From 2dcaa1511c6b6e5f96d0977381827ced5064dc92 Mon Sep 17 00:00:00 2001
From: Michael Hoffmann <mhoffm@posteo.de>
Date: Wed, 4 Sep 2024 13:38:05 +0200
Subject: [PATCH] API: expose lowest TSDB timestamp in /api/v1/status/tsdb

Add information about the lowest timestamp in the TSDB to /api/v1/status/tsdb.
This feature would be useful to have in Thanos so that the Thanos Sidecar can
adjust its advertised range so we can more precisely prune endpoints during fan-out.

Signed-off-by: Michael Hoffmann <mhoffm@posteo.de>
---
 web/api/v1/api.go                             | 17 ++++++++--
 .../src/pages/tsdbStatus/TSDBStatus.test.tsx  |  9 +++++
 .../src/pages/tsdbStatus/TSDBStatus.tsx       | 33 ++++++++++++++++---
 3 files changed, 53 insertions(+), 6 deletions(-)

diff --git a/web/api/v1/api.go b/web/api/v1/api.go
index d58be211f..eb98fb6c7 100644
--- a/web/api/v1/api.go
+++ b/web/api/v1/api.go
@@ -1577,9 +1577,15 @@ type HeadStats struct {
 	MaxTime       int64  `json:"maxTime"`
 }
 
+// TSDBStats has information about the TSDB.
+type TSDBStats struct {
+	MinTime int64 `json:"minTime"`
+}
+
 // TSDBStatus has information of cardinality statistics from postings.
 type TSDBStatus struct {
 	HeadStats                   HeadStats  `json:"headStats"`
+	TSDBStats                   TSDBStats  `json:"tsdbStats"`
 	SeriesCountByMetricName     []TSDBStat `json:"seriesCountByMetricName"`
 	LabelValueCountByLabelName  []TSDBStat `json:"labelValueCountByLabelName"`
 	MemoryInBytesByLabelName    []TSDBStat `json:"memoryInBytesByLabelName"`
@@ -1613,12 +1619,18 @@ func (api *API) serveTSDBStatus(r *http.Request) apiFuncResult {
 		return apiFuncResult{nil, &apiError{errorInternal, fmt.Errorf("error gathering runtime status: %w", err)}, nil, nil}
 	}
 	chunkCount := int64(math.NaN())
+	lowestTimestamp := int64(math.NaN())
 	for _, mF := range metrics {
-		if *mF.Name == "prometheus_tsdb_head_chunks" {
+		switch *mF.Name {
+		case "prometheus_tsdb_head_chunks":
 			m := mF.Metric[0]
 			if m.Gauge != nil {
 				chunkCount = int64(m.Gauge.GetValue())
-				break
+			}
+		case "prometheus_tsdb_lowest_timestamp":
+			m := mF.Metric[0]
+			if m.Gauge != nil {
+				lowestTimestamp = int64(m.Gauge.GetValue())
 			}
 		}
 	}
@@ -1630,6 +1642,7 @@ func (api *API) serveTSDBStatus(r *http.Request) apiFuncResult {
 			MaxTime:       s.MaxTime,
 			NumLabelPairs: s.IndexPostingStats.NumLabelPairs,
 		},
+		TSDBStats:                   TSDBStats{MinTime: lowestTimestamp},
 		SeriesCountByMetricName:     TSDBStatsFromIndexStats(s.IndexPostingStats.CardinalityMetricsStats),
 		LabelValueCountByLabelName:  TSDBStatsFromIndexStats(s.IndexPostingStats.CardinalityLabelStats),
 		MemoryInBytesByLabelName:    TSDBStatsFromIndexStats(s.IndexPostingStats.LabelValueStats),
diff --git a/web/ui/react-app/src/pages/tsdbStatus/TSDBStatus.test.tsx b/web/ui/react-app/src/pages/tsdbStatus/TSDBStatus.test.tsx
index b7c683115..7cdea61e5 100644
--- a/web/ui/react-app/src/pages/tsdbStatus/TSDBStatus.test.tsx
+++ b/web/ui/react-app/src/pages/tsdbStatus/TSDBStatus.test.tsx
@@ -20,6 +20,9 @@ const fakeTSDBStatusResponse: {
       minTime: 1591516800000,
       maxTime: 1598896800143,
     },
+    tsdbStats: {
+      minTime: 1591516800000,
+    },
     labelValueCountByLabelName: [
       {
         name: '__name__',
@@ -64,6 +67,9 @@ const fakeEmptyTSDBStatusResponse: {
       minTime: 9223372036854776000,
       maxTime: -9223372036854776000,
     },
+    tsdbStats: {
+      minTime: 9223372036854776000,
+    },
     labelValueCountByLabelName: [],
     seriesCountByMetricName: [],
     memoryInBytesByLabelName: [],
@@ -84,6 +90,9 @@ const fakeInvalidTimestampTSDBStatusResponse: {
       minTime: 9223372036854776000,
       maxTime: -9223372036854776000,
     },
+    tsdbStats: {
+      minTime: 9223372036854776000,
+    },
     labelValueCountByLabelName: [],
     seriesCountByMetricName: [],
     memoryInBytesByLabelName: [],
diff --git a/web/ui/react-app/src/pages/tsdbStatus/TSDBStatus.tsx b/web/ui/react-app/src/pages/tsdbStatus/TSDBStatus.tsx
index bc4dfe99b..3e9069b55 100644
--- a/web/ui/react-app/src/pages/tsdbStatus/TSDBStatus.tsx
+++ b/web/ui/react-app/src/pages/tsdbStatus/TSDBStatus.tsx
@@ -19,8 +19,13 @@ interface HeadStats {
   maxTime: number;
 }
 
+interface TSDBStats {
+  minTime: number;
+}
+
 export interface TSDBMap {
   headStats: HeadStats;
+  tsdbStats: TSDBStats;
   seriesCountByMetricName: Stats[];
   labelValueCountByLabelName: Stats[];
   memoryInBytesByLabelName: Stats[];
@@ -45,29 +50,49 @@ export const TSDBStatusContent: FC<TSDBMap> = ({
     }
   };
   const { chunkCount, numSeries, numLabelPairs, minTime, maxTime } = headStats;
-  const stats = [
+  const headStatsKV = [
     { header: 'Number of Series', value: numSeries },
     { header: 'Number of Chunks', value: chunkCount },
     { header: 'Number of Label Pairs', value: numLabelPairs },
     { header: 'Current Min Time', value: `${unixToTime(minTime)}` },
     { header: 'Current Max Time', value: `${unixToTime(maxTime)}` },
   ];
+  const tsdbStatsKV = [{ header: 'Current Min Time', value: `${unixToTime(minTime)}` }];
   return (
     <div>
       <h2>TSDB Status</h2>
-      <h3 className="p-2">Head Stats</h3>
+      <h3 className="p-2">TSDB Stats</h3>
       <div className="p-2">
         <Table bordered size="sm" striped>
           <thead>
             <tr>
-              {stats.map(({ header }) => {
+              {tsdbStatsKV.map(({ header }) => {
                 return <th key={header}>{header}</th>;
               })}
             </tr>
           </thead>
           <tbody>
             <tr>
-              {stats.map(({ header, value }) => {
+              {tsdbStatsKV.map(({ header, value }) => {
+                return <td key={header}>{value}</td>;
+              })}
+            </tr>
+          </tbody>
+        </Table>
+      </div>
+      <h3 className="p-2">Head Stats</h3>
+      <div className="p-2">
+        <Table bordered size="sm" striped>
+          <thead>
+            <tr>
+              {headStatsKV.map(({ header }) => {
+                return <th key={header}>{header}</th>;
+              })}
+            </tr>
+          </thead>
+          <tbody>
+            <tr>
+              {headStatsKV.map(({ header, value }) => {
                 return <td key={header}>{value}</td>;
               })}
             </tr>