In the alternator and cql-pytest test frameworks, we have some convenient
contextmanager-based functions that allows us to create a temporary
resource (e.g., a table) that will be automatically deleted, for
example:
with create_stream_test_table(...) as table:
test_something(table)
However, our implementation of these functions wasn't safe. We had
code looking like:
table = ...
yield table
table.delete()
The thinking was that the cleanup part (the table.delete()) will be
called after the user's code. However, if the user's code threw
(i.e., a failed assertion), the cleanup wasn't called... When the user's
code throws, it looks as if the "yield" throws. So the correct code
should look like:
table = ...
try:
yield table
finally:
table.delete()
Python's contextmanager documentation indeed gives this idiom in its
example.
This patch fixes all contextmanager implementations in our tests to do
the cleanup even if the user's "with" block throws.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20210428083748.552203-1-nyh@scylladb.com>
72 lines
2.7 KiB
Python
72 lines
2.7 KiB
Python
# Copyright 2020 ScyllaDB
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#
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# This file is part of Scylla.
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#
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# Scylla is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Affero General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# Scylla is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU Affero General Public License
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# along with Scylla. If not, see <http://www.gnu.org/licenses/>.
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##################################################################
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# Various utility functions which are useful for multiple tests.
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# Note that fixtures aren't here - they are in conftest.py.
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import string
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import random
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import time
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from contextlib import contextmanager
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def random_string(length=10, chars=string.ascii_uppercase + string.digits):
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return ''.join(random.choice(chars) for x in range(length))
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# A function for picking a unique name for test keyspace or table.
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# This name doesn't need to be quoted in CQL - it only contains
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# lowercase letters, numbers, and underscores, and starts with a letter.
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unique_name_prefix = 'cql_test_'
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def unique_name():
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current_ms = int(round(time.time() * 1000))
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# If unique_name() is called twice in the same millisecond...
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if unique_name.last_ms >= current_ms:
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current_ms = unique_name.last_ms + 1
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unique_name.last_ms = current_ms
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return unique_name_prefix + str(current_ms)
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unique_name.last_ms = 0
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# A utility function for creating a new temporary keyspace with given options.
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# It can be used in a "with", as:
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# with new_test_keyspace(cql, '...') as keyspace:
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# This is not a fixture - see those in conftest.py.
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@contextmanager
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def new_test_keyspace(cql, opts):
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keyspace = unique_name()
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cql.execute("CREATE KEYSPACE " + keyspace + " " + opts)
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try:
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yield keyspace
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finally:
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cql.execute("DROP KEYSPACE " + keyspace)
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# A utility function for creating a new temporary table with a given schema.
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# It can be used in a "with", as:
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# with new_test_table(cql, keyspace, '...') as table:
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# This is not a fixture - see those in conftest.py.
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@contextmanager
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def new_test_table(cql, keyspace, schema, extra=""):
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table = keyspace + "." + unique_name()
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cql.execute("CREATE TABLE " + table + "(" + schema + ")" + extra)
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try:
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yield table
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finally:
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cql.execute("DROP TABLE " + table)
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def project(column_name_string, rows):
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"""Returns a list of column values from each of the rows."""
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return [getattr(r, column_name_string) for r in rows]
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