Until now, the lists of streams in the `cdc_streams_descriptions` table
for a given generation were stored in a single collection. This solution
has multiple problems when dealing with large clusters (which produce
large lists of streams):
1. large allocations
2. reactor stalls
3. mutations too large to even fit in commitlog segments
This commit changes the schema of the table as described in issue #7993.
The streams are grouped according to token ranges, each token range
being represented by a separate clustering row. Rows are inserted in
reasonably large batches for efficiency.
The table is renamed to enable easy upgrade. On upgrade, the latest CDC
generation's list of streams will be (re-)inserted into the new table.
Yet another table is added: one that contains only the generation
timestamps clustered in a single partition. This makes it easy for CDC
clients to learn about new generations. It also enables an elegant
two-phase insertion procedure of the generation description: first we
insert the streams; only after ensuring that a quorum of replicas
contains them, we insert the timestamp. Thus, if any client observes a
timestamp in the timestamps table (even using a ONE query),
it means that a quorum of replicas must contain the list of streams.
---
Nodes automatically ensure that the latest CDC generation's list of
streams is present in the streams description table. When a new
generation appears, we only need to update the table for this
generation; old generations are already inserted.
However, we've changed the description table (from
`cdc_streams_descriptions` to `cdc_streams_descriptions_v2`). The
existing mechanism only ensures that the latest generation appears in
the new description table. We add an additional procedure that
rewrites the older generations as well, if we find that it is necessary
to do so (i.e. when some CDC log tables may contain data in these
generations).
Closes#8116
* github.com:scylladb/scylla:
tests: add a simple CDC cql pytest
cdc: add config option to disable streams rewriting
cdc: rewrite streams to the new description table
cql3: query_processor: improve internal paged query API
cdc: introduce no_generation_data_exception exception type
docs: cdc: mention system.cdc_local table
cdc: coroutinize do_update_streams_description
sys_dist_ks: split CDC streams table partitions into clustered rows
cdc: use chunked_vector for streams in streams_version
cdc: remove `streams_version::expired` field
system_distributed_keyspace: use mutation API to insert CDC streams
storage_service: don't use `sys_dist_ks` before it is started
(cherry picked from commit f0950e023d)
4b7319a870