ansible: implement streaming in Connection.put_file().

This is the function the copy module uses.

ansible_mitogen/connection.py

@@ -41,7 +41,7 @@ import mitogen.utils
 
 import ansible_mitogen.target
 import ansible_mitogen.process
-from ansible_mitogen.services import ContextService
+import ansible_mitogen.services
 
 
 LOG = logging.getLogger(__name__)
@@ -160,7 +160,7 @@ class Connection(ansible.plugins.connection.ConnectionBase):
     def _wrap_connect(self, on_error, kwargs):
         dct = mitogen.service.call(
             context=self.parent,
-            handle=ContextService.handle,
+            handle=ansible_mitogen.services.ContextService.handle,
             method='get',
             kwargs=mitogen.utils.cast(kwargs),
         )
@@ -300,7 +300,7 @@ class Connection(ansible.plugins.connection.ConnectionBase):
             if context:
                 mitogen.service.call(
                     context=self.parent,
-                    handle=ContextService.handle,
+                    handle=ansible_mitogen.services.ContextService.handle,
                     method='put',
                     kwargs={
                         'context': context
@@ -398,12 +398,25 @@ class Connection(ansible.plugins.connection.ConnectionBase):
 
     def put_file(self, in_path, out_path):
         """
-        Implement put_file() by caling the corresponding
-        ansible_mitogen.target function in the target.
+        Implement put_file() by streamily transferring the file via
+        FileService.
 
         :param str in_path:
             Local filesystem path to read.
         :param str out_path:
             Remote filesystem path to write.
         """
-        self.put_data(out_path, ansible_mitogen.target.read_path(in_path))
+        mitogen.service.call(
+            context=self.parent,
+            handle=ansible_mitogen.services.FileService.handle,
+            method='register',
+            kwargs={
+                'path': mitogen.utils.cast(in_path)
+            }
+        )
+        self.call(
+            ansible_mitogen.target.transfer_file,
+            context=self.parent,
+            in_path=in_path,
+            out_path=out_path
+        )

ansible_mitogen/target.py

@@ -66,7 +66,22 @@ _fork_parent = None
 
 
 def _get_file(context, path, out_fp):
-    LOG.debug('get_file(): fetching %r from %r', path, context)
+    """
+    Streamily download a file from the connection multiplexer process in the
+    controller.
+
+    :param mitogen.core.Context context:
+        Reference to the context hosting the FileService that will be used to
+        fetch the file.
+    :param bytes in_path:
+        FileService registered name of the input file.
+    :param bytes out_path:
+        Name of the output path on the local disk.
+    :returns:
+        :data:`True` on success, or :data:`False` if the transfer was
+        interrupted and the output should be discarded.
+    """
+    LOG.debug('_get_file(): fetching %r from %r', path, context)
     recv = mitogen.core.Receiver(router=context.router)
     size = mitogen.service.call(
         context=context,
@@ -85,12 +100,11 @@ def _get_file(context, path, out_fp):
 
     if out_fp.tell() != size:
         LOG.error('get_file(%r): receiver was closed early, controller '
-                  'is likely shutting down. Truncating output file.', path)
-        out_fp.truncate(0)
+                  'is likely shutting down.', path)
 
     LOG.debug('target.get_file(): fetched %d bytes of %r from %r',
               size, path, context)
-    return size
+    return out_fp.tell() == size
 
 
 def get_file(context, path):
@@ -109,11 +123,39 @@ def get_file(context, path):
     """
     if path not in _file_cache:
         io = cStringIO.StringIO()
-        _get_file(context, path, io)
+        if not _get_file(context, path, io):
+            raise IOError('transfer of %r was interrupted.' % (path,))
         _file_cache[path] = io.getvalue()
     return _file_cache[path]
 
 
+def transfer_file(context, in_path, out_path):
+    """
+    Streamily download a file from the connection multiplexer process in the
+    controller.
+
+    :param mitogen.core.Context context:
+        Reference to the context hosting the FileService that will be used to
+        fetch the file.
+    :param bytes in_path:
+        FileService registered name of the input file.
+    :param bytes out_path:
+        Name of the output path on the local disk.
+    """
+    fp = open(out_path+'.tmp', 'wb', mitogen.core.CHUNK_SIZE)
+    try:
+        try:
+            if not _get_file(context, in_path, fp):
+                raise IOError('transfer of %r was interrupted.' % (in_path,))
+        except Exception:
+            os.unlink(fp.name)
+            raise
+    finally:
+        fp.close()
+
+    os.rename(out_path + '.tmp', out_path)
+
+
 @mitogen.core.takes_econtext
 def start_fork_parent(econtext):
     """