## Problem
Currently we do not have metrics for autovacuum.
## Summary of changes
Added a metric that extracts the top 5 DBs with oldest mxid and frozen
xid. Tables that were vacuumed recently should have younger value (or
younger age).
Related Issue: https://github.com/neondatabase/cloud/issues/27296
## Problem
Exporting `file_cache_used` which specifies the number of used chunks in
the LFC. This helps calculate LFC utilization as: `file_cache_used_pages
/ (file_cache_used * file_cache_chunk_size_pages)`
## Summary of changes
Exporting `file_cache_used`.
Related Issue: https://github.com/neondatabase/cloud/issues/26688
## Problem
Original Slack discussion:
https://neondb.slack.com/archives/C04DGM6SMTM/p1739915430147169
TL;DR in Postgres, it's totally normal to have 'invalid' DBs (state
after the interrupted `DROP DATABASE`). Yet, some of our metrics
collected with `sql_exporter` try to get the size of such invalid DBs.
Typical log lines:
```
time=2025-03-05T16:30:32.368Z level=ERROR source=promhttp.go:52 msg="Error gathering metrics" error="[from Gatherer #1] [collector=neon_collector,query=pg_stats_userdb] pq: [NEON_SMGR] [reqid 0] could not read db size of db 173228 from page server at lsn 0/44A0E8C0"
time=2025-03-05T16:30:32.369Z level=ERROR source=promhttp.go:52 msg="Error gathering metrics" error="[from Gatherer #1] [collector=neon_collector,query=db_total_size] pq: [NEON_SMGR] [reqid 0] could not read db size of db 173228 from page server at lsn 0/44A0E8C0"
```
## Summary of changes
Ignore invalid DBs in these two metrics -- `pg_stats_userdb` and
`db_total_size`
This PR adds a new key to neon.neon_lfc_stats —
'file_cache_chunk_size_pages'. It just returns the value of
BLOCKS_PER_CHUNK from the LFC implementation.
The new value should (eventually) allow changing the chunk size without
breaking any places that rely on LFC stats values measured in number of
chunks.
See neondatabase/cloud#25170 for more.
## Problem
It was reported as `gauge`, but it's actually a `counter`.
Also add `_total` suffix as that's the convention for counters.
The corresponding flux-fleet PR:
https://github.com/neondatabase/flux-fleet/pull/386
The original value that we get is measured in microseconds. It comes
from a calculation using Postgres' GetCurrentTimestamp(), whihc is
implemented in terms of gettimeofday(2).
Signed-off-by: Tristan Partin <tristan@neon.tech>
This will tell us how much time the compute has spent throttled if
pageserver/safekeeper cannot keep up with WAL generation.
Signed-off-by: Tristan Partin <tristan@neon.tech>
We can't call pg_current_wal_lsn() if we are a standby instance (read
replica). Any attempt to call this function while in recovery results
in:
ERROR: recovery is in progress
Signed-off-by: Tristan Partin <tristan@neon.tech>
Checkpointer related statistics moved from pg_stat_bgwriter to
pg_stat_checkpointer, so we need to adjust our queries accordingly.
Signed-off-by: Tristan Partin <tristan@neon.tech>
There are quite a few benefits to this approach:
- Reduce config duplication
- The two sql_exporter configs were super similar with just a few
differences
- Pull SQL queries into standalone files
- That means we could run a SQL formatter on the file in the future
- It also means access to syntax highlighting
- In the future, run different queries for different PG versions
- This is relevant because right now, we have queries that are failing
on PG 17 due to catalog updates
Signed-off-by: Tristan Partin <tristan@neon.tech>
