issue #199: ansible: stop writing temp files for new style modules

While adding support for non-new style module types, NewStyleRunner
began writing modules to a temporary file, and sys.argv was patched to
actually include the script filename. The argv change was never required
to fix any particular bug, and a search of the standard modules reveals
no argv users. Update argv[0] to be '', like an interactive interpreter
would have.

While fixing #210, new style runner began setting __file__ to the
temporary file path in order to allow apt.py to discover the Ansiballz
temporary directory. 5 out of 1,516 standard modules follow this
pattern, but in each case, none actually attempt to access __file__,
they just call dirname on it. Therefore do not write the contents of
file, simply set it to the path as it would exist, within a real
temporary directory.

Finally move temporary directory creation out of runner and into target.
Now a single directory exists for the duration of a run, and is emptied
by runner.py as necessary after each task invocation.

This could be further extended to stop rewriting non-new-style modules
in a with_items loop, but that's another step.

Finally the last bullet point in the documentation almost isn't a lie
again.

ansible_mitogen/runner.py

@@ -74,7 +74,7 @@ def reopen_readonly(fp):
     """
     Replace the file descriptor belonging to the file object `fp` with one
     open on the same file (`fp.name`), but opened with :py:data:`os.O_RDONLY`.
-    This enables temporary files to be executed on Linux, which usually theows
+    This enables temporary files to be executed on Linux, which usually throws
     ``ETXTBUSY`` if any writeable handle exists pointing to a file passed to
     `execve()`.
     """
@@ -106,14 +106,6 @@ class Runner(object):
         self.raw_params = raw_params
         self.args = args
         self.env = env
-        self._temp_dir = None
-
-    def get_temp_dir(self):
-        if not self._temp_dir:
-            self._temp_dir = tempfile.mkdtemp(prefix='ansible_mitogen_')
-            # https://github.com/dw/mitogen/issues/239
-            #ansible_mitogen.target.make_temp_directory(self.remote_tmp)
-        return self._temp_dir
 
     def setup(self):
         """
@@ -128,8 +120,16 @@ class Runner(object):
         implementation simply restores the original environment.
         """
         self._env.revert()
-        if self._temp_dir:
-            shutil.rmtree(self._temp_dir)
+        self._cleanup_temp()
+
+    def _cleanup_temp(self):
+        for name in os.listdir(ansible_mitogen.target.temp_dir):
+            if name in ('.', '..'):
+                continue
+
+            path = os.path.join(ansible_mitogen.target.temp_dir, name)
+            LOG.debug('Deleting %r', path)
+            ansible_mitogen.target.prune_tree(path)
 
     def _run(self):
         """
@@ -214,13 +214,15 @@ class ProgramRunner(Runner):
         super(ProgramRunner, self).setup()
         self._setup_program()
 
+    program_fp = None
+
     def _setup_program(self):
         """
         Create a temporary file containing the program code. The code is
         fetched via :meth:`_get_program`.
         """
         name = 'ansible_module_' + os.path.basename(self.path)
-        path = os.path.join(self.get_temp_dir(), name)
+        path = os.path.join(ansible_mitogen.target.temp_dir, name)
         self.program_fp = open(path, 'wb')
         self.program_fp.write(self._get_program())
         self.program_fp.flush()
@@ -247,6 +249,7 @@ class ProgramRunner(Runner):
         """
         Delete the temporary program file.
         """
+        if self.program_fp:
             self.program_fp.close()
         super(ProgramRunner, self).revert()
 
@@ -284,7 +287,7 @@ class ArgsFileRunner(Runner):
         self.args_fp = tempfile.NamedTemporaryFile(
             prefix='ansible_mitogen',
             suffix='-args',
-            dir=self.get_temp_dir(),
+            dir=ansible_mitogen.target.temp_dir,
         )
         self.args_fp.write(self._get_args_contents())
         self.args_fp.flush()
@@ -361,22 +364,33 @@ class NewStyleRunner(ScriptRunner):
     def setup(self):
         super(NewStyleRunner, self).setup()
         self._stdio = NewStyleStdio(self.args)
-        self._argv = TemporaryArgv([self.program_fp.name])
+        # It is possible that not supplying the script filename will break some
+        # module, but this has never been a bug report. Instead act like an
+        # interpreter that had its script piped on stdin.
+        self._argv = TemporaryArgv([''])
 
     def revert(self):
         self._argv.revert()
         self._stdio.revert()
         super(NewStyleRunner, self).revert()
 
+    def _setup_args(self):
+        pass
+
+    def _setup_program(self):
+        pass
+
     def _get_code(self):
+        self.source = ansible_mitogen.target.get_file(
+            context=self.service_context,
+            path=self.path,
+        )
+
         try:
             return self._code_by_path[self.path]
         except KeyError:
             return self._code_by_path.setdefault(self.path, compile(
-                source=ansible_mitogen.target.get_file(
-                    context=self.service_context,
-                    path=self.path,
-                ),
+                source=self.source,
                 filename=self.path,
                 mode='exec',
                 dont_inherit=True,
@@ -384,14 +398,21 @@ class NewStyleRunner(ScriptRunner):
 
     def _run(self):
         code = self._get_code()
+
         mod = types.ModuleType('__main__')
-        mod.__file__ = self.program_fp.name
         mod.__package__ = None
-        d = vars(mod)
+        # Some Ansible modules use __file__ to find the Ansiballz temporary
+        # directory. We must provide some temporary path in __file__, but we
+        # don't want to pointlessly write the module to disk when it never
+        # actually needs to exist. So just pass the filename as it would exist.
+        mod.__file__ = os.path.join(
+            ansible_mitogen.target.temp_dir,
+            'ansible_module_' + os.path.basename(self.path),
+        )
         e = None
 
         try:
-            exec code in d, d
+            exec code in vars(mod)
         except SystemExit, e:
             pass
 

ansible_mitogen/services.py

@@ -270,7 +270,7 @@ class ContextService(mitogen.service.Service):
 
         # We don't need to wait for the result of this. Ideally we'd check its
         # return value somewhere, but logs will catch a failure anyway.
-        context.call_async(ansible_mitogen.target.start_fork_parent)
+        context.call_async(ansible_mitogen.target.init_child)
 
         if os.environ.get('MITOGEN_DUMP_THREAD_STACKS'):
             from mitogen import debug

ansible_mitogen/target.py

@@ -33,6 +33,7 @@ for file transfer, module execution and sundry bits like changing file modes.
 
 from __future__ import absolute_import
 import cStringIO
+import errno
 import grp
 import json
 import logging
@@ -58,6 +59,10 @@ import mitogen.service
 
 LOG = logging.getLogger(__name__)
 
+#: Set by init_child() to the single temporary directory that will exist for
+#: the duration of the process.
+temp_dir = None
+
 #: Caching of fetched file data.
 _file_cache = {}
 
@@ -191,8 +196,67 @@ def transfer_file(context, in_path, out_path, sync=False, set_owner=False):
     os.utime(out_path, (metadata['atime'], metadata['mtime']))
 
 
+def prune_tree(path):
+    """
+    Like shutil.rmtree(), but log errors rather than discard them, and do not
+    waste multiple os.stat() calls discovering whether the object can be
+    deleted, just try deleting it instead.
+    """
+    try:
+        os.unlink(path)
+        return
+    except OSError, e:
+        if not (os.path.isdir(path) and
+                e.args[0] in (errno.EPERM, errno.EISDIR)):
+            LOG.error('prune_tree(%r): %s', path, e)
+            return
+
+    try:
+        # Ensure write access for readonly directories. Ignore error in case
+        # path is on a weird filesystem (e.g. vfat).
+        os.chmod(path, int('0700', 8))
+    except OSError, e:
+        LOG.warning('prune_tree(%r): %s', path, e)
+
+    try:
+        for name in os.listdir(path):
+            if name not in ('.', '..'):
+                prune_tree(os.path.join(path, name))
+        os.rmdir(path)
+    except OSError, e:
+        LOG.error('prune_tree(%r): %s', path, e)
+
+
+def _on_broker_shutdown():
+    """
+    Respond to broker shutdown (graceful termination by parent, or loss of
+    connection to parent) by deleting our sole temporary directory.
+    """
+    prune_tree(temp_dir)
+
+
+def reset_temp_dir(econtext):
+    """
+    Create one temporary directory to be reused by all runner.py invocations
+    for the lifetime of the process. The temporary directory is changed for
+    each forked job, and emptied as necessary runner.py::_cleanup_temp() after
+    each module invocation.
+
+    The result is that a context need only create and delete one directory
+    during startup and shutdown, and no further filesystem writes need occur
+    assuming no modules execute that create temporary files.
+    """
+    global temp_dir
+    # https://github.com/dw/mitogen/issues/239
+    temp_dir = tempfile.mkdtemp(prefix='ansible_mitogen_')
+
+    # This must be reinstalled in forked children too, since the Broker
+    # instance from the parent process does not carry over to the new child.
+    mitogen.core.listen(econtext.broker, 'shutdown', _on_broker_shutdown)
+
+
 @mitogen.core.takes_econtext
-def start_fork_parent(econtext):
+def init_child(econtext):
     """
     Called by ContextService immediately after connection; arranges for the
     (presently) spotless Python interpreter to be forked, where the newly
@@ -206,6 +270,7 @@ def start_fork_parent(econtext):
     global _fork_parent
     mitogen.parent.upgrade_router(econtext)
     _fork_parent = econtext.router.fork()
+    reset_temp_dir(econtext)
 
 
 @mitogen.core.takes_econtext
@@ -321,6 +386,7 @@ def run_module_async(job_id, kwargs, econtext):
     """
     try:
         try:
+            reset_temp_dir(econtext)
             _run_module_async(job_id, kwargs, econtext)
         except Exception:
             LOG.exception('_run_module_async crashed')
@@ -331,7 +397,9 @@ def run_module_async(job_id, kwargs, econtext):
 def make_temp_directory(base_dir):
     """
     Handle creation of `base_dir` if it is absent, in addition to a unique
-    temporary directory within `base_dir`.
+    temporary directory within `base_dir`. This is the temporary directory that
+    becomes 'remote_tmp', not the one used by Ansiballz. It always uses the
+    system temporary directory.
 
     :returns:
         Newly created temporary directory.

tests/ansible/lib/modules/custom_python_detect_environment.py

@@ -14,6 +14,7 @@ def main():
     module = AnsibleModule(argument_spec={})
     module.exit_json(
         argv=sys.argv,
+        __file__=__file__,
         argv_types=[str(type(s)) for s in sys.argv],
         env=dict(os.environ),
         cwd=os.getcwd(),