Add unit test to check stopping gatherers on source config update

Author: 0xgouda

internal/reaper/reaper_test.go

@@ -94,4 +94,57 @@ func TestReaper_LoadSources(t *testing.T) {
 		assert.NoError(t, r.LoadSources())
 		assert.Equal(t, 4, len(r.monitoredSources), "Expected four monitored sources after resetting groups")
 	})
+
+	t.Run("Test source config update stops gatherers", func(t *testing.T) {
+		// Track if cancel functions were called
+		cancelCalled := make(map[string]bool)
+
+		source1 := sources.Source{
+			Name:      "Source1",
+			IsEnabled: true,
+			Kind:      sources.SourcePostgres,
+			ConnStr:   "postgres://localhost:5432/db1",
+			Metrics:   map[string]float64{"metric1": 60, "metric2": 120},
+		}
+
+		reader := &testutil.MockSourcesReaderWriter{
+			GetSourcesFunc: func() (sources.Sources, error) {
+				return sources.Sources{source1}, nil
+			},
+		}
+
+		r := NewReaper(ctx, &cmdopts.Options{SourcesReaderWriter: reader})
+		assert.NoError(t, r.LoadSources())
+		assert.Equal(t, 1, len(r.monitoredSources), "Expected one monitored source after initial load")
+
+		for i := range 2 {
+			dbMetric1 := "Source1" + dbMetricJoinStr + "metric1"
+			dbMetric2 := "Source1" + dbMetricJoinStr + "metric2"
+
+			cancelCalled[dbMetric1] = false
+			cancelCalled[dbMetric2] = false
+
+			r.cancelFuncs[dbMetric1] = func() { cancelCalled[dbMetric1] = true }
+			r.cancelFuncs[dbMetric2] = func() { cancelCalled[dbMetric2] = true }
+
+			if i == 0 {
+				// Change conn str to trigger config change
+				source1.ConnStr = "postgres://localhost:5432/db1_updated"
+			} else {
+				// Change metric1 interval to trigger config change
+				source1.Metrics = map[string]float64{"metric1": 30, "metric2": 120}
+			}
+
+			// Load sources again with updated config
+			assert.NoError(t, r.LoadSources())
+
+			// Verify cancel functions were called
+			assert.True(t, cancelCalled[dbMetric1], "Expected cancel function for metric1 to be called")
+			assert.True(t, cancelCalled[dbMetric2], "Expected cancel function for metric2 to be called")
+
+			// Verify cancel funcs were removed from the map
+			assert.Nil(t, r.cancelFuncs[dbMetric1], "Expected cancel function for metric1 to be removed")
+			assert.Nil(t, r.cancelFuncs[dbMetric2], "Expected cancel function for metric2 to be removed")
+		}
+	})
 }