Optimize template (#28044)

* Optimize template

* In fixing template to handle diff correctly #24477, I introduced more
  round trips to the remote end which slowed things down  The new code now
  uses one fewer round trips than the old code.
* Reimplement a large part of template by calling the copy action plugin
  instead of doing it in template's code.  This reduces the code in
  template and gives us one place to fix bugs and optimize.
* Add a follow parameter to template that mirrors the follow parameters
  for file and copy.
* Fix copy's diff handling (probably broken in my rewrite for in 2.4
  development)
* Adjusted when copy creates tmp dirs to rduce round trips in copy and
  template.

Fixes #27956

CHANGELOG.md

@@ -149,6 +149,9 @@ Ansible Changes By Release
   absolute path.
 - The archive module has a new parameter exclude_path which lists paths to exclude from the archive
 - The yum module has a new parameter security which limits state=latest to security updates
+- The template module gained a follow parameter to match with copy and file.
+  Like those modules, template defaults this parameter to False.  Previously,
+  template hardcoded this to true.
 
 ### New Modules
 - aci

lib/ansible/modules/files/template.py

@@ -81,6 +81,13 @@ options:
         if the destination does not exist.
     type: bool
     default: 'yes'
+  follow:
+    description:
+      - This flag indicates that filesystem links in the destination, if they exist, should be followed.
+      - Previous to Ansible 2.4, this was hardcoded as C(yes).
+    type: bool
+    default: 'no'
+    version_added: "2.4"
 notes:
   - For Windows you can use M(win_template) which uses '\r\n' as C(newline_sequence).
   - Including a string that uses a date in the template will result in the template being marked 'changed' each time

lib/ansible/plugins/action/copy.py

@@ -219,6 +219,12 @@ class ActionModule(ActionBase):
         else:
             dest_file = self._connection._shell.join_path(dest)
 
+        # Create a tmp path if missing only if this is not recursive.
+        # If this is recursive we already have a tmp path.
+        if delete_remote_tmp:
+            if tmp is None or "-tmp-" not in tmp:
+                tmp = self._make_tmp_path()
+
         # Attempt to get remote file info
         dest_status = self._execute_remote_stat(dest_file, all_vars=task_vars, follow=follow, tmp=tmp, checksum=force)
 
@@ -246,19 +252,13 @@ class ActionModule(ActionBase):
         if local_checksum != dest_status['checksum']:
             # The checksums don't match and we will change or error out.
 
-            # Create a tmp path if missing only if this is not recursive.
-            # If this is recursive we already have a tmp path.
-            if delete_remote_tmp:
-                if tmp is None or "-tmp-" not in tmp:
-                    tmp = self._make_tmp_path()
-
             if self._play_context.diff and not raw:
                 result['diff'].append(self._get_diff_data(dest_file, source_full, task_vars))
 
             if self._play_context.check_mode:
                 self._remove_tempfile_if_content_defined(content, content_tempfile)
-                module_return = dict(changed=True)
-                return module_return
+                result['changed'] = True
+                return result
 
             # Define a remote directory that we will copy the file to.
             tmp_src = self._connection._shell.join_path(tmp, 'source')
@@ -321,7 +321,7 @@ class ActionModule(ActionBase):
             # If checksums match, and follow = True, find out if 'dest' is a link. If so,
             # change it to point to the source of the link.
             if follow:
-                dest_status_nofollow = self._execute_remote_stat(dest_file, all_vars=task_vars, follow=False)
+                dest_status_nofollow = self._execute_remote_stat(dest_file, all_vars=task_vars, tmp=tmp, follow=False)
                 if dest_status_nofollow['islnk'] and 'lnk_source' in dest_status_nofollow.keys():
                     dest = dest_status_nofollow['lnk_source']
 
@@ -345,7 +345,8 @@ class ActionModule(ActionBase):
         if not module_return.get('checksum'):
             module_return['checksum'] = local_checksum
 
-        return module_return
+        result.update(module_return)
+        return result
 
     def _get_file_args(self):
         new_module_args = {'recurse': False}

lib/ansible/plugins/action/template.py

@@ -18,10 +18,12 @@ from __future__ import (absolute_import, division, print_function)
 __metaclass__ = type
 
 import os
+import shutil
+import tempfile
 
 from ansible import constants as C
 from ansible.errors import AnsibleError, AnsibleFileNotFound
-from ansible.module_utils._text import to_text
+from ansible.module_utils._text import to_bytes, to_text
 from ansible.module_utils.parsing.convert_bool import boolean
 from ansible.plugins.action import ActionBase
 from ansible.template import generate_ansible_template_vars
@@ -58,6 +60,7 @@ class ActionModule(ActionBase):
         source = self._task.args.get('src', None)
         dest = self._task.args.get('dest', None)
         force = boolean(self._task.args.get('force', True), strict=False)
+        follow = boolean(self._task.args.get('follow', False), strict=False)
         state = self._task.args.get('state', None)
         newline_sequence = self._task.args.get('newline_sequence', self.DEFAULT_NEWLINE_SEQUENCE)
         variable_start_string = self._task.args.get('variable_start_string', None)
@@ -92,20 +95,6 @@ class ActionModule(ActionBase):
         if 'failed' in result:
             return result
 
-        # Expand any user home dir specification
-        dest = self._remote_expand_user(dest)
-
-        directory_prepended = False
-        if dest.endswith(os.sep):
-            # Optimization.  trailing slash means we know it's a directory
-            directory_prepended = True
-            dest = self._connection._shell.join_path(dest, os.path.basename(source))
-        else:
-            # Find out if it's a directory
-            dest_stat = self._execute_remote_stat(dest, task_vars, True, tmp=tmp)
-            if dest_stat['exists'] and dest_stat['isdir']:
-                dest = self._connection._shell.join_path(dest, os.path.basename(source))
-
         # Get vault decrypted tmp file
         try:
             tmp_source = self._loader.get_real_file(source)
@@ -160,70 +149,35 @@ class ActionModule(ActionBase):
         finally:
             self._loader.cleanup_tmp_file(tmp_source)
 
-        if not tmp:
-            tmp = self._make_tmp_path()
-
-        local_checksum = checksum_s(resultant)
-        remote_checksum = self.get_checksum(dest, task_vars, not directory_prepended, source=source, tmp=tmp)
-        if isinstance(remote_checksum, dict):
-            # Error from remote_checksum is a dict.  Valid return is a str
-            result.update(remote_checksum)
-            return result
-
-        diff = {}
-        new_module_args = self._task.args.copy()
-
-        # remove newline_sequence from standard arguments
-        new_module_args.pop('newline_sequence', None)
-        new_module_args.pop('block_start_string', None)
-        new_module_args.pop('block_end_string', None)
-        new_module_args.pop('variable_start_string', None)
-        new_module_args.pop('variable_end_string', None)
-        new_module_args.pop('trim_blocks', None)
-
-        if (remote_checksum == '1') or (force and local_checksum != remote_checksum):
-
-            result['changed'] = True
-            # if showing diffs, we need to get the remote value
-            if self._play_context.diff:
-                diff = self._get_diff_data(dest, resultant, task_vars, source_file=False)
-
-            if not self._play_context.check_mode:  # do actual work through copy
-                xfered = self._transfer_data(self._connection._shell.join_path(tmp, 'source'), resultant)
-
-                # fix file permissions when the copy is done as a different user
-                self._fixup_perms2((tmp, xfered))
-
-                # run the copy module
-                new_module_args.update(
-                    dict(
-                        src=xfered,
-                        dest=dest,
-                        original_basename=os.path.basename(source),
-                        follow=True,
-                    ),
-                )
-                result.update(self._execute_module(module_name='copy', module_args=new_module_args, task_vars=task_vars, tmp=tmp, delete_remote_tmp=False))
-
-            if result.get('changed', False) and self._play_context.diff:
-                result['diff'] = diff
+        new_task = self._task.copy()
+        new_task.args.pop('newline_sequence', None)
+        new_task.args.pop('block_start_string', None)
+        new_task.args.pop('block_end_string', None)
+        new_task.args.pop('variable_start_string', None)
+        new_task.args.pop('variable_end_string', None)
+        new_task.args.pop('trim_blocks', None)
+        try:
+            tempdir = tempfile.mkdtemp()
+            result_file = os.path.join(tempdir, os.path.basename(source))
+            with open(result_file, 'wb') as f:
+                f.write(to_bytes(resultant, errors='surrogate_or_strict'))
 
-        else:
-            # when running the file module based on the template data, we do
-            # not want the source filename (the name of the template) to be used,
-            # since this would mess up links, so we clear the src param and tell
-            # the module to follow links.  When doing that, we have to set
-            # original_basename to the template just in case the dest is
-            # a directory.
-            new_module_args.update(
+            new_task.args.update(
                 dict(
-                    src=None,
-                    original_basename=os.path.basename(source),
-                    follow=True,
+                    src=result_file,
+                    dest=dest,
+                    follow=follow,
                 ),
             )
-            result.update(self._execute_module(module_name='file', module_args=new_module_args, task_vars=task_vars, tmp=tmp, delete_remote_tmp=False))
-
-        self._remove_tmp_path(tmp)
+            copy_action = self._shared_loader_obj.action_loader.get('copy',
+                                                                    task=new_task,
+                                                                    connection=self._connection,
+                                                                    play_context=self._play_context,
+                                                                    loader=self._loader,
+                                                                    templar=self._templar,
+                                                                    shared_loader_obj=self._shared_loader_obj)
+            result.update(copy_action.run(task_vars=task_vars))
+        finally:
+            shutil.rmtree(tempdir)
 
         return result