
diff --git a/client/src/components/Dashboard/UpstreamResponses.js b/client/src/components/Dashboard/UpstreamResponses.js
new file mode 100644
index 00000000..af98c3ba
--- /dev/null
+++ b/client/src/components/Dashboard/UpstreamResponses.js
@@ -0,0 +1,76 @@
+import React from 'react';
+import ReactTable from 'react-table';
+import PropTypes from 'prop-types';
+import { withTranslation, Trans } from 'react-i18next';
+
+import Card from '../ui/Card';
+import Cell from '../ui/Cell';
+import DomainCell from './DomainCell';
+
+import { getPercent } from '../../helpers/helpers';
+import { STATUS_COLORS } from '../../helpers/constants';
+
+const CountCell = (totalBlocked) => (
+    function cell(row) {
+        const { value } = row;
+        const percent = getPercent(totalBlocked, value);
+
+        return (
+            <Cell
+                value={value}
+                percent={percent}
+                color={STATUS_COLORS.green}
+            />
+        );
+    }
+);
+
+const UpstreamResponses = ({
+    t,
+    refreshButton,
+    topUpstreamsResponses,
+    dnsQueries,
+    subtitle,
+}) => (
+    <Card
+        title={t('top_upstreams')}
+        subtitle={subtitle}
+        bodyType="card-table"
+        refresh={refreshButton}
+    >
+        <ReactTable
+            data={topUpstreamsResponses.map(({ name: domain, count }) => ({
+                domain,
+                count,
+            }))}
+            columns={[
+                {
+                    Header: <Trans>upstream</Trans>,
+                    accessor: 'domain',
+                    Cell: DomainCell,
+                },
+                {
+                    Header: <Trans>requests_count</Trans>,
+                    accessor: 'count',
+                    maxWidth: 190,
+                    Cell: CountCell(dnsQueries),
+                },
+            ]}
+            showPagination={false}
+            noDataText={t('no_upstreams_data_found')}
+            minRows={6}
+            defaultPageSize={100}
+            className="-highlight card-table-overflow--limited stats__table"
+        />
+    </Card>
+);
+
+UpstreamResponses.propTypes = {
+    topUpstreamsResponses: PropTypes.array.isRequired,
+    dnsQueries: PropTypes.number.isRequired,
+    refreshButton: PropTypes.node.isRequired,
+    subtitle: PropTypes.string.isRequired,
+    t: PropTypes.func.isRequired,
+};
+
+export default withTranslation()(UpstreamResponses);
diff --git a/client/src/components/Dashboard/index.js b/client/src/components/Dashboard/index.js
index 54354979..efbe5865 100644
--- a/client/src/components/Dashboard/index.js
+++ b/client/src/components/Dashboard/index.js
@@ -21,6 +21,8 @@ import PageTitle from '../ui/PageTitle';
 import Loading from '../ui/Loading';
 import './Dashboard.css';
 import Dropdown from '../ui/Dropdown';
+import UpstreamResponses from './UpstreamResponses';
+import UpstreamAvgTime from './UpstreamAvgTime';
 
 const Dashboard = ({
     getAccessList,
@@ -136,12 +138,12 @@ const Dashboard = ({
         <PageTitle title={t('dashboard')} containerClass="page-title--dashboard">
             <div className="page-title__protection">
                 <button
-                        type="button"
-                        className={buttonClass}
-                        onClick={() => {
-                            toggleProtection(protectionEnabled);
-                        }}
-                        disabled={processingProtection}
+                    type="button"
+                    className={buttonClass}
+                    onClick={() => {
+                        toggleProtection(protectionEnabled);
+                    }}
+                    disabled={processingProtection}
                 >
                     {protectionDisabledDuration
                         ? `${t('enable_protection_timer')} ${getRemaningTimeText(protectionDisabledDuration)}`
@@ -160,9 +162,9 @@ const Dashboard = ({
                 </Dropdown>}
             </div>
             <button
-                    type="button"
-                    className="btn btn-outline-primary btn-sm"
-                    onClick={getAllStats}
+                type="button"
+                className="btn btn-outline-primary btn-sm"
+                onClick={getAllStats}
             >
                 <Trans>refresh_statics</Trans>
             </button>
@@ -185,53 +187,68 @@ const Dashboard = ({
                     </div>
                 )}
                 <Statistics
-                        interval={msToDays(stats.interval)}
-                        dnsQueries={stats.dnsQueries}
-                        blockedFiltering={stats.blockedFiltering}
-                        replacedSafebrowsing={stats.replacedSafebrowsing}
-                        replacedParental={stats.replacedParental}
-                        numDnsQueries={stats.numDnsQueries}
-                        numBlockedFiltering={stats.numBlockedFiltering}
-                        numReplacedSafebrowsing={stats.numReplacedSafebrowsing}
-                        numReplacedParental={stats.numReplacedParental}
-                        refreshButton={refreshButton}
+                    interval={msToDays(stats.interval)}
+                    dnsQueries={stats.dnsQueries}
+                    blockedFiltering={stats.blockedFiltering}
+                    replacedSafebrowsing={stats.replacedSafebrowsing}
+                    replacedParental={stats.replacedParental}
+                    numDnsQueries={stats.numDnsQueries}
+                    numBlockedFiltering={stats.numBlockedFiltering}
+                    numReplacedSafebrowsing={stats.numReplacedSafebrowsing}
+                    numReplacedParental={stats.numReplacedParental}
+                    refreshButton={refreshButton}
                 />
             </div>
             <div className="col-lg-6">
                 <Counters
-                        subtitle={subtitle}
-                        refreshButton={refreshButton}
+                    subtitle={subtitle}
+                    refreshButton={refreshButton}
                 />
             </div>
             <div className="col-lg-6">
                 <Clients
-                        subtitle={subtitle}
-                        dnsQueries={stats.numDnsQueries}
-                        topClients={stats.topClients}
-                        clients={dashboard.clients}
-                        autoClients={dashboard.autoClients}
-                        refreshButton={refreshButton}
-                        processingAccessSet={access.processingSet}
-                        disallowedClients={access.disallowed_clients}
+                    subtitle={subtitle}
+                    dnsQueries={stats.numDnsQueries}
+                    topClients={stats.topClients}
+                    clients={dashboard.clients}
+                    autoClients={dashboard.autoClients}
+                    refreshButton={refreshButton}
+                    processingAccessSet={access.processingSet}
+                    disallowedClients={access.disallowed_clients}
                 />
             </div>
             <div className="col-lg-6">
                 <QueriedDomains
-                        subtitle={subtitle}
-                        dnsQueries={stats.numDnsQueries}
-                        topQueriedDomains={stats.topQueriedDomains}
-                        refreshButton={refreshButton}
+                    subtitle={subtitle}
+                    dnsQueries={stats.numDnsQueries}
+                    topQueriedDomains={stats.topQueriedDomains}
+                    refreshButton={refreshButton}
                 />
             </div>
             <div className="col-lg-6">
                 <BlockedDomains
-                        subtitle={subtitle}
-                        topBlockedDomains={stats.topBlockedDomains}
-                        blockedFiltering={stats.numBlockedFiltering}
-                        replacedSafebrowsing={stats.numReplacedSafebrowsing}
-                        replacedSafesearch={stats.numReplacedSafesearch}
-                        replacedParental={stats.numReplacedParental}
-                        refreshButton={refreshButton}
+                    subtitle={subtitle}
+                    topBlockedDomains={stats.topBlockedDomains}
+                    blockedFiltering={stats.numBlockedFiltering}
+                    replacedSafebrowsing={stats.numReplacedSafebrowsing}
+                    replacedSafesearch={stats.numReplacedSafesearch}
+                    replacedParental={stats.numReplacedParental}
+                    refreshButton={refreshButton}
+                />
+            </div>
+            <div className="col-lg-6">
+                <UpstreamResponses
+                    subtitle={subtitle}
+                    dnsQueries={stats.numDnsQueries}
+                    topUpstreamsResponses={stats.topUpstreamsResponses}
+                    refreshButton={refreshButton}
+                />
+            </div>
+            <div className="col-lg-6">
+                <UpstreamAvgTime
+                    subtitle={subtitle}
+                    topUpstreamsAvgTime={stats.topUpstreamsAvgTime}
+                    refreshButton={refreshButton}
                 />
             </div>
         </div>}
diff --git a/client/src/components/ui/Cell.js b/client/src/components/ui/Cell.js
index 9ede87d5..4fb850d6 100644
--- a/client/src/components/ui/Cell.js
+++ b/client/src/components/ui/Cell.js
@@ -1,25 +1,39 @@
 import React from 'react';
 import PropTypes from 'prop-types';
+
 import LogsSearchLink from './LogsSearchLink';
 import { formatNumber } from '../../helpers/helpers';
 
 const Cell = ({
-    value, percent, color, search,
-}) => <div className="stats__row">
-    <div className="stats__row-value mb-1">
-        <strong><LogsSearchLink search={search}>{formatNumber(value)}</LogsSearchLink></strong>
-        <small className="ml-3 text-muted">{percent}%</small>
+    value,
+    percent,
+    color,
+    search,
+}) => (
+    <div className="stats__row">
+        <div className="stats__row-value mb-1">
+            <strong>
+                {search ? (
+                    <LogsSearchLink search={search}>
+                        {formatNumber(value)}
+                    </LogsSearchLink>
+                ) : (
+                    formatNumber(value)
+                )}
+            </strong>
+            <small className="ml-3 text-muted">{percent}%</small>
+        </div>
+        <div className="progress progress-xs">
+            <div
+                className="progress-bar"
+                style={{
+                    width: `${percent}%`,
+                    backgroundColor: color,
+                }}
+            />
+        </div>
     </div>
-    <div className="progress progress-xs">
-        <div
-            className="progress-bar"
-            style={{
-                width: `${percent}%`,
-                backgroundColor: color,
-            }}
-        />
-    </div>
-</div>;
+);
 
 Cell.propTypes = {
     value: PropTypes.number.isRequired,
diff --git a/client/src/reducers/stats.js b/client/src/reducers/stats.js
index a1c63e14..a7baeabe 100644
--- a/client/src/reducers/stats.js
+++ b/client/src/reducers/stats.js
@@ -58,6 +58,8 @@ const stats = handleActions(
                 num_replaced_safebrowsing: numReplacedSafebrowsing,
                 num_replaced_safesearch: numReplacedSafesearch,
                 avg_processing_time: avgProcessingTime,
+                top_upstreams_responses: topUpstreamsResponses,
+                top_upstrems_avg_time: topUpstreamsAvgTime,
             } = payload;
 
             const newState = {
@@ -77,6 +79,8 @@ const stats = handleActions(
                 numReplacedSafebrowsing,
                 numReplacedSafesearch,
                 avgProcessingTime,
+                topUpstreamsResponses,
+                topUpstreamsAvgTime,
             };
 
             return newState;
diff --git a/internal/dnsforward/stats.go b/internal/dnsforward/stats.go
index b142c86f..18cb9268 100644
--- a/internal/dnsforward/stats.go
+++ b/internal/dnsforward/stats.go
@@ -139,10 +139,14 @@ func (s *Server) updateStats(
 	clientIP string,
 ) {
 	pctx := ctx.proxyCtx
-	e := stats.Entry{
+	e := &stats.Entry{
 		Domain: aghnet.NormalizeDomain(pctx.Req.Question[0].Name),
 		Result: stats.RNotFiltered,
-		Time:   uint32(elapsed / 1000),
+		Time:   elapsed,
+	}
+
+	if pctx.Upstream != nil {
+		e.Upstream = pctx.Upstream.Address()
 	}
 
 	if clientID := ctx.clientID; clientID != "" {
diff --git a/internal/dnsforward/stats_test.go b/internal/dnsforward/stats_test.go
index 49cfb68a..0b8cae2e 100644
--- a/internal/dnsforward/stats_test.go
+++ b/internal/dnsforward/stats_test.go
@@ -41,11 +41,11 @@ type testStats struct {
 	// without actually implementing all methods.
 	stats.Interface
 
-	lastEntry stats.Entry
+	lastEntry *stats.Entry
 }
 
 // Update implements the [stats.Interface] interface for *testStats.
-func (l *testStats) Update(e stats.Entry) {
+func (l *testStats) Update(e *stats.Entry) {
 	if e.Domain == "" {
 		return
 	}
diff --git a/internal/stats/http.go b/internal/stats/http.go
index 38f6be55..d6d37b0f 100644
--- a/internal/stats/http.go
+++ b/internal/stats/http.go
@@ -19,6 +19,9 @@ import (
 // The key is either a client's address or a requested address.
 type topAddrs = map[string]uint64
 
+// topAddrsFloat is like [topAddrs] but the value is float64 number.
+type topAddrsFloat = map[string]float64
+
 // StatsResp is a response to the GET /control/stats.
 type StatsResp struct {
 	TimeUnits string `json:"time_units"`
@@ -27,6 +30,9 @@ type StatsResp struct {
 	TopClients []topAddrs `json:"top_clients"`
 	TopBlocked []topAddrs `json:"top_blocked_domains"`
 
+	TopUpstreamsResponses []topAddrs      `json:"top_upstreams_responses"`
+	TopUpstreamsAvgTime   []topAddrsFloat `json:"top_upstreams_avg_time"`
+
 	DNSQueries []uint64 `json:"dns_queries"`
 
 	BlockedFiltering     []uint64 `json:"blocked_filtering"`
diff --git a/internal/stats/stats.go b/internal/stats/stats.go
index 851aea98..614b2ca8 100644
--- a/internal/stats/stats.go
+++ b/internal/stats/stats.go
@@ -5,7 +5,6 @@ package stats
 import (
 	"fmt"
 	"io"
-	"net"
 	"net/netip"
 	"os"
 	"sync"
@@ -80,7 +79,7 @@ type Interface interface {
 	io.Closer
 
 	// Update collects the incoming statistics data.
-	Update(e Entry)
+	Update(e *Entry)
 
 	// GetTopClientIP returns at most limit IP addresses corresponding to the
 	// clients with the most number of requests.
@@ -225,7 +224,7 @@ func (s *StatsCtx) Start() {
 	go s.periodicFlush()
 }
 
-// Close implements the io.Closer interface for *StatsCtx.
+// Close implements the [io.Closer] interface for *StatsCtx.
 func (s *StatsCtx) Close() (err error) {
 	defer func() { err = errors.Annotate(err, "stats: closing: %w") }()
 
@@ -256,8 +255,9 @@ func (s *StatsCtx) Close() (err error) {
 	return udb.flushUnitToDB(tx, s.curr.id)
 }
 
-// Update implements the Interface interface for *StatsCtx.
-func (s *StatsCtx) Update(e Entry) {
+// Update implements the [Interface] interface for *StatsCtx.  e must not be
+// nil.
+func (s *StatsCtx) Update(e *Entry) {
 	s.confMu.Lock()
 	defer s.confMu.Unlock()
 
@@ -265,8 +265,9 @@ func (s *StatsCtx) Update(e Entry) {
 		return
 	}
 
-	if e.Result == 0 || e.Result >= resultLast || e.Domain == "" || e.Client == "" {
-		log.Debug("stats: malformed entry")
+	err := e.validate()
+	if err != nil {
+		log.Debug("stats: updating: validating entry: %s", err)
 
 		return
 	}
@@ -280,15 +281,10 @@ func (s *StatsCtx) Update(e Entry) {
 		return
 	}
 
-	clientID := e.Client
-	if ip := net.ParseIP(clientID); ip != nil {
-		clientID = ip.String()
-	}
-
-	s.curr.add(e.Result, e.Domain, clientID, uint64(e.Time))
+	s.curr.add(e)
 }
 
-// WriteDiskConfig implements the Interface interface for *StatsCtx.
+// WriteDiskConfig implements the [Interface] interface for *StatsCtx.
 func (s *StatsCtx) WriteDiskConfig(dc *Config) {
 	s.confMu.RLock()
 	defer s.confMu.RUnlock()
@@ -412,6 +408,12 @@ func (s *StatsCtx) flush() (cont bool, sleepFor time.Duration) {
 		return true, time.Second
 	}
 
+	return s.flushDB(id, limit, ptr)
+}
+
+// flushDB flushes the unit to the database.  confMu and currMu are expected to
+// be locked.
+func (s *StatsCtx) flushDB(id, limit uint32, ptr *unit) (cont bool, sleepFor time.Duration) {
 	db := s.db.Load()
 	if db == nil {
 		return true, 0
diff --git a/internal/stats/stats_internal_test.go b/internal/stats/stats_internal_test.go
index 9a173f65..43d79949 100644
--- a/internal/stats/stats_internal_test.go
+++ b/internal/stats/stats_internal_test.go
@@ -50,11 +50,11 @@ func TestStats_races(t *testing.T) {
 	testutil.CleanupAndRequireSuccess(t, s.Close)
 
 	writeFunc := func(start, fin *sync.WaitGroup, waitCh <-chan unit, i int) {
-		e := Entry{
+		e := &Entry{
 			Domain: fmt.Sprintf("example-%d.org", i),
 			Client: fmt.Sprintf("client_%d", i),
 			Result: Result(i)%(resultLast-1) + 1,
-			Time:   uint32(time.Since(startTime).Milliseconds()),
+			Time:   time.Since(startTime),
 		}
 
 		start.Done()
diff --git a/internal/stats/stats_test.go b/internal/stats/stats_test.go
index 37b82163..bcfdc643 100644
--- a/internal/stats/stats_test.go
+++ b/internal/stats/stats_test.go
@@ -9,6 +9,7 @@ import (
 	"path/filepath"
 	"sync/atomic"
 	"testing"
+	"time"
 
 	"github.com/AdguardTeam/AdGuardHome/internal/stats"
 	"github.com/AdguardTeam/golibs/netutil"
@@ -72,24 +73,29 @@ func TestStats(t *testing.T) {
 
 	t.Run("data", func(t *testing.T) {
 		const reqDomain = "domain"
+		const respUpstream = "upstream"
 
-		entries := []stats.Entry{{
-			Domain: reqDomain,
-			Client: cliIPStr,
-			Result: stats.RFiltered,
-			Time:   123456,
+		entries := []*stats.Entry{{
+			Domain:   reqDomain,
+			Client:   cliIPStr,
+			Result:   stats.RFiltered,
+			Time:     time.Microsecond * 123456,
+			Upstream: respUpstream,
 		}, {
-			Domain: reqDomain,
-			Client: cliIPStr,
-			Result: stats.RNotFiltered,
-			Time:   123456,
+			Domain:   reqDomain,
+			Client:   cliIPStr,
+			Result:   stats.RNotFiltered,
+			Time:     time.Microsecond * 123456,
+			Upstream: respUpstream,
 		}}
 
 		wantData := &stats.StatsResp{
-			TimeUnits:  "hours",
-			TopQueried: []map[string]uint64{0: {reqDomain: 1}},
-			TopClients: []map[string]uint64{0: {cliIPStr: 2}},
-			TopBlocked: []map[string]uint64{0: {reqDomain: 1}},
+			TimeUnits:             "hours",
+			TopQueried:            []map[string]uint64{0: {reqDomain: 1}},
+			TopClients:            []map[string]uint64{0: {cliIPStr: 2}},
+			TopBlocked:            []map[string]uint64{0: {reqDomain: 1}},
+			TopUpstreamsResponses: []map[string]uint64{0: {respUpstream: 2}},
+			TopUpstreamsAvgTime:   []map[string]float64{0: {respUpstream: 0.123456}},
 			DNSQueries: []uint64{
 				0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 				0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2,
@@ -138,14 +144,16 @@ func TestStats(t *testing.T) {
 
 		_24zeroes := [24]uint64{}
 		emptyData := &stats.StatsResp{
-			TimeUnits:            "hours",
-			TopQueried:           []map[string]uint64{},
-			TopClients:           []map[string]uint64{},
-			TopBlocked:           []map[string]uint64{},
-			DNSQueries:           _24zeroes[:],
-			BlockedFiltering:     _24zeroes[:],
-			ReplacedSafebrowsing: _24zeroes[:],
-			ReplacedParental:     _24zeroes[:],
+			TimeUnits:             "hours",
+			TopQueried:            []map[string]uint64{},
+			TopClients:            []map[string]uint64{},
+			TopBlocked:            []map[string]uint64{},
+			TopUpstreamsResponses: []map[string]uint64{},
+			TopUpstreamsAvgTime:   []map[string]float64{},
+			DNSQueries:            _24zeroes[:],
+			BlockedFiltering:      _24zeroes[:],
+			ReplacedSafebrowsing:  _24zeroes[:],
+			ReplacedParental:      _24zeroes[:],
 		}
 
 		req = httptest.NewRequest(http.MethodGet, "/control/stats", nil)
@@ -187,7 +195,7 @@ func TestLargeNumbers(t *testing.T) {
 
 		for i := 0; i < cliNumPerHour; i++ {
 			ip := net.IP{127, 0, byte((i & 0xff00) >> 8), byte(i & 0xff)}
-			e := stats.Entry{
+			e := &stats.Entry{
 				Domain: fmt.Sprintf("domain%d.hour%d", i, h),
 				Client: ip.String(),
 				Result: stats.RNotFiltered,
diff --git a/internal/stats/unit.go b/internal/stats/unit.go
index 8de01aa0..e135fe84 100644
--- a/internal/stats/unit.go
+++ b/internal/stats/unit.go
@@ -11,17 +11,19 @@ import (
 	"github.com/AdguardTeam/golibs/log"
 	"github.com/AdguardTeam/golibs/stringutil"
 	"go.etcd.io/bbolt"
+	"golang.org/x/exp/maps"
 	"golang.org/x/exp/slices"
 )
 
-// TODO(a.garipov): Rewrite all of this.  Add proper error handling and
-// inspection.  Improve logging.  Decrease complexity.
-
 const (
 	// maxDomains is the max number of top domains to return.
 	maxDomains = 100
+
 	// maxClients is the max number of top clients to return.
 	maxClients = 100
+
+	// maxUpstreams is the max number of top upstreams to return.
+	maxUpstreams = 100
 )
 
 // UnitIDGenFunc is the signature of a function that generates a unique ID for
@@ -63,11 +65,30 @@ type Entry struct {
 	// Domain is the domain name requested.
 	Domain string
 
+	// Upstream is the upstream DNS server.
+	Upstream string
+
 	// Result is the result of processing the request.
 	Result Result
 
-	// Time is the duration of the request processing in milliseconds.
-	Time uint32
+	// Time is the duration of the request processing.
+	Time time.Duration
+}
+
+// validate returs an error if entry is not valid.
+func (e *Entry) validate() (err error) {
+	switch {
+	case e.Result == 0:
+		return errors.Error("result code is not set")
+	case e.Result >= resultLast:
+		return fmt.Errorf("unknown result code %d", e.Result)
+	case e.Domain == "":
+		return errors.Error("domain is empty")
+	case e.Client == "":
+		return errors.Error("client is empty")
+	default:
+		return nil
+	}
 }
 
 // unit collects the statistics data for a specific period of time.
@@ -82,6 +103,13 @@ type unit struct {
 	// clients stores the number of requests from each client.
 	clients map[string]uint64
 
+	// upstreamsResponses stores the number of responses from each upstream.
+	upstreamsResponses map[string]uint64
+
+	// upstreamsTimeSum stores the sum of processing time in microseconds of
+	// responses from each upstream.
+	upstreamsTimeSum map[string]uint64
+
 	// nResult stores the number of requests grouped by it's result.
 	nResult []uint64
 
@@ -95,7 +123,7 @@ type unit struct {
 	// nTotal stores the total number of requests.
 	nTotal uint64
 
-	// timeSum stores the sum of processing time in milliseconds of each request
+	// timeSum stores the sum of processing time in microseconds of each request
 	// written by the unit.
 	timeSum uint64
 }
@@ -103,11 +131,13 @@ type unit struct {
 // newUnit allocates the new *unit.
 func newUnit(id uint32) (u *unit) {
 	return &unit{
-		domains:        map[string]uint64{},
-		blockedDomains: map[string]uint64{},
-		clients:        map[string]uint64{},
-		nResult:        make([]uint64, resultLast),
-		id:             id,
+		domains:            map[string]uint64{},
+		blockedDomains:     map[string]uint64{},
+		clients:            map[string]uint64{},
+		upstreamsResponses: map[string]uint64{},
+		upstreamsTimeSum:   map[string]uint64{},
+		nResult:            make([]uint64, resultLast),
+		id:                 id,
 	}
 }
 
@@ -135,10 +165,17 @@ type unitDB struct {
 	// Clients is the number of requests from each client.
 	Clients []countPair
 
+	// UpstreamsResponses is the number of responses from each upstream.
+	UpstreamsResponses []countPair
+
+	// UpstreamsTimeSum is the sum of processing time in microseconds of
+	// responses from each upstream.
+	UpstreamsTimeSum []countPair
+
 	// NTotal is the total number of requests.
 	NTotal uint64
 
-	// TimeAvg is the average of processing times in milliseconds of all the
+	// TimeAvg is the average of processing times in microseconds of all the
 	// requests in the unit.
 	TimeAvg uint32
 }
@@ -218,12 +255,14 @@ func (u *unit) serialize() (udb *unitDB) {
 	}
 
 	return &unitDB{
-		NTotal:         u.nTotal,
-		NResult:        append([]uint64{}, u.nResult...),
-		Domains:        convertMapToSlice(u.domains, maxDomains),
-		BlockedDomains: convertMapToSlice(u.blockedDomains, maxDomains),
-		Clients:        convertMapToSlice(u.clients, maxClients),
-		TimeAvg:        timeAvg,
+		NTotal:             u.nTotal,
+		NResult:            append([]uint64{}, u.nResult...),
+		Domains:            convertMapToSlice(u.domains, maxDomains),
+		BlockedDomains:     convertMapToSlice(u.blockedDomains, maxDomains),
+		Clients:            convertMapToSlice(u.clients, maxClients),
+		UpstreamsResponses: convertMapToSlice(u.upstreamsResponses, maxUpstreams),
+		UpstreamsTimeSum:   convertMapToSlice(u.upstreamsTimeSum, maxUpstreams),
+		TimeAvg:            timeAvg,
 	}
 }
 
@@ -262,21 +301,29 @@ func (u *unit) deserialize(udb *unitDB) {
 	u.domains = convertSliceToMap(udb.Domains)
 	u.blockedDomains = convertSliceToMap(udb.BlockedDomains)
 	u.clients = convertSliceToMap(udb.Clients)
+	u.upstreamsResponses = convertSliceToMap(udb.UpstreamsResponses)
+	u.upstreamsTimeSum = convertSliceToMap(udb.UpstreamsTimeSum)
 	u.timeSum = uint64(udb.TimeAvg) * udb.NTotal
 }
 
 // add adds new data to u.  It's safe for concurrent use.
-func (u *unit) add(res Result, domain, cli string, dur uint64) {
-	u.nResult[res]++
-	if res == RNotFiltered {
-		u.domains[domain]++
+func (u *unit) add(e *Entry) {
+	u.nResult[e.Result]++
+	if e.Result == RNotFiltered {
+		u.domains[e.Domain]++
 	} else {
-		u.blockedDomains[domain]++
+		u.blockedDomains[e.Domain]++
 	}
 
-	u.clients[cli]++
-	u.timeSum += dur
+	u.clients[e.Client]++
+	t := uint64(e.Time.Microseconds())
+	u.timeSum += t
 	u.nTotal++
+
+	if e.Upstream != "" {
+		u.upstreamsResponses[e.Upstream]++
+		u.upstreamsTimeSum[e.Upstream] += t
+	}
 }
 
 // flushUnitToDB puts udb to the database at id.
@@ -390,9 +437,11 @@ func (s *StatsCtx) getData(limit uint32) (StatsResp, bool) {
 		return StatsResp{
 			TimeUnits: "days",
 
-			TopBlocked: []topAddrs{},
-			TopClients: []topAddrs{},
-			TopQueried: []topAddrs{},
+			TopBlocked:            []topAddrs{},
+			TopClients:            []topAddrs{},
+			TopQueried:            []topAddrs{},
+			TopUpstreamsResponses: []topAddrs{},
+			TopUpstreamsAvgTime:   []topAddrsFloat{},
 
 			BlockedFiltering:     []uint64{},
 			DNSQueries:           []uint64{},
@@ -416,21 +465,35 @@ func (s *StatsCtx) getData(limit uint32) (StatsResp, bool) {
 		log.Fatalf("len(dnsQueries) != limit: %d %d", len(dnsQueries), limit)
 	}
 
+	return s.dataFromUnits(units, dnsQueries, firstID, timeUnit), true
+}
+
+// dataFromUnits collects and returns the statistics data.
+func (s *StatsCtx) dataFromUnits(
+	units []*unitDB,
+	dnsQueries []uint64,
+	firstID uint32,
+	timeUnit TimeUnit,
+) (resp StatsResp) {
+	topUpstreamsResponses, topUpstreamsAvgTime := topUpstreamsPairs(units)
+
 	data := StatsResp{
-		DNSQueries:           dnsQueries,
-		BlockedFiltering:     statsCollector(units, firstID, timeUnit, func(u *unitDB) (num uint64) { return u.NResult[RFiltered] }),
-		ReplacedSafebrowsing: statsCollector(units, firstID, timeUnit, func(u *unitDB) (num uint64) { return u.NResult[RSafeBrowsing] }),
-		ReplacedParental:     statsCollector(units, firstID, timeUnit, func(u *unitDB) (num uint64) { return u.NResult[RParental] }),
-		TopQueried:           topsCollector(units, maxDomains, s.ignored, func(u *unitDB) (pairs []countPair) { return u.Domains }),
-		TopBlocked:           topsCollector(units, maxDomains, s.ignored, func(u *unitDB) (pairs []countPair) { return u.BlockedDomains }),
-		TopClients:           topsCollector(units, maxClients, nil, topClientPairs(s)),
+		DNSQueries:            dnsQueries,
+		BlockedFiltering:      statsCollector(units, firstID, timeUnit, func(u *unitDB) (num uint64) { return u.NResult[RFiltered] }),
+		ReplacedSafebrowsing:  statsCollector(units, firstID, timeUnit, func(u *unitDB) (num uint64) { return u.NResult[RSafeBrowsing] }),
+		ReplacedParental:      statsCollector(units, firstID, timeUnit, func(u *unitDB) (num uint64) { return u.NResult[RParental] }),
+		TopQueried:            topsCollector(units, maxDomains, s.ignored, func(u *unitDB) (pairs []countPair) { return u.Domains }),
+		TopBlocked:            topsCollector(units, maxDomains, s.ignored, func(u *unitDB) (pairs []countPair) { return u.BlockedDomains }),
+		TopUpstreamsResponses: topUpstreamsResponses,
+		TopUpstreamsAvgTime:   topUpstreamsAvgTime,
+		TopClients:            topsCollector(units, maxClients, nil, topClientPairs(s)),
 	}
 
 	// Total counters:
 	sum := unitDB{
 		NResult: make([]uint64, resultLast),
 	}
-	timeN := 0
+	var timeN uint32
 	for _, u := range units {
 		sum.NTotal += u.NTotal
 		sum.TimeAvg += u.TimeAvg
@@ -450,7 +513,7 @@ func (s *StatsCtx) getData(limit uint32) (StatsResp, bool) {
 	data.NumReplacedParental = sum.NResult[RParental]
 
 	if timeN != 0 {
-		data.AvgProcessingTime = float64(sum.TimeAvg/uint32(timeN)) / 1000000
+		data.AvgProcessingTime = microsecondsToSeconds(float64(sum.TimeAvg / timeN))
 	}
 
 	data.TimeUnits = "hours"
@@ -458,7 +521,7 @@ func (s *StatsCtx) getData(limit uint32) (StatsResp, bool) {
 		data.TimeUnits = "days"
 	}
 
-	return data, true
+	return data
 }
 
 func topClientPairs(s *StatsCtx) (pg pairsGetter) {
@@ -474,3 +537,66 @@ func topClientPairs(s *StatsCtx) (pg pairsGetter) {
 		return clients
 	}
 }
+
+// topUpstreamsPairs returns sorted lists of number of total responses and the
+// average of processing time for each upstream.
+func topUpstreamsPairs(
+	units []*unitDB,
+) (topUpstreamsResponses []topAddrs, topUpstreamsAvgTime []topAddrsFloat) {
+	upstreamsResponses := topAddrs{}
+	upstreamsTimeSum := topAddrsFloat{}
+
+	for _, u := range units {
+		for _, cp := range u.UpstreamsResponses {
+			upstreamsResponses[cp.Name] += cp.Count
+		}
+
+		for _, cp := range u.UpstreamsTimeSum {
+			upstreamsTimeSum[cp.Name] += float64(cp.Count)
+		}
+	}
+
+	upstreamsAvgTime := topAddrsFloat{}
+
+	for u, n := range upstreamsResponses {
+		total := upstreamsTimeSum[u]
+
+		if total != 0 {
+			upstreamsAvgTime[u] = microsecondsToSeconds(total / float64(n))
+		}
+	}
+
+	upstreamsPairs := convertMapToSlice(upstreamsResponses, maxUpstreams)
+	topUpstreamsResponses = convertTopSlice(upstreamsPairs)
+
+	return topUpstreamsResponses, prepareTopUpstreamsAvgTime(upstreamsAvgTime)
+}
+
+// microsecondsToSeconds converts microseconds to seconds.
+//
+// NOTE:  Frontend expects time duration in seconds as floating-point number
+// with double precision.
+func microsecondsToSeconds(n float64) (r float64) {
+	const micro = 1e-6
+
+	return n * micro
+}
+
+// prepareTopUpstreamsAvgTime returns sorted list of average processing times
+// of the DNS requests from each upstream.
+func prepareTopUpstreamsAvgTime(
+	upstreamsAvgTime topAddrsFloat,
+) (topUpstreamsAvgTime []topAddrsFloat) {
+	keys := maps.Keys(upstreamsAvgTime)
+
+	slices.SortFunc(keys, func(a, b string) (sortsBefore bool) {
+		return upstreamsAvgTime[a] > upstreamsAvgTime[b]
+	})
+
+	topUpstreamsAvgTime = make([]topAddrsFloat, 0, len(upstreamsAvgTime))
+	for _, k := range keys {
+		topUpstreamsAvgTime = append(topUpstreamsAvgTime, topAddrsFloat{k: upstreamsAvgTime[k]})
+	}
+
+	return topUpstreamsAvgTime
+}
diff --git a/internal/stats/unit_internal_test.go b/internal/stats/unit_internal_test.go
new file mode 100644
index 00000000..ea3bff50
--- /dev/null
+++ b/internal/stats/unit_internal_test.go
@@ -0,0 +1,177 @@
+package stats
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestUnit_Deserialize(t *testing.T) {
+	testCases := []struct {
+		db   *unitDB
+		name string
+		want unit
+	}{{
+		name: "empty",
+		want: unit{
+			domains:            map[string]uint64{},
+			blockedDomains:     map[string]uint64{},
+			clients:            map[string]uint64{},
+			nResult:            []uint64{0, 0, 0, 0, 0, 0},
+			id:                 0,
+			nTotal:             0,
+			timeSum:            0,
+			upstreamsResponses: map[string]uint64{},
+			upstreamsTimeSum:   map[string]uint64{},
+		},
+		db: &unitDB{
+			NResult:            []uint64{0, 0, 0, 0, 0, 0},
+			Domains:            []countPair{},
+			BlockedDomains:     []countPair{},
+			Clients:            []countPair{},
+			NTotal:             0,
+			TimeAvg:            0,
+			UpstreamsResponses: []countPair{},
+			UpstreamsTimeSum:   []countPair{},
+		},
+	}, {
+		name: "basic",
+		want: unit{
+			domains: map[string]uint64{
+				"example.com": 1,
+			},
+			blockedDomains: map[string]uint64{
+				"example.net": 1,
+			},
+			clients: map[string]uint64{
+				"127.0.0.1": 2,
+			},
+			nResult: []uint64{0, 1, 1, 0, 0, 0},
+			id:      0,
+			nTotal:  2,
+			timeSum: 246912,
+			upstreamsResponses: map[string]uint64{
+				"1.2.3.4": 2,
+			},
+			upstreamsTimeSum: map[string]uint64{
+				"1.2.3.4": 246912,
+			},
+		},
+		db: &unitDB{
+			NResult: []uint64{0, 1, 1, 0, 0, 0},
+			Domains: []countPair{{
+				"example.com", 1,
+			}},
+			BlockedDomains: []countPair{{
+				"example.net", 1,
+			}},
+			Clients: []countPair{{
+				"127.0.0.1", 2,
+			}},
+			NTotal:  2,
+			TimeAvg: 123456,
+			UpstreamsResponses: []countPair{{
+				"1.2.3.4", 2,
+			}},
+			UpstreamsTimeSum: []countPair{{
+				"1.2.3.4", 246912,
+			}},
+		},
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := unit{}
+			got.deserialize(tc.db)
+			require.Equal(t, tc.want, got)
+		})
+	}
+}
+
+func TestTopUpstreamsPairs(t *testing.T) {
+	testCases := []struct {
+		db            *unitDB
+		name          string
+		wantResponses []topAddrs
+		wantAvgTime   []topAddrsFloat
+	}{{
+		name: "empty",
+		db: &unitDB{
+			NResult:            []uint64{0, 0, 0, 0, 0, 0},
+			Domains:            []countPair{},
+			BlockedDomains:     []countPair{},
+			Clients:            []countPair{},
+			NTotal:             0,
+			TimeAvg:            0,
+			UpstreamsResponses: []countPair{},
+			UpstreamsTimeSum:   []countPair{},
+		},
+		wantResponses: []topAddrs{},
+		wantAvgTime:   []topAddrsFloat{},
+	}, {
+		name: "basic",
+		db: &unitDB{
+			NResult:        []uint64{0, 0, 0, 0, 0, 0},
+			Domains:        []countPair{},
+			BlockedDomains: []countPair{},
+			Clients:        []countPair{},
+			NTotal:         0,
+			TimeAvg:        0,
+			UpstreamsResponses: []countPair{{
+				"1.2.3.4", 2,
+			}},
+			UpstreamsTimeSum: []countPair{{
+				"1.2.3.4", 246912,
+			}},
+		},
+		wantResponses: []topAddrs{{
+			"1.2.3.4": 2,
+		}},
+		wantAvgTime: []topAddrsFloat{{
+			"1.2.3.4": 0.123456,
+		}},
+	}, {
+		name: "sorted",
+		db: &unitDB{
+			NResult:        []uint64{0, 0, 0, 0, 0, 0},
+			Domains:        []countPair{},
+			BlockedDomains: []countPair{},
+			Clients:        []countPair{},
+			NTotal:         0,
+			TimeAvg:        0,
+			UpstreamsResponses: []countPair{
+				{"3.3.3.3", 8},
+				{"2.2.2.2", 4},
+				{"4.4.4.4", 16},
+				{"1.1.1.1", 2},
+			},
+			UpstreamsTimeSum: []countPair{
+				{"3.3.3.3", 800_000_000},
+				{"2.2.2.2", 40_000_000},
+				{"4.4.4.4", 16_000_000_000},
+				{"1.1.1.1", 2_000_000},
+			},
+		},
+		wantResponses: []topAddrs{
+			{"4.4.4.4": 16},
+			{"3.3.3.3": 8},
+			{"2.2.2.2": 4},
+			{"1.1.1.1": 2},
+		},
+		wantAvgTime: []topAddrsFloat{
+			{"4.4.4.4": 1000},
+			{"3.3.3.3": 100},
+			{"2.2.2.2": 10},
+			{"1.1.1.1": 1},
+		},
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			gotResponses, gotAvgTime := topUpstreamsPairs([]*unitDB{tc.db})
+			assert.Equal(t, tc.wantResponses, gotResponses)
+			assert.Equal(t, tc.wantAvgTime, gotAvgTime)
+		})
+	}
+}
diff --git a/openapi/CHANGELOG.md b/openapi/CHANGELOG.md
index 7c68a47b..64495ca5 100644
--- a/openapi/CHANGELOG.md
+++ b/openapi/CHANGELOG.md
@@ -4,6 +4,16 @@
 
 ## v0.108.0: API changes
 
+## v0.107.36: API changes
+
+### The new fields `"top_upstreams_responses"` and `"top_upstreams_avg_time"` in `Stats` object
+
+* The new field `"top_upstreams_responses"` in `GET /control/stats` method
+  shows the total number of responses from each upstream.
+
+* The new field `"top_upstrems_avg_time"` in `GET /control/stats` method shows
+  the average processing time in seconds of requests from each upstream.
+
 ## v0.107.30: API changes
 
 ### `POST /control/version.json` and `GET /control/dhcp/interfaces` content type
diff --git a/openapi/openapi.yaml b/openapi/openapi.yaml
index b1519843..64f376e4 100644
--- a/openapi/openapi.yaml
+++ b/openapi/openapi.yaml
@@ -1728,7 +1728,7 @@
         'avg_processing_time':
           'type': 'number'
           'format': 'float'
-          'description': 'Average time in milliseconds on processing a DNS'
+          'description': 'Average time in seconds on processing a DNS request'
           'example': 0.34
         'top_queried_domains':
           'type': 'array'
@@ -1742,6 +1742,19 @@
           'type': 'array'
           'items':
             '$ref': '#/components/schemas/TopArrayEntry'
+        'top_upstreams_responses':
+          'type': 'array'
+          'description': 'Total number of responses from each upstream.'
+          'items':
+            '$ref': '#/components/schemas/TopArrayEntry'
+          'maxItems': 100
+        'top_upstreams_avg_time':
+          'type': 'array'
+          'description': >
+            Average processing time in seconds of requests from each upstream.
+          'items':
+            '$ref': '#/components/schemas/TopArrayEntry'
+          'maxItems': 100
         'dns_queries':
           'type': 'array'
           'items':
@@ -1761,12 +1774,13 @@
     'TopArrayEntry':
       'type': 'object'
       'description': >
-        Represent the number of hits per key (domain or client IP).
+        Represent the number of hits or time duration per key (url, domain, or
+        client IP).
       'properties':
         'domain_or_ip':
-          'type': 'integer'
+          'type': 'number'
       'additionalProperties':
-          'type': 'integer'
+          'type': 'number'
     'StatsConfig':
       'type': 'object'
       'description': 'Statistics configuration'
diff --git a/scripts/make/go-lint.sh b/scripts/make/go-lint.sh
index 458a68cf..b0f2f6b1 100644
--- a/scripts/make/go-lint.sh
+++ b/scripts/make/go-lint.sh
@@ -184,6 +184,7 @@ run_linter gocognit --over 10\
 	./internal/next/\
 	./internal/rdns/\
 	./internal/schedule/\
+	./internal/stats/\
 	./internal/tools/\
 	./internal/version/\
 	./internal/whois/\
@@ -196,7 +197,6 @@ run_linter gocognit --over 19 ./internal/dnsforward/ ./internal/home/
 run_linter gocognit --over 18 ./internal/aghtls/
 run_linter gocognit --over 17 ./internal/filtering ./internal/filtering/rewrite/
 run_linter gocognit --over 15 ./internal/aghos/ ./internal/dhcpd/
-run_linter gocognit --over 14 ./internal/stats/
 run_linter gocognit --over 12 ./internal/updater/
 run_linter gocognit --over 11 ./internal/aghtest/