issue #321: take remote_tmp and system_tmpdirs into account.

Can't simply ignore these settings as some users may have weird noexec
filesystems.

ansible_mitogen/loaders.py

@@ -37,10 +37,12 @@ try:
     from ansible.plugins.loader import connection_loader
     from ansible.plugins.loader import module_loader
     from ansible.plugins.loader import module_utils_loader
+    from ansible.plugins.loader import shell_loader
     from ansible.plugins.loader import strategy_loader
 except ImportError:  # Ansible <2.4
     from ansible.plugins import action_loader
     from ansible.plugins import connection_loader
     from ansible.plugins import module_loader
     from ansible.plugins import module_utils_loader
+    from ansible.plugins import shell_loader
     from ansible.plugins import strategy_loader

ansible_mitogen/mixins.py

@@ -315,6 +315,7 @@ class ActionModuleMixin(ansible.plugins.action.ActionBase):
         # module_common and ensures no second temporary directory or atexit
         # handler is installed.
         self._connection._connect()
+        if not module_args.get('_ansible_tmpdir', object()):
             module_args['_ansible_tmpdir'] = self._connection.get_temp_dir()
 
         return ansible_mitogen.planner.invoke(

ansible_mitogen/services.py

@@ -46,8 +46,12 @@ import os.path
 import sys
 import threading
 
+import ansible.constants
+
 import mitogen
 import mitogen.service
+import mitogen.utils
+import ansible_mitogen.loaders
 import ansible_mitogen.module_finder
 import ansible_mitogen.target
 
@@ -69,6 +73,19 @@ else:
      )
 
 
+def _get_candidate_temp_dirs():
+    # Force load of plugin to ensure ConfigManager has definitions loaded.
+    ansible_mitogen.loaders.shell_loader.get('sh')
+    options = ansible.constants.config.get_plugin_options('shell', 'sh')
+
+    # Pre 2.5 this came from ansible.constants.
+    remote_tmp = (options.get('remote_tmp') or
+                  ansible.constants.DEFAULT_REMOTE_TMP)
+    dirs = list(options.get('system_tmpdirs', ('/var/tmp', '/tmp')))
+    dirs.insert(0, remote_tmp)
+    return mitogen.utils.cast(dirs)
+
+
 class Error(Exception):
     pass
 
@@ -252,6 +269,18 @@ class ContextService(mitogen.service.Service):
         for fullname in self.ALWAYS_PRELOAD:
             self.router.responder.forward_module(context, fullname)
 
+    _candidate_temp_dirs = None
+
+    def _get_candidate_temp_dirs(self):
+        """
+        Return a list of locations to try to create the single temporary
+        directory used by the run. This simply caches the (expensive) plugin
+        load of :func:`_get_candidate_temp_dirs`.
+        """
+        if self._candidate_temp_dirs is None:
+            self._candidate_temp_dirs = _get_candidate_temp_dirs()
+        return self._candidate_temp_dirs
+
     def _connect(self, key, spec, via=None):
         """
         Actual connect implementation. Arranges for the Mitogen connection to
@@ -298,8 +327,11 @@ class ContextService(mitogen.service.Service):
                                 lambda: self._on_stream_disconnect(stream))
 
         self._send_module_forwards(context)
-        init_child_result = context.call(ansible_mitogen.target.init_child,
-                                         log_level=LOG.getEffectiveLevel())
+        init_child_result = context.call(
+            ansible_mitogen.target.init_child,
+            log_level=LOG.getEffectiveLevel(),
+            candidate_temp_dirs=self._get_candidate_temp_dirs(),
+        )
 
         if os.environ.get('MITOGEN_DUMP_THREAD_STACKS'):
             from mitogen import debug

ansible_mitogen/target.py

@@ -70,26 +70,29 @@ import ansible_mitogen.runner
 LOG = logging.getLogger(__name__)
 
 MAKE_TEMP_FAILED_MSG = (
-    "Unable to create a temporary directory for the persistent interpreter.\n"
-    "This likely means no system-supplied TMP directory can be written to.\n"
+    "Unable to find a useable temporary directory. This likely means no\n"
+    "system-supplied TMP directory can be written to, or all directories\n"
+    "were mounted on 'noexec' filesystems.\n"
     "\n"
     "The following paths were tried:\n"
     "    %(namelist)s\n"
     "\n"
-    "The original exception was:\n"
-    "\n"
-    "%(exception)s"
+    "Please check '-vvv' output for a log of individual path errors."
 )
 
 
-#: Set by init_child() to the single temporary directory that will exist for
-#: the duration of the process.
-temp_dir = None
-
 #: Initialized to an econtext.parent.Context pointing at a pristine fork of
 #: the target Python interpreter before it executes any code or imports.
 _fork_parent = None
 
+#: Set by init_child() to a list of candidate $variable-expanded and
+#: tilde-expanded directory paths that may be usable as a temporary directory.
+_candidate_temp_dirs = None
+
+#: Set by reset_temp_dir() to the single temporary directory that will exist
+#: for the duration of the process.
+temp_dir = None
+
 
 def get_small_file(context, path):
     """
@@ -203,6 +206,53 @@ def _on_broker_shutdown():
     prune_tree(temp_dir)
 
 
+def find_good_temp_dir():
+    """
+    Given a list of candidate temp directories extracted from ``ansible.cfg``
+    and stored in _candidate_temp_dirs, combine it with the Python-builtin list
+    of candidate directories used by :mod:`tempfile`, then iteratively try each
+    in turn until one is found that is both writeable and executable.
+    """
+    paths = [os.path.expandvars(os.path.expanduser(p))
+             for p in _candidate_temp_dirs]
+    paths.extend(tempfile._candidate_tempdir_list())
+
+    for path in paths:
+        try:
+            tmp = tempfile.NamedTemporaryFile(
+                prefix='ansible_mitogen_find_good_temp_dir',
+                dir=path,
+            )
+        except (OSError, IOError) as e:
+            LOG.debug('temp dir %r unusable: %s', path, e)
+            continue
+
+        try:
+            try:
+                os.chmod(tmp.name, int('0700', 8))
+            except OSError as e:
+                LOG.debug('temp dir %r unusable: %s: chmod failed: %s',
+                          path, e)
+                continue
+
+            try:
+                # access(.., X_OK) is sufficient to detect noexec.
+                if not os.access(tmp.name, os.X_OK):
+                    raise OSError('filesystem appears to be mounted noexec')
+            except OSError as e:
+                LOG.debug('temp dir %r unusable: %s: %s', path, e)
+                continue
+
+            LOG.debug('Selected temp directory: %r (from %r)', path, paths)
+            return path
+        finally:
+            tmp.close()
+
+    raise IOError(MAKE_TEMP_FAILED_MSG % {
+        'paths': '\n    '.join(paths),
+    })
+
+
 @mitogen.core.takes_econtext
 def reset_temp_dir(econtext):
     """
@@ -218,13 +268,8 @@ def reset_temp_dir(econtext):
     global temp_dir
     # https://github.com/dw/mitogen/issues/239
 
-    try:
-        temp_dir = tempfile.mkdtemp(prefix='ansible_mitogen_')
-    except IOError:
-        raise IOError(MAKE_TEMP_FAILED_MSG % {
-            'namelist': '\n    '.join(tempfile._candidate_tempdir_list()),
-            'exception': traceback.format_exc()
-        })
+    basedir = find_good_temp_dir()
+    temp_dir = tempfile.mkdtemp(prefix='ansible_mitogen_', dir=basedir)
 
     # This must be reinstalled in forked children too, since the Broker
     # instance from the parent process does not carry over to the new child.
@@ -232,7 +277,7 @@ def reset_temp_dir(econtext):
 
 
 @mitogen.core.takes_econtext
-def init_child(econtext, log_level):
+def init_child(econtext, log_level, candidate_temp_dirs):
     """
     Called by ContextService immediately after connection; arranges for the
     (presently) spotless Python interpreter to be forked, where the newly
@@ -245,6 +290,9 @@ def init_child(econtext, log_level):
 
     :param int log_level:
         Logging package level active in the master.
+    :param list[str] candidate_temp_dirs:
+        List of $variable-expanded and tilde-expanded directory names to add to
+        candidate list of temporary directories.
 
     :returns:
         Dict like::
@@ -258,6 +306,9 @@ def init_child(econtext, log_level):
         the controller will use to start forked jobs, and `home_dir` is the
         home directory for the active user account.
     """
+    global _candidate_temp_dirs
+    _candidate_temp_dirs = candidate_temp_dirs
+
     global _fork_parent
     mitogen.parent.upgrade_router(econtext)
     _fork_parent = econtext.router.fork()

docs/ansible.rst

@@ -443,23 +443,30 @@ In summary, for each task Ansible may create one or more of:
 * ``$TMPDIR/ansible_<modname>_payload_.../`` owned by the become user,
 * ``$TMPDIR/ansible-module-tmp-.../`` owned by the become user.
 
-The extension must create a temporary directory to maintain compatibility with
-Ansible, since many modules introspect :data:`sys.argv` in order to find a
-directory where they may write temporary files, however for simplicity only
-one such directory exists for the lifetime of each interpreter, stored in a
-system-supplied temporary directory, and always privately owned by the target
-user account.
-
-The ``remote_tmp`` path is unused, since Ansible does not make exclusive use of
-it, existing semantics are untenable, environments exist with read-only home
-directories where the default ``remote_tmp`` path (``~/.ansible/tmp``) cannot
-be used, and new-style modules always depended on the existence of a
-system-supplied directory anyway, so no requirement is introduced by simply
-ignoring ``remote_tmp``.
+A directory must be created in order to maintain compatibility with Ansible,
+as many modules introspect :data:`sys.argv` in order to find a directory where
+they may write files, however for only one such directory exists for the
+lifetime of each interpreter, its location is consistent for each target
+account, and it is always privately owned by that account.
+
+The following candidate paths are tried until one is found that is writeable
+and appears live on a filesystem that does not have ``noexec`` enabled:
+
+1. The ``$variable`` and tilde-expanded ``remote_tmp`` setting from
+   ``ansible.cfg``.
+2. The ``$variable`` and tilde-expanded ``system_tmpdirs`` setting from
+   ``ansible.cfg``.
+3. The ``TMPDIR`` environment variable.
+4. The ``TEMP`` environment variable.
+5. The ``TMP`` environment variable.
+6. ``/tmp``
+7. ``/var/tmp``
+8. ``/usr/tmp``
+9. The current working directory.
 
 As the directory is created once at startup, and its content is managed by code
 running remotely, no additional network roundtrips are required to create and
-destroy it for each task requiring temporary file storage.
+destroy it for each task requiring temporary storage.
 
 
 .. _ansible_process_env:

tests/ansible/lib/modules/custom_python_detect_environment.py

@@ -3,6 +3,7 @@
 # interpreter I run within.
 
 from ansible.module_utils.basic import AnsibleModule
+from ansible.module_utils.basic import get_module_path
 from ansible.module_utils import six
 
 import os
@@ -30,6 +31,7 @@ def main():
         hostname=socket.gethostname(),
         username=pwd.getpwuid(os.getuid()).pw_name,
         module_tmpdir=getattr(module, 'tmpdir', None),
+        module_path=get_module_path(),
     )
 
 if __name__ == '__main__':