Fix default reserve MB

machinery/src/capture/cleanup_test.go

@@ -196,3 +196,24 @@ func TestRecordingsNeedCleanup_DefaultDiskReserve(t *testing.T) {
 		t.Fatalf("expected no cleanup when free space (%dMB) exceeds the 1MB reserve", availableMB)
 	}
 }
+
+// The default 5% reserve must never truncate to 0MB on small disks, otherwise
+// cleanup would only trigger once the disk is completely full.
+func TestDefaultReserveMB(t *testing.T) {
+	cases := []struct {
+		totalMB int64
+		want    int64
+	}{
+		{totalMB: 0, want: 1},   // no/unknown disk size still reserves 1MB
+		{totalMB: 10, want: 1},  // 5% = 0MB -> floored to 1MB
+		{totalMB: 19, want: 1},  // 5% = 0MB -> floored to 1MB
+		{totalMB: 20, want: 1},  // 5% = exactly 1MB
+		{totalMB: 100, want: 5}, // 5% = 5MB
+		{totalMB: 1000, want: 50},
+	}
+	for _, c := range cases {
+		if got := defaultReserveMB(c.totalMB); got != c.want {
+			t.Errorf("defaultReserveMB(%d) = %d, want %d", c.totalMB, got, c.want)
+		}
+	}
+}

machinery/src/capture/main.go

@@ -118,12 +118,25 @@ func recordingsNeedCleanup(recordingsDirectory string, configuration *models.Con
 
 	reserveMB := configuration.Config.MinFreeSpace
 	if reserveMB <= 0 {
-		reserveMB = totalMB * 5 / 100 // keep 5% of the disk free by default
+		reserveMB = defaultReserveMB(totalMB)
 	}
 
 	return availableMB <= reserveMB, nil
 }
 
+// defaultReserveMB returns the free-space reserve (MB) to keep on the recordings
+// disk when AGENT_AUTO_CLEAN_MIN_FREE_SPACE is not set: 5% of the disk total,
+// but never below 1MB. On very small disks 5% truncates to 0MB, which would
+// disable the reserve entirely (cleanup only once availableMB <= 0), so we floor
+// it at 1MB to preserve the intended "keep some space free" behaviour.
+func defaultReserveMB(totalMB int64) int64 {
+	reserveMB := totalMB * 5 / 100
+	if reserveMB < 1 {
+		reserveMB = 1
+	}
+	return reserveMB
+}
+
 // pickRecordingToCleanup chooses which recording to delete to free space in the
 // recordings directory. It returns the oldest recording that has already been
 // uploaded (no pending marker with the same name in cloudDirectory). Only when