This change integrates service level functionality into the CQL authentication and connection handling:
- Add scheduling_group_name to client_data to track service level assignments
- Extend SASL challenge interface to expose authenticated username
- Modify connection processing to support tenant switching:
- Add switch_tenant() method to handle scheduling group changes
- Add process_until_tenant_switch() to handle request processing boundaries
- Implement no_tenant() default executor
- Add execute_under_tenant_type for scheduling group management
- Update connection lifecycle to properly handle service level changes:
- Initialize connections with default scheduling group
- Support dynamic scheduling group updates when service levels change
- Ensure proper cleanup of scheduling group assignments
The changes enable proper scheduling group assignment and management based on
authenticated users' service levels, while maintaining backward compatibility
for connections without service level assignments.
Now, when the user logs in and the connection becomes authenticated, the
processing loop of the connection is switched to the scheduling group
that corresponds to the service level assigned to the logged in user.
The scheduling group is also updated when the service level assigned to
this user changes.
Starting from this commit, the scheduling groups managed by the service
level controller are actually being used by user workload.
If authentication is enabled, but STARTUP isn't followed by REGISTER (which is optional, and in practice only happens on only one of a driver's connections — because there's no point listening for the same events on multiple connections), connections are wrongly displayed in the system.clients as AUTHENTICATING instead of READY, even when they are ready.
This commit fixes this problem.
Fixes: scylladb/scylladb#12640Closesscylladb/scylladb#21774
This reverts commit 324b3c43c0.
It isn't safe to do asynchronous calls in `for_each_gently`, as the
connection may be disconnected while a call in callback preempts.
Fixesscylladb/scylla#21801
when building scylla with the standard library from GCC-14.2, shipped by
fedora 41, we have following build failure:
```
/home/kefu/.local/bin/clang++ -DDEBUG -DDEBUG_LSA_SANITIZER -DFMT_SHARED -DSANITIZE -DSCYLLA_BUILD_MODE=debug -DSCYLLA_ENABLE_ERROR_INJECTION -DSEASTAR_API_LEVEL=7 -DSEASTAR_DEBUG -DSEASTAR_DEBUG_PROMISE -DSEASTAR_DEBUG_SHARED_PTR -DSEASTAR_DEFAULT_ALLOCATOR -DSEASTAR_LOGGER_COMPILE_TIME_FMT -DSEASTAR_LOGGER_TYPE_STDOUT -DSEASTAR_SCHEDULING_GROUPS_COUNT=16 -DSEASTAR_SHUFFLE_TASK_QUEUE -DSEASTAR_SSTRING -DSEASTAR_TYPE_ERASE_MORE -DXXH_PRIVATE_API -DCMAKE_INTDIR=\"Debug\" -I/home/kefu/dev/scylladb -I/home/kefu/dev/scylladb/build/gen -I/home/kefu/dev/scylladb/seastar/include -I/home/kefu/dev/scylladb/build/seastar/gen/include -I/home/kefu/dev/scylladb/build/seastar/gen/src -isystem /home/kefu/dev/scylladb/abseil -g -Og -g -gz -std=gnu++23 -fvisibility=hidden -Wall -Werror -Wextra -Wno-error=deprecated-declarations -Wimplicit-fallthrough -Wno-c++11-narrowing -Wno-deprecated-copy -Wno-mismatched-tags -Wno-missing-field-initializers -Wno-overloaded-virtual -Wno-unsupported-friend -Wno-unused-parameter -ffile-prefix-map=/home/kefu/dev/scylladb/build=. -march=x86-64-v3 -mpclmul -Xclang -fexperimental-assignment-tracking=disabled -Werror=unused-result -fstack-clash-protection -fsanitize=address -fsanitize=undefined -MD -MT CMakeFiles/scylla-main.dir/Debug/init.cc.o -MF CMakeFiles/scylla-main.dir/Debug/init.cc.o.d -o CMakeFiles/scylla-main.dir/Debug/init.cc.o -c /home/kefu/dev/scylladb/init.cc
In file included from /home/kefu/dev/scylladb/init.cc:12:
In file included from /home/kefu/dev/scylladb/db/config.hh:20:
In file included from /home/kefu/dev/scylladb/locator/abstract_replication_strategy.hh:26:
/home/kefu/dev/scylladb/locator/tablets.hh:410:30: error: unexpected type name 'size_t': expected expression
410 | return boost::irange<size_t>(0, tablet_count()) | boost::adaptors::transformed([] (size_t i) {
| ^
/home/kefu/dev/scylladb/locator/tablets.hh:410:23: error: no member named 'irange' in namespace 'boost'
410 | return boost::irange<size_t>(0, tablet_count()) | boost::adaptors::transformed([] (size_t i) {
| ~~~~~~~^
/home/kefu/dev/scylladb/locator/tablets.hh:410:38: error: left operand of comma operator has no effect [-Werror,-Wunused-value]
410 | return boost::irange<size_t>(0, tablet_count()) | boost::adaptors::transformed([] (size_t i) {
| ^
3 errors generated.
[16/782] Building CXX object CMakeFiles/scylla-main.dir/Debug/keys.cc.o
[17/782] Building CXX object CMakeFiles/scylla-main.dir/Debug/counters.cc.o
[18/782] Building CXX object CMakeFiles/scylla-main.dir/Debug/partition_slice_builder.cc.o
[19/782] Building CXX object CMakeFiles/scylla-main.dir/Debug/mutation_query.cc.o
FAILED: CMakeFiles/scylla-main.dir/Debug/mutation_query.cc.o
/home/kefu/.local/bin/clang++ -DDEBUG -DDEBUG_LSA_SANITIZER -DFMT_SHARED -DSANITIZE -DSCYLLA_BUILD_MODE=debug -DSCYLLA_ENABLE_ERROR_INJECTION -DSEASTAR_API_LEVEL=7 -DSEASTAR_DEBUG -DSEASTAR_DEBUG_PROMISE -DSEASTAR_DEBUG_SHARED_PTR -DSEASTAR_DEFAULT_ALLOCATOR -DSEASTAR_LOGGER_COMPILE_TIME_FMT -DSEASTAR_LOGGER_TYPE_STDOUT -DSEASTAR_SCHEDULING_GROUPS_COUNT=16 -DSEASTAR_SHUFFLE_TASK_QUEUE -DSEASTAR_SSTRING -DSEASTAR_TYPE_ERASE_MORE -DXXH_PRIVATE_API -DCMAKE_INTDIR=\"Debug\" -I/home/kefu/dev/scylladb -I/home/kefu/dev/scylladb/build/gen -I/home/kefu/dev/scylladb/seastar/include -I/home/kefu/dev/scylladb/build/seastar/gen/include -I/home/kefu/dev/scylladb/build/seastar/gen/src -isystem /home/kefu/dev/scylladb/abseil -g -Og -g -gz -std=gnu++23 -fvisibility=hidden -Wall -Werror -Wextra -Wno-error=deprecated-declarations -Wimplicit-fallthrough -Wno-c++11-narrowing -Wno-deprecated-copy -Wno-mismatched-tags -Wno-missing-field-initializers -Wno-overloaded-virtual -Wno-unsupported-friend -Wno-unused-parameter -ffile-prefix-map=/home/kefu/dev/scylladb/build=. -march=x86-64-v3 -mpclmul -Xclang -fexperimental-assignment-tracking=disabled -Werror=unused-result -fstack-clash-protection -fsanitize=address -fsanitize=undefined -MD -MT CMakeFiles/scylla-main.dir/Debug/mutation_query.cc.o -MF CMakeFiles/scylla-main.dir/Debug/mutation_query.cc.o.d -o CMakeFiles/scylla-main.dir/Debug/mutation_query.cc.o -c /home/kefu/dev/scylladb/mutation_query.cc
In file included from /home/kefu/dev/scylladb/mutation_query.cc:12:
In file included from /home/kefu/dev/scylladb/schema/schema_registry.hh:17:
In file included from /home/kefu/dev/scylladb/replica/database.hh:11:
In file included from /home/kefu/dev/scylladb/locator/abstract_replication_strategy.hh:26:
/home/kefu/dev/scylladb/locator/tablets.hh:410:30: error: unexpected type name 'size_t': expected expression
410 | return boost::irange<size_t>(0, tablet_count()) | boost::adaptors::transformed([] (size_t i) {
| ^
/home/kefu/dev/scylladb/locator/tablets.hh:410:23: error: no member named 'irange' in namespace 'boost'
410 | return boost::irange<size_t>(0, tablet_count()) | boost::adaptors::transformed([] (size_t i) {
| ~~~~~~~^
/home/kefu/dev/scylladb/locator/tablets.hh:410:38: error: left operand of comma operator has no effect [-Werror,-Wunused-value]
410 | return boost::irange<size_t>(0, tablet_count()) | boost::adaptors::transformed([] (size_t i) {
| ^
In file included from /home/kefu/dev/scylladb/mutation_query.cc:12:
In file included from /home/kefu/dev/scylladb/schema/schema_registry.hh:17:
In file included from /home/kefu/dev/scylladb/replica/database.hh:37:
In file included from /home/kefu/dev/scylladb/db/snapshot-ctl.hh:20:
/home/kefu/dev/scylladb/tasks/task_manager.hh:403:54: error: no member named 'irange' in namespace 'boost'
403 | co_await coroutine::parallel_for_each(boost::irange(0u, smp::count), [&tm, id, &res, &func] (unsigned shard) -> future<> {
| ~~~~~~~^
4 errors generated.
```
so let's take the opportunity to switch from `boost::irange` to
`std::views::iota`.
in this change, we:
- switch from boost::irange to std::views::iota for better standard library compatibility
- retain boost::irange where step parameter is used, as std::views::iota doesn't support it
- this change partially modernizes our range usage while maintaining
- existing functionality
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#20924
Rebounce the msg to another shard if needed,
e.g. in the case of tablet migration.
An example for that, as given by Tomasz Grabiec:
> Bouncing happens when executing LWT statement in
> modification_statement::execute_with_condition by returning a
> special result message kind. The code assumes that after
> jumping to the shard from the bounce request, the result
> message is the regular one and not yet another bounce.
> There is no problem with vnodes, because shards don't change.
> With tablets, they can change at run time on migration.
Fixesscylladb/scylladb#15465
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
`cql_server::connection::process_on_shard` is made a co-routine to
make sure captured objects' lifetime is managed by the source shard,
avoiding error prone inter-shard objects transfers.
It is currently unused in `process_on_shard`, which
generates an empty service_permit.
The next patch may call process_on_shard in a loop,
so it can't simply move the permit to the callee
and better hold on to it until processing completes.
`cql_server::connection::process` was turned into
a coroutine in this patch to hold on to the permit parameter
in a simple way. This is a preliminary step to changing
`if (bounce_msg)` to `while (bounce_msg)` that will allow
rebouncing the message in case it moved yet again when
yielding in `process_on_shard`.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
So it can safely passed between shards, as will be needed
in the following patch that handles a (re)bounce_to_shard result
from process_fn that's called by `process_on_shard` on the
`move_to_shard`.
With that in mind, pass the `bounce_to_shard` payload
to `process_on_shard` rather than the foreign shared ptr
since the latter grabs what it needs from it on entry
and the shared_ptr can be released on the calling shard.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Quoting Avi Kivity:
> Out of scope: we should consider detemplating this.
As a follow-up we should consider that and pass
a function object as process_fn, just make sure
there are no drawbacks.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Bind variables in CQL have two formats: positional (`?`) where a
variable is referred to by its relative position in the statement,
and named (`:var`), where the user is expected to supply a
name->value mapping.
In 19a6e69001 we identified the case where a named bind variable
appears twice in a query, and collapsed it to a single entry in the
statement metadata. Without this, a driver using the named variable
syntax cannot disambiguate which variable is referred to.
However, it turns out that users can use the positional call form
even with the named variable syntax, by using the positional
API of the driver. To support this use case, we add a configuration
variable to disable the same-variable detection.
Because the detection has to happen when the entire statement is
visible, we have to supply the configuration to the parser. We
call it the `dialect` and pass it from all callers. The alternative
would be to add a pre-prepare call similar to fill_prepare_context that
rewrites all expressions in a statement to deduplicate variables.
A unit test is added.
Fixes#15559
A dialect is a different way to interpret the same CQL statement.
Examples:
- how duplicate bind variable names are handled (later in this series)
- whether `column = NULL` in LWT can return true (as is now) or
whether it always returns NULL (as in SQL)
Currently, dialect is an empty structure and will be filled in later.
It is passed to query_processor methods that also accept a CQL string,
and from there to the parser. It is part of the prepared statement cache
key, so that if the dialect is changed online, previous parses of the
statement are ignored and the statement is prepared again.
The patch is careful to pick up the dialect at the entry point (e.g.
CQL protocol server) so that the dialect doesn't change while a statement
is parsed, prepared, and cached.
Add a CQL server testing API with and endpoint to dump
service level parameters of all CQL connections.
This endpoint will be later used to test functionality of
automated updating CQL connections parameters.
connections
Trigger update of service level param on every cql connection.
In enterprise, the method needs also to update connections' scheduling
group.
In the following patch, we will add a method to update service levels
parameters for each cql connections.
To support this, this patch allows to pass async function as a parameter
to `for_each_gently()` method.
assert() is traditionally disabled in release builds, but not in
scylladb. This hasn't caused problems so far, but the latest abseil
release includes a commit [1] that causes a 1000 insn/op regression when
NDEBUG is not defined.
Clearly, we must move towards a build system where NDEBUG is defined in
release builds. But we can't just define it blindly without vetting
all the assert() calls, as some were written with the expectation that
they are enabled in release mode.
To solve the conundrum, change all assert() calls to a new SCYLLA_ASSERT()
macro in utils/assert.hh. This macro is always defined and is not conditional
on NDEBUG, so we can later (after vetting Seastar) enable NDEBUG in release
mode.
[1] 66ef711d68Closesscylladb/scylladb#20006
because transport/server.cc has the complete definition of event_notifier, the
compiler can default-generate the destructor of `cql_server` with the necessary
information. otherwise, clang-19 would fail to build, like:
```
FAILED: CMakeFiles/scylla.dir/Dev/main.cc.o
/home/kefu/.local/bin/clang++ -DBOOST_PROGRAM_OPTIONS_DYN_LINK -DBOOST_PROGRAM_OPTIONS_NO_LIB -DDEVEL -DFMT_SHARED -DSCYLLA_BUILD_MODE=dev -DSCYLLA_ENABLE_ERROR_INJECTION -DSEASTAR_API_LEVEL=7 -DSEASTAR_ENABLE_ALLOC_FAILURE_INJECTION -DSEASTAR_LOGGER_COMPILE_TIME_FMT -DSEASTAR_LOGGER_TYPE_STDOUT -DSEASTAR_SCHEDULING_GROUPS_COUNT=16 -DSEASTAR_SSTRING -DSEASTAR_TYPE_ERASE_MORE -DXXH_PRIVATE_API -DCMAKE_INTDIR=\"Dev\" -I/home/kefu/dev/scylladb -I/home/kefu/dev/scylladb/build/gen -I/home/kefu/dev/scylladb/seastar/include -I/home/kefu/dev/scylladb/build/seastar/gen/include -I/home/kefu/dev/scylladb/build/seastar/gen/src -I/home/kefu/dev/scylladb/build -isystem /home/kefu/dev/scylladb/build/rust -isystem /home/kefu/dev/scylladb/abseil -O2 -std=gnu++23 -fvisibility=hidden -Wall -Werror -Wextra -Wno-error=deprecated-declarations -Wimplicit-fallthrough -Wno-c++11-narrowing -Wno-deprecated-copy -Wno-mismatched-tags -Wno-missing-field-initializers -Wno-overloaded-virtual -Wno-unsupported-friend -Wno-enum-constexpr-conversion -Wno-unused-parameter -ffile-prefix-map=/home/kefu/dev/scylladb=. -march=westmere -U_FORTIFY_SOURCE -Werror=unused-result -fstack-clash-protection -MD -MT CMakeFiles/scylla.dir/Dev/main.cc.o -MF CMakeFiles/scylla.dir/Dev/main.cc.o.d -o CMakeFiles/scylla.dir/Dev/main.cc.o -c /home/kefu/dev/scylladb/main.cc
In file included from /home/kefu/dev/scylladb/main.cc:11:
In file included from /usr/include/yaml-cpp/yaml.h:10:
In file included from /usr/include/yaml-cpp/parser.h:11:
In file included from /usr/lib/gcc/x86_64-redhat-linux/14/../../../../include/c++/14/memory:78:
/usr/lib/gcc/x86_64-redhat-linux/14/../../../../include/c++/14/bits/unique_ptr.h:91:16: error: invalid application of 'sizeof' to an incomplete type 'cql_transport::cql_server::event_notifier'
91 | static_assert(sizeof(_Tp)>0,
| ^~~~~~~~~~~
/usr/lib/gcc/x86_64-redhat-linux/14/../../../../include/c++/14/bits/unique_ptr.h:398:4: note: in instantiation of member function 'std::default_delete<cql_transport::cql_server::event_notifier>::operator()' requested here
398 | get_deleter()(std::move(__ptr));
| ^
/home/kefu/dev/scylladb/transport/server.hh:135:7: note: in instantiation of member function 'std::unique_ptr<cql_transport::cql_server::event_notifier>::~unique_ptr' requested here
135 | class cql_server : public seastar::peering_sharded_service<cql_server>, public generic_server::server {
| ^
/home/kefu/dev/scylladb/transport/server.hh:135:7: note: in implicit destructor for 'cql_transport::cql_server' first required here
/home/kefu/dev/scylladb/transport/server.hh:149:11: note: forward declaration of 'cql_transport::cql_server::event_notifier'
149 | class event_notifier;
| ^
1 error generated.
```
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
When preparing statement, the server code first does it on non-local
shards, then on local one. The former call is done the hard way, while
there's a short sugar sharded<> class method doing it.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Closesscylladb/scylladb#19485
since we've dropped the thift support, the `client_type` is always
`cql`, there is no need to differentiate different clients anymore.
so, we change `make_client_key()` so that it only return the IP address
and port.
Refs #3811
Refs #18416
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
thrift support was deprecated since ScyllaDB 5.2
> Thrift API - legacy ScyllaDB (and Apache Cassandra) API is
> deprecated and will be removed in followup release. Thrift has
> been disabled by default.
so let's drop it. in this change,
* thrift protocol support is dropped
* all references to thrift support in document are dropped
* the "thrift_version" column in system.local table is
preserved for backward compatibility, as we could load
from an existing system.local table which still contains
this clolumn, so we need to write this column as well.
* "/storage_service/rpc_server" is only preserved for
backward compatibility with java-based nodetool.
* `rpc_port` and `start_rpc` options are preserved, but
they are marked as "Unused". so that the new release
of scylladb can consume existing scylla.yaml configurations
which might contain these settings. by making them
deprecated, user will be able get warned, and update
their configurations before we actually remove them
in the next major release.
Fixes#3811Fixes#18416
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
get0() dates back from the days where Seastar futures carried tuples, and get0() was a way to get the first (and usually only) element. Now it's a distraction, and Seastar is likely to deprecate and remove it.
Replace with seastar::future::get(), which does the same thing.
Closesscylladb/scylladb#17130
* github.com:scylladb/scylladb:
treewide: replace seastar::future::get0() with seastar::future::get()
sstable: capture return value of get0() using auto
utils: result_loop: define result_type with decayed type
[avi: add another one that snuck in while this was cooking]
get0() dates back from the days where Seastar futures carried tuples, and
get0() was a way to get the first (and usually only) element. Now
it's a distraction, and Seastar is likely to deprecate and remove it.
Replace with seastar::future::get(), which does the same thing.
Add an option to listen on the maintenance socket. It is set up on an unix domain socket
and the metrics are disabled.
This enables having an independent authentication mechanism for this socket.
To start the maintenance socket, a new cql_controller has to be created
with
`db::maintenance_socket_enabled::yes` argument.
Creating maintenance socket will raise an exception if
* the path is longer than 107 chars (due to linux limits),
* a file or a directory already exists in the path.
The indentation is fixed in the next commit.
in fmt v10, it does not cast unaligned<T> to T when formatting it,
instead it insists on finding a matched fmt::formatter<> specialization for it.
that's why we have FTBFS with fmt v10 when printing
these packed<T> variables with fmtlib v10.
in this change, we just cast them to the underlying types before
formatting them. because seastar::unaligned<T> does not provide
a method for accessing the raw value, neither does it provide
a type alias of the type of the underlying raw value, we have
to cast to the type without deducing it from the printed value.
Refs #13245
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#16167
A custom payload can now be added to response_message.
If it is set, it will be sent to client and the custom_payload
flag will be set.
write_string_bytes_map method is added to response class
and a missing custom_payload flag is added to
cql_frame_flags.
This patch mark scylla_transport_cql_errors_total with skip_when_empty
flag.
It reduces the overhead for metrics for types that are never reported.
Signed-off-by: Amnon Heiman <amnon@scylladb.com>
Currently we hold group0_guard only during DDL statement's execute()
function, but unfortunately some statements access underlying schema
state also during check_access() and validate() calls which are called
by the query_processor before it calls execute. We need to cover those
calls with group0_guard as well and also move retry loop up. This patch
does it by introducing new function to cql_statement class take_guard().
Schema altering statements return group0 guard while others do not
return any guard. Query processor takes this guard at the beginning of a
statement execution and retries if service::group0_concurrent_modification
is thrown. The guard is passed to the execute in query_state structure.
Fixes: #13942
Message-ID: <ZNsynXayKim2XAFr@scylladb.com>
This reverts commit 70b5360a73. It generates
a failure in group0_test .test_concurrent_group0_modifications in debug
mode with about 4% probability.
Fixes#15050
Currently we hold group0_guard only during DDL statement's execute()
function, but unfortunately some statements access underlying schema
state also during check_access() and validate() calls which are called
by the query_processor before it calls execute. We need to cover those
calls with group0_guard as well and also move retry loop up. This patch
does it by introducing new function to cql_statement class take_guard().
Schema altering statements return group0 guard while others do not
return any guard. Query processor takes this guard at the beginning of a
statement execution and retries if service::group0_concurrent_modification
is thrown. The guard is passed to the execute in query_state structure.
Fixes: #13942
Message-ID: <ZNSWF/cHuvcd+g1t@scylladb.com>
we print the stream id in the logging messages, but in this case,
we forgot to pass `stream` to `log::debug()`. but the placeholder
for `stream` was added. if the underlying fmtlib actually formats
the argument with the format string, it would throw.
fortunately, we don't enable debug level logging often, guess that's
why we haven't spotted this issue yet.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes#14620
this change is a follow-up of 4f5fcb02fd,
the goal is to avoid the programming oversights like
```c++
trace(trace_ptr, "foo {} with {} but {} is {}");
```
as `trace(const trace_state_ptr& p, const std::string& msg)` is
a better match than the templated one, i.e.,
`trace(const trace_state_ptr& p, fmt::format_string<T...> fmt, T&&...
args)`. so we cannot detect this with the compile-time format checking.
so let's just drop this overload, and update its callers to use
the other overload.
The change was suggested by Avi. the example also came from him.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes#14188
The expression system uses managed_bytes_opt for values, but result_set
uses bytes_opt. This means that processing values from the result set
in expressions requires a copy.
Out of the two, managed_bytes_opt is the better choice, since it prevents
large contiguous allocations for large blobs. So we switch result_set
to use managed_bytes_opt. Users of the result_set API are adjusted.
The db::function interface is not modified to limit churn; instead we
convert the types on entry and exit. This will be adjusted in a following
patch.
`current_scheduling_group()` returns a temporary value, and `name()`
returns a reference, so we cannot capture the return value by reference,
and use the reference after this expression is evaluated. this would
cause undefined behavior. so let's just capture it by value.
this change also silence following warning from GCC-13:
```
/home/kefu/dev/scylladb/transport/server.cc:204:11: error: possibly dangling reference to a temporary [-Werror=dangling-reference]
204 | auto& cur_sg_name = current_scheduling_group().name();
| ^~~~~~~~~~~
/home/kefu/dev/scylladb/transport/server.cc:204:56: note: the temporary was destroyed at the end of the full expression ‘seastar::current_scheduling_group().seastar::scheduling_group::name()’
204 | auto& cur_sg_name = current_scheduling_group().name();
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~
```
Fixes#13719
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes#13724
Common compression libraries work on contiguous buffers.
Contiguous buffers are a problem for the allocator. However, as long as they are short-lived,
we can avoid the expensive allocations by reusing buffers across tasks.
This idea is already applied to the compression of CQL frames, but with some deficiencies.
`utils: redesign reusable_buffer` attempts to improve upon it in a few ways. See its commit message for an extended discussion.
Compression buffer reuse also happens in the zstd SSTable compressor, but the implementation is misguided. Every `zstd_processor` instance reuses a buffer, but each instance has its own buffer. This is very bad, because a healthy database might have thousands of concurrent instances (because there is one for each sstable reader). Together, the buffers might require gigabytes of memory, and the reuse actually *increases* memory pressure significantly, instead of reducing it.
`zstd: share buffers between compressor instances` aims to improve that by letting a single buffer be shared across all instances on a shard.
Closes#13324
* github.com:scylladb/scylladb:
zstd: share buffers between compressor instances
utils: redesign reusable_buffer
Large contiguous buffers put large pressure on the allocator
and are a common source of reactor stalls. Therefore, Scylla avoids
their use, replacing it with fragmented buffers whenever possible.
However, the use of large contiguous buffers is impossible to avoid
when dealing with some external libraries (i.e. some compression
libraries, like LZ4).
Fortunately, calls to external libraries are synchronous, so we can
minimize the allocator impact by reusing a single buffer between calls.
An implementation of such a reusable buffer has two conflicting goals:
to allocate as rarely as possible, and to waste as little memory as
possible. The bigger the buffer, the more likely that it will be able
to handle future requests without reallocation, but also the memory
memory it ties up.
If request sizes are repetitive, the near-optimal solution is to
simply resize the buffer up to match the biggest seen request,
and never resize down.
However, if we anticipate pathologically large requests, which are
caused by an application/configuration bug and are never repeated
again after they are fixed, we might want to resize down after such
pathological requests stop, so that the memory they took isn't tied
up forever.
The current implementation of reusable buffers handles this by
resizing down to 0 every 100'000 requests.
This patch attempts to solve a few shortcomings of the current
implementation.
1. Resizing to 0 is too aggressive. During regular operation, we will
surely need to resize it back to the previous size again. If something
is allocated in the hole left by the old buffer, this might cause
a stall. We prefer to resize down only after pathological requests.
2. When resizing, the current implementation allocates the new buffer
before freeing the old one. This increases allocator pressure for no
reason.
3. When resizing up, the buffer is resized to exactly the requested
size. That is, if the current size is 1MiB, following requests
of 1MiB+1B and 1MiB+2B will both cause a resize.
It's preferable to limit the set of possible sizes so that every
reset doesn't tend to cause multiple resizes of almost the same size.
The natural set of sizes is powers of 2, because that's what the
underlying buddy allocator uses. No waste is caused by rounding up
the allocation to a power of 2.
4. The interval of 100'000 uses is both too low and too arbitrary.
This is up for discussion, but I think that it's preferable to base
the dynamics of the buffer on time, rather than the number of uses.
It's more predictable to humans.
The implementation proposed in this patch addresses these as follows:
1. Instead of resizing down to 0, we resize to the biggest size
seen in the last period.
As long as at least one maximal (up to a power of 2) "normal" request
appears each period, the buffer will never have to be resized.
2. The capacity of the buffer is always rounded up to the nearest
power of 2.
3. The resize down period is no longer measured in number of requests
but in real time.
Additionally, since a shared buffer in asynchronous code is quite a
footgun, some rudimentary refcounting is added to assert that only
one reference to the buffer exists at a time, and that the buffer isn't
downsized while a reference to it exists.
Fixes#13437
instead of copying the `config` parameter, move away from it.
this change also prepares for a non-copyable config. if the class
of `config` is not copyable, we will not be able to initialize
the member variable by copying from the given `config` parameter.
after the live-updateable config change, the `_config` member
variable will contain instances of utils::observer<>, which is
not copyable, but is move-constructable, hence in this change,
we just move away from the give `config`.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
This patch extends a previous patch that added these metrics globally:
- cql_requests_count
- cql_request_bytes
- cql_response_bytes
This patch adds a "scheduling_group_name" label to these metrics and changes corresponding
counters to be accounted on a per-scheduling-group level.
As a bonus this patch also marks all 3 metrics as 'skip_when_empty'.
Ref #13061
Signed-off-by: Vlad Zolotarov <vladz@scylladb.com>
Message-Id: <20230321201412.3004845-1-vladz@scylladb.com>
