Listen on unix socket

[Digenis]

This allows securing the app from users on the same system,
provided that the effective group id of scrapyd's process is properly chosen.

[Digenis]

Perhaps the app should also stop using tcp by default.

[codecov]

Codecov Report

Merging #325 into master will decrease coverage by 0.54%.
The diff coverage is 61.53%.

@@            Coverage Diff             @@
##           master     #325      +/-   ##
==========================================
- Coverage   68.77%   68.23%   -0.55%     
==========================================
  Files          16       16              
  Lines         823      831       +8     
  Branches       96       89       -7     
==========================================
+ Hits          566      567       +1     
- Misses        229      234       +5     
- Partials       28       30       +2

Impacted Files	Coverage Δ
scrapyd/app.py	88.63% <61.53%> (-11.37%)	⬇️
scrapyd/webservice.py	28.2% <0%> (-1.71%)	⬇️

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[codecov]

Codecov Report

Merging #325 into master will decrease coverage by 0.3%.
The diff coverage is 61.53%.

@@            Coverage Diff             @@
##           master     #325      +/-   ##
==========================================
- Coverage   68.77%   68.47%   -0.31%     
==========================================
  Files          16       16              
  Lines         823      831       +8     
  Branches       96       98       +2     
==========================================
+ Hits          566      569       +3     
- Misses        229      232       +3     
- Partials       28       30       +2

Impacted Files	Coverage Δ
scrapyd/app.py	88.63% <61.53%> (-11.37%)	⬇️

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[pawelmhm]

integrated with current master here https://github.com/scrapy/scrapyd/compare/uds?expand=1

[pawelmhm]

I'm not certain if I understand the logic here, is this really meant to start both TCPServer and UnixServer? Or is there some intention to allow to disable and stop TCPServer by setting http_port to zero? If 2nd option, if we want to add option to disable TCP this should be explicitly documented in docs.

Because with this implementation if someone just adds uds_path without removing http_port it will start both of them, unixserver and tcp. Is that expected?

[jpmckinney]

The problem (authentication) seems to be equally solved by HTTP basic authentication, which is already merged. (The Unix socket strategy is to use filesystem permissions to prevent other users from connecting to the socket.)

Since this is not related to any feature request issue (i.e. no clear demand), I'll close.

[jpmckinney]

Done in #510