solidsnack / pg_stat_sysinfo

Query system statistics with SQL.

pg_stat_sysinfo

Collects system statistics.

----
CREATE EXTENSION pg_stat_sysinfo;
CREATE EXTENSION
----
SELECT * FROM pg_stat_sysinfo_collect();
      metric      |   dimensions |              at              |       value
------------------+--------------+------------------------------+--------------------
 load_average     | duration:1m  | 2023-01-17 20:40:24.74495+00 |       4.3427734375
 load_average     | duration:5m  | 2023-01-17 20:40:24.74495+00 |        2.740234375
 load_average     | duration:15m | 2023-01-17 20:40:24.74495+00 |           2.390625
 cpu_usage        |              | 2023-01-17 20:40:24.74495+00 |   0.12653848528862
 memory_usage     |              | 2023-01-17 20:40:24.74495+00 | 10.022946522725185
 memory_size      |              | 2023-01-17 20:40:24.74495+00 |         7966543872
 memory_available |              | 2023-01-17 20:40:24.74495+00 |         7168061440
 swap_usage       |              | 2023-01-17 20:40:24.74495+00 |                  0
 swap_size        |              | 2023-01-17 20:40:24.74495+00 |                  0
 swap_available   |              | 2023-01-17 20:40:24.74495+00 |                  0
 disk_usage       | fs:/         | 2023-01-17 20:40:24.74495+00 |  48.68292833372914
 disk_size        | fs:/         | 2023-01-17 20:40:24.74495+00 |        66404147200
 disk_available   | fs:/         | 2023-01-17 20:40:24.74495+00 |        34076663808
 disk_usage       | fs:/boot/efi | 2023-01-17 20:40:24.74495+00 |  4.986992082951202
 disk_size        | fs:/boot/efi | 2023-01-17 20:40:24.74495+00 |          109422592
 disk_available   | fs:/boot/efi | 2023-01-17 20:40:24.74495+00 |          103965696
(16 rows)

Enabling Caching Collector

Add the extension library to shared_preload_libraries and set the collection interval:

shared_preload_libraries = 'pg_stat_sysinfo.so'
pg_stat_sysinfo.interval = '1s'   # Accepts any time format Postgres recognizes

The cache is stored in Postgres shared memory. Up to 1280 KiB is cached -- over an hour, in most cases, at 1 query per second.

----
CREATE EXTENSION pg_stat_sysinfo;
CREATE EXTENSION
----
SELECT DISTINCT min(at) AS oldest,
       max(at) - min(at) AS during
  FROM pg_stat_sysinfo;
            oldest             |     during
-------------------------------+-----------------
 2023-01-17 20:04:46.220977+00 | 00:55:55.908972
(1 row)

----
SELECT DISTINCT dimensions FROM pg_stat_sysinfo;
   dimensions
----------------

 duration:1m
 duration:5m
 duration:15m
 disk:/
 disk:/boot/efi
(6 rows)

Basic cache statistics are available:

----
SELECT * FROM pg_stat_sysinfo_cache_summary();
 bytes_used | items
------------+-------
     563159 |  3587
(1 row)

Configuration Changes

The pg_stat_sysinfo.interval can be updated by changing postgres.conf and sending SIGHUP to the Postgres server process. The cache worker will use the new interval from that point forward.

If a long enough time has passed between server startup and a SIGHUP, or between one SIGHUP and another, the cache worker will refresh the disk metadata. This will allow it to pick up any disks that have been added to or removed from the system.