1/*
2** Zabbix
3** Copyright (C) 2001-2021 Zabbix SIA
4**
5** This program is free software; you can redistribute it and/or modify
6** it under the terms of the GNU General Public License as published by
7** the Free Software Foundation; either version 2 of the License, or
8** (at your option) any later version.
9**
10** This program is distributed in the hope that it will be useful,
11** but WITHOUT ANY WARRANTY; without even the implied warranty of
12** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13** GNU General Public License for more details.
14**
15** You should have received a copy of the GNU General Public License
16** along with this program; if not, write to the Free Software
17** Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
18**/
19
20package postgres
21
22import (
23	"context"
24	"errors"
25
26	"github.com/jackc/pgx/v4"
27	"zabbix.com/pkg/zbxerr"
28)
29
30// bgwriterHandler executes select  with statistics from pg_stat_bgwriter
31// and returns JSON if all is OK or nil otherwise.
32func bgwriterHandler(ctx context.Context, conn PostgresClient,
33	_ string, _ map[string]string, _ ...string) (interface{}, error) {
34	var bgwriterJSON string
35
36	query := `
37  SELECT row_to_json (T)
38    FROM (
39          SELECT
40              checkpoints_timed
41            , checkpoints_req
42            , checkpoint_write_time
43            , checkpoint_sync_time
44            , buffers_checkpoint
45            , buffers_clean
46            , maxwritten_clean
47            , buffers_backend
48            , buffers_backend_fsync
49            , buffers_alloc
50          FROM pg_catalog.pg_stat_bgwriter
51		  ) T ;`
52
53	row, err := conn.QueryRow(ctx, query)
54	if err != nil {
55		return nil, zbxerr.ErrorCannotFetchData.Wrap(err)
56	}
57
58	err = row.Scan(&bgwriterJSON)
59	if err != nil {
60		if errors.Is(err, pgx.ErrNoRows) {
61			return nil, zbxerr.ErrorEmptyResult.Wrap(err)
62		}
63
64		return nil, zbxerr.ErrorCannotFetchData.Wrap(err)
65	}
66
67	return bgwriterJSON, nil
68}
69