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fix(google.auth.compute_engine.metadata): add retry to google.auth.co…
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…mpute_engine._metadata.get()

Initial fix of issue googleapis#211 was done in CL googleapis#323, but only for .ping()
This one is adding same behaviour & tests for .get() method, as the problem still occurres
See the issue for details

Refs: googleapis#323
Resolves: googleapis#211
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DaniilAnichin committed Dec 19, 2019
1 parent 09001f9 commit 1226931
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Showing 3 changed files with 77 additions and 5 deletions.
23 changes: 21 additions & 2 deletions google/auth/compute_engine/_metadata.py
Original file line number Diff line number Diff line change
Expand Up @@ -99,7 +99,7 @@ def ping(request, timeout=_METADATA_DEFAULT_TIMEOUT, retry_count=3):
return False


def get(request, path, root=_METADATA_ROOT, recursive=False):
def get(request, path, root=_METADATA_ROOT, recursive=False, retry_count=3):
"""Fetch a resource from the metadata server.
Args:
Expand All @@ -111,6 +111,8 @@ def get(request, path, root=_METADATA_ROOT, recursive=False):
recursive (bool): Whether to do a recursive query of metadata. See
https://cloud.google.com/compute/docs/metadata#aggcontents for more
details.
retry_count (int): How many times to attempt connecting to metadata
server using above timeout.
Returns:
Union[Mapping, str]: If the metadata server returns JSON, a mapping of
Expand All @@ -129,7 +131,24 @@ def get(request, path, root=_METADATA_ROOT, recursive=False):

url = _helpers.update_query(base_url, query_params)

response = request(url=url, method="GET", headers=_METADATA_HEADERS)
retries = 0
while retries < retry_count:
try:
response = request(url=url, method="GET", headers=_METADATA_HEADERS)
break

except exceptions.TransportError:
_LOGGER.info(
"Compute Engine Metadata server unavailable on" "attempt %s of %s",
retries + 1,
retry_count,
)
retries += 1
else:
raise exceptions.TransportError(
"Failed to retrieve {} from the Google Compute Engine"
"metadata service. Compute Engine Metadata server unavailable".format(url)
)

if response.status == http_client.OK:
content = _helpers.from_bytes(response.data)
Expand Down
2 changes: 1 addition & 1 deletion setup.py
Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,7 @@
with io.open("README.rst", "r") as fh:
long_description = fh.read()

version = "1.10.0"
version = "1.11.0"

setup(
name="google-auth",
Expand Down
57 changes: 55 additions & 2 deletions tests/compute_engine/test__metadata.py
Original file line number Diff line number Diff line change
Expand Up @@ -30,14 +30,17 @@
PATH = "instance/service-accounts/default"


def make_request(data, status=http_client.OK, headers=None):
def make_request(data, status=http_client.OK, headers=None, retry=False):
response = mock.create_autospec(transport.Response, instance=True)
response.status = status
response.data = _helpers.to_bytes(data)
response.headers = headers or {}

request = mock.create_autospec(transport.Request)
request.return_value = response
if retry:
request.side_effect = [exceptions.TransportError(), response]
else:
request.return_value = response

return request

Expand All @@ -55,6 +58,20 @@ def test_ping_success():
)


def test_ping_success_retry():
request = make_request("", headers=_metadata._METADATA_HEADERS, retry=True)

assert _metadata.ping(request)

request.assert_called_with(
method="GET",
url=_metadata._METADATA_IP_ROOT,
headers=_metadata._METADATA_HEADERS,
timeout=_metadata._METADATA_DEFAULT_TIMEOUT,
)
assert request.call_count == 2


def test_ping_failure_bad_flavor():
request = make_request("", headers={_metadata._METADATA_FLAVOR_HEADER: "meep"})

Expand Down Expand Up @@ -105,6 +122,25 @@ def test_get_success_json():
assert result[key] == value


def test_get_success_retry():
key, value = "foo", "bar"

data = json.dumps({key: value})
request = make_request(
data, headers={"content-type": "application/json"}, retry=True
)

result = _metadata.get(request, PATH)

request.assert_called_with(
method="GET",
url=_metadata._METADATA_ROOT + PATH,
headers=_metadata._METADATA_HEADERS,
)
assert request.call_count == 2
assert result[key] == value


def test_get_success_text():
data = "foobar"
request = make_request(data, headers={"content-type": "text/plain"})
Expand Down Expand Up @@ -154,6 +190,23 @@ def test_get_failure():
)


def test_get_failure_connection_failed():
request = make_request("")
request.side_effect = exceptions.TransportError()

with pytest.raises(exceptions.TransportError) as excinfo:
_metadata.get(request, PATH)

assert excinfo.match(r"Compute Engine Metadata server unavailable")

request.assert_called_with(
method="GET",
url=_metadata._METADATA_ROOT + PATH,
headers=_metadata._METADATA_HEADERS,
)
assert request.call_count == 3


def test_get_failure_bad_json():
request = make_request("{", headers={"content-type": "application/json"})

Expand Down

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