ReactorAlreadyInstalledError

[glyph]

$ mktmpenv
...
$ pip install txacme
...
Successfully installed Twisted-16.4.1 acme-0.9.3 attrs-16.2.0 cffi-1.8.3 cryptography-1.5.2 eliot-0.11.0 enum34-1.1.6 funcsigs-1.0.2 idna-2.1 ipaddress-1.0.17 mock-2.0.0 ndg-httpsclient-0.4.2 pbr-1.10.0 pem-16.1.0 pyOpenSSL-16.2.0 pyasn1-0.1.9 pyasn1-modules-0.0.8 pycparser-2.16 pyrfc3339-1.0 pyrsistent-0.11.13 pytz-2016.7 requests-2.11.1 service-identity-16.0.0 six-1.10.0 treq-15.1.0 txacme-0.9.0 txsni-0.1.6 zope.interface-4.3.2
$ twist --help
Traceback (most recent call last):
  File "/Users/glyph/.virtualenvs/tmp-4d999315aefd700e/bin/twist", line 11, in <module>
    sys.exit(Twist.main())
  File "/Users/glyph/.virtualenvs/tmp-4d999315aefd700e/lib/python2.7/site-packages/twisted/application/twist/_twist.py", line 132, in main
    options = cls.options(argv)
  File "/Users/glyph/.virtualenvs/tmp-4d999315aefd700e/lib/python2.7/site-packages/twisted/application/twist/_twist.py", line 38, in options
    options.parseOptions(argv[1:])
  File "/Users/glyph/.virtualenvs/tmp-4d999315aefd700e/lib/python2.7/site-packages/twisted/application/twist/_options.py", line 157, in parseOptions
    self.installReactor()
  File "/Users/glyph/.virtualenvs/tmp-4d999315aefd700e/lib/python2.7/site-packages/twisted/application/twist/_options.py", line 77, in installReactor
    self["reactor"] = installReactor(name)
  File "/Users/glyph/.virtualenvs/tmp-4d999315aefd700e/lib/python2.7/site-packages/twisted/application/reactors.py", line 82, in installReactor
    installer.install()
  File "/Users/glyph/.virtualenvs/tmp-4d999315aefd700e/lib/python2.7/site-packages/twisted/application/reactors.py", line 60, in install
    namedAny(self.moduleName).install()
  File "/Users/glyph/.virtualenvs/tmp-4d999315aefd700e/lib/python2.7/site-packages/twisted/internet/selectreactor.py", line 198, in install
    installReactor(reactor)
  File "/Users/glyph/.virtualenvs/tmp-4d999315aefd700e/lib/python2.7/site-packages/twisted/internet/main.py", line 32, in installReactor
    raise error.ReactorAlreadyInstalledError("reactor already installed")
twisted.internet.error.ReactorAlreadyInstalledError: reactor already installed

This doesn't happen with twisted[tls], so I'm assuming it's txacme's fault, but I haven't investigated much further than this.

[mithrandi]

This seems to be fixed in master already (I can reproduce with txacme 0.9.0, but not with master), but I don't actually know what's going on here, so it may still warrant further investigation.

[glyph]

I can reproduce with master. Try mktmpenv; pip install git+https://github.com/mithrandi/txacme; twist --help ?

[glyph]

Actually it's pretty straightforward. When building the plugin cache, we get the traceback because the txacme endpoint plugin imports twisted.web.client (among other things) that installs the reactor at module scope. Once the cache is built it's fine.

[mithrandi]

Oh, that explains it; I was using a -e install so the plugin cache was already built.

[mithrandi]

So uh... how do we actually fix this?

[mithrandi]

I guess I can move the endpoint parser into its own module, and it can lazily import everything else.

[glyph]

Yeah, plugins just have to be lazy about almost everything. Or we could make Twisted comprehensively forbid importing the reactor at module level :)

[glyph]

Thanks!!