ovirt-img: support json output

Add json as an output option, to print
the progress in jsonlines[1] format.
A consistent machine readable format, that
can be later parsed.

$ ovirt-img  download-disk -c engine --output json <disk_id> download.raw
{"transferred": 0, elapsed: 0.0, "description": "setting up"}
...
{"transferred": 249561088, "size": 261095424, elapsed: 1.234567, "description": "downloading image"}
{"transferred": 256901120, "size": 261095424, elapsed: 1.345678, "description": "downloading image"}
{"transferred": 261095424, "size": 261095424, elapsed: 1.456789, "description": "finalizing transfer"}
...

[1] https://jsonlines.org/

Fixes: #154
Signed-off-by: Albert Esteve <aesteve@redhat.com>

ovirt_imageio/client/_options.py

@@ -46,7 +46,7 @@ def __repr__(self):
 
 
 log_level = Choices("log_level", ("debug", "info", "warning", "error"))
-output_format = Choices("output_format", ("text",))
+output_format = Choices("output_format", ("text", "json"))
 
 
 def bool_string(value):

ovirt_imageio/client/_ui.py

@@ -1,6 +1,7 @@
 # SPDX-FileCopyrightText: Red Hat, Inc.
 # SPDX-License-Identifier: GPL-2.0-or-later
 
+import json
 import sys
 import threading
 import time
@@ -9,6 +10,7 @@
 
 
 FORMAT_TEXT = "text"
+FORMAT_JSON = "json"
 
 DEFAULT_WIDTH = 79
 
@@ -54,8 +56,25 @@ def draw(self, elapsed, value, transferred, size=None,
         self._write_line(line, end)
 
 
+class JsonFormat(OutputFormat):
+
+    def draw(self, elapsed, value, transferred, size=None,
+             phase=None, last=False):
+        progress = {
+            'transferred': transferred,
+            'elapsed': elapsed,
+            'description': phase or "",
+        }
+        if size is not None:
+            progress["size"] = size
+
+        line = json.dumps(progress)
+        self._write_line(line)
+
+
 OUTPUT_FORMAT = {
     FORMAT_TEXT: TextFormat,
+    FORMAT_JSON: JsonFormat,
 }
 
 

test/client_options_test.py

@@ -346,6 +346,7 @@ def test_transfer_options_disabled(config):
 
 @pytest.mark.parametrize("output", [
     "text",
+    "json",
 ])
 def test_output_option(config, output):
     parser = _options.Parser()

test/client_ui_test.py

@@ -2,6 +2,7 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
 import pytest
+import json
 
 from ovirt_imageio import client
 from ovirt_imageio._internal.units import MiB, GiB
@@ -28,7 +29,7 @@ def flush(self):
         pass
 
 
-def test_draw():
+def test_draw_text():
     fake_time = FakeTime()
     f = FakeFile()
 
@@ -84,6 +85,68 @@ def test_draw():
     assert f.last == line.ljust(79) + "\n"
 
 
+def test_draw_json():
+    fake_time = FakeTime()
+    f = FakeFile()
+
+    # Size is unknown at this point.
+    pb = client.ProgressBar(
+        phase="setting up", output=f, format="json", now=fake_time)
+    assert json.loads(f.last) == {
+        "transferred": 0,
+        "elapsed": 0.0,
+        "description": "setting up",
+    }
+
+    # Size was updated, but no bytes were transferred yet.
+    fake_time.now += 0.1
+    pb.size = 3 * GiB
+    assert json.loads(f.last) == {
+        "transferred": 0,
+        "elapsed": fake_time.now,
+        "description": "setting up",
+        "size": 3 * GiB,
+    }
+
+    # Phase was updated.
+    fake_time.now += 0.2
+    pb.phase = "downloading image"
+    assert json.loads(f.last) == {
+        "transferred": 0,
+        "elapsed": fake_time.now,
+        "description": "downloading image",
+        "size": 3 * GiB,
+    }
+
+    # All data transferred.
+    fake_time.now += 2.0
+    pb.update(3 * GiB)
+    assert json.loads(f.last) == {
+        "transferred": 3 * GiB,
+        "elapsed": fake_time.now,
+        "description": "downloading image",
+        "size": 3 * GiB,
+    }
+
+    # Cleaning up after download.
+    pb.phase = "cleaning up"
+    assert json.loads(f.last) == {
+        "transferred": 3 * GiB,
+        "elapsed": fake_time.now,
+        "description": "cleaning up",
+        "size": 3 * GiB,
+    }
+
+    # Closing prints the final line.
+    pb.close()
+    assert json.loads(f.last) == {
+        "transferred": 3 * GiB,
+        "elapsed": fake_time.now,
+        "description": "cleaning up",
+        "size": 3 * GiB,
+    }
+
+
 def test_with_size():
     fake_time = FakeTime()
     f = FakeFile()