fix(spanner): use future date to avoid time drift (GoogleCloudPlatform#4471)

fixes GoogleCloudPlatform#4197

Author: Takashi Matsuo

spanner/cloud-client/snippets.py

@@ -1407,6 +1407,13 @@ def query_data_with_timestamp_parameter(instance_id, database_id):
  database = instance.database(database_id)
 
  example_timestamp = datetime.datetime.utcnow().isoformat() + "Z"
+ # [END spanner_query_with_timestamp_parameter]
+ # Avoid time drift on the local machine.
+ # https://github.com/GoogleCloudPlatform/python-docs-samples/issues/4197.
+ example_timestamp = (
+ datetime.datetime.utcnow() + datetime.timedelta(days=1)
+ ).isoformat() + "Z"
+ # [START spanner_query_with_timestamp_parameter]
  param = {
  'last_update_time': example_timestamp
  }

spanner/cloud-client/snippets_test.py

@@ -363,9 +363,6 @@ def test_query_data_with_string(capsys):
 
 
 def test_query_data_with_timestamp_parameter(capsys):
- # Wait 5 seconds to avoid a time drift issue for the next query:
- # https://github.com/GoogleCloudPlatform/python-docs-samples/issues/4197.
- time.sleep(5)
  snippets.query_data_with_timestamp_parameter(INSTANCE_ID, DATABASE_ID)
  out, _ = capsys.readouterr()
  assert 'VenueId: 4, VenueName: Venue 4, LastUpdateTime:' in out