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CDC has to create CDC streams that are co-located with corresponding BaseTable data. This is not always easy. Especially for small vnodes. This PR introduces new partitioner which allows us to easily find such stream ids that the stream belongs to a given vnode and shard.
The idea is that a partitioner accepts only keys that are a blob composed of two int64 numbers. The first number is the token of the key.
Tests: unit(dev), dtests(CDC)
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* haaawk-cdc_partitioner:
cdc:use CDCPartitioner for CDC Log
dht: Add find_first_token_for_shard
dht: use long_token in token::to_int64
cdc: add CDCPartitioner
stream_id: add token_from_bytes static function
i_partitioner: Stop distinguishing whether keys order is preserved
This will allow deterministic stream_id generation
and would remove the risk of not being able to generate
a stream id for some vnode.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
And do the same with CDC_STREAMS_TIMESTAMP.
The code that took a list of tokens represented as a string inside
versioned_value (for gossiping) and deserialized it into
an `unordered_set<dht::token>` lived in the storage_service module,
while the code that did the serializing (set -> string) lived in
versioned_value. There was a similar situation with the CDC generation
timestamp.
To increase maintanability and reusability, the deserialization code is
now placed next to the serialization code in versioned_value.
Furthermore, the `make_full_token_string`, `make_token_string`, and
`make_cdc_streams_timestamp_string` (serialization functions) are moved
out of versioned_value::factory and made static methods of
versioned_value instead.
In new CDC Log format stream_id is represented by a single
blob column so it makes sense to store it in the same form
everywhere - including internal CDC tables.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Use std::set::insert that takes range instead of
looping through elements and adding them one by one.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
In new CDC Log format we store only a single stream_id column.
This means generate_topology_description has to use appropriate
schema for generating tokens for stream_ids.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
New CDC Log format stores stream ids as blobs.
It makes sense to keep them internally in the same form.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Previously we had stream_id_1 and stream_id_2 columns
of type long each. They were forming a partition key.
In a new format we want a single stream_id column that
forms a partition key. To be able to still store two
longs, the new column will have type blob and its value
will be concatenated bytes of two longs that
partition key is composed of.
We still want partition key to logically be two longs
because those two values will be used by a custom partitioner
later once we implement it.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
CDC can get all it needs from a config and does not need
partitioner.
For base table specific operations CDC is using partitioner
from that table (obtained with schema::get_partitioner).
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
and replace all calls to dht::global_partitioner().get_token
dht::get_token is better because it takes schema and uses it
to obtain partitioner instead of using a global partitioner.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Since token representation is fixed now, all the partitioners
will share the sharding logic. It makes sense now to keep
the logic in common super class and separate header that's
included only in i_partitioner.cc.
shard_of and token_for_next_shard are now implemented in
i_partitioner. They would be non-virtual but we have to
keep them virtual because one test is overriding them
to enforce some specific sharding.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Snitch forms a class hierarchy which get_shard_count and
get_ignore_msb_bits ignore (their returned values only depend on the
gossiper's state).
Besides, these functions just don't belong there.
Snitch has nothing to do with shard_count or ignore_msb_bits.
In future commits this will be used by nodes learning about other nodes
entering NORMAL status. The joining node proposes a new generation of streams,
whose timestamp is gossiped by the node.
cdc::topology_description describes a mapping of tokens to CDC streams.
The cdc::generate_topology_description function is given:
1. a set of tokens which split the token ring into token ranges (vnodes),
2. information on how each token range is distributed among its owning
node's shards
and tries to generate a set of CDC stream identifiers such that for each
shard and vnode pair there exists a stream whose token falls into this
vnode and is owned by this shard.
It then builds a cdc::topology_description which maps tokens to these
found stream identifiers, such that if token T is owned by shard S in
vnode V, it gets mapped to the stream identifier generated for (S, V).
This is a class that will be used for storing information
required to perform CDC operations, i.e. assignment of token ranges to
CDC streams.
It is serializable to bytes and will be stored
in such a form in a distributed table accessible
by all nodes.
