quantity prevents index_reader from reading all index entries of a summary
entry that span more than min_index_interval entries. That can happen after
introduction of size-based sampling, and consequently, sstable will not be
able to return a key which logical position in summary entry is beyond
min_index_interval. It's ok to not use quantity because index_reader will
read all indexes until either next summary entry or end of file is reached.
Fixes test_sstable_conforms_to_mutation_source
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20170812045821.25269-1-raphaelsc@scylladb.com>
Currently, a summary entry is added after min_index_interval index
entries were written. Not taking into account size of index entries
becomes a problem with large partitions which may create big index
entries due to promoted indexes. Read performance is affected as a
consequence because index entries spanned by summary are all read
from disk to serve request.
What we wanna do is to also add a summary entry after index reaches
a boundary. To deal with oversampling, we want to write 1 byte to
summary for every 2000 bytes written to data file (this will be
eventually made into an option in the config file).
Both conditions must be met to avoid under or oversampling.
That way, the amount of data needed from index file to satify the
request is drastically reduced.
Fixes#1842.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
A seletion contains - in addition to the list of sstables - a next_token
which is a hint as to what is the next best token to call select() with.
This should be the smallest token such that at the next call to
select() the least number of new sstables will be returned, without
skipping any.
index's file output stream uses write behind but it's not closed
when sstable write fails and that may lead to crash.
It happened before for data file (which is obviously easier to
reproduce for it) and was fixed by 0977f4fdf8.
Fixes#2673.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20170807171146.10243-1-raphaelsc@scylladb.com>
"This series ensures the always write correct cell names to promoted
index cell blocks, taking into account the eoc of range tombstones.
Fixes#2333"
* 'pi-cell-name/v1' of github.com:duarten/scylla:
tests/sstable_mutation_test: Test promoted index blocks are monotonic
sstables: Consider eoc when flushing pi block
sstables: Extract out converting bound_kind to eoc
This allows a queued flush to start while we fsync the current
sstable, which helps reduce the overall time new writes are blocked on
dirty memory.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
The write_monitor provides callbacks to inform an observer of the
state of the ongoing sstable write.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This allows a queued flush to start while we fsync the current
sstable, which helps reduce the overall time new writes are blocked on
dirty memory.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
The write_monitor provides callbacks to inform an observer of the
state of the ongoing sstable write.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
When flushing a promoted index block using a range tombstone cell name
as a bound, use the right eoc value instead of always writing
composite::eoc::none.
Fixes#2333
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
When a sstable reader is fast forwarded some index entries may be read
(and compared) multiple times. This patch makes sure that once a token
is computed we keep it around and reuse if the entry is accessed again.
Each sstable index lookup involves a binary search in the summary and
each time a partition key of summary entry is compared with anything its
token needs to be calculated.
Since we keep summary in the memory all the time it is better to also
keep the tokens around.
streamed_mutation::impl::fill_buffer() is supposed to either push
mutation fragments to the buffer or set EOS flag. However, it was
possible that mp_row_consumer would return proceed::no if a skip was
needed without satisfying any of these conditions.
"This patchset restricts background writers - such as compactions,
streaming flushes and memtable flushes to a maximum amount of CPU usage
through a seastar::thread_scheduling_group.
The said maximum is recommended to be set 50 % - it is default
disabled, but can be adjusted through a configuration option until we
are able to auto-tune this.
The second patch in this series provides a preview on how such auto-tune
would look like. By implementing a simple controller we automatically
adjust the quota for the memtable writer processes, so that the rate at
which bytes come in is equal to the rates at which bytes are flushed.
Tail latencies are greatly reduced by this series, and heavy spikes that
previously appeared on CPU-bound workloads are no more."
* 'memtable-controller-v5' of https://github.com/glommer/scylla:
simple controller for memtable/streaming writer shares.
restrict background writers to 50 % of CPU.
We are using C* 3.x compatible layout in schema tables but want to
keep using the 1.7 layout in memory for compatibility during rolling
upgrade. This patch switches the schema and schema_builder classes
back to the old layout. Translation of layout happens when converting
to/from schema mutations.
Notable changes:
1) Includes a revert of commit 6260f31e08
"thrift: Update CQL mapping of static CFs".
2) Brings back the "default_validation_class" schema attribute. In v3
it can be dervied from column definitions, but in v2 it can't, so
we have to store it.
3) legacy_schema_migrator and schema_builder don't have to do
conversions to v3, this is now handled by the v3_columns
class. schema_builder works with the same layout as schema, that
is v2.
4) Includes a revert of commit 66991a7ccb
"v3 schema test fixes"
Fixes#2555.
In scylla, we have foreground processes, which are latency sensitive and
need to be responded to as fast as possible in order to maintain good
latency profiles, and background process, which are less so.
The most important background processes we have during normal write
workload operations are memtable writes and sstable compactions. Those
processes are quite CPU-intensive, and left unchecked will easily
dominate the CPU. Lower values of task-quota usually help, as it will
force those processes to preempt more, but aren't enough to guarantee
good isolation. We have seen boxes with good NVMe storage having their
throughput reduced to less than half of the original baseline in a short
dive down for the duration of a compaction.
In the long run, our goal is to leverage the CPU scheduler to make sure
that those processes are balanced with respect to all the others.
However, the current state of affairs is causing grievances as this very
moment. Thankfully, those processes live in a seastar::thread, that
ships with its own rudimentary bandwidth control mechanism: the
scheduling group.
The goal of this patch is to wrap background processes together in a
scheduling group, and assign to such group 50 % of our CPU power; the
remainder being left to foreground processes.
While we pride ourselves in dynamically adjusting things to the
workload, we won't be able to do this properly before the CPU scheduler
lands - and let's face it, leaving background processes run wild is not
adaptative either. Every workload would benefit most from a different
value for such shares, but 50 % is as fair as it gets if we really need
static partitining in the mean time.
As a defense against unforeseen consequences, we'll leave the actual
value as an option, but will do our best to hide it - as this is not a
tunable that we want to be part of a normal Scylla setup. The most
convenient place for this tunable is still db::config, so we can easily
pass it down to the database layer - but we will not document it in the
yaml, and will clearly note in the help string that it is not supposed
to be tuned.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
it will be later converted to C++. Imported from latest scylla-
tools-java repository. Checked that it doesn't lack anything.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
if we are compacting level 1 into level 2, we only want to demote
a sstable from level 3 or higher.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
L0 compaction triggers quadratic behavior when many newly created
sstables are needed for promotion due to their size being relatively
low to max sstable size parameter. So until L0 is worth promoting,
the strategy will compact every new sstable with all the existing
ones in L0. To fix it, let's do STCS on level 0 until it becomes
worth promoting.
Fixes#2432.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
get rid of unneeded loop for dealing with suspect sstables and
std::advance because vector allows random access.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
some comments are no longer relevant, especially the ones that
talk about dealing with busy sstables due to parallel compaction,
which isn't done by us for lcs.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
can_promote flag will be used to carry info about whether or not
level 0 can promoted. That will avoid a single iteration for higher
levels too which can contain tens of thousands of sstables.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
I will split code for higher levels compaction into functions first
before putting it into its own function too.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
