Agend Flow crash after client reboot

[timo1707]

What's wrong?

after rebooting windows 10 clients the grafana agent flow service wont start anymore

when deleting C:\ProgramData\Grafana Agent Flow\data\module.file.logs\loki.source.windowsevent.application the service can start again

Steps to reproduce

using below config on windows and reboot the client

System information

WIN10 x64

Software version

v0.34 & v0.35.4

Configuration

/********************************************
 * LOKI SCRAPE
 ********************************************/
loki.source.windowsevent "application"  {
    eventlog_name = "Application"
    forward_to = [loki.process.extract_labels.receiver]
}

/********************************************
 * LOKI REGEX LABELS
 ********************************************/
loki.process "extract_labels" {
  forward_to = [loki.relabel.hostname.receiver]
  stage.regex {
    expression = "\"event_id\":(?P<event_id>\\d+),\"level\":(?P<severity>\\d+)"
  }
  stage.labels {
    values = {
      "level"  = "severity",
      "event_id" = "event_id",
    }
  }
}

loki.relabel "hostname" {
  forward_to = [loki.write.default.receiver]

  rule {
    action       = "replace"
    target_label = "computer"
    replacement  = constants.hostname
  }
}

/********************************************
 * LOKI WRITE
 ********************************************/
loki.write "default" {
    endpoint {
        url ="https://redacted"
        tenant_id = "redacted"
    }
}

Logs

runtime error: index out of range [0] with length 0

goroutine 207 [running]:
github.com/grafana/loki/clients/pkg/promtail/targets/windows/win_eventlog.formatEventString(0x1, 0xc001a7bd10?, 0x200?)
	/go/pkg/mod/github.com/grafana/[email protected]/clients/pkg/promtail/targets/windows/win_eventlog/win_eventlog.go:532 +0x1db
github.com/grafana/loki/clients/pkg/promtail/targets/windows/win_eventlog.(*EventFetcher).renderEvent(_, 

level=error msg="service exited with error" err="exit status 2" exit_code=2

[rfratto]

Thanks for reporting! Sounds like it got corrupted on reboot, and we need to find a way to handle that more gracefully.