std::ranges::{push,pop}_heap() will only generate default comparator if
the compared types are fully ordered. So we need to pass std::less<>
explicitely as comparator for the code to compile.
Calculate a buffer fill hint and pass it to
shard_reader_v2::fill_buffer(), so the underlying buffer-fill can be
optimized to avoid multiple cross shard round-trips, as well as possible
evict-recreate cycles.
The buffer hint mechanism is opt-in, enabled via the new
multishard_reader_buffer_hint parameter.
When the hint is provided, respect it: make sure the returned buffer is
of the requested size, stopping early if the stop_token is seen.
To reduce the amount of possible eviction-recreate cycles while the
buffer is filled, disable auto-pause for the duration of the
fill_reader_buffer() call. For this purpose, auto_pause_disable_guard is
added to evictable_reader_v2.
The hint will tell the shard reader exactly how much data to produce, to
avoid multiple cross-shard round-trips and possible evict-recreate
cycles.
The hint is neither used yet or calculated yet, this is coming in the
next patches.
Passing an admitted permit -- i.e. one with count resources on it -- to
the multishard reader, will possibly result in a deadlock, because the
permit of the multishard reader is destroyed after the permits of its
child readers. Therefore its semaphore resources won't be automatically
released until children acquire their own resources.
This creates a dependency (an edge in the "resource allocation graph"),
where the semaphore used by the multishard reader depends on the
semaphores used by children. When such dependencies create a cycle, and
permits are acquired by different reads in just the right order, a
deadlock will happen.
Users of the multishard reader have to be aware of this gotcha -- and of
course they aren't. This is small wonder, considering that not even the
documentation on the multishard reader mentions this problem.
To work around this, the user has to call
`reader_permit::release_base_resources()` on the permit, before passing
it to the multishard reader.
On multiple occasions, developers (including the very author of the
multishard reader), forgot or didn't know about this and this resulted
in deadlocks down the line.
This is a design-flaw of the multishard reader, which is addressed in
this patch, after which, it is safe to pass admitted or not admitted
permits to the multishard reader, it will handle the call to
`release_base_resources()` if needed.
* seastar ec5da7a6...69f88e2f (38):
> build: s/Sanitizers_COMPILER_OPTIONS/Sanitizers_COMPILE_OPTIONS
> test: Update httpd test with request/reply body writing sugar
> http: Add sugar to request and response body writers
> utils: Add util::write_to_stream() helper
> seastar-addr2line: adjust llvm termination regex
> README.md: add Crimson project
> rpc: conditionally use fmt::runtime() based on SEASTAR_LOGGER_COMPILE_TIME_FMT
> build: check the combination of Sanitizers
> tls: clear session ticket before releasing
> print: remove dead code
> doc/lambda-coroutine-fiasco: reword for better readability
> rpc: fix compilation error caused by fmt::runtime()
> tutorial: explain the use case of rethrow_exception and coroutine::exception
> reactor: print more informative error when io_submit fails
> README.md: note GitHub discussions
> prometheus: `fmt::print` to stringstream directly
> doc: add document for testing with seastar
> seastar/testing: only include used headers
> test: Add abortable http client test cases
> http/client: Add abortable make_request() API method
> http/client: Abort established connections
> http/client: Handle abort source in pool wait
> http/client: Add abort source to factory::make() method
> http/client: Pass abort_source here and there
> http/client: Idnentation fix after previous patch
> http/client: Merge some continuations explicitly
> signal: add seastar signal api
> httpd: remove unused prometheus structs
> print: use fmtlib's fmt::format_string in format()
> rpc: do not use seastar::format() in rpc logger
> treewide: s/format/seastar::format/
> prometheus: sanitize label value for text protocol
> tests: unit test prometheus wire format
> io-tester: Introduce batches to rate-based submission
> io-tester: Generalize issueing request and collecting its result
> io-tester: Cancel intent once
> io-tester: Dont carry rps/parallelism variables over lambdas
> io-tester: Simplify in-flight management
The breaking changes in the seastar submodule necessitate corresponding
modifications in our code. These changes must be implemented together in
a single commit to maintain consistency. So that each commit is buildable.
following changes are included in addition to seastar submodule update:
* instead of passing a `const char*` for the format string, pass a
templated `fmt::format_string<...>`, this depends on the
`seastar::format()` change in seastar.
* explicitly call `fmt::runtime()` if the format string is not a
consteval expression. this depends on the `seastar::format()` change
in seastar. as `seastar::format()` does not accept a plain
`const char*` which is not constexpr anymore.
* pass abort_source to `dns_connection_factory::make()`. this depends on
the change in seastar, which added a `abort_source*` argument to
the pure virtual member function of `connection_factory::make()`.
* call call {fmt,seastar}::format() explicitly. this is a follow up of
3e84d43f, which takes care of all places where we should call
`fmt::format()` and `seastar::format()` explicitly to disambiguate the
`format()` call. but more `format()` call made their way into the source
tree after 3e84d43f. so we need fix them as well.
* include used header in tests
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Update seastar submodule
Please enter the commit message for your changes. Lines starting
Closesscylladb/scylladb#20649
before this change, we rely on `using namespace seastar` to use
`seastar::format()` without qualifying the `format()` with its
namespace. this works fine until we changed the parameter type
of format string `seastar::format()` from `const char*` to
`fmt::format_string<...>`. this change practically invited
`seastar::format()` to the club of `std::format()` and `fmt::format()`,
where all members accept a templated parameter as its `fmt`
parameter. and `seastar::format()` is not the best candidate anymore.
despite that argument-dependent lookup (ADT for short) favors the
function which is in the same namespace as its parameter, but
`using namespace` makes `seastar::format()` more competitive,
so both `std::format()` and `seastar::format()` are considered
as the condidates.
that is what is happening scylladb in quite a few caller sites of
`format()`, hence ADT is not able to tell which function the winner
in the name lookup:
```
/__w/scylladb/scylladb/mutation/mutation_fragment_stream_validator.cc:265:12: error: call to 'format' is ambiguous
265 | return format("{} ({}.{} {})", _name_view, s.ks_name(), s.cf_name(), s.id());
| ^~~~~~
/usr/bin/../lib/gcc/x86_64-redhat-linux/14/../../../../include/c++/14/format:4290:5: note: candidate function [with _Args = <const std::basic_string_view<char> &, const seastar::basic_sstring<char, unsigned int, 15> &, const seastar::basic_sstring<char, unsigned int, 15> &, const utils::tagged_uuid<table_id_tag> &>]
4290 | format(format_string<_Args...> __fmt, _Args&&... __args)
| ^
/__w/scylladb/scylladb/seastar/include/seastar/core/print.hh:143:1: note: candidate function [with A = <const std::basic_string_view<char> &, const seastar::basic_sstring<char, unsigned int, 15> &, const seastar::basic_sstring<char, unsigned int, 15> &, const utils::tagged_uuid<table_id_tag> &>]
143 | format(fmt::format_string<A...> fmt, A&&... a) {
| ^
```
in this change, we
change all `format()` to either `fmt::format()` or `seastar::format()`
with following rules:
- if the caller expects an `sstring` or `std::string_view`, change to
`seastar::format()`
- if the caller expects an `std::string`, change to `fmt::format()`.
because, `sstring::operator std::basic_string` would incur a deep
copy.
we will need another change to enable scylladb to compile with the
latest seastar. namely, to pass the format string as a templated
parameter down to helper functions which format their parameters.
to miminize the scope of this change, let's include that change when
bumping up the seastar submodule. as that change will depend on
the seastar change.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
The reconcilable_result is built as it would be constructed for
forward read queries for tables with reversed order.
Mutations constructed for reversed queries are consumed forward.
Drop overloaded reversed functions that reverse read_command and
reconcilable_result directly and keep only those requiring smart
pointers. They are not used any more.
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
flat_mutation_reader_v2 was introduced in a pair of commits in 2021:
e3309322c3 "Clone flat_mutation_reader related classes into v2 variants"
08b5773c12 "Adapt flat_mutation_reader_v2 to the new version of the API"
as a replacement for flat_mutation_reader, using range_tombstone_change
instead of range_tombstone to represent represent range tombstones. See
those commits for more information.
The transition was incremental; the last use of the original
flat_mutation_reader was removed in 2022 in commit
026f8cc1e7 "db: Use mutation_partition_v2 in mvcc"
In turn, flat_mutation_reader was introduced in 2017 in commit
748205ca75 "Introduce flat_mutation_reader"
To transition from a mutation_reader that nested rows within
a partition in a separate stream, to a flat reader that streamed
partitions and rows in the same stream.
Here, we reclaim the original name and rename the awkward
flat_mutation_reader_v2 to mutation_reader.
Note that mutation_fragment_v2 remains since we still use the original
for compatibilty, sometimes.
Some notes about the transition:
- files were also renamed. In one case (flat_mutation_reader_test.cc), the
rename target already existed, so we rename to
mutation_reader_another_test.cc.
- a namespace 'mutation_reader' with two definitions existed (in
mutation_reader_fwd.hh). Its contents was folded into the mutation_reader
class. As a result, a few #includes had to be adjusted.
Closesscylladb/scylladb#19356
in theory, std::result_of_t should have been removed in C++20. and
std::invoke_result_t is available since C++17. thanks to libstdc++,
the tree is compiling. but we should not rely on this.
so, in this change, we replace all `std::result_of_t` with
`std::invoke_result_t`. actually, clang + libstdc++ is already warning
us like:
```
In file included from /home/runner/work/scylladb/scylladb/multishard_mutation_query.cc:9:
In file included from /home/runner/work/scylladb/scylladb/schema/schema_registry.hh:11:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/unordered_map:38:
Warning: /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/type_traits:2624:5: warning: 'result_of<void (noop_compacted_fragments_consumer::*(noop_compacted_fragments_consumer &))()>' is deprecated: use 'std::invoke_result' instead [-Wdeprecated-declarations]
2624 | using result_of_t = typename result_of<_Tp>::type;
| ^
/home/runner/work/scylladb/scylladb/mutation/mutation_compactor.hh:518:43: note: in instantiation of template type alias 'result_of_t' requested here
518 | if constexpr (std::is_same_v<std::result_of_t<decltype(&GCConsumer::consume_end_of_stream)(GCConsumer&)>, void>) {
|
```
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#18835
when compiling with clang-tidy, it warngs:
```
[6/9] Building CXX object readers/CMakeFiles/readers.dir/multishard.cc.o
/home/kefu/dev/scylladb/readers/multishard.cc:84:53: warning: 'fut_and_result' used after it was moved [bugprone-use-after-move]
84 | auto result = std::get<1>(std::move(fut_and_result));
| ^
/home/kefu/dev/scylladb/readers/multishard.cc:79:34: note: move occurred here
79 | _read_ahead_future = std::get<0>(std::move(fut_and_result));
| ^
```
but this warning is but a false alarm, as we are not really moving away
the *whole* tuple, we are just move away an element from it. but
clang-tidy cannot tell which element we are actually moving. so, silence
both places of `std::move()`.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#18363
When the reader is currently paused, it is resumed, fast-forwarded, then
paused again. The fast forwarding part can throw and this will lead to
destroying the reader without it being closed first.
Add a try-catch surrounding this part in the code. Also mark
`maybe_pause()` and `do_pause()` as noexcept, to make it clear why
that part doesn't need to be in the try-catch.
Fixes: #16606Closesscylladb/scylladb#16630
Fixes some typos as found by codespell run on the code.
In this commit, I was hoping to fix only comments, not user-visible alerts, output, etc.
Follow-up commits will take care of them.
Refs: https://github.com/scylladb/scylladb/issues/16255
Signed-off-by: Yaniv Kaul <yaniv.kaul@scylladb.com>
The evictable reader must ensure that each buffer fill makes forward
progress, i.e. the last fragment in the buffer has a position larger
than the last fragment from the previous buffer-fill. Otherwise, the
reader could get stuck in an infinite loop between buffer fills, if the
reader is evicted in-between.
The code guranteeing this forward progress had a bug: the comparison
between the position after the last buffer-fill and the current
last fragment position was done in the wrong direction.
So if the condition that we wanted to achieve was already true, we would
continue filling the buffer until partition end which may lead to OOMs
such as in #13491.
There was already a fix in this area to handle `partition_start`
fragments correctly - #13563 - but it missed that the position
comparison was done in the wrong order.
Fix the comparison and adjust one of the tests (added in #13563) to
detect this case.
Fixes#13491
This is not strictly necessary, as the multishard reader will be later
avoided altogether for tablet-based tables, but it is a step towards
converting all code to use the erm->get_sharder() instead of
schema::get_sharder().
In that level no io_priority_class-es exist. Instead, all the IO happens
in the context of current sched-group. File API no longer accepts prio
class argument (and makes io_intent arg mandatory to impls).
So the change consists of
- removing all usage of io_priority_class
- patching file_impl's inheritants to updated API
- priority manager goes away altogether
- IO bandwidth update is performed on respective sched group
- tune-up scylla-gdb.py io_queues command
The first change is huge and was made semi-autimatically by:
- grep io_priority_class | default_priority_class
- remove all calls, found methods' args and class' fields
Patching file_impl-s is smaller, but also mechanical:
- replace io_priority_class& argument with io_intent* one
- pass intent to lower file (if applicatble)
Dropping the priority manager is:
- git-rm .cc and .hh
- sed out all the #include-s
- fix configure.py and cmakefile
The scylla-gdb.py update is a bit hairry -- it needs to use task queues
list for IO classes names and shares, but to detect it should it checks
for the "commitlog" group is present.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Closes#13963
In https://github.com/scylladb/scylladb/pull/13482 we renamed the reader permit states to more descriptive names. That PR however only covered only the states themselves and their usages, as well as the documentation in `docs/dev`.
This PR is a followup to said PR, completing the name changes: renaming all symbols, names, comments etc, so all is consistent and up-to-date.
Closes#13573
* github.com:scylladb/scylladb:
reader_concurrency_semaphore: misc updates w.r.t. recent permit state name changes
reader_concurrency_semaphore: update permit members w.r.t. recent permit state name changes
reader_concurrency_semaphore: update RAII state guard classes w.r.t. recent permit state name changes
reader_concurrency_semaphore: update API w.r.t. recent permit state name changes
reader_concurrency_semaphore: update stats w.r.t. recent permit state name changes
The evictable reader must ensure that each buffer fill makes forward
progress, i.e. the last fragment in the buffer has a position larger
than the last fragment from the last buffer-fill. Otherwise, the reader
could get stuck in an infinite loop between buffer fills, if the reader
is evicted in-between.
The code guranteeing this forward change has a bug: when the next
expected position is a partition-start (another partition), the code
would loop forever, effectively reading all there is from the underlying
reader.
To avoid this, add a special case to ignore the progress guarantee loop
altogether when the next expected position is a partition start. In this
case, progress is garanteed anyway, because there is exactly one
partition-start fragment in each partition.
Fixes: #13491Closes#13563
When creating the reader, the lifecycle policy might return one that was
saved on the last page and survived in the cache. This reader might have
skipped some fast-forwarding ranges while sitting in the cache. To avoid
using a reader reading a stale range (from the read's POV), check its
read range and fast forward it if necessary.
And propagate it down to where it is created. This will be used to add
trace points for semaphore related events, but this will come in the
next patches.
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
Timouts are benign, especially on a read-ahead that turned out to be not
needed at all. They just introduce noise in the logs, so silence them.
Fixes: #12435Closes#12441
This fixes a long standing bug related to handling of non-full
clustering keys, issue #1446.
after_key() was creating a position which is after all keys prefixed
by a non-full key, rather than a position which is right after that
key.
This will issue will be caught by cql_query_test::test_compact_storage
in debug mode when mutation_partition_v2 merging starts inserting
sentinels at position after_key() on preemption.
It probably already causes problems for such keys.
do_full_buffer() is an eclectic mix of coroutines and continuations.
That makes it hard to follow what is running sequentially and
concurrently.
Convert it into a pure coroutine by changing internal continuations
to lambda coroutines. These lambda coroutines are guarded with
seastar::coroutine::lambda. Furthermore, a future that is co_awaited
is converted to immediate co_await (without an intermediate future),
since seastar::coroutine::lambda only works if the coroutine is awaited
in the same statement it is defined on.
Commit 8ab57aa added a yield to the buffer-copy loop, which means that
the copy can yield before done and the multishard reader might see the
half-copied buffer and consider the reader done (because
`_end_of_stream` is already set) resulting in the dropping the remaining
part of the buffer and in an invalid stream if the last copied fragment
wasn't a partition-end.
Fixes: #11561
