[tahoe-lafs-trac-stream] [Tahoe-LAFS] #3925: revamp "tahoe run"

[Tahoe-LAFS]

#3925: revamp "tahoe run"
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 Reporter:  meejah       |          Owner:
     Type:  enhancement  |         Status:  new
 Priority:  normal       |      Milestone:  undecided
Component:  unknown      |        Version:  n/a
 Keywords:               |  Launchpad Bug:
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 In the past, "tahoe run" was based around the (old) Twisted daemonization
 / runner command called "twistd".

 As part of this, "twistd.pid" files are written out. Another consequence
 is that twistd's options are also available to "tahoe run".

 We have since removed the ability of "tahoe run" to daemonize itself --
 instead users are encouraged to use their favourite damonization software.

 We would like to change how the PID-files work a little to match magic-
 folder and to give any "parent process" a better chance of determining if
 the pid-file is stale.

 This means adding the creation-time of the process. That is, the pid-file
 will look like ``PID create-time\n``. The creation-time helps in case a
 process-id is recycled: it is then possible to determine if that process
 is tahoe (because the creation-time will match) or something else (the
 creation time will be newer).

 We could simply write _another_ PID-file with the above information,
 however it seems like now might be a good time to get rid of the twistd
 dependency/use entirely.

 However, that's technically a backwards-incompatible change because tahoe-
 run currently takes all of the twistd top-level options....it's _possible_
 some of these are actually useful, but a lot of them seem pretty
 "twistd"-specific, and I'm not sure what actually happens if you specify
 any of them.

 I tried ``tahoe run testgrid/bob --profile foo.profile`` for example, but
 did not get a "foo.profile" file (which is I assume how that option is
 supposed to work).

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Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/3925>
Tahoe-LAFS <https://Tahoe-LAFS.org>
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