Influx DB: truncate timestamps to whole seconds to save disk space

[Al2Klimov]

This reverts:

• Influx DB: don't unneccessarily truncate timestamps to whole seconds #9599

More precise timestamps need more storage, see:

fixes #9948

[yhabteab]

Used image:

  influxdb:
    image: influxdb:latest
    container_name: influxdb
    ports:
      - "8086:8086"
    volumes:
      - influxdb_data:/var/lib/influxdb2

Create an influxdb user and a bucket via the user interface. Then simply execute the following script:

NOTE: The timestamps are always last metric timestamp + 5m.

Second precision

#!/bin/bash

start=$(date +%s);
for i in {0..29}; do
  for j in {0..99999}; do
    printf 'filldisk,icinga=213 unit="bytes",value=%d%d %d\n' $i $j $((start + $i + $j * 300))
  done > data.txt

  curl -fsSX POST --data-binary @data.txt --header "Authorization: Token P8Rpymn1CSDKVwEBRSZ40ADLyTESPzwNEids60kdXYh_6jGpatuc0Iek_I22DETP9dd_BRPNGcEQWHU6C2s3HQ==" 'http://localhost:8086/write?db=bucketsecondprecision&precision=s'
done

Result:

root@eb1feac020da:/# du -sh /var/lib/influxdb2/engine/data/ef4fda1e37d8d95e/
8.3M    /var/lib/influxdb2/engine/data/ef4fda1e37d8d95e/

Nanosecond precision

#!/bin/bash

start=$(date +%s);
for i in {0..29}; do
  for j in {0..99999}; do
    printf 'filldisk,icinga=213 unit="bytes",value=%d%d %09d\n' $i $j $((start + $i + $j * 300))
  done > data.txt

  curl -fsSX POST --data-binary @data.txt --header "Authorization: Token P8Rpymn1CSDKVwEBRSZ40ADLyTESPzwNEids60kdXYh_6jGpatuc0Iek_I22DETP9dd_BRPNGcEQWHU6C2s3HQ==" 'http://localhost:8086/write?db=bucketnanosecondprecision&precision=ns'
done

Result:

root@eb1feac020da:/# du -sh /var/lib/influxdb2/engine/data/f39177df6a8dce01/
16M     /var/lib/influxdb2/engine/data/f39177df6a8dce01/

Conclusion

Metrics with nanosecond granularity occupy twice as much storage space as metrics with second precision.