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Stop relying on SERVER_SOFTWARE being set #1704

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merged 5 commits into from Oct 18, 2019
Merged

Stop relying on SERVER_SOFTWARE being set #1704

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37706bb
Stop relying on SERVER_SOFTWARE being set
zevdg Oct 3, 2019
f650fda
fix formatting
zevdg Oct 3, 2019
6166dd5
format with black
zevdg Oct 3, 2019
53e4d99
report only first generation runtimes as sandboxed
zevdg Oct 7, 2019
14353c9
remove all usage of is_prod_appengine_mvms
zevdg Oct 7, 2019
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19 changes: 9 additions & 10 deletions src/urllib3/contrib/_appengine_environ.py
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Expand Up @@ -6,27 +6,26 @@


def is_appengine():
return is_local_appengine() or is_prod_appengine() or is_prod_appengine_mvms()
return "APPENGINE_RUNTIME" in os.environ


def is_appengine_sandbox():
return is_appengine() and not is_prod_appengine_mvms()
"""Deprecated. Use is_appengine instead."""
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This changes the foundational behavior of this method. It should detect if the app is running under the legacy 2.7 runtime in App Engine standard. Making it detect any app engine runtime is likely to cause user code to fail.

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I guess I don't really know what the "foundational behavior" of this method is supposed to be. I couldn't find any documentation for this function, so I only had the old code to go on which I interpreted as "all appengine runtimes except managed VMs are sandboxed."

Given that managed VMs are decommissioned, it seemed that now the situation is that "all appengine runtimes are sandboxed." Am I missing something?

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So "sandboxed" here is a bit weird. You'll have to kinda go back to when this was written - which was before gVisor.

When urllib3 first added rudimentary support for App Engine, there was App Engine (with no qualifier) in a heavily (ptrace) sandboxed environment and there was App Engine managed VMs which had a much less severe KVM sandbox. Urllib3 can run as usual in the KVM sandbox, but can't run as usual in the ptrace sandbox. So this function is used to determine "can I really use sockets and ssl the in a normal way?" which breaks down to this table these days:

Standard legacy 2.7: no
Standard 3.x: yes
Flexible 2.x or 3.x: yes

So this function should return True only in the legacy 2.7 runtime or when using the legacy 2.7 runtime with devappserver. User code uses this function to determine whether or not to use the AppEngineManager (and therefore urlfetch) instead of the normal PoolManager (and therefore sockets).

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That makes sense. I've changed the function to return True for the python27 runtime and added some documentation to explain the behavior.

return is_appengine()


def is_local_appengine():
return (
"APPENGINE_RUNTIME" in os.environ
and "Development/" in os.environ["SERVER_SOFTWARE"]
return is_appengine() and os.environ.get("SERVER_SOFTWARE", "").startswith(
"Development/"
)


def is_prod_appengine():
return (
"APPENGINE_RUNTIME" in os.environ
and "Google App Engine/" in os.environ["SERVER_SOFTWARE"]
and not is_prod_appengine_mvms()
return is_appengine() and os.environ.get("SERVER_SOFTWARE", "").startswith(
"Google App Engine/"
)


def is_prod_appengine_mvms():
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return os.environ.get("GAE_VM", False) == "true"
"""Deprecated."""
return False