ansible: fix put_file() for large temporary files.

Reverts 49736b3a, large file copies can't avoid the RTT.

The parent stack must be blocked while FileService progresses, as unlike
the small file path, it does not make a snapshot of the (possibly
temporary) file passed by the action plug-in. So we need to keep that
file alive while the service runs.

Add a new integration test and a new soak test to cover both.

ansible_mitogen/connection.py

@@ -880,13 +880,11 @@ class Connection(ansible.plugins.connection.ConnectionBase):
             path=mitogen.utils.cast(in_path)
         )
 
-        # A roundtrip is always necessary for the target to request the file
-        # from FileService, however, by pipelining the transfer function, the
-        # subsequent step (probably a module invocation) can get its
-        # dependencies and function call in-flight before the transfer is
-        # complete. This saves at least 1 RTT between the transfer completing
-        # and the start of the follow-up task.
-        self.get_chain().call_no_reply(
+        # For now this must remain synchronous, as the action plug-in may have
+        # passed us a temporary file to transfer. A future FileService could
+        # maintain an LRU list of open file descriptors to keep the temporary
+        # file alive, but that requires more work.
+        self.get_chain().call(
             ansible_mitogen.target.transfer_file,
             context=self.parent,
             in_path=in_path,

docs/changelog.rst

@@ -53,11 +53,6 @@ Enhancements
   a 250 ms link from 30 seconds to 10 seconds compared to v0.2.2, down from 120
   seconds compared to vanilla.
 
-* `49736b3a <https://github.com/dw/mitogen/commit/49736b3a>`_: avoid a
-  roundtrip when transferring files larger than 124KiB, removing a delay
-  between waiting for the transfer to complete and start of the follow-up
-  action.
-
 * `#337 <https://github.com/dw/mitogen/issues/337>`_: To avoid a scaling
   limitation, a PTY is no longer allocated for an SSH connection unless the
   configuration specifies a password.

tests/ansible/integration/action/all.yml

@@ -1,3 +1,4 @@
+- import_playbook: copy.yml
 - import_playbook: fixup_perms2__copy.yml
 - import_playbook: low_level_execute_command.yml
 - import_playbook: make_tmp_path.yml

tests/ansible/integration/action/copy.yml

@@ -0,0 +1,66 @@
+# Verify copy module for small and large files, and inline content.
+
+- name: integration/action/synchronize.yml
+  hosts: test-targets
+  any_errors_fatal: true
+  tasks:
+    - copy:
+        dest: /tmp/copy-tiny-file
+        content:
+          this is a tiny file.
+      connection: local
+
+    - copy:
+        dest: /tmp/copy-large-file
+        # Must be larger than Connection.SMALL_SIZE_LIMIT.
+        content: "{% for x in range(200000) %}x{% endfor %}"
+      connection: local
+
+    # end of making files
+
+    - file:
+        state: absent
+        path: "{{item}}"
+      with_items:
+      - /tmp/copy-tiny-file.out
+      - /tmp/copy-large-file.out
+      - /tmp/copy-tiny-inline-file.out
+      - /tmp/copy-large-inline-file.out
+
+    # end of cleaning out files
+
+    - copy:
+        dest: /tmp/copy-large-file.out
+        src: /tmp/copy-large-file
+
+    - copy:
+        dest: /tmp/copy-tiny-file.out
+        src: /tmp/copy-tiny-file
+
+    - copy:
+        dest: /tmp/copy-tiny-inline-file.out
+        content: "tiny inline content"
+
+    - copy:
+        dest: /tmp/copy-large-inline-file.out
+        content: |
+          {% for x in range(200000) %}y{% endfor %}
+
+    # stat results
+
+    - stat:
+        path: "{{item}}"
+      with_items:
+      - /tmp/copy-tiny-file.out
+      - /tmp/copy-large-file.out
+      - /tmp/copy-tiny-inline-file.out
+      - /tmp/copy-large-inline-file.out
+      register: stat
+
+    - assert:
+        that:
+        - stat.results[0].stat.checksum == "f29faa9a6f19a700a941bf2aa5b281643c4ec8a0"
+        - stat.results[1].stat.checksum == "62951f943c41cdd326e5ce2b53a779e7916a820d"
+        - stat.results[2].stat.checksum == "b26dd6444595e2bdb342aa0a91721b57478b5029"
+        - stat.results[3].stat.checksum == "d675f47e467eae19e49032a2cc39118e12a6ee72"
+

tests/ansible/soak/_file_service_loop.yml

@@ -0,0 +1,6 @@
+  - file:
+      path: /tmp/foo-{{inventory_hostname}}
+      state: absent
+  - copy:
+      dest: /tmp/foo-{{inventory_hostname}}
+      content: "{{content}}"

tests/ansible/soak/file_service.yml

@@ -0,0 +1,6 @@
+- hosts: all
+  tasks:
+  - set_fact:
+      content: "{% for x in range(126977) %}x{% endfor %}"
+  - include_tasks: _file_service_loop.yml
+    with_sequence: start=1 end=100