client_state holds a state to generate monotonically increasing unique
timestamp. Queries with a SERIAL consistency level need it to generate
a paxos round.
In this patch we implement the Expected parameter for the UpdateItem,
PutItem and DeleteItem operations. This parameter allows a conditional
update - i.e., do an update only if the existing value of the item
matches some condition.
This is the older form of conditional updates, but is still used by many
applications, including Amazon's Tic-Tac-Toe demo.
As usual, we do not yet provide isolation guarantees for read-modify-write
operations - the item is simply read before the modification, and there is
no protection against concurrent operation. This will of course need to be
addressed in the future.
The Expected parameter has a relatively large number of variations, and most
of them are supported by this code, except that currenly only two comparison
operators are supported (EQ and BEGINS_WITH) out of the 13 listed in the
documentation. The rest will be implemented later.
This patch also includes comprehensive tests for the Expected feature.
These tests are almost exhaustive, except for one missing part (labled FIXME) -
among the 13 comparison operations, the tests only check the EQ and BEGINS_WITH
operators. We'll later need to add checks to the rest of them as well.
As usual, all the tests pass on Amazon DynamoDB, and after this patch all
of them succeed on Alternator too.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190905125558.29133-1-nyh@scylladb.com>
In order for Spark jobs to work correctly, a hardcoded PAY_PER_REQUEST
billing mode entry is returned when describing a table with
a DescribeTable request.
Also, one test case in test_describe_table.py is no longer marked XFAIL.
Message-Id: <a4e6d02788d8be48b389045e6ff8c1628240197c.1567688894.git.sarna@scylladb.com>
With this patch, LocalSecondaryIndexes can be added to a table
during its creation. The implementation is heavily shared
with GlobalSecondaryIndexes and as such suffers from the same TODOs:
projections, describing more details in DescribeTable, etc.
Currently, we reserve the name ATTRS_COLUMN_NAME ("attrs") - the user
cannot use it as a key column name (key of the base table or GSI or LSI)
because we use this name for the attribute map we add to the schema.
Currently, if the user does attempt to create such a key column, the
result is undefined (sometimes corrupt sstables, sometimes outright crashes).
This patches fixes it to become a clean error, saying that this column name is
currently reserved.
The test test_create_table_special_column_name now cleanly fails, instead
of crashing Scylla, so it is converted from "skip" to "xfail".
Eventually we need to solve this issue completely (e.g., in rare cases
rename columns to allow us to reserve a name like ATTRS_COLUMN_NAME,
or alternatively, instead of using a fixed name ATTRS_COLUMN_NAME pick a
different one different from the key column names). But until we do,
better fail with a clear error instead of a crash.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190901102832.7452-1-nyh@scylladb.com>
When an unsupported expression parameter is encountered -
KeyConditionExpression, ConditionExpression or FilterExpression
are such - alternator will return an error instead of ignoring
the parameter.
Creating an underlying materialized view with 2 regular base columns
is risky in Scylla, as second's column liveness will not be correctly
taken into account when ensuring view row liveness.
Still, in case specific conditions are met:
* the regular base column value is always present in the base row
* no TTLs are involved
then the materialized view will behave as expected.
Creating a GSI with 2 base regular columns issues a warning,
as it should be performed with care.
Message-Id: <5ce8642c1576529d43ea05e5c4bab64d122df829.1567159633.git.sarna@scylladb.com>
It is important that BillingMode should default to PROVISIONED, as it
does on DynamoDB. This allows old clients, which don't specify
BillingMode at all, to specify ProvisionedThroughput as allowed with
PROVISIONED.
Also added a test case for this case (where BillingMode is absent).
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190829193027.7982-1-nyh@scylladb.com>
When querying on a missing index, DynamoDB returns different errors in
case the entire table is missing (ResourceNotFoundException) or the table
exists and just the index is missing (ValidationException). We didn't
make this distinction, and always returned ValidationException, but this
confuses clients that expect ResourceNotFoundException - e.g., Amazon's
Tic-Tac-Toe demo.
This patch adds a test for the first case (the completely missing table) -
we already had a test for the second case - and returns the correct
error codes. As usual the test passes against DynamoDB as well as Alternator,
ensure they behave the same.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190829174113.5558-1-nyh@scylladb.com>
Updating key columns is not allowed in UpdateItem requests,
but the series introducing GSI support for regular columns
also introduced redundant duplicates checks of this kind.
This condition is already checked in resolve_update_path helper function
and existing test_update_expression_cannot_modify_key test makes sure that
the condition is checked.
Message-Id: <00f83ab631f93b263003fb09cd7b055bee1565cd.1567086111.git.sarna@scylladb.com>
The code previously used clustering_key::from_singular() to compute
a clustering key value. It works fine, but has two issues:
1. involves one redundant deserialization stage compared to
from_single_value
2. does not work with compound clustering keys, which can appear
when using indexes
The DescribeTable request now contains the list of index names
as well. None of the attributes of the list are marked as 'required'
in the documentation, so currently the implementation provides
index names only.
In order to be able to create a Global Secondary Index over a regular
column, this column is upgraded from being a map entry to being a full
member of the schema. As such, it's possible to use this column
definition in the underlying materialized view's key.
In order to prepare alternator for adding regular columns to schema,
i.e. in order to create a materialized view over them,
the code is changed so that updating no longer assumes that only keys
are included in the table schema.
Since in the future we may want to have more regular columns
in alternator tables' schemas, the code is changed accordingly,
so all regular columns will be fetched instead of just the attribute
map.
If no regular column attributes are passed to PutItem, the attr
collector serializes an empty collection mutation nonetheless
and sends it. It's redundant, so instead, if the attr colector
is empty, the collection does not get serialized and sent to replicas.
Keeping an instance of client_state is a convenient way of being able
to use tracing for alternator. It's also currently used in paging,
so adding a client state to executor removes the need of keeping
a dummy value.
If a user tries to create a table with a unsupported feature -
a local secondary index, a used-defined encryption key or supporting
streams (CDC), let's refuse the table creation, so the application
doesn't continue thinking this feature is available to it.
The "Tags" feature is also not supported, but it is more harmless
(it is used mostly for accounting purposes) so we do not fail the
table creation because of it.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190818125528.9091-1-nyh@scylladb.com>
In CQL, before a user can create a table, they must create a keyspace to
contain this table and, among other things, specify this keyspace's RF.
But in the DynamoDB API, there is no "create keyspace" operation - the
user just creates a table, and there is no way, and no opportunity,
to specify the requested RF. Presumably, Amazon always uses the same
RF for all tables, most likely 3, although this is not officially
documented anywhere.
The existing code creates the keyspace during Scylla boot, with RF=1.
This RF=1 always works, and is a good choice for a one-node test run,
but was a really bad choice for a real cluster with multiple nodes, so
this patch fixes this choice:
With this patch, the keyspace creation is delayed - it doesn't happen
when the first node of the cluster boots, but only when the user creates
the first table. Presumably, at that time, the cluster is already up,
so at that point we can make the obvious choice automatically: a one-node
cluster will get RF=1, a >=3 node cluster will get RF=3. The choice of
RF is logged - and the choice of RF=1 is considered a warning.
Note that with this patch, keyspace creation is still automatic as it
was before. The user may manually create the keyspace via CQL, to
override this automatic choice. In the future we may also add additional
keyspace configuration options via configuration flags or new REST
requests, and the keyspace management code will also likely change
as we start to support clusters with multiple regions and global
tables. But for now, I think the automatic method is easiest for
users who want to test-drive Alternator without reading lengthy
instructions on how to set up the keyspace.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190820180610.5341-1-nyh@scylladb.com>
We allow BillingMode to be set to either PAY_PER_REQUEST (the default)
or PROVISIONED, although neither mode is fully implemented: In the former
case the payment isn't accounted, and in the latter case the throughput
limits are not enforced.
But other settings for BillingMode are now refused, and we add a new test
to verify that.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190818122919.8431-1-nyh@scylladb.com>
Currently Alternator starts all Scylla requests (including both reads
and writes) without any timeout set. Because of bugs and/or network
problems, Requests can theoretically hang and waste Scylla request for
hours, long after the client has given up on them and closed their
connection.
The DynamoDB protocol doesn't let a user specify which timeout to use,
so we should just use something "reasonable", in this patch 10 seconds.
Remember that all DynamoDB read and write requests are small (even scans
just scan a small piece), so 10 seconds should be above and beyond
anything we actually expect to see in practice.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190812105132.18651-1-nyh@scylladb.com>
It turns out that recent rjson patches introduced some buggy
tabs instead of spaces due to bad IDE configuration. The indentation
is restored to spaces.
Alternator allows passing hash and sort key restrictions
as filters - it is, however, better to incorporate these restrictions
directly into partition and clustering ranges, if possible.
It's also necessary, as optimizations inside restrictions_filter
assume that it will not be fed unneeded rows - e.g. if filtering
is not needed on partition key restrictions, they will not be checked.
Some underlying operations (e.g. paging) make use of cql_stats
structure from CQL3. As such, cql_stats structure is added
to alternator stats in order to gather and use these statistics.
This patch adds partial support for GSI (Global Secondary Index) in
Alternator, implemented using a materialized view in Scylla.
This initial version only supports the specific cases of the index indexing
a column which was already part of the base table's key - e.g., indexing
what used to be a sort key (clustering key) in the base table. Indexing
of non-key attributes (which today live in a map) is not yet supported in
this version.
Creation of a table with GSIs is supported, and so is deleting the table.
UpdateTable which adds a GSI to an existing table is not yet supported.
Query and Scan operations on the index are supported.
DescribeTable does not yet list the GSIs as it should.
Seven previously-failing tests now pass, so their "xfail" tag is removed.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20190808090256.12374-1-nyh@scylladb.com>
With libjsoncpp we were forced to work around the problem of
non-noexcept constructors by using an intermediate unique pointer.
Objects provided by rapidjson have correct noexcept specifiers,
so the workaround can be dropped.
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.
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>
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>
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>
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 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>
