Dictionary contents are kept in the list of "compression options" in the
header of `CompressionInfo.db`, and they are loaded from disk into
memory when the `sstable::compression` object is populated.
After the decompressor for the SSTable is created based on those
dict contents, they are not needed in RAM anymore. And since
they take up a sizeable amount of memory, we would like to free them.
In this patch, we discard all "hidden compression options"
(currently: only the dictionary contents) from the
`sstable::compression` object right after the decompressor is created.
(Those options are not supposed to be used for anything else anyway).
Before this commit, "compression options" written into
CompressionInfo.db (and used to construct a decompressor)
have a 1:1 correspondence to "compression options" specified
in the schema.
But we want to add a new "compression option" -- the compression
dictionary -- which will be written into CompressionInfo.db
and used to construct decompressors, but won't be specified in the
schema.
To reconcile that, in this commit we introduce the notion of a "hidden
option". If an option name in `CompressionInfo.db` begins with a dot,
then this option will be used to construct decompressors, but won't
be visible for other uses. (I.e. for the `sstable_info` API call
and for recovering a fake `schema` from `CompressionInfo.db` in the
`scylla sstable` tool).
Then, we introduce the hidden `.dictionary.{0,1,2,..}` options,
which hold the contents of the dictionary blob for this SSTable.
(The dictionary is split into several parts because the SSTable
format limits the length of a single option value to 16 bits,
and dictionaries usually have a length greater than that).
This commit only introduces helpers which translate dictionary blobs
into "options" for CompressionInfo.db, and vice-versa, but it doesn't
use those helpers yet. They will be used in later commits.
Following up on the previous commit, we avoid constructing
a compressor in the `sstable_info` API call, and we instead
read the compression options from the `sstable::compression`.
SSTable readers and writers use `compressor` objects to compress and
decompress chunks of SSTable data files.
`compressor` objects are read-only, so only one of them is needed
for each SSTable. Before this commit, each reader and writer has
its own `compressor` object. This isn't necessary, but it's okay.
But later in this series it will stop being okay, because the creation
of a `compressor` will become an expensive cross-shard
operation (because it might require sharing a compression dictionary
from another shard). So we have to adjust the code so that there is
only once `compressor` per sstable, not one per reader/writer.
We stuff the ownership of this compressor into `sstable::compression`.
To make the ownership clear, we remove `compression_ptr` shared
pointers from readers and writers, and make them access the
compressor via the `sstable::compression` instead.
Note: this commit is meant to be a code refactoring only and is not intended
to change the observable behaviour.
Today `schema` contains a `compression_parameters`.
`compression_parameters` contains an instance of
`compressor`, and SSTable writers just share that instance.
This is fine because `compressor` is a stateless object,
functionally dependent on the schema.
But in later parts of the series, we will break this functional
dependency by adding dictionaries to compressors. Two writers
for the same schema might have different dictionaries, so they won't
be able to just share a single instance contained in the schema.
And when that happens, having a `compressor` instance
in the `schema`/`compression_parameters` will become awkward,
since it won't be actually used. It will be only a container for options.
In addition, for performance reasons, we will want to share some pieces
of compressors across shards, which will require -- in the general case --
a construction of a compressor to be asynchronous, and therefore not
possible inside the constructor of `compression_parameters`.
This commit modifies `compression_parameters` so that it doesn't hold or
construct instances of `compressor`.
Before this patch, the `compressor` instance constructed in
`compression_parameters` has an additional role of validating and
holding compressor-specific options.
(Today the only such option is the zstd compression level).
This means that the pieces of logic responsible for compressor-specific
options have to be rewritten. That ends up being the bulk of this commit.
Before this patch, `compressor` is designed to be a proper abstract
class, where the creator of a compressor doesn't even know
what he's creating -- he passes a name, and it gets turned into a
`compressor` behind a scenes.
But later, when creation of compressors will involve looking up
dictionaries, this abstraction will only get in the way.
So we give up on keeping `compressor` abstract, and instead of
using "opaque" names we turn to an explicit enum of possible compressor types.
The main point of this patch is to add the `algorithm` enum and the `algorithm_to_name()`
function. The rest of the patch switches the `compressor::name()` function
to use `algorithm_to_name()` instead of the passed-by-constructor
`compressor::_name`, to keep a single source of truth for the names.
Fixes a race condition where COMPRESSOR_NAME in zstd.cc could be
initialized before compressor::namespace_prefix due to undefined
global variable initialization order across translation units. This
was causing ZstdCompressor to be unregistered in release builds,
making it impossible to create tables with Zstd compression.
Replace the global namespace_prefix variable with a function that
returns the fully qualified compressor name. This ensures proper
initialization order and fixes the registration of the ZstdCompressor.
Fixesscylladb/scylladb#22444
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#22451
now that we are allowed to use C++23. we now have the luxury of using
`std::ranges::find_if`.
in this change, we:
- replace `boost::find_if` with `std::ranges::find_if`
- remove all `#include <boost/range/algorithm/find_if.hpp>`
to reduce the dependency to boost for better maintainability, and
leverage standard library features for better long-term support.
this change is part of our ongoing effort to modernize our codebase
and reduce external dependencies where possible.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
The compressed and checksummed data sources offer digest checking as an
optional feature. It can be enabled via the boolean template parameter
`check_digest`. If enabled, the data sources calculate the actual digest
chunk-by-chunk whenever `get()` is called, and compare with the expected
digest when all data have been read. If the actual digest cannot be
calculated due to a partial read or skip, the data sources treat this
condition as an internal error.
Relax this constraint by allowing the data sources to handle digest
checks as best effort, i.e., continue to operate with digest checking
disabled if the actual digest cannot be calculated.
We will use this in later patches to enable digest checking for
compaction. Compaction can cause both partial reads and skips (e.g., in
case of cleanup compaction) and we cannot predict skips beforehand.
Signed-off-by: Nikos Dragazis <nikolaos.dragazis@scylladb.com>
This PR builds upon the PR for checksum validation (#20207) to further enhance scrub's corruption detection capabilities by validating digests as well. The digest (full checksum) is the checksum over the entire data, as opposed to per-chunk checksums which apply to individual chunks. Until now, digests were not examined on any code paths. This PR integrates digest checking into the compressed/checksummed data sources as an optional feature and enables it only through the validation path of the sstable layer (`sstable::validate()`). The validation path is used by the following tools:
* scrub in validate mode
* `sstable validate`
All other reads, including normal user reads, are unaffected by this change.
The PR consists of:
* Extensions to the compressed and checksummed data sources to support digest checking. The data sources receive the expected digest as a parameter and calculate the actual digest incrementally across multiple get() calls. The check happens on the get() call that reaches EOF and results to an exception if the digest is invalid. A digest check requires reading the whole file range. Therefore, a partial read or skip() is treated as an internal error.
* A new shareable digest component loaded on demand by the validation code. No lifecycle management.
* Grouping of old scrub/validate tests for compressed and uncompressed SSTables to reduce code duplication.
* scrub/validate tests for SSTables with valid checksums but invalid digests, and SSTables with no digests at all.
* scrub/validate tests with 3.x Cassandra SSTables to ensure compatibility.
Refs #19058.
New feature, no backport is needed.
Closesscylladb/scylladb#20720
* github.com:scylladb/scylladb:
test: Test scrub/validate with SSTables from Cassandra
compaction: Make quarantine optional for perform_sstable_scrub()
test: Make random schema optional in scrub_test_framework
test: Add tests for invalid digests
test: Merge scrub/validate tests for compressed and uncompressed cases
sstables: Verify digests on validation path
sstables: Check if digest component exists
sstables: Add digest in the SSTable components
sstables: Add digest check in compressed data source
sstables: Add digest check in checksummed data source
Following the addition of digest check in the checksummed data source,
add the same feature to the compressed data source as well. This ensures
consistent behavior across any type of SSTable.
This is added as an optional feature so that we can preserve the current
behavior, that is verify only the per-chunk checksums during normal user
reads. To ensure zero cost at runtime when disabled, we introduce the
on/off switch as a template parameter.
The digest calculation for compressed SSTables depends on the SSTable
format, hence the new template argument for the checksum mode. This is
consistent with the compressed data sink.
Signed-off-by: Nikos Dragazis <nikolaos.dragazis@scylladb.com>
The `skip()` method of the compressed data source implementation uses an
assert statement to check if the given offset is valid.
Replace this with `on_internal_error()` to fail gracefully. An invalid
offset shouldn't bring the whole server down.
Also, enhance the error message for unsynced compressed readers.
Signed-off-by: Nikos Dragazis <nikolaos.dragazis@scylladb.com>
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
this change helps to silence the warning of `-Wmissing-braces` from
clang. in general, we can initialize an object without constructor
with braces. this is called aggregate initialization.
but the standard does allow us to initialize each element using
either copy-initialization or direct-initialization. but in our case,
neither of them applies, so the clang warns like
```
suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
options.elements.push_back({bytes(k.begin(), k.end()), bytes(v.begin(), v.end())});
^~~~~~~~~~~~~~~~~~~~~~~~~
{ }
```
in this change,
also, take the opportunity to use structured binding to simplify the
related code.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Currently, the reader might dereference a null pointer
if the input stream reaches eof prematurely,
and read_exactly returns an empty temporary_buffer.
Detect this condition before dereferencing the buffer
and sstables::malformed_sstable_exception.
Fixes#13599
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Closes#13600
Use the recently added `request_memory()` to aquire the memory units for
the I/O. This allows blocking all but one readers when memory
consumption grows too high.
Convert decompressed temporary buffers into tracked buffers just before
returning them to the upper layer. This ensures these buffers are known
to the reader concurrency semaphore and it has an accurate view of the
actual memory consumption of reads.
Fixes: #12448Closes#12454
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
This warning can catch a virtual function that thinks it
overrides another, but doesn't, because the two functions
have different signatures. This isn't very likely since most
of our virtual functions override pure virtuals, but it's
still worth having.
Enable the warning and fix numerous violations.
Closes#9347
Cassandra 3.0 deprecated the 'sstable_compression' attribute and added
'class' as a replacement. Follow by supporting both.
The SSTABLE_COMPRESSION variable is renamed to SSTABLE_COMPRESSION_DEPRECATED
to detect all uses and prevent future misuse.
To prevent old-version nodes from seeing the new name, the
compression_parameters class preserves the key name when it is
constructed from an options map, and emits the same key name when
asked to generate an options map.
Existing unit tests are modified to use the new name, and a test
is added to ensure the old name is still supported.
Fixes#8948.
Closes#8949
The current log is useless when checksum fails, you don't know
which compressed chunk failed checksum, the expected and the
actual checksum, the size of chunk and so on.
Before:
compressed chunk failed checksum
Now:
compressed chunk of size 3735 at file offset 406491 failed checksum, expected=0, actual=1422312584
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
This change just moves the place from which the output_stream
knows the compression::uncompressed_chunk_length() value.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
... and tests. Printin a pointer in logs is considered to be a bad practice,
so the proposal is to keep this explicit (with fmt::ptr) and allow it for
.debug and .trace cases.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
This is a bit simpler as we don't have to pass in the options and
moves the calls to make_file_output_stream to places where we can
handle futures.
Signed-off-by: Rafael Ávila de Espíndola <espindola@scylladb.com>
Seastar recently lost support for the experimental Concepts Technical
Specification (TS) and gained support for C++20 concepts. Re-enable
concepts in Scylla by updating our use of concepts to the C++20
standard.
This change:
- peels off uses of the GCC6_CONCEPT macro
- removes inclusions of <seastar/gcc6-concepts.hh>
- replaces function-style concepts (no longer supported) with
equation-style concepts
- semicolons added and removed as needed
- deprecated std::is_pod replaced by recommended replacement
- updates return type constraints to use concepts instead of
type names (either std::same_as or std::convertible_to, with
std::same_as chosen when possible)
No attempt is made to improve the concepts; this is a specification
update only.
Message-Id: <20200531110254.2555854-1-avi@scylladb.com>
"
Refs #4726
Implement the api portion of a "describe sstables" command.
Adds rest types for collecting both fixed and dynamic attributes, some grouped. Allows extensions to add attributes as well. (Hint hint)
"
* 'sstabledesc' of https://github.com/elcallio/scylla:
api/storage_service: Add "sstable_info" command
sstables/compress: Make compressor pointer accessible from compression info
sstables.hh: Add attribute description API to file extension
sstables.hh: Add compression component accessor
sstables.hh: Make "has_component" public
This commit also fixes a bug in sstables/compress.cc, where chunk length in bytes
was passed to the compressor as chunk length in kilobytes. Fortunately,
none of the compressors implemented until now used this parameter.
Signed-off-by: Kamil Braun <kbraun@scylladb.com>
Replace stdx::optional and stdx::string_view with the C++ std
counterparts.
Some instances of boost::variant were also replaced with std::variant,
namely those that called seastar::visit.
Scylla now requires GCC 8 to compile.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
Message-Id: <20190108111141.5369-1-duarte@scylladb.com>
This patch adds compatibility for Cassandra's "chunk_size_in_kb", as
well as it keeps Scylla's "chunk_size_kb" compression parameter.
Fixes#3669
Tests: unit (release)
v2: use variable instead of array
v3: fix commited files
Signed-off-by: Juliana Oliveira <juliana@scylladb.com>
Message-Id: <20181211215840.GA7379@shenzou.localdomain>
checksum_combine() is much slower than re-feeding the buffer to
checksum() for the zlib CRC32 checksummer.
Introduce Checksum::prefer_combine() to determine this and select
more optimal behavior for given checksummer.
Improves performance of memtable flush with compression enabled by 30%.
Fixes#3546
Both older origin and scylla writes "known" compressor names (i.e. those
in origin namespace) unqualified (i.e. LZ4Compressor).
This behaviour was not preserved in the virtualization change. But
probably should be.
Message-Id: <20180627110930.1619-1-calle@scylladb.com>
Previously, compressed_output_stream used to calculate checksum of the
supplied chunk and pass it to the 'compression' object to combine with
the full checksum calculated on prior writes.
Now, all the checksum calculation happens inside
compressed_output_stream and 'compression' only stores the result.
This is done to loosen ties between two classes and simplify
compressed_output_stream customisation with various checksum algorithms.
Signed-off-by: Vladimir Krivopalov <vladimir@scylladb.com>
Make a "compressor" an actual class, that can be implemented and
registered via class registry.
For "common" compressors, the objects will be shared, but complex
implementors can be semi-stateful.
sstable compression is split into two parts: The "static" config
which is shared across shards, and a "local" one, which holds
a compressor pointer. The latter is encapsulated, along with
actual compressed data writers, in sstables/compress.cc.
For compression (write), compression writer is instansiated
with the settings active in table metadata.
For decompression (read), compression reader is instansiated
with the settings stored in sstable metadata, which can
differ from the currently active table metadata.
v2:
* Structured patch sets differently (dependencies)
* Added more comments/api descs
* Added patch to move all sstable compression into compress.cc,
effectively separating top-level virtual compressor object
from sstable io knowledge
v3:
* Rebased
v4:
* Moved all sstable compression logic/knowledge into
compress.cc (local compression). Merged the two patches
(separation just confuses reader).
Race condition was introduced by commit 028c7a0888, which introduces chunk offset
compression, because a reading state is kept in the compress structure which is
supposed to be immutable and can be shared among shards owning the same sstable.
So it may happen that shard A updates state while shard B relies on information
previously set which leads to incorrect decompression, which in turn leads to
read misbehaving.
We could serialize access to at() which would only lead to contention issues for
shared sstables, but that can be avoided by moving state out of compress structure
which is expected to be immutable after sstable is loaded and feeded to shards that
own it. Sequential accessor (wraps state and reference to segmented_offset) is
added to prevent at() and push_back() interfaces from being polluted.
Tests: release mode.
Fixes#3148.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20180205192432.23405-1-raphaelsc@scylladb.com>
The encoding logic was incorrect for big endian systems (shift needed
to be in the opposite direction). Rather than fix that issue I have
re-written the relevant code to restrict the storage format to little
endian byte order on all systems. My hope is that this will be a bit
easier to maintain.
Message-Id: <20171211124454.77488-1-mike.munday@ibm.com>
Previously _current_bucket_segment_index was used differently depending on
whether update_position_trackers() is used in a random or sequential
access. In the former case was used as the absolute index of the segment
(independent of the buckets) and in the latter as the relative index of
the segment within its bucket. This caused problems when there was a
switch between random and sequential access, meaning one could get different
results for an at() call depending on what was the previous at() call.
Fix this by consistently using _current_bucket_segment_index as - like its
name suggest - the bucket relative segment index.
Ref #1946.
Signed-off-by: Botond Dénes <bdenes@scylladb.com>
Message-Id: <7f68ac1d32c80e8dea6dfa11be02acaa961bce2a.1503924927.git.bdenes@scylladb.com>
