Vero Monitor Service

This probe is currently at the experimental stage.

Description

The log_mon probe tails a log file, counting newly-appended lines matching includePattern (and not matching excludePattern). It tracks a byte offset between runs — only counts new lines, resets on truncation/rotation.

Config fields

Field	Type	Required	Default	Description
`type`	`string`	Yes	—	Must be `"log_mon"`
`filePath`	`string`	Yes	—	Log file path to scan
`includePattern`	`string`	Yes	—	Regex for lines to count
`excludePattern`	`string`	No	—	Regex to exclude lines that matched include
`maxAgeSeconds`	`int64`	No	—	Skip scan if file hasn’t changed within this many seconds
`readFromEnd`	`bool`	No	`true`	`true`: start from EOF on first run. `false`: start from beginning

Metrics

Metric	Type	Description
`vms.log_mon.match_count`	gauge	Number of matching lines in this run

Example config

{
  "type": "log_mon",
  "filePath": "/var/log/app/app.log",
  "includePattern": "ERROR|FATAL",
  "excludePattern": "healthcheck",
  "maxAgeSeconds": 300
}

Notes

Reads up to 8 MiB per run. Remainder is picked up on the next tick.
Only counts complete lines (ending with \n).
File truncation (size drops below offset) resets to offset 0.