Soon, reader_resource_tracker will only be constructible after the
reader has been admitted. This means that the resource tracker cannot be
preconstructed and just captured by the lambda stored in the mutation
source and instead has to be passed in along the other parameters.
'"The issue is triggered by compaction of sstables of level higher than 0.
The problem happens when interval map of partitioned sstable set stores
intervals such as follow:
[-9223362900961284625 : -3695961740249769322 ]
(-3695961740249769322 : -3695961103022958562 ]
When selector is called for first interval above, the exclusive lower
bound of the second interval is returned as next token, but the
inclusivess info is not returned.
So reader_selector was returning that there *were* new readers when
the current token was -3695961740249769322 because it was stored in
selector position field as inclusive, but it's actually exclusive.
This false positive was leading to infinite recursion in combined
reader because sstable set's incremental selector itself knew that
there were actually *no* new readers, and therefore *no* progress
could be made."
Fixes #2908.'
* 'high_level_compaction_infinite_recursion_fix_v4' of github.com:raphaelsc/scylla:
tests: test for infinite recursion bug when doing high-level compaction
Fix potential infinite recursion when combining mutations for leveled compaction
dht: make it easier to create ring_position_view from token
dht: introduce is_min/max for ring_position
(cherry picked from commit 375ed938b4)
Migrate all the places that used memtable::make_reader to use
memtable::make_flat_reader and remove memtable::make_reader.
* seastar-dev.git haaawk/remove_memtable_make_reader_v2_rebased:
Remove memtable::make_reader
Stop using memtable::make_reader in row_cache_stress_test
Stop using memtable::make_reader in row_cache_test
Stop using memtable::make_reader in mutation_test
Stop using memtable::make_reader in streamed_mutation_test
Stop using memtable::make_reader in memtable_snapshot_source.hh
Stop using memtable::make_reader in memtable::apply
Add consume_partitions(flat_mutation_reader& reader, Consumer consumer)
Add default parameter values in make_combined_reader
Migrate test_virtual_dirty_accounting_on_flush to flat reader
Migrate test_adding_a_column_during_reading_doesnt_affect_read_result
Simplify flat_reader_assertions& produces(const mutation& m)
Migrate test_partition_version_consistency_after_lsa_compaction_happens
flat_mutation_reader: Allow setting buffer capacity
Add next_mutation() to flat_mutation_reader_assertions
cf::for_all_partitions::iteration_state: don't store schema_ptr
read_mutation_from_flat_mutation_reader: don't take schema_ptr
Migrate test_fast_forward_to_after_memtable_is_flushed to flat reader
(cherry picked from commit b0a56a91c2)
"While aa8c2cbc16 'Merge "Migrate sstables
to flat_mutation_reader" from Piotr' has converted the low-level sstable
reader to the new flat_mutation_reader interface there were still
multiple readers related to sstables that required converting,
including:
- restricted reader
- filtering reader
- single partition sstable reader
This series completes their conversion to the flat stream interface."
* tag 'flat_mutation_reader-sstable-readers/v2' of https://github.com/pdziepak/scylla:
db: convert single_key_sstalbe_reader to flat streams
db: fully convert incremental_reader_selector to flat readers
db: make make_range_sstable_reader() return flat reader
db: make column_family::make_reader() return flat reader
db: make column_family::make_sstable_reader() return a flat reader
filtering_reader: switch to flat mutation fragment streams
filtering_reader: pass a const dht::decorated_key& to the callback
mutation_reader: drop make_restricted_reader()
db: use make_restricted_flat_reader
mutation_reader: convert restricted reader to flat streams
(cherry picked from commit 6cb3b29168)
When fast forwarding is enabled and all readers positioned inside the
current partition return EOS, return EOS from the combined-reader
too. Instead of skipping to the next partition if there are idle readers
(positioned at some later partition) available. This will cause rows to
be skipped in some cases.
The fix is to distinguish EOS'd readers that are only halted (waiting
for a fast-forward) from thoose really out of data. To achieve this we
track the last fragment-kind the reader emitted. If that was a
partition-end then the reader is out of data, otherwise it might emit
more fragments after a fast-forward. Without this additional information
it is impossible to determine why a reader reached EOS and the code
later may make the wrong decision about whether the combined-reader as
a whole is at EOS or not.
Also when fast-forwarding between partition-ranges or calling
next_partition() we set the last fragment-kind of forwarded readers
because they should emit a partition-start, otherwise they are out of
data.
Signed-off-by: Botond Dénes <bdenes@scylladb.com>
Message-Id: <6f0b21b1ec62e1197de6b46510d5508cdb4a6977.1512569218.git.bdenes@scylladb.com>
(cherry picked from commit 9661769313)
"Convert combined_mutation_reader into a flat_mutation_reader impl. For
now - in the name of incremental progress - all consumers are updated to
use the combined reader through the
mutation_reader_from_flat_mutation_reader adaptor. The combined reader also
uses all it's sub mutation_readers through the
flat_mutation_reader_from_mutation_reader adaptor."
* 'bdenes/flatten-combined-reader-v8' of https://github.com/denesb/scylla:
Add unit tests for the combined reader - selector interactions
Add flat_mutation_reader overload of make_combined_reader
Flatten the implementation of combined_mutation_reader
Add mutation_fragment_merger
mutation_fragment::apply(): handle partition start and end too
Add non-const overload of partition_start::partition_tombstone()
Make combined_mutation_reader a flat_mutation_reader
Move the mutation merging logic to combined_mutation_reader
Remove the unnecessary indirection of mutation_reader_merger::next()
Move the implementation of combined_mutation_reader into mutation_reader_merger
Remove unused mutation_and_reader::less_compare and operator<
(cherry picked from commit 046991b0b7)
The following patches convert sstable writers to use flat mutation
readers instead of the legacy mutation_reader interface.
Writers were already using flat consumer interface and used
consume_flattened_in_thread(), so most of the work was limited to
providing an appropriate equivalent for flat mutation readers.
* https://github.com/pdziepak/scylla.git flat_mutation_reader-sstable-write/v1:
flat_mutation_reader: move consumer_adapter out of consume()
flat_mutation_reader: introduce consume_in_thread()
tests/flat_mutation_reader: test consume_in_thread()
sstables: switch write_components() to flat_mutation_reader
streamed_mutation: drop streamed_mutation_returning()
sstables: convert compaction to flat_mutation_reader
mutation_reader: drop consume_flattened_in_thread()
(cherry picked from commit 596ebaed1f)
Introduce sstable::read_row_flat and sstable::read_range_rows_flat methods
and use them in sstable::as_mutation_source.
* https://github.com/scylladb/seastar-dev/tree/haaawk/flat_reader_sstables_v3:
Introduce conversion from flat_mutation_reader to streamed_mutation
Add sstables::read_rows_flat and sstables::read_range_rows_flat
Turn sstable_mutation_reader into a flat_mutation_reader
sstable: add getter for filter_tracker
Move mp_row_consumer methods implementations to the bottom
Remove unused sstable_mutation_reader constructor
Replace "sm" with "partition" in get_next_sm and on_sm_finished
Move advance_to_upper_bound above sstable_mutation_reader
Store sstable_mutation_reader pointer in mp_row_consumer
Stop using streamed_mutation in consumer and reader
Stop using streamed_mutation in sstable_data_source
Delete sstable_streamed_mutation
Introduce sstable::read_row_flat
Migrate sstable::as_mutation_source to flat_mutation_reader
Remove single_partition_reader_adaptor
Merge data_consume_context::impl into data_consume_context
Create data_consume_context_opt.
Merge on_partition_finished into mark_partition_finished
Check _partition_finished instead of _current_partition_key
Merge sstable_data_source into sstable_mutation_reader
Remove sstable_data_source
Remove get_next_partition and partition_header
(cherry picked from commit aa8c2cbc16)
These patches convert queries (data, mutation and counter) to flat
mutation readers. All of them already use consume_flattened() to
consume a flat stream of data, so the only major missing thing
was adding support for reversed partitions to
flat_mutation_reader::consume().
* pdziepak flat_mutation_reader-queries/v3-rebased:
flat_mutation_reader: keep reference to decorated key valid
flat_muation_reader: support consuming reversed partitions
tests/flat_mutation_reader: add test for
flat_mutation_reader::consume()
mutation_partition: convert queries to flat_mutation_readers
tests/row_cache_stress_test: do not use consume_flattened()
mutation_reader: drop consume_flattened()
streamed_mutation: drop reverse_streamed_mutation()
(cherry picked from commit 6969a235f3)
flat_mutation_reader::partition_range_forwarding and
mutation_reader::forwarding are aliases of the same type. The change was
necessary in order to make mutation_reader::forwarding available in
flat_mutation_reader.hh even though it is included by mutation_reader.hh
This concept will be used both in flat_mutation_reader.hh
and mutation_reader.hh. mutation_reader.hh includes
flat_mutation_reader.hh so we have to move the concept to
make it accessible in both files.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
This will be used as an intermediate state of migration
from mutation_reader to flat_mutation_reader.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
There will be a second implementation that will be used by
sources that are converted to flat_mutation_reader.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
query::full_slice doesn't select any regular or static columns, which
is at odds with the expectations of its users. This patch replaces it
with the schema::full_slice() version.
Refs #2885
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
Message-Id: <1507732800-9448-2-git-send-email-duarte@scylladb.com>
"This changeset is the first step to flatten mutation_reader.
Then it introduces new mutation_fragment types for partition header and end of partition.
Using those a new flat_mutation_reader is defined.
Finally it introduces converters between new flat_mutation_reader and
old mutation_reader."
* 'haaawk/flattened_mutation_reader_v12' of github.com:scylladb/seastar-dev:
Add tests for flat_mutation_reader
Introduce conversion from flat_mutation_reader to mutation_reader
Introduce conversion from mutation_reader to flat_mutation_reader
Introduce flat_mutation_reader
Extract FlattenedConsumer concept using GCC6_CONCEPT
Introduce partition_end mutation_fragment
Introduce a position for end of partition
Introduce partition_start mutation_fragment
Introduce FragmentConsumer
Introduce a position for partition start
streamed_mutation: Extract concepts using GCC6_CONCEPT macro
This type of mutation_fragment will be used in new mutation_reader
to signal the beginning of the next partition.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Update description of existing reader count metrics, add memory
consumption metrics. Use labels to distinguish between system, user and
streaming reads related metrics.
Restrict readers based on their memory consumption, instead of the count
of the top-level readers. To do this an interposer is installed at the
input_stream level which tracks buffers emmited by the stream. This way
we can have an accurate picture of the readers' actual memory
consumption.
New readers will consume 16k units from the semaphore up-front. This is
to account their own memory-consumption, apart from the buffers they
will allocate. Creating the reader will be deferred to when there are
enough resources to create it. As before only new readers will be
blocked on an exhausted semaphore, existing readers can continue to
work.
Restrict readers based on their memory consumption, instead of the count
of the top-level readers. To do this an interposer is installed at the
input_stream level which tracks buffers emmited by the stream. This way
we can have an accurate picture of the readers' actual memory
consumption.
New readers will consume 16k units from the semaphore up-front. This is
to account their own memory-consumption, apart from the buffers they
will allocate. Creating the reader will be deferred to when there are
enough resources to create it. As before only new readers will be
blocked on an exhausted semaphore, existing readers can continue to
work.
Every mutation source can have a presence checker. By default all
answer "maybe contains".
Having this on mutation_source level will be useful for simplifying
cache update flow. The cache can ask the right snapshot for a presence
checker rather than relying on database to know when and how to make
the right one which preserves all invariants.
This will be especially useful once all updates of the underlying
mutation source of cache (e.g. sstable list) will have to go through
cache for safety reasons.
Exhausted readers can be fast forwarded, so we have to keep them
around. However, if the current reader is not fast forwardable, then
we can drop those readers and their buffers.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
combined_mutation_reader now accepts as a constructor argument a
reader_selector instance whoose task is to create new readers on
each call to operator()() if needed and possible.
This way it is possible to control how readers are created through
different specializations of reader_selector.
The previous logic is refactored into list_reader_selector which
is using a pre-provided mutation_reader list and forwards all of them to
combined_mutation_reader at once.
mutation source sometimes ignore fast forwarding parameter so
this change adds assertion to check that this parameter
can be safely ignored.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
By default make_reader_returning creates a reader that does not
support fast forwarding but the second parameter can be used to
make it support fast forwarding.
[tgrabiec: Improve title]
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
In commit c63e88d556, support was added for
fast_forward_to() in data_consume_rows(). Because an input stream's end
cannot be changed after creation, that patch ignores the specified end
byte, and uses the end of file as the end position of the stream.
As result of this, even when we want to read a specific byte range (e.g.,
in the repair code to checksum the partitions in a given range), the code
reads an entire 128K buffer around the end byte, or significantly more, with
read-ahead enabled. This causes repair to do more than 10 times the amount
of I/O it really has to do in the checksumming phase (which in the current
implementation, reads small ranges of partitions at a time).
This patch has two levels:
1. In the lower level, sstable::data_consume_rows(), which reads all
partitions in a given disk byte range, now gets another byte position,
"last_end". That can be the range's end, the end of the file, or anything
in between the two. It opens the disk stream until last_end, which means
1. we will never read-ahead beyond last_end, and 2. fast_fordward_to() is
not allowed beyond last_end.
2. In the upper level, we add to the various layers of sstable readers,
mutation readers, etc., a boolean flag mutation_reader::forwarding, which
says whether fast_forward_to() is allowed on the stream of mutations to
move the stream to a different partition range.
Note that this flag is separate from the existing boolean flag
streamed_mutation::fowarding - that one talks about skipping inside a
single partition, while the flag we are adding is about switching the
partition range being read. Most of the functions that previously
accepted streamed_mutation::forwarding now accept *also* the option
mutation_reader::forwarding. The exception are functions which are known
to read only a single partition, and not support fast_forward_to() a
different partition range.
We note that if mutation_reader::forwarding::no is requested, and
fast_forward_to() is forbidden, there is no point in reading anything
beyond the range's end, so data_consume_rows() is called with last_end as
the range's end. But if forwarding::yes is requested, we use the end of the
file as last_end, exactly like the code before this patch did.
Importantly, we note that the repair's partition reading code,
column_family::make_streaming_reader, uses mutation_reader::forwarding::no,
while the other existing reading code will use the default forwarding::yes.
In the future, we can further optimize the amount of bytes read from disk
by replacing forwarding::yes by an actual last partition that may ever be
read, and use its byte position as the last_end passed to data_consume_rows.
But we don't do this yet, and it's not a regression from the existing code,
which also opened the file input stream until the end of the file, and not
until the end of the range query. Moreover, such an improvement will not
improve of anything if the overall range is always very large, in which
case not over-reading at its end will not improve performance.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20170619152629.11703-1-nyh@scylladb.com>
This reverts commit 317d7fc253 (and also the
related 2c57ab84b2). It causes crashes
during range scans, reported by Gleb:
"To reproduce I run SELECT * FROM keyspace1.standard1; on typical c-s
dataset and 3 node cluster.
Backtrace:
at /home/gleb/work/seastar/seastar/core/apply.hh:36
rvalue=<unknown type in /home/gleb/work/seastar/build/release/scylla, CU 0x54cf307, DIE 0x55ebf2a>) at /home/gleb/work/seastar/seastar/core/do_with.hh:57
range=std::vector of length 6, capacity 8 = {...}) at /home/gleb/work/seastar/seastar/core/future-util.hh:142
at ./seastar/core/future.hh:890
at /home/gleb/work/seastar/seastar/core/future-util.hh:119
at /home/gleb/work/seastar/seastar/core/future-util.hh:142
The typo went unnoticed since the compiler picked up the global scope's
forwarding_tag. The bug made streamed_mutation::forwarding and
mutation_reader::forwarding the same type, but fortunately there were
no type mixups due to this.
In commit c63e88d556, support was added for
fast_forward_to() in data_consume_rows(). Because an input stream's end
cannot be changed after creation, that patch ignores the specified end
byte, and uses the end of file as the end position of the stream.
As result of this, even when we want to read a specific byte range (e.g.,
in the repair code to checksum the partitions in a given range), the code
reads an entire 128K buffer around the end byte, or significantly more, with
read-ahead enabled. This causes repair to do more than 10 times the amount
of I/O it really has to do in the checksumming phase (which in the current
implementation, reads small ranges of partitions at a time).
This patch has two levels:
1. In the lower level, sstable::data_consume_rows(), which reads all
partitions in a given disk byte range, now gets another byte position,
"last_end". That can be the range's end, the end of the file, or anything
in between the two. It opens the disk stream until last_end, which means
1. we will never read-ahead beyond last_end, and 2. fast_fordward_to() is
not allowed beyond last_end.
2. In the upper level, we add to the various layers of sstable readers,
mutation readers, etc., a boolean flag mutation_reader::forwarding, which
says whether fast_forward_to() is allowed on the stream of mutations to
move the stream to a different partition range.
Note that this flag is separate from the existing boolean flag
streamed_mutation::fowarding - that one talks about skipping inside a
single partition, while the flag we are adding is about switching the
partition range being read. Most of the functions that previously
accepted streamed_mutation::forwarding now accept *also* the option
mutation_reader::forwarding. The exception are functions which are known
to read only a single partition, and not support fast_forward_to() a
different partition range.
We note that if mutation_reader::forwarding::no is requested, and
fast_forward_to() is forbidden, there is no point in reading anything
beyond the range's end, so data_consume_rows() is called with last_end as
the range's end. But if forwarding::yes is requested, we use the end of the
file as last_end, exactly like the code before this patch did.
Importantly, we note that the repair's partition reading code,
column_family::make_streaming_reader, uses mutation_reader::forwarding::no,
while the other existing reading code will use the default forwarding::yes.
In the future, we can further optimize the amount of bytes read from disk
by replacing forwarding::yes by an actual last partition that may ever be
read, and use its byte position as the last_end passed to data_consume_rows.
But we don't do this yet, and it's not a regression from the existing code,
which also opened the file input stream until the end of the file, and not
until the end of the range query. Moreover, such an improvement will not
improve of anything if the overall range is always very large, in which
case not over-reading at its end will not improve performance.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20170614072122.13473-1-nyh@scylladb.com>
