[tor-bugs] #33951 [Internal Services/Service - cache]: mtail floods its logs with garbage

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#33951: mtail floods its logs with garbage
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     Reporter:  anarcat                            |      Owner:  anarcat
         Type:  defect                             |     Status:  assigned
     Priority:  Medium                             |  Milestone:
    Component:  Internal Services/Service - cache  |    Version:
     Severity:  Normal                             |   Keywords:
Actual Points:                                     |  Parent ID:
       Points:                                     |   Reviewer:
      Sponsor:                                     |
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 we seen ton of this garbage in the mtail logs:

 {{{
 I0421 18:43:02.307808   21142 file.go:168] file type does not support
 deadline
 }}}

 there's a lot to unpack here:

  * weird log format: the first word is `IMMDD`, that is the above message
 is from April 21st (the I is for "Irrelevant character", i guess?)
  * 21142 is the pid
  * `file type does not support deadline` is an error from the golang
 standard library and occurs when someone calls `SetReadDeadline` on a file
 that doesn't support it

 This happens every minute or so. It gathers about a gigabyte of logs a
 month or two.

 In later versions of mtail, this is fixed by making turning the "warning"
 (technically, it's an "Info" message, but those are displayed
 unconditionnally) into a "verbose" (technically `V(2)`) message that
 doesn't get shown by default.

 The package from buster doesn't have that fix, but the current version in
 unstable (rc24) does have it.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/33951>
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