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// Copyright 2023 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package collector
import (
"context"
"github.com/prometheus/client_golang/prometheus"
)
const replicationSubsystem = "replication"
func init() {
registerCollector(replicationSubsystem, defaultEnabled, NewPGReplicationCollector)
}
type PGReplicationCollector struct {
}
func NewPGReplicationCollector(collectorConfig) (Collector, error) {
return &PGReplicationCollector{}, nil
}
var (
pgReplicationLag = prometheus.NewDesc(
prometheus.BuildFQName(
namespace,
replicationSubsystem,
"lag_seconds",
),
"Replication lag behind master in seconds",
[]string{}, nil,
)
pgReplicationIsReplica = prometheus.NewDesc(
prometheus.BuildFQName(
namespace,
replicationSubsystem,
"is_replica",
),
"Indicates if the server is a replica",
[]string{}, nil,
)
pgReplicationLastReplay = prometheus.NewDesc(
prometheus.BuildFQName(
namespace,
replicationSubsystem,
"last_replay_seconds",
),
"Age of last replay in seconds",
[]string{}, nil,
)
pgReplicationQuery = `SELECT
CASE
WHEN NOT pg_is_in_recovery() THEN 0
WHEN pg_last_wal_receive_lsn () = pg_last_wal_replay_lsn () THEN 0
ELSE GREATEST (0, EXTRACT(EPOCH FROM (now() - pg_last_xact_replay_timestamp())))
END AS lag,
CASE
WHEN pg_is_in_recovery() THEN 1
ELSE 0
END as is_replica,
GREATEST (0, EXTRACT(EPOCH FROM (now() - pg_last_xact_replay_timestamp()))) as last_replay`
)
func (c *PGReplicationCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
db := instance.getDB()
row := db.QueryRowContext(ctx,
pgReplicationQuery,
)
var lag float64
var isReplica int64
var replayAge float64
err := row.Scan(&lag, &isReplica, &replayAge)
if err != nil {
return err
}
ch <- prometheus.MustNewConstMetric(
pgReplicationLag,
prometheus.GaugeValue, lag,
)
ch <- prometheus.MustNewConstMetric(
pgReplicationIsReplica,
prometheus.GaugeValue, float64(isReplica),
)
ch <- prometheus.MustNewConstMetric(
pgReplicationLastReplay,
prometheus.GaugeValue, replayAge,
)
return nil
}
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