With the default value of 12, a node's range is partitioned into
4096 * smp::count sub-ranges which are queried sequentually for a range
scan. If the number of rows in the table is smaller than the required
result size, we will query all of them. This can take so long that we
time out.
A better fix is to query multiple sub-ranges in parallel and merge them,
but for that we need to resurrect the non-sequential merger.
"Clusters with a large number of nodes, or a low number of vnodes, and a
high number of shards, or a combination, suffer from an aliasing problem:
both vnodes and intra-node sharding consider the most significant bits
to select the owning node and owning shard respectively. Since the same
bits are used for both, a low number of vnodes leads to some shards
being overcommitted relative to others.
This series fixes the problem by sharding on bits 0:47 of the token
(murmur3 partitioner only), leaving the most significant 12 bits for
vnodes. Simulation shows that this value provides reasonable sharding
for 100-node, 30-shard clusters.
In order to prevent re-sharding sstables on each boot, token ranges for
the range are stored in a new sub-component of the sstable Statistics
component. With the default 12 ignored bits we have 4096 token ranges
for non-Level-compacted SSTables, which takes some space but is still
reasonable.
Fixes #1277."
Sharding on the most significant token bits aliases with the vnode mechanism,
which also uses the most significant bits; this requires a huge number of
vnodes to achieve good sharding.
This patch teaches the murmur3 partitioner to ignore the most significant
N bits when calculating a token's hard, so we use token bits which still have
some entropy. In effect, with changes the token range layout from
shard 0
shard 1
...
shard S-1
to
shard 0
shard 1
...
shard S-1
shard 0
shard 1
...
shard S-1
...
shard 0
shard 1
...
shard S-1
Where the number of repetitions of the block is 2^(ignored msb bits).
For compatibility, the default is zero ignored bits, matching the pre-patch
state, until we wire things up.
Instead of calculating the owning shard from the sstable's partition
key range, delegate to the new sstable method for getting owning shard
infomation. This insulates us from changes in the sharding algorithm.
When we load an sstable, we don't know beforehand which shards it belongs
to; we don't want to open it until we do. Add a method that allows us
to read just the sharding data, without opening anything else.
Add a metadata component that describes token ranges that are spanned by
this sstable. With the current sharding algorithm, where each shard owns
a single token range, the first/last partition key is sufficient to
describing sharding information, but for multi-range algorithms, this
is not sufficient.
We have a semaphore controlling the amount of background work generated
by the memtable flush process. However, because we are not moving it
inside the memtable post-flush continuation, the units are being
released when we star the flush and not when we finish it.
That's not the intended behavior and that can cause flushes to
accumulate.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Message-Id: <b7dc1866ed3473b9b1862c433d59c5ebd8575dbc.1479839600.git.glauber@scylladb.com>
Instead of calculating the offset for each statistic component manually,
use a loop to iterate over all components, accumulating the offset as we
go along.
Introduce a new function that reuses the file_writer code to compute
the serialized size of an sstable object, by serializing it into memory
and discarding the result.
write() doesn't need to change its input; so change it to const.
The only snag is that describe_type() isn't and can't be made const-correct,
so cheat when it is called and const_cast the input.
This helps in writing a generic serialized_size() that is const correct,
in the next patch.
Recently we have changed our shutdown strategy to wait for the
_request_controller semaphore to make sure no other allocations are
in-flight. That was done to fix an actual issue.
The problem is that this wasn't done early enough. We acquire the
semaphore after we have already marked ourselves as _shutdown and
released the timer.
That means that if there is an allocation in flight that needs to use a
new segment, it will never finish - and we'll therefore neve acquire
the semaphore.
Fix it by acquiring it first. At this point the allocations will all be
done and gone, and then we can shutdown everything else.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Message-Id: <5c2a2f20e3832b6ea37d6541897519a9307294ed.1479765782.git.glauber@scylladb.com>
storage_proxy has an optimization where it tries to query multiple token
ranges concurrently to satisfy very large requests (an optimization which is
likely meaningless when paging is enabled, as it always should be). However,
the rows-per-range code severely underestimates the number of rows per range,
resulting in a large number of "read-ahead" internal queries being performed,
the results of most of which are discarded.
Fix by disabling this code. We should likely remove it completely, but let's
start with a band-aid that can be backported.
Fixes#1863.
Message-Id: <20161120165741.2488-1-avi@scylladb.com>
We current pass a region group to the memtable, but after so many recent
changes, that is a bit too low level. This patch changes that so we pass
a memtable list instead.
Doing that also has a couple of advantages. Mainly, during flush we must
get to a memtable to a memtable_list. Currently we do that by going to
the memtable to a column family through the schema, and from there to
the memtable_list.
That, however, involves calling virtual functions in a derived class,
because a single column family could have both streaming and normal
memtables. If we pass a memtable_list to the memtable, we can keep
pointer, and when needed get the memtable_list directly.
Not only that gets rid of the inheritance for aesthetic reasons, but
that inheritance is not even correct anymore. Since the introduction of
the big streaming memtables, we now have a plethora of lists per column
family and this transversal is totally wrong. We haven't noticed before
because we were flushing the memtables based on their individual sizes,
but it has been wrong all along for edge cases in which we would have to
resort to size-based flush. This could be the case, for instance, with
various plan_ids in flight at the same time.
At this point, there is no more reason to keep the derived classes for
the dirty_memory_manager. I'm only keeping them around to reduce
clutter, although they are useful for the specialized constructors and
to communicate to the reader exactly what they are. But those can be
removed in a follow up patch if we want.
The old memtable constructor signature is kept around for the benefit of
two tests in memtable_tests which have their own flush logic. In the
future we could do something like we do for the SSTable tests, and have
a proxy class that is friends with the memtable class. That too, is left
for the future.
Fixes#1870
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Message-Id: <811ec9e8e123dc5fc26eadbda82b0bae906657a9.1479743266.git.glauber@scylladb.com>
Now that access to the size_estimates system is virtualized, we no
longer need the recorder.
Fixes#1616
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch add a virtual mutation_reader so that queries
to the size_estimates system table are handled by the engine
without needing to perform any IO.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
Virtual readers allow queries to selected tables, usually system
tables, to be answered by the engine. This is useful for tables which
aren't written by users and whose contents can be calculated on
demand.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch changes the get_local_tokens() function in storage_service
to return a future instead of requiring running under a seastar::thread.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch add the slice() function to nonwrapping range, which uses
its bounds to slice an input sequence.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch extracts a pair of functions from mutation_partition to
calculate the lower and upper bounds of a sequence from a
nonwrapping_range.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch adds a function to system_keyspace responsible for creating
a mutation to a partition of the size_estimates system table from a
set of range_estimates.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch changes the range_estimates struct so that the tokens are
represented as utf8 encoded bytes. This will make future patches
require less conversions.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch ensures we can convert the maximum_token to an sstring.
For Cassandra, the minimum and maximum tokens have the same
representation. So, we use the string representation of the
maximum_token for the maximum_token.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
"This series is just a cleanup which intention is to deal with all
confusion related to the way T::memory_usage() functions work.
* T::memory_usage() which returned external memory usage are renamed
to T::external_memory_usage()
* T::memory_usage() is introduced where needed to avoid repeating
sizeof(T) + T::external_memory_usage()"
Paweł Dziepak (6):
rename memory_usage() to external_memory_usage() where applicable
streamed_mutation: add memory_usage() to mutation fragment types
keys: add memory_usage()
partition_snapshot_accounter: use range_tombstone::memory_usage()
mutation_rebuilder: use memory_usage()
frozen_mutation: use memory_usage()
In the last iterations of this patchset, we have moved explicit flushes
to acquire the semaphore directly and the coalescing inside the
memtable_list. As a result, we are no longer keeping any kind of action
for them inside the condition variable. Checking for them has no longer
a purpose.
This is a cleanup patch that remove does checks.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Message-Id: <732676ccfe4ac93eb57aa799ec94b841499a01a6.1479500646.git.glauber@scylladb.com>
If a Column Family is non-durable, then its flushes will never create a
memtable flush reader. Our current flush logic depends on that being
created and destroyed to release the semaphore permits on the flush.
We will remove the permits ourselves it there is an exception, but not
under normal circumnstances. Given this issue, however, it would be more
adequate to always try to remove the permits after we flush. If the
permits were already removed by the flush reader, then this test will
just see that the permit is not in the map and return. But if it is
still there, then it is removed.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Message-Id: <049334c3b4bef620af2c7c045e6c84347dcf9013.1479498026.git.glauber@scylladb.com>
This patch introduces memory_usage() to static_row, clustering_row and
range_tombstone so that we can avoid repeating sizeof(T) +
x.external_memory_usage().
Signed-off-by: Paweł Dziepak <pdziepak@scylladb.com>
Renaming the function to external_memory_usage() makes it clear that
sizeof(T) is not included, something that was a source of confusion in
the past.
Signed-off-by: Paweł Dziepak <pdziepak@scylladb.com>
"Fixes #1856
Commitlog replay reads are being issued without a priority. That means
they will lose to compaction every time."
* 'issue-1856-v2' of github.com:glommer/scylla:
commitlog: use read ahead for replay requests
commitlog: use commitlog priority for replay
commitlog: close replay file
We supported install CentOS7 .rpm on RHEL7, but we haven't supported
building on RHEL7, since there is little difference between CentOS,
and that causes build error.
This patch fixes the error, now we can produce .rpm for RHEL7 wihout
using CentOS.
Signed-off-by: Takuya ASADA <syuu@scylladb.com>
Message-Id: <1479431134-8032-1-git-send-email-syuu@scylladb.com>
