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Fix bugs mentioned in #908 #910

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Merged
merged 2 commits into from
Sep 13, 2023
Merged

Fix bugs mentioned in #908 #910

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be93bff
Fix bugs mentioned in #908
sysadmind Sep 13, 2023
d2a0225
Fix db rows.Close in pg_stat_walreceiver
sysadmind Sep 13, 2023
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2 changes: 1 addition & 1 deletion collector/pg_stat_activity_autovacuum.go
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Original file line number Diff line number Diff line change
Expand Up @@ -45,7 +45,7 @@ var (
statActivityAutovacuumQuery = `
SELECT
SPLIT_PART(query, '.', 2) AS relname,
EXTRACT(xact_start) AS timestamp_seconds
EXTRACT(EPOCH FROM xact_start) AS timestamp_seconds
FROM
pg_catalog.pg_stat_activity
WHERE
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8 changes: 5 additions & 3 deletions collector/pg_stat_walreceiver.go
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Expand Up @@ -107,13 +107,13 @@ var (
trim(both '''' from substring(conninfo from 'host=([^ ]*)')) as upstream_host,
slot_name,
status,
(receive_start_lsn- '0/0') % (2^52)::bigint as receive_start_lsn,
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These are used in fmt.Sprintf below and I think the % is causing the problem. I can't actually get this collector to finish running the query against my local docker.

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I was able to reproduce this issue, and I found that calling hasFlushedLSNRows.Close() before running the second query fixes it. Presumably there is some deadlock waiting for one cursor to be closed before opening another on the same connection.

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Probably worth switching these to prepared statements.

(receive_start_lsn- '0/0') %% (2^52)::bigint as receive_start_lsn,
%s
receive_start_tli,
received_tli,
extract(epoch from last_msg_send_time) as last_msg_send_time,
extract(epoch from last_msg_receipt_time) as last_msg_receipt_time,
(latest_end_lsn - '0/0') % (2^52)::bigint as latest_end_lsn,
(latest_end_lsn - '0/0') %% (2^52)::bigint as latest_end_lsn,
extract(epoch from latest_end_time) as latest_end_time,
substring(slot_name from 'repmgr_slot_([0-9]*)') as upstream_node
FROM pg_catalog.pg_stat_wal_receiver
Expand All @@ -127,14 +127,16 @@ func (c *PGStatWalReceiverCollector) Update(ctx context.Context, instance *insta
return err
}

defer hasFlushedLSNRows.Close()
hasFlushedLSN := hasFlushedLSNRows.Next()
var query string
if hasFlushedLSN {
query = fmt.Sprintf(pgStatWalReceiverQueryTemplate, "(flushed_lsn - '0/0') % (2^52)::bigint as flushed_lsn,\n")
} else {
query = fmt.Sprintf(pgStatWalReceiverQueryTemplate, "")
}

hasFlushedLSNRows.Close()

rows, err := db.QueryContext(ctx, query)
if err != nil {
return err
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13 changes: 12 additions & 1 deletion collector/pg_xlog_location.go
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Expand Up @@ -16,7 +16,9 @@ package collector
import (
"context"

"github.com/blang/semver/v4"
"github.com/go-kit/log"
"github.com/go-kit/log/level"
"github.com/prometheus/client_golang/prometheus"
)

Expand Down Expand Up @@ -50,8 +52,17 @@ var (
`
)

func (PGXlogLocationCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
func (c PGXlogLocationCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
db := instance.getDB()

// xlog was renmaed to WAL in PostgreSQL 10
// https://wiki.postgresql.org/wiki/New_in_postgres_10#Renaming_of_.22xlog.22_to_.22wal.22_Globally_.28and_location.2Flsn.29
after10 := instance.version.Compare(semver.MustParse("10.0.0"))
if after10 >= 0 {
level.Warn(c.log).Log("msg", "xlog_location collector is not available on PostgreSQL >= 10.0.0, skipping")
return nil
}

rows, err := db.QueryContext(ctx,
xlogLocationQuery)

Expand Down