Unhelpful log message: "getLedger: Unable to find ledger" (Version: 1.8.0-rc2)

[mDuo13]

Issue Description

The following error message shows up a lot and doesn't seem to provide much useful context:

2021-Nov-22 22:33:31.416336072 UTC Protocol:WRN [034] getLedger: Unable to find ledger
2021-Nov-22 22:33:35.400680627 UTC Protocol:WRN [026] getLedger: Unable to find ledger
2021-Nov-22 22:33:35.400726583 UTC Protocol:WRN [026] getLedger: Unable to find ledger
2021-Nov-22 22:33:39.379804757 UTC Protocol:WRN [034] getLedger: Unable to find ledger
2021-Nov-22 22:33:43.310797790 UTC Protocol:WRN [034] getLedger: Unable to find ledger
2021-Nov-22 22:33:43.335856225 UTC Protocol:WRN [002] getLedger: Unable to find ledger
2021-Nov-22 22:33:43.335908021 UTC Protocol:WRN [002] getLedger: Unable to find ledger

Steps to Reproduce

• Start server. Some of these messages will show up automatically in the log if you have levels set to WRN+

• You can probably get it to write a lot more of them if you use the crawl shards command with a limit of 3, e.g. sending this WebSocket command:

    {
        "command": "crawl_shards",
        "limit": 3 
    }
  

Expected Result

Log messages should not be written at the WRN level if they aren't at least somewhat concerning. This one seems to occur a lot during normal operation.

Also, there's very little to go on to figure out what caused it or what type of problem it might indicate.

Actual Result

This is among the most common log messages in 1.8.0-rc2 even when the server appears to be functioning OK.

Environment

Arch Linux, x86_64, 32 GB RAM
rippled 1.8.0-rc2, self-compiled

Supporting Files

It looks like the message comes from here:

https://github.com/ripple/rippled/blob/f0c237e0018b5e4637dc66c3bb3fc705b33d12f8/src/ripple/overlay/impl/PeerImp.cpp#L3368

However, I don't know this code well enough to see how it gets to this case and if it should be treated as warning level.