Optionally validate entry point at build time #521

wisechengyi · 2018-07-09T00:19:54Z

Resolves #508

Problem

Current behavior allows building a pex that cannot execute:

[omerta ~]$ pex requests -e qqqqqqqqqqqq -o test.pex
[omerta ~]$ ./test.pex
Traceback (most recent call last):
  File ".bootstrap/_pex/pex.py", line 367, in execute
  File ".bootstrap/_pex/pex.py", line 293, in _wrap_coverage
  File ".bootstrap/_pex/pex.py", line 325, in _wrap_profiling
  File ".bootstrap/_pex/pex.py", line 410, in _execute
  File ".bootstrap/_pex/pex.py", line 468, in execute_entry
  File ".bootstrap/_pex/pex.py", line 473, in execute_module
  File "/Users/kwilson/Python/CPython-2.7.13/lib/python2.7/runpy.py", line 182, in run_module
    mod_name, loader, code, fname = _get_module_details(mod_name)
  File "/Users/kwilson/Python/CPython-2.7.13/lib/python2.7/runpy.py", line 107, in _get_module_details
    raise error(format(e))
ImportError: No module named qqqqqqqqqqqq

Solution

Verify entry point at build time. E.g. a.b.c:m means we will try to do from a.b.c import m in a separate process.

Result

$ find hello
hello
hello/test.py
hello/tree.py

# Invalid module
$ python bin.py -D hello -e invalid.module  -o x.pex --validate-entry-point
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: No module named invalid.module
Traceback (most recent call last):
  File "bin.py", line 758, in <module>
    main()
  File "bin.py", line 743, in main
    pex_builder.build(tmp_name, verify_entry_point=options.validate_ep)
  File "/Users/yic/workspace/pex/pex/pex_builder.py", line 529, in build
    self.freeze(bytecode_compile=bytecode_compile, verify_entry_point=verify_entry_point)
  File "/Users/yic/workspace/pex/pex/pex_builder.py", line 514, in freeze
    self._verify_entry_point()
  File "/Users/yic/workspace/pex/pex/pex_builder.py", line 263, in _verify_entry_point
    raise self.InvalidEntryPoint('Failed to:`{}`'.format(import_statement))
pex.pex_builder.InvalidEntryPoint: Failed to:`import invalid.module`

# invalid method
$ python bin.py -D hello -e test:invalid_method  -o x.pex --validate-entry-point
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: cannot import name invalid_method
Traceback (most recent call last):
  File "bin.py", line 758, in <module>
    main()
  File "bin.py", line 743, in main
    pex_builder.build(tmp_name, verify_entry_point=options.validate_ep)
  File "/Users/yic/workspace/pex/pex/pex_builder.py", line 529, in build
    self.freeze(bytecode_compile=bytecode_compile, verify_entry_point=verify_entry_point)
  File "/Users/yic/workspace/pex/pex/pex_builder.py", line 514, in freeze
    self._verify_entry_point()
  File "/Users/yic/workspace/pex/pex/pex_builder.py", line 263, in _verify_entry_point
    raise self.InvalidEntryPoint('Failed to:`{}`'.format(import_statement))
pex.pex_builder.InvalidEntryPoint: Failed to:`from test import invalid_method`

# without the flag, invalid method still works
$ python bin.py -D hello -e test:invalid_method  -o x.pex

wisechengyi · 2018-07-09T00:21:08Z

Hi @kwlzn please kindly take an initial look for sanity. I am still working on tests, so will ping when it's fully ready.

jsirois

This will be a useful feature but I think there are a few fundamental issues here to address.

jsirois · 2018-07-09T01:25:09Z

pex/pex_builder.py

@@ -238,6 +303,7 @@ def set_entry_point(self, entry_point):
    The entry point may also be specified via ``PEXBuilder.set_executable``.
    """
    self._ensure_unfrozen('Setting an entry point')
+    self._verify_entry_point(entry_point)


Since this is a builder, order of building is not guaranteed and you can't verify until after a freeze since not all requirements or files may yet be added.

Any pointer for a better place?

In freeze, where you know there can be no more code or requirement additions.

jsirois · 2018-07-09T01:27:08Z

pex/pex_builder.py

+                                   .format(ep_method, file_candidates))
+
+  def _gather_file_candidates(self, entry_point_elements):
+    # 1. Find the files matching a.b.c:m, which is a/b/c.py


It could also be a/b/c/__init__.py, ... or be a dynamically generated module! I think you really have to try to import the symbol after a freeze to avoid all the corner cases.

Importing the code feels quite sketchy, even out of process, because they could have bad side effect or even security concerns.

How do you feel about putting verifying entry point behind an option, stating that it would only check for static method in

a/b/c.py

a/b/c/__init__.py
and allow people to skip static check by disabling it?

If validation is opt-in, it seems like import would be the way to go. The user is going to run the pex after all and suffer the side-effects soon anyhow when they do so! Basically, this is forced to be a half measure one way or the other, so the choice comes down to avoiding side-effects at build time (they'll happen at runtime) for the X% of cases that have this pathology, or not supporting Y% of cases that have bizarre dynamic module generation. I'm really not sure what these percentages are or what is the better way to go. Import just seems attractive since it's robust: ie it's what pex does at runtime. Parsing is new logic.

Yeah that's fair. Importing could also get around ast parsing difference between python 2 and 3.

So I am going to do the importing, and then put it behind an option with default disabled.

wisechengyi

@jsirois ready for a second round sanity check. test still incoming.

wisechengyi · 2018-07-18T05:09:19Z

pex/pex_builder.py

    if bytecode_compile:
      self._precompile_source()
    self._frozen = True

-  def build(self, filename, bytecode_compile=True):
+  def build(self, filename, bytecode_compile=True, verify_entry_point=False):


This is the interface pants will call, correct?

changing it in a way to keep backwards compatibility.

Yes, but see above.

jsirois

Looks good, but a cleanup suggestion re subprocess / Executor and a bigger change idea to consider.

jsirois · 2018-07-18T16:32:01Z

pex/pex_builder.py

+    else:
+      raise self.InvalidEntryPoint("Fail to parse: `{}`".format(entry_point))
+
+    args = [self._interpreter.binary, '-c', import_statement]


Execution via subprocess was consolidated to Executor, so this code should use that instead of subprocess directly.

A bit more true to the runtime environment the entry point will be executed in would be something like:

with named_temporary_file() as fp: fp.write(import_statement) fp.close() result = PEX(self.chroot().path()).run([fp.name], env={'PEX_INTERPRETER': '1'}) if result != 0: raise self.InvalidEntryPoint('Failed to validate entrypoint {}'.format(entry_point))

This though unfortunately creates a circular PEX <-> PEXBuilder dep. Better I think to lift the check to the PEX constructor which could be plumbed both from pex.bin.pex and from API users (Pants).

Moved the verification step into class PEX(object):

def __init__(self, ..., verify_entry_point=False):

jsirois · 2018-07-18T16:32:33Z

pex/pex_builder.py

    if bytecode_compile:
      self._precompile_source()
    self._frozen = True

-  def build(self, filename, bytecode_compile=True):
+  def build(self, filename, bytecode_compile=True, verify_entry_point=False):


Yes, but see above.

jsirois

It looks like the one non-isort/non-style CI shard failure is legit but not related to this PR.

LGTM mod one latent bug pointed out re not using the builder's interpreter to perform the import check and completion of test work.

jsirois · 2018-07-19T17:29:29Z

pex/pex.py

+      ep_method = ep_split[1]
+      import_statement = 'from {} import {}'.format(ep_module, ep_method)
+    else:
+      raise InvalidEntryPoint("Fail to parse: `{}`".format(entry_point))


Failure or Failed would make more sense here.

jsirois · 2018-07-19T17:30:39Z

pex/bin/pex.py

@@ -741,7 +753,7 @@ def main(args=None):
    pex_builder.freeze()

    log('Running PEX file at %s with args %s' % (pex_builder.path(), cmdline), v=options.verbosity)
-    pex = PEX(pex_builder.path(), interpreter=pex_builder.interpreter)
+    pex = PEX(pex_builder.path(), interpreter=pex_builder.interpreter, verify_entry_point=options.validate_ep)


jsirois · 2018-07-19T17:31:34Z

pex/bin/pex.py

+      default=False,
+      action='store_true',
+      help='Validate the entry point by importing it in separate process. Warning: this could have '
+           'side effect. For example, entry point `a.b.c:m` will translate to '


'side effects.

jsirois · 2018-07-19T17:40:58Z

pex/bin/pex.py

@@ -732,6 +741,9 @@ def main(args=None):
      tmp_name = options.pex_name + '~'
      safe_delete(tmp_name)
      pex_builder.build(tmp_name)
+      if options.validate_ep:


You could be more uniform, more correct and fail faster with:

pex_builder = build_pex(reqs, options, resolver_options_builder) pex_builder.freeze() pex = PEX(pex_builder.path(), interpreter=pex_builder.interpreter, verify_entry_point=options.validate_ep) if options.pex_name is not None: ...

As things stand, in the options.pex_name branch, the pex is zipped up before the entrypoint validation which could be wasted work. Worse though is that the builder's custom interpreter, if any, is not used. This could be a problem if the current running interpreter does not match what the built pex needs and syntax differs (a 2/3 split).

Moved things up to fail fast.

jsirois · 2018-07-19T17:42:10Z

pex/pex.py

@@ -520,3 +522,31 @@ def run(self, args=(), with_chroot=False, blocking=True, setsid=False, **kwargs)
                                    stderr=kwargs.pop('stderr', None),
                                    **kwargs)
    return process.wait() if blocking else process
+
+  def do_entry_point_verification(self):


Given comments above re uniformity in performing the validation, I'd make this _private.

wisechengyi · 2018-07-20T22:56:53Z

looks like PEX.run would ignore -c arg.

$ python '/var/folders/yt/pxdd3gp96530xh_116kskmkh0000gn/T/tmp8rQWfk' -c 'print 123'
hello

executed the entry point (print hello) rather than -c which prints 123.
Going to try

with named_temporary_file() as fp:
  fp.write(import_statement)
  fp.close()
  result = PEX(self.chroot().path()).run([fp.name], env={'PEX_INTERPRETER': '1'})
  if result != 0:
    raise self.InvalidEntryPoint('Failed to validate entrypoint {}'.format(entry_point))

as suggested earlier.

wisechengyi · 2018-07-20T23:36:12Z

Updated. Tests incoming.

wisechengyi · 2018-07-21T05:15:07Z

Tests added. Ready for final review.

jsirois

Thanks Yi!

There was no proncipled reason to use it. Neither the originating commit or its originiating issue refer to Pillow and the tests themselves don't implicate anything being required except a 3rdparty lib. See: + pex-tool#521 + pex-tool#508

wisechengyi added 7 commits July 6, 2018 21:44

initial

6a45d41

can verify file existence

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can verify both

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works fine

67e7010

cmt

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rev init

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nit

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wisechengyi added 5 commits July 17, 2018 17:11

use import to check entry point validity

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fmt

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option

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flag works

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reorder sig

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wisechengyi force-pushed the vm_pr branch from ee4b3a5 to dd9ea02 Compare July 18, 2018 04:56

diff module and method

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fmt

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execute a file containing import

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remove dup code

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privatize do_entry_point_verification

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wisechengyi changed the title ~~Validate entry point at build time~~ Optionally validate entry point at build time Jul 23, 2018

wisechengyi merged commit d1f946c into master Jul 23, 2018

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Optionally validate entry point at build time #521

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Optionally validate entry point at build time #521

Optionally validate entry point at build time #521

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