In commit 44a1daf we added the ability to read system tables through
the DynamoDB API (actually, the Scan and Query requests only).
This ability is useful for tests, and can also be useful to users who
want to read information that is only available through system tables.
This patch adds support also for *writing* into system tables. This will
be useful for Alternator tests, were we want to temporarily change
some live-updatable configuration option - and so far haven't been
able to do that like we did do in some cql-pytest tests.
For reasons explained in issue #23218, only superuser roles are allowed to
write to system tables - it is not enough for the role to be granted
MODIFY permissions on the system table or on ALL KEYSPACES. Moreover,
the ability to modify system tables carries special risks, so this
patch only allows writes to the system tables if a new configuration
option "alternator_allow_system_table_write" turned on. This option is
turned off by default.
This patch also includes a test for this new configuration-writing
capability. The test scripts test/alternator/run and test.py now
run Scylla with alternator_allow_system_table_write turned on, but
the new test can also run without this option, and will be skipped
in that case (to allow running the test suite against some manually-
run instance of Scylla).
Fixes: #12348
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
a896e2dbb9