Adding compute-legacy-endpoint-access sample (GoogleCloudPlatform#2517)

Author: chansmith97

compute/metadata/detect_legacy_usage.py

@@ -0,0 +1,63 @@
+import json
+import requests
+import time
+
+"""Example of using the Metadata Server to watch deprecated endpoint accesses.
+
+For more information, see the README.md under /compute.
+"""
+
+
+METADATA_URL = 'http://metadata.google.internal/computeMetadata/v1'
+METADATA_HEADERS = {'Metadata-Flavor': 'Google'}
+
+
+# [START compute_wait_for_legacy_usage]
+def wait_for_legacy_usage(callback):
+    url = '{}/instance/legacy-endpoint-access'.format(METADATA_URL)
+    last_etag = '0'
+    counts = None
+    while True:
+        r = requests.get(
+            url,
+            params={
+                'last_etag': last_etag,
+                'recursive': True,
+                'wait_for_change': True
+            },
+            headers=METADATA_HEADERS)
+        if r.status_code == 503:  # Metadata server unavailable
+            print('Metadata server unavailable. Sleeping for 1 second.')
+            time.sleep(1)
+            continue
+        if r.status_code == 404:  # Feature not yet supported
+            print('Legacy endpoint access not supported. Sleeping for 1 hour.')
+            time.sleep(3600)
+            continue
+        r.raise_for_status()
+
+        last_etag = r.headers['etag']
+        access_info = json.loads(r.text)
+        if not counts:
+            counts = access_info
+        if access_info != counts:
+            diff = {
+                ver: access_info[ver] - counts[ver] for ver in counts
+            }
+            counts = access_info
+            callback(diff)
+            # [END compute_wait_for_legacy_usage]
+
+
+def legacy_callback(diff):
+    print(
+        'Since last message, {} new requests to 0.1 endpoints and {} new '
+        'requests to v1beta1 endpoints.'.format(diff['0.1'], diff['v1beta1']))
+
+
+def main():
+    wait_for_legacy_usage(legacy_callback)
+
+
+if __name__ == '__main__':
+    main()

compute/metadata/detect_legacy_usage_test.py

@@ -0,0 +1,91 @@
+import mock
+import requests
+import json
+
+import detect_legacy_usage
+
+
+def execute_test(requests_mock, *responses):
+    callback_mock = mock.Mock()
+    requests_mock.codes.ok = requests.codes.ok
+    requests_mock.get.side_effect = responses + (StopIteration(),)
+    try:
+        detect_legacy_usage.wait_for_legacy_usage(callback_mock)
+    except StopIteration:
+        return callback_mock
+
+
+@mock.patch('detect_legacy_usage.requests')
+@mock.patch('detect_legacy_usage.time')
+def test_metadata_server_unavailable(time_mock, requests_mock):
+    # Metadata server unavailable
+    response_mock = mock.Mock()
+    response_mock.status_code = 503
+
+    callback_mock = execute_test(requests_mock, response_mock)
+
+    assert callback_mock.call_count == 0
+    assert time_mock.sleep.call_count == 1
+    assert time_mock.sleep.call_args_list[0][0] == (1,)
+
+
+@mock.patch('detect_legacy_usage.requests')
+@mock.patch('detect_legacy_usage.time')
+def test_endpoint_does_not_exist(time_mock, requests_mock):
+    # legacy-endpoint-access url unavailable (removed or not yet supported)
+    response_mock = mock.Mock()
+    response_mock.status_code = 404
+
+    callback_mock = execute_test(requests_mock, response_mock)
+
+    assert callback_mock.call_count == 0
+    assert time_mock.sleep.call_count == 1
+    assert time_mock.sleep.call_args_list[0][0] == (3600,)
+
+
+@mock.patch('detect_legacy_usage.requests')
+@mock.patch('detect_legacy_usage.time')
+def test_callback_called_on_change(time_mock, requests_mock):
+    # Response 1 has starting counts (should not trigger callback)
+    response1_data = {'0.1': 5, 'v1beta1': 10}
+    response1_mock = mock.Mock()
+    response1_mock.status_code = 200
+    response1_mock.text = json.dumps(response1_data)
+    response1_mock.headers = {'etag': '1'}
+
+    # Response 2 has different data
+    response2_data = {'0.1': 6, 'v1beta1': 10}
+    response2_mock = mock.Mock()
+    response2_mock.status_code = 200
+    response2_mock.text = json.dumps(response2_data)
+    response2_mock.headers = {'etag': '2'}
+
+    callback_mock = execute_test(requests_mock, response1_mock, response2_mock)
+
+    # One change so callback is called once
+    assert callback_mock.call_count == 1
+    assert callback_mock.call_args_list[0][0] == ({'0.1': 1, 'v1beta1': 0},)
+    assert time_mock.sleep.call_count == 0
+
+
+@mock.patch('detect_legacy_usage.requests')
+@mock.patch('detect_legacy_usage.time')
+def test_callback_not_called_without_change(time_mock, requests_mock):
+    # Response 1 has starting counts (should not trigger callback)
+    response1_data = {'0.1': 5, 'v1beta1': 10}
+    response1_mock = mock.Mock()
+    response1_mock.status_code = 200
+    response1_mock.text = json.dumps(response1_data)
+    response1_mock.headers = {'etag': '1'}
+
+    # Response 2 has the same data (no change)
+    response2_mock = mock.Mock()
+    response2_mock.status_code = 200
+    response2_mock.text = json.dumps(response1_data)
+    response2_mock.headers = {'etag': '1'}
+
+    callback_mock = execute_test(requests_mock, response1_mock, response2_mock)
+
+    # No change so callback is not called
+    assert callback_mock.call_count == 0
+    assert time_mock.sleep.call_count == 0