[pashagolub]

Summary

backends counts idle-in-transaction sessions but does not say how long they have been idle. The new gauge longest_idle_in_tx_seconds holds the seconds since the oldest idle-in-transaction client session, aborted ones included, entered that state. It is null when there is no such session.

 (select count(*) from sa_snapshot where state = 'idle in transaction' and backend_type = 'client backend') as idleintransaction,
+(select round(extract(epoch from max(now() - state_change)), 3)::float from sa_snapshot
+  where state in ('idle in transaction', 'idle in transaction (aborted)')
+    and backend_type = 'client backend') as longest_idle_in_tx_seconds,

It uses state_change, not xact_start, so a transaction that worked for ten minutes and then paused for one second shows 1 s. longest_tx_seconds already reports the transaction age.

Both v13 sessions overview dashboards get a new panel after "Longest TX duration":

 Sessions overview (postgres, prometheus)
   Longest TX duration
+  Longest idle-in-transaction duration
   ...

The second commit fixes the v13 postgres dashboards, which cast the fractional *_seconds columns of backends to int/int8. Postgres rejects that cast, so the panels returned errors instead of data. They now cast to float in sessions-overview, global-health and recommendations.

Evidence

• Before: backends had no idle age column. The v13 dashboard cast failed:

  select ('{"s":12.345}'::jsonb->>'s')::int8
  ERROR:  invalid input syntax for type bigint: "12.345"
  

  After: the new SQL against postgres:19beta2-alpine:

  no idle-in-tx session                     longest_idle_in_tx_seconds = null,  idleintransaction = 0
  begin; select 1; then wait 3 s            longest_idle_in_tx_seconds = 3.212, idleintransaction = 1
  begin; select 1/0; then wait 2 s          longest_idle_in_tx_seconds = 2.214, idleintransaction = 0
  

  The same cast with ::float returns 12.345. TestBackendsColumns checks that every backends column, the new one included, stays in the SQL. Lint and go test ./... pass.

Merge Danger

Door: two-way

The change adds a column and panels and renames nothing. Reverting removes them.

Blast Radius: small

Sinks store one more field per backends row, and Prometheus exposes one more series, pgwatch_backends_longest_idle_in_tx_seconds, per database. The v12 postgres dashboards still have the int cast bug in 11 queries.

[coveralls]

Coverage Report for CI Build 39777029889

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No base build found for commit 201f822 on v7.
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Coverage: 89.684%

Details

• Patch coverage: No coverable lines changed in this PR.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

Requires a base build to compare against. How to fix this →

---

Coverage Stats

Relevant Lines:	5661
Covered Lines:	5077
Line Coverage:	89.68%
Coverage Strength:	0.9 hits per line

---

💛 - Coveralls

[Copilot]

🟢 Approval recommended

No blocking issues were identified; the remaining review comments are non-blocking documentation nits.

2 open issues

• Clarify vacuum impact of aborted idle transactions · New
• Clarify vacuum impact of aborted idle transactions · New

What changed in this PR

Adds longest_idle_in_tx_seconds to the backends metric and exposes it in the PostgreSQL and Prometheus v13 sessions dashboards. It also corrects affected fractional-duration casts.

Changes:

• Calculates the oldest client session’s idle-in-transaction duration, including aborted sessions.
• Adds a contract test covering the complete backends column set.
• Adds dashboard panels and updates duration casts to float.

File	Description
pkg/​metrics/​metrics.yaml	Defines and documents the new idle-in-transaction duration gauge.
pkg/​metrics/​metrics_yaml_test.go	Verifies the complete backends SQL column contract.
grafana/​prometheus/​v13/​sessions-overview-prometheus.json	Adds the Prometheus sessions panel and dashboard placement.
grafana/​postgres/​v13/​sessions-overview.json	Adds the PostgreSQL sessions panel and fixes fractional duration casts.
grafana/​postgres/​v13/​recommendations.json	Fixes fractional duration casts in recommendation queries.
grafana/​postgres/​v13/​global-health.json	Fixes the fractional transaction-duration cast.

_{Review effort: Lite}