ansible: initial mitogen_host_pinned strategy.

Author: dw

ansible_mitogen/plugins/strategy/mitogen_host_pinned.py

@@ -0,0 +1,67 @@
+# Copyright 2017, David Wilson
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+# 1. Redistributions of source code must retain the above copyright notice,
+# this list of conditions and the following disclaimer.
+#
+# 2. Redistributions in binary form must reproduce the above copyright notice,
+# this list of conditions and the following disclaimer in the documentation
+# and/or other materials provided with the distribution.
+#
+# 3. Neither the name of the copyright holder nor the names of its contributors
+# may be used to endorse or promote products derived from this software without
+# specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+
+from __future__ import absolute_import
+import os.path
+import sys
+
+#
+# This is not the real Strategy implementation module, it simply exists as a
+# proxy to the real module, which is loaded using Python's regular import
+# mechanism, to prevent Ansible's PluginLoader from making up a fake name that
+# results in ansible_mitogen plugin modules being loaded twice: once by
+# PluginLoader with a name like "ansible.plugins.strategy.mitogen", which is
+# stuffed into sys.modules even though attempting to import it will trigger an
+# ImportError, and once under its canonical name, "ansible_mitogen.strategy".
+#
+# Therefore we have a proxy module that imports it under the real name, and
+# sets up the duff PluginLoader-imported module to just contain objects from
+# the real module, so duplicate types don't exist in memory, and things like
+# debuggers and isinstance() work predictably.
+#
+
+BASE_DIR = os.path.abspath(
+    os.path.join(os.path.dirname(__file__), '../../..')
+)
+
+if BASE_DIR not in sys.path:
+    sys.path.insert(0, BASE_DIR)
+
+import ansible_mitogen.loaders
+import ansible_mitogen.strategy
+
+
+Base = ansible_mitogen.loaders.strategy_loader.get('host_pinned', class_only=True)
+
+if Base is None:
+    raise ImportError(
+        'The host_pinned strategy is only available in Ansible 2.7 or newer.'
+    )
+
+class StrategyModule(ansible_mitogen.strategy.StrategyMixin, Base):
+    pass

docs/ansible.rst

@@ -70,8 +70,9 @@ Installation
 
    The ``strategy`` key is optional. If omitted, the
    ``ANSIBLE_STRATEGY=mitogen_linear`` environment variable can be set on a
-   per-run basis. Like ``mitogen_linear``, the ``mitogen_free`` strategy exists
-   to mimic the ``free`` strategy.
+   per-run basis. Like ``mitogen_linear``, the ``mitogen_free`` and
+   ``mitogen_host_pinned`` strategies exists to mimic the ``free`` and
+   ``host_pinned`` strategies.
 
 4. If targets have a restrictive ``sudoers`` file, add a rule like: