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

Author: aesteve-rh

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", ("human"))
+output_format = Choices("output_format", ("human", "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 = 'human'
+FORMAT_JSON = 'json'
 
 DEFAULT_WIDTH = 79
 
@@ -30,19 +32,23 @@ def __init__(self, now, size=None, width=DEFAULT_WIDTH):
         # TODO: use current terminal width instead.
         self._width = width
 
+    @property
+    def elapsed(self):
+        return self._now() - self._start
+
     def draw(self, value, transferred, phase=None, last=False):
         raise NotImplementedError
 
 
 class TextFormat(OutputFormat):
 
     def draw(self, value, transferred, phase=None, last=False):
-        elapsed = self._now() - self._start
         progress = f"{max(0, value):3d}%" if self.size else "----"
         done = util.humansize(transferred)
-        rate = util.humansize((transferred / elapsed) if elapsed else 0)
+        rate = util.humansize(
+            (transferred / self.elapsed) if self.elapsed else 0)
         phase = f" | {phase}" if phase else ""
-        line = f"[ {progress} ] {done}, {elapsed:.2f} s, {rate}/s{phase}"
+        line = f"[ {progress} ] {done}, {self.elapsed:.2f} s, {rate}/s{phase}"
 
         # Using "\r" moves the cursor to the first column, so the next progress
         # will overwrite this one. If this is the last progress, we use "\n" to
@@ -53,9 +59,21 @@ def draw(self, value, transferred, phase=None, last=False):
         return line.ljust(self._width, " ") + end
 
 
+class JsonFormat(OutputFormat):
+
+    def draw(self, value, transferred, phase=None, last=False):
+        return json.dumps({
+            'transferred': transferred,
+            'size': self.size,
+            'elapsed': self.elapsed,
+            'description': phase or "",
+        }) + '\n'
+
+
 FORMATTER = {
     None: TextFormat,
     FORMAT_TEXT: TextFormat,
+    FORMAT_JSON: JsonFormat,
 }
 
 

test/client_options_test.py

@@ -346,6 +346,7 @@ def test_transfer_options_disabled(config):
 
 @pytest.mark.parametrize("format", [
     "human",
+    "json",
 ])
 def test_output_option(config, format):
     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
@@ -84,6 +85,111 @@ def test_draw():
     assert f.last == line.ljust(79) + "\n"
 
 
+def test_json_format():
+    fake_time = FakeTime()
+    f = FakeFile()
+
+    # Size is unknown at this point.
+    pb = client.ProgressBar(
+        phase="setting up", output=f, format="json", now=fake_time)
+    line_data = {
+        "transferred": 0,
+        "size": None,
+        "elapsed": 0.0,
+        "description": "setting up",
+    }
+    line = f'{json.dumps(line_data)}'
+    assert f.last == line + "\n"
+
+    # Size was updated, but no bytes were transferred yet.
+    fake_time.now += 0.1
+    pb.size = 3 * GiB
+    line_data = {
+        "transferred": 0,
+        "size": 3 * GiB,
+        "elapsed": fake_time.now,
+        "description": "setting up",
+    }
+    line = f'{json.dumps(line_data)}'
+    assert f.last == line + "\n"
+
+    # Phase was updated.
+    fake_time.now += 0.2
+    pb.phase = "downloading image"
+    line_data = {
+        "transferred": 0,
+        "size": 3 * GiB,
+        "elapsed": fake_time.now,
+        "description": "downloading image",
+    }
+    line = f'{json.dumps(line_data)}'
+    assert f.last == line + "\n"
+
+    # Write some data...
+    fake_time.now += 0.8
+    pb.update(512 * MiB)
+    line_data = {
+        "transferred": 512 * MiB,
+        "size": 3 * GiB,
+        "elapsed": fake_time.now,
+        "description": "downloading image",
+    }
+    line = f'{json.dumps(line_data)}'
+    assert f.last == line + "\n"
+
+    # Write zeros (much faster)...
+    fake_time.now += 0.2
+    pb.update(2 * GiB)
+    line_data = {
+        "transferred": 2560 * MiB,
+        "size": 3 * GiB,
+        "elapsed": fake_time.now,
+        "description": "downloading image",
+    }
+    line = f'{json.dumps(line_data)}'
+    assert f.last == line + "\n"
+
+    # More data, slow down again...
+    fake_time.now += 1.0
+    pb.update(512 * MiB)
+    line_data = {
+        "transferred": 3 * GiB,
+        "size": 3 * GiB,
+        "elapsed": fake_time.now,
+        "description": "downloading image",
+    }
+    line = f'{json.dumps(line_data)}'
+    assert f.last == line + "\n"
+
+    # Cleaning up after download.
+    pb.phase = "cleaning up"
+    line_data = {
+        "transferred": 3 * GiB,
+        "size": 3 * GiB,
+        "elapsed": fake_time.now,
+        "description": "cleaning up",
+    }
+    line = f'{json.dumps(line_data)}'
+    assert f.last == line + "\n"
+
+    # Cleaning can take few seconds, lowing the rate.
+    fake_time.now += 3.0
+    pb.phase = "download completed"
+    line_data = {
+        "transferred": 3 * GiB,
+        "size": 3 * GiB,
+        "elapsed": fake_time.now,
+        "description": "download completed",
+    }
+    line = f'{json.dumps(line_data)}'
+    assert f.last == line + "\n"
+
+    # Closing prints the final line with no comma.
+    pb.close()
+    line = f'{json.dumps(line_data)}'
+    assert f.last == line + "\n"
+
+
 def test_with_size():
     fake_time = FakeTime()
     f = FakeFile()