The Alternator CreateTable operation currently performs several schema-
changing operations separately - one by one: It creates a keyspace,
a table in that keyspace and possibly also multiple views, and it sets
tags on the table. A consequence of this is that concurrent CreateTable
and DeleteTable operations (for example) can result in unexpected errors
or inconsistent states - for example CreateTable wants to create the
table in the keyspace it just created, but a concurrent DeleteTable
deleted it. We have two issues about this problem (#6391 and #9868)
and three tests (test_table.py::test_concurrent_create_and_delete_table)
reproducing it.
In this patch we fix these problems by switching to the modern Scylla
schema-changing API: Instead of doing several schema-changing
operations one by one, we create a vector of schema mutation performing
all these operations - and then perform all these mutations together.
When the experimental Raft-based schema modifications is enabled, this
completely solves the races, and the tests begin to pass. However, if
the experimental Raft mode is not enabled, these tests continue to fail
because there is still no locking while applying the different schema
mutations (not even on a single node). So I put a special fixture
"fails_without_raft" on these tests - which means that the tests
xfail if run without raft, and expected to pass when run on Raft.
Indeed, after this patch
test/alternator/run --raft test_table.py::test_concurrent_create_and_delete_table
shows three passing tests (they also pass if we drastically improve the
number of iterations), while
test/alternator/run test_table.py::test_concurrent_create_and_delete_table
shows three xfailing tests.
All other Alternator tests pass as before with this patch, verifying
that the handling of new tables, new views, tags, and CDC log tables,
all happen correctly even after this patch.
A note about the implementation: Before this patch, the CreateTable code
used high-level functions like prepare_new_column_family_announcement().
These high-level functions become unusable if we write multiple schema
operations to one list of mutations, because for example this function
validates that the keyspace had already been created - when it hasn't
and that's the whole point. So instead we had to use lower-level
function like add_table_or_view_to_schema_mutation() and
before_create_column_family(). However, despite being lower level,
these functions were public so I think it's reasonable to use them,
and we probably have no other alternative.
Fixes#6391Fixes#9868
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
We add reproducing tests for two known Alternator issues, #6391 and #9868,
which involve the non-atomicity of table creation. Creating a table
currently involves multiple steps - creating a keyspace, a table,
materialized views, and tags. If some of these steps succeed and some
fail, we get an InternalServerError and potentially leave behind some
half-built table.
Both issues will be solved by making better use of the new Raft-based
capabilities of making multiple modifications to the schema atomically,
but this patch doesn't fix the problem - it just proves it exist.
The new tests involve two threads - one repeatedly trying to create a
table with a GSI or with tags - and the other thread repeatedly trying
to delete the same table under its feet. Both bugs are reproduced almost
immediately.
Note that like all test/alternator tests, the new tests are usually run on
just one node. So when we fix the bug and these tests begin to pass,
it will not be a proof that concurrent schema modification works safely
on *different* nodes. To prove that, we will also need a multi-node test.
However, this test can prove that we used Raft-based schema modification
correctly - and if we assume that the Raft-based schema modification
feature is itself correct, then we can be sure that CreateTable will be
correct also across multiple nodes. Although it won't hurt to check it
directly.
Refs #6391
Refs #9868
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20220207223100.207074-1-nyh@scylladb.com>
Instead of lengthy blurbs, switch to single-line, machine-readable
standardized (https://spdx.dev) license identifiers. The Linux kernel
switched long ago, so there is strong precedent.
Three cases are handled: AGPL-only, Apache-only, and dual licensed.
For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0),
reasoning that our changes are extensive enough to apply our license.
The changes we applied mechanically with a script, except to
licenses/README.md.
Closes#9937
When the UpdateTable operation is called for a non-existent table, the
appropriate error is ResourceNotFoundException, but before this patch
we ran into an exception, which resulted in an ugly "internal server
error".
In this patch we use the existing get_table() function which most other
operations use, and which does all the appropriate verifications and
generates the appropriate Alternator api_error instead of letting
internal Scylla exceptions escape to the user.
This patch also includes a test for UpdateTable on a non-existent table,
which used to fail before this patch and pass afterwards. We also add a
test for DeleteTable in the same scenario, and see it didn't have this
bug. As usual, both tests pass on DynamoDB, which confirms we generate
the right error codes.
Fixes#9747.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20211206181605.1182431-1-nyh@scylladb.com>
Ever since we started testing Alternator with tests written in Python
and using Amazon's "boto3" library, one limitation kept annoying us:
Boto3 verifies the validity of the request parameters before passing
them on to the server. It verifies that mandatory parameters are not
missing, that parameters have the right types, and sometimes even the
right ranges - all in the library before ever sending the request.
This meant that in many cases, we couldn't get good test coverage for
Alternator's server-side handling of *wrong* parameters.
As it turns out, it is trivial to tell boto3 to *not* do its client-side
request validation, with the `parameter_validation=False` config flag.
We just never noticed that such a flag existed :-)
So this patch adds this flag. It then fixes a few tests which expected
ParameterValidationError - this error is the client-side validation
failure, but should now be replaced by checking the server-side error.
The patch also adds a couple of invalid parameter checks that we
couldn't do before because of boto3's eagerness to check them on the
client side. We can add a lot more of these error tests in the future,
now that we got rid of client-side validation.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20211005095514.537226-1-nyh@scylladb.com>
We have a utility function test_table_name() to create a unique name for
a test table. The funny thing is, that because this function starts with
the string "test_", pytest believes it's a test. This doesn't cause any
problems (it's consider a *passing* test), but it's nevertheless strange
to see it listed on the list of tests.
So in this page, we trivially rename this function to unique_table_name(),
a name why pytest doesn't think is the name of test.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
In conftest.py we have several fixtures creating shared tables which many
test files can share, so they are marked with the "session" scope - all
the tests in the testing session may share the same instance. This is fine.
Some of test files have additional fixtures for creating special tables
needed only in those files. Those were also, unnecessarily, marked
"session" scope as well. This means that these temporary tables are
only deleted at the very end of test suite, event though they can be
deleted at the end of the test file which needed them. This is exactly
what the "module" fixture scope is, so this patch changes all the
fixtures private to one test file to be "module".
After this patch, the teardown of the last test in the suite goes down
from 4 seconds to just 1.5 seconds (it's still long because there are
still plenty of session-scoped fixtures in conftest.py).
Another small benefit is that the peak disk usage of the test suite is
lower, because some of the temporary tables are deleted sooner.
This patch does not change any test functionality, and also does not
make any test faster - it just changes the order of the fixture
teardowns.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20210317175036.1773774-1-nyh@scylladb.com>
The test test_table.py::test_table_streams_on creates tables with various
stream types, and then immediately deletes them without testing anything.
This is a slow test (taking almost a full second on my laptop), and is
redundant because in test_streams.py we have tests which create tables
with streams in the same way - but then actually test that things work
with these streams. So this test might as well be removed, and this is
what we do in this patch.
Removing this test shaves another second from the Alternator test suite's
run time.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20210317230530.1780849-1-nyh@scylladb.com>
While Alternator doesn't yet support creating a table with a different
"server-side encryption" (a.k.a. encryption-at-rest) parameters, the
SSESpecification option with Enabled=false should still be allowed, as
it is just the default, and means exactly the same as would a missing
SSESpecification.
This patch also adds a test for this case, which failed on Alternator
before this patch.
Fixes#7031.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200812205853.173846-1-nyh@scylladb.com>
Since alternator is based on Scylla, two "already exists" error types
can appear when trying to create a table - that a table itself exists,
or that its keyspace does. That's however an implementation detail,
since alternator does not have a notion of keyspaces at all.
This patch unifies the error message to simply mention that a table
already exists, and comes with a more robust test case.
If the keyspace already exists, table creation will still be attempted.
Fixes#6340
Tests: alternator(local, remote)
To make the tests in alternator-test runnable by test.py, we need to
move the directory alternator-test/ to test/alternator, because test.py
only looks for tests in subdirectories of test/. Then, we need to create
a test/alternator/suite.yaml saying that this test directory is of type
"Run", i.e., it has a single run script "run" which runs all its tests.
The "run" script had to be slightly modified to be aware of its new
location relative to the source directory.
To run the Alternator tests from test.py, do:
./test.py --mode dev alternator
Note that in this version, the "--mode" has no effect - test/alternator/run
always runs the latest compiled Scylla, regardless of the chosen mode.
The Alternator tests can still be run manually and individually against
a running Scylla or DynamoDB as before - just go to the test/alternator
directory (instead of alternator-test previously) and run "pytest" with
the desired parameters.
Fixes#6046
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
