refactor(log): ingore error log when journal is disable

[BlackHole1]

There is no systemd and journal in our distribution, and when using ignition, many warning logs are printed. The changes in this PR will check if there is a journal in the current distribution, and if not, it will not pass the logs to the journal.

Notes: The distro Alpine has no journal. Add conditional to avoid failure due to logging method not being available.

[BlackHole1]

Friendly ping @jlebon

[prestist]

Hello! sorry for the delay and thank you for adding this change, and 100% that makes sense. Could you make two small changes.

• include in your commit message the distribution that you are referring to
  i.e somthing like: "the distro x has no journal. Add conditional to avoid failure due to logging method not being available. "
• add a item to the release notes under changes sub-header

[BlackHole1]

@prestist Done

[prestist]

@BlackHole1 sorry I still am seeing some spelling/grammar issues with your commit message wdyt about this?

exec/engine: log to journal only when available

Alpine Linux does not include systemd’s journal, which causes Ignition to emit warnings when attempting to log. This PR introduces a check to determine if the journal is available on the current distribution, and skips logging to the journal when it is not present.

Signed-off-by: Kevin Cui [email protected]

Also can you please add an comment to the release notes? talking about this under changes for the unreleased version.

[BlackHole1]

@prestist Thank you for your review suggestions！

[prestist]

@BlackHole1 I took a closer look at the code and the symptoms, have you tested this code change? I suspect you will still get that warning.

[BlackHole1]

@prestist Sorry I'm late. I just did some testing locally. The issue you're worried about won't happen.

package main

import (
	"fmt"

	"github.com/coreos/go-systemd/v22/journal"
)

func main() {
	fmt.Println("====> test journal.Enabled()")
	for i := 0; i < 10; i++ {
		fmt.Println(journal.Enabled())
	}

	fmt.Println("====> test journal.Send()")

	for i := 0; i < 10; i++ {
		if err := journal.Send("MESSAGE=Hello, World!", journal.PriInfo, nil); err != nil {
			fmt.Println("Send Error: ", err)
		}
	}
}

[BlackHole1]

Friendly ping @prestist :)

[jlebon]

One nit, but looks sane to me

[BlackHole1]

@jlebon Done