Profiling alternator implied that JSON parsing takes up a fair amount
of CPU, and as such should be optimized. libjsoncpp is a standard
library for handling JSON objects, but it also proves slower than
rapidjson, which is hereby used instead.
The results indicated that libjsoncpp used roughly 30% of CPU
for a single-shard alternator instance under stress, while rapidjson
dropped that usage to 18% without optimizations.
Future optimizations should include eliding object copying, string copying
and perhaps experimenting with different JSON allocators.
Migrating from libjsoncpp to rapidjson proved to be beneficial
for parsing performance. As a first step, a set of helper functions
is provided to ease the migration process.
error.hh file implicitly assumed that seastar:: namespace is available
when it's included, which is not always the case. To remedy that,
seastar::httpd namespace is used explicitly.
Our CreateTable handler assumed that the function
migration_manager::announce_new_column_family()
returns a failed future if the table already exists. But in some of
our code branches, this is not the case - the function itself throws
instead of returning a failed future. The solution is to use
seastar::futurize_apply() to handle both possibilities (direct exception
or future holding an exception).
This fixes a failure of the test_table.py::test_create_table_already_exists
test case.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
This adds a new document, docs/alternator.md, about Alternator.
The scope of this document should be expanded in the future. We begin
here by introducing Alternator and its current compatibility level with
Amazon DynamoDB, but it should later grow to explain the design of Alternator
and how it maps the DynamoDB data model onto Scylla's.
Whether this document should remain a short high-level overview, or a long
and detailed design document, remains an open question.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190805085340.17543-1-nyh@scylladb.com>
The function attrs_type() return a supposedly singleton, but because
it is a seastar::shared_ptr we can't use the same one for multiple
threads, and need to use a separate one per thread.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190804163933.13772-1-nyh@scylladb.com>
The CQL type singletons like utf8_type et al. are separate for separate
shards and cannot be used across shards. So whatever hash tables we use
to find them, also needs to be per-shard. If we fail to do this, we
get errors running the debug build with multiple shards.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190804165904.14204-1-nyh@scylladb.com>
Expand the GSI test suite. The most important new test is
test_gsi_key_not_in_index(), where the index's key includes just one of
the base table's key columns, but not a second one. In this case, the
Scylla implementation will nevertheless need to add the second key column
to the view (as a clustering key), even though it isn't considered a key
column by the DynamoDB API.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190718085606.7763-1-nyh@scylladb.com>
Our ListTables implementation uses get_column_families(), which lists both
base tables and materialized views. We will use materialized views to
implement DynamoDB's secondary indexes, and those should not be listed in
the results of ListTables.
The patch also includes a test for this.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190717133103.26321-2-nyh@scylladb.com>
The list_tables() utility function was used only in test_table.py
but I want to use it elsewhere too (in GSI test) so let's move it
to util.py.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190717133103.26321-1-nyh@scylladb.com>
As in case of set_diff, an exception message in set_sum should include
the user-provided request (ADD) rather than our internal helper function
set_sum.
Although we do not support GSI yet, until now we silently ignored
CreateTable's GSI parameter, and the user wouldn't know the table
wasn't created as intended.
In this patch, GSI is still unsupported, but now CreateTable will
fail with an error message that GSI is not supported.
We need to change some of the tests which test the error path, and
expect an error - but should not consider a table creation error
as the expected error.
After this patch, test_gsi.py still fails all the tests on
Alternator, but much more quickly :-)
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190711161420.18547-1-nyh@scylladb.com>
The test case for adding two sets with common values is added.
This case is a stub, because boto3 transforms the result into a Python
set, which removes duplicates on its own. A proper TODO is left
in order to migrate this case to a lower-level API and check
the returned JSON directly for lack of duplicates.
The Query operation's conditions can be used to search for a particular
hash key or both hash and sort keys - but not any other combinations.
We previously forgot to verify most errors, so in this patch we add
missing verifications - and tests to confirm we fail the query when
DynamoDB does.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190711132720.17248-1-nyh@scylladb.com>
Add more tests for GSI - tests that DescribeTable describes the GSI,
and test the case of more than one GSI for a base table.
Unfortunately, creating an empty table with two GSIs routinely takes
on DynamoDB more than a full minute (!), so because we now have a
test with two GSIs, I had to increase the timeout in create_test_table().
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190711112911.14703-1-nyh@scylladb.com>
The holds_path() utility function is actually used to check if a value
needs read before write, so its name is changed to more fitting
check_needs_read_before_write.
Alternator currently keeps an item's attributes inside a map, and we
had a serious bug in the way we build mutations for this map:
We didn't know there was a requirement to build this mutation sorted by
the attribute's name. When we neglect to do this sorting, this confuses
Scylla's merging algorithms, which assume collection cells are thus
sorted, and the result can be duplicate cells in a collection, and the
visible effect is a mutation that seems to be ignored - because both
old and new values exist in the collection.
So this patch includes a new helper class, "attribute_collector", which
helps collect attribute updates (put and del) and extract them in correctly
sorted order. This helper class also eliminates some duplication of
arcane code to create collection cells or deletions of collection cells.
This patch includes a simple test that previously failed, and one xfail
test that failed just because of this bug (this was the test that exposed
this bug). Both tests now succeed.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190709160858.6316-1-nyh@scylladb.com>
This patch adds what is hopefully an exhaustive test suite for the
global secondary indexing (GSI) feature, and all its various
complications and corner cases of how GSIs can be created, deleted,
named, written, read, and more (the tests are heavily documented to
explain what they are testing).
All these tests pass on DynamoDB, and fail on Alternator, so they are
marked "xfail". As we develop the GSI feature in Alternator piece by
piece, we should make these tests start to pass.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190708160145.13865-1-nyh@scylladb.com>
This adds another test for BatchWriteItem: That if one of the operations is
invalid - e.g., has a wrong key type - the entire batch is rejected, and not
none of its operations are done - even the valid ones.
The test succeeds, because we already handle this case correctly.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190707134610.30613-1-nyh@scylladb.com>
Test an operation like SET #one = #two, where the RHS has a reference
to a name, rather than the name itself. Also verify that DynamoDB
gives an error if ExpressionAttributeNames includes names not needed
by neither left or right hand side of such assignments.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190708133311.11843-1-nyh@scylladb.com>
In order to serve update requests that depend on read-before-write,
a proper helper function which fetches the existing item with a given
key from the database is added.
This read-before-write mechanism is not considered safe, because it
provides no linearizability guarantees and offers no synchronization
protection. As such, it should be consider a placeholder that works
fine on a single machine and/or no concurrent access to the same key.
The calculate_value utility function is going to need more context
in order to resolve paths present in the right-hand side of update_item
operators: update_info and schema.
Historically, resolving a path checked for key columns, which are not
allowed to be on the left-hand side of the assignment. However, path
resolving will now also be used for right-hand side, where it should
be allowed to use the key value.
In order to implement read-before-write in the future, calculate_value
now accepts an additional parameter: previous_item. If read-before-write
was performed, previous_item will contain an item for the given key
which already exists in the database at the time of the update.
This patch moves the create_test_table() utility function, which creates
a test table with a unique name, from the fixtures (conftest.py) to
util.py. This will allow reusing this function in tests which need to
create tables but not through the existing fixtures. In particular
we will need to do this for GSI (global secondary index) tests
in the next patch.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190708104438.5830-1-nyh@scylladb.com>
The tests we had for BatchWriteItem's refusal to accept duplicate keys
only used test_table_s, with just a hash key. This patch adds tests
for test_table, i.e., a table with both hash and sort keys - to check
that we check duplicates in that case correctly as well.
Moreover, the expanded tests also verify that although identical
keys are not allowed, keys with just one component (hash or sort key)
the same but the other not the same - are fine.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190705191737.22235-1-nyh@scylladb.com>
Even when running against a local Alternator, Boto3 wants to know the
region name, and AWS credentials, even though they aren't actually needed.
For a local run, we can supply garbage values for these settings, to
allow a user who never configured AWS to run tests locally.
Running against "--aws" will, of course, still require the user to
configure AWS.
Also modified the README to be clearer, and more focused on the local
runs.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190708121420.7485-1-nyh@scylladb.com>
For "--aws" tests, use the default region chosen by the user in the
AWS configuration (~/.aws/config or environment variable), instead of
hard-coding "us-east-1".
Patch by Pekka Enberg.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190708105852.6313-1-nyh@scylladb.com>
Calculating value represented as 'v1 + v2' or 'v1 - v2' was previously
implemented with a double type, which offers limited precision.
From now on, these computations are based on big_decimal, which
allows returning values without losing precision.
This patch depends on 'add big_decimal arithmetic operators' series.
Message-Id: <f741017fe3d3287fa70618068bdc753bfc903e74.1562318971.git.sarna@scylladb.com>
Move some common utility functions to a common file "util.py"
instead of repeating them in many test files.
The utility functions include random_string(), random_bytes(),
full_scan(), full_query(), and multiset() (the more general
version, which also supports freezing nested dicts).
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190705081013.1796-1-nyh@scylladb.com>
