Unlike with vnodes, each tablet is served only by a single
shard, and it is associated with a memtable that, when
flushed, it creates sstables which token-range is confined
to the tablet owning them.
On one hand, this allows for far better agility and elasticity
since migration of tablets between nodes or shards does not
require rewriting most if not all of the sstables, as required
with vnodes (at the cleanup phase).
Having too few tablets might limit performance due not
being served by all shards or by imbalance between shards
caused by quantization. The number of tabelts per table has to be
a power of 2 with the current design, and when divided by the
number of shards, some shards will serve N tablets, while others
may serve N+1, and when N is small N+1/N may be significantly
larger than 1. For example, with N=1, some shards will serve
2 tablet replicas and some will serve only 1, causing an imbalance
of 100%.
Now, simply allocating a lot more tablets for each table may
theoretically address this problem, but practically:
a. Each tablet has memory overhead and having too many tablets
in the system with many tables and many tablets for each of them
may overwhelm the system's and cause out-of-memory errors.
b. Too-small tablets cause a proliferation of small sstables
that are less efficient to acces, have higher metadata overhead
(due to per-sstable overhead), and might exhaust the system's
open file-descriptors limitations.
The options introduced in this change can help the user tune
the system in two ways:
1. Sizing the table to prevent unnecessary tablet splits
and migrations. This can be done when the table is created,
or later on, using ALTER TABLE.
2. Controlling min_per_shard_tablet_count to improve
tablet balancing, for hot tables.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
This change introduces a new audit subsystem that allows tracking and logging of database operations for security and compliance purposes. Key features include:
- Configurable audit logging to either syslog or a dedicated system table (audit.audit_log)
- Selective auditing based on:
- Operation categories (QUERY, DML, DDL, DCL, AUTH, ADMIN)
- Specific keyspaces
- Specific tables
- New configuration options:
- audit: Controls audit destination (none/syslog/table)
- audit_categories: Comma-separated list of operation categories to audit
- audit_tables: Specific tables to audit
- audit_keyspaces: Specific keyspaces to audit
- audit_unix_socket_path: Path for syslog socket
- audit_syslog_write_buffer_size: Buffer size for syslog writes
The audit logs capture details including:
- Operation timestamp
- Node and client IP addresses
- Operation category and query
- Username
- Success/failure status
- Affected keyspace and table names
The interface is not used anywhere anymore, so we can
remove it safely. It has been replaced by custom
functions for each keyspace element and `cql3::description`.
We add a new parameter in functions used to generate instances
of `cql3::description` for types related to situations where we
might not need a create statement. An example of such a scenario
could be `DESCRIBE TYPES`.
We're removing `data_dictionary::keyspace_element`.
Before we can do that, we need to substitute the existing
methods used for describing keyspace elements with their
new versions returning `cql3::description`.
That's what happens in this commit.
feature_service.hh is a high-level header that integrates much
of the system functionality, so including it in lower-level headers
causes unnecessary rebuilds. Specifically, when retiring features.
Fix by removing feature_service.hh from headers, and supply forward
declarations and includes in .cc where needed.
Closesscylladb/scylladb#18005
When tablets are enabled and a keyspace being described has them
explicitly disabled or non-automatic initial value of zero, include this
into the returned describe statement too
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Other than being fmt v10 compatible, it's also shorter and easier to
read, thanks to fmt::join() helper
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Closesscylladb/scylladb#17115
It's only testing code that wants to call new_keyspace with existing
schemas, all the other callers either construct the ks metadata
directly, or use convenience new_keyspace with explicitly empty schemas.
By and large it's nicer if new_keyspace() doesn't requires this
argument.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Almost all callers call new_keyspace with durable writes ON, so it's
worth having default value for it
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
There's a cascade of keyspace_metadata constructors each adding one
default argument to the prevuous one. All this can be expressed shorter
with the help of native default argument
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
The object in question fully describes the keyspace to be created and,
among other things, contains replication strategy options. Next patches
move the "initial_tablets" option out of those options and keep it
separately, so the ks metadata should also carry this option separately.
This patch is _just_ extending the metadata creation API, in fact the
new field is unused (write-only) so all the places that need to provide
this data keep it disengaged and are explicitly marked with FIXME
comment. Next patches will fix that.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Part of moving the responsibility for applying
and notifying keyspace schema changes from
schema_tables to the database so that the
database can control the order of applying the changes
across shards and when to notify its listeners.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Tables need to know which storage their sstables need to be located at,
so class table needs to have itw reference of the storage options. The
thing can be inherited from the keyspace metadata.
Tests sometimes create table without keyspace at hand. For those use
default-initialized storage options (which is local storage).
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Today the storage options are embedded into metadata object. In the
future the storage options will need to be somehow referenced by the
class table too. Using plan reference doesn't look safe, turn the
storage options into lw-shared-ptr instead.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Schema related files are moved there. This excludes schema files that
also interact with mutations, because the mutation module depends on
the schema. Those files will have to go into a separate module.
Closes#12858
The STORAGE option is designed to hold a map of options
used for customizing storage for given keyspace.
The option is kept in a system_schema.scylla_keyspaces table.
The option is only available if the whole cluster is aware
of it - guarded by a cluster feature.
Example of the table contents:
```
cassandra@cqlsh> select * from system_schema.scylla_keyspaces;
keyspace_name | storage_options | storage_type
---------------+------------------------------------------------+--------------
ksx | {'bucket': '/tmp/xx', 'endpoint': 'localhost'} | S3
```
Instead of lengthy blurbs, switch to single-line, machine-readable
standardized (https://spdx.dev) license identifiers. The Linux kernel
switched long ago, so there is strong precedent.
Three cases are handled: AGPL-only, Apache-only, and dual licensed.
For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0),
reasoning that our changes are extensive enough to apply our license.
The changes we applied mechanically with a script, except to
licenses/README.md.
Closes#9937
