Commit Graph

10529 Commits

Author SHA1 Message Date
Duarte Nunes
1d45f19c78 create_view_statement: Use cf_properties
This patch uses cf_properties instead to add the missing attributes to
the create_view_statement class.

Fixes #1766

Signed-off-by: Duarte Nunes <duarte@scylladb.com>
2016-10-18 01:18:52 +00:00
Duarte Nunes
7c58b7e764 unimplemented: Add materialized views
This patch adds the VIEWS element to the cause enum so we can
mark failures due to incomplete support of materialized views.

Signed-off-by: Duarte Nunes <duarte@scylladb.com>
2016-10-18 01:18:52 +00:00
Duarte Nunes
7c28ed3dfc schema: Extract default compressor
This patch extracts the definition of the default compressor into the
compression_parameters class, so that the table and view creation
statements don't have to explicitly deal with it.

Signed-off-by: Duarte Nunes <duarte@scylladb.com>
2016-10-18 01:18:52 +00:00
Duarte Nunes
dc470e6a36 cql3: Extract cf_properties
This patch extracts the cf_properties class, which contains common
attributes of tables and materialized views.

Signed-off-by: Duarte Nunes <duarte@scylladb.com>
2016-10-18 01:18:51 +00:00
Takuya ASADA
587d375e19 main: exit with 1 when verify_seastar_io_scheduler() failed
Since we are exiting Scylla process in engine().at_exit() using
::_exit(0), even verify_seastar_io_scheduler() throwing an exception,
scylla always exit with 0.

Systemd misunderstands scylla-server.service was shutdown successfully
because of this, so we need to pass correct exit code to ::_exit() here.

Fixes #1674

Signed-off-by: Takuya ASADA <syuu@scylladb.com>
Message-Id: <1475065607-15486-1-git-send-email-syuu@scylladb.com>
2016-10-17 13:57:00 +03:00
Avi Kivity
163088c6af Merge seastar upstream
* seastar 207bf3d...ccd8649 (3):
  > Merge "Augment semaphore with non-blocking operations" from Glauber
  > Merge "More dynamic fstream patches" from Paweł
  > Merge "fstream: add dynamic adjustments based on stream history" from Paweł
2016-10-17 12:49:17 +03:00
Avi Kivity
65c27ccf21 bytes_ostream: make max_chunk_size() an inline function
Fixes debug build looking for a variable definition and not finding it.
2016-10-17 11:49:33 +03:00
Avi Kivity
c0a1ad0b77 bytes_ostream: use larger allocations
A 1MB response will require 2000 allocations with the current 512-byte
chunk size.  Increase it exponentially to reduce allocation count for
larger responses (still respecting the upper limit).
Message-Id: <1476369152-1245-1-git-send-email-avi@scylladb.com>
2016-10-16 10:05:48 +01:00
Tomasz Grabiec
d836e8f64b tests: memtable: Add tests for flushing reader
Message-Id: <1476454187-11462-1-git-send-email-tgrabiec@scylladb.com>
2016-10-14 15:11:06 +01:00
Tomasz Grabiec
63784fd921 db: Fix corruption of partition_entry
Memory accounting code was attaching partition_snapshot to
partition_entry in order to calculate the size of partition_version
object. However, it is only allowed if partition_entry doesn't have
any snapshot attached already. In this case it always has one, created
by the flushing reader.

Change the accounting code to reuse existing partition_snapshot reference.

Fixes #1746
Message-Id: <1476449160-9252-1-git-send-email-tgrabiec@scylladb.com>
2016-10-14 15:10:48 +01:00
Paweł Dziepak
d08cffd3c7 lsa: avoid exceptions during segment_zone creation
LSA tries to allocate zones as large as possible (while still leaving
enough free space for the standard allocator). It uses the amount of
free memory in order to guess how much it can get, but that obviously
doesn't account for fragmentation and the allocation attempt may fail.

This patch changes the LSA code so that it doesn't throw in case zone
couldn't be created but just returns a null pointer which should be
more performant if the LSA memory cannot grow any more.

Fixes #1394.

Signed-off-by: Paweł Dziepak <pdziepak@scylladb.com>
Message-Id: <1476435031-5601-1-git-send-email-pdziepak@scylladb.com>
2016-10-14 11:08:24 +02:00
Amnon Heiman
7829da13b4 scylla_setup: Reorder questions and actions
The expected behaviour in the scylla_setup script is that a question
will be followed by the answer.

For example, after asking if the scylla should be run as a service the
relevant actions will be taken before the following question.

This patch address two such mis-orders:
1. the scylla-housekeeping depends on the scylla-server, but the
setup should first setup the scylla-server service and only then ask
(and install if needed) the scylla-housekeeping.
2. The node_exporter should be placed after the io_setup is done.

Fixes #1739

Signed-off-by: Amnon Heiman <amnon@scylladb.com>
Message-Id: <1476370098-25617-1-git-send-email-amnon@scylladb.com>
2016-10-13 18:29:36 +03:00
Pekka Enberg
3b4e6cdc5e abstract_replication_strategy: Fix exception type if class not found
Change abstract_replication_strategy::create_replication_strategy() to
throw exceptions::configuration_error if replication strategy class
lookup to make sure the error is converted to the correct CQL response.

Fixes #1755

Message-Id: <1476361262-28723-1-git-send-email-penberg@scylladb.com>
2016-10-13 17:39:28 +03:00
Tomasz Grabiec
e617bcd8a7 logalloc: disable abort on allocation failure in places in which it is benign
Some places start big expecting allocation failure, then reduce the
requested size. Let's not abort in such cases.

Message-Id: <1476295120-32047-1-git-send-email-tgrabiec@scylladb.com>
2016-10-13 10:53:32 +03:00
Avi Kivity
13e9d4c8e3 Merge seastar upstream
* seastar f937fb0...207bf3d (11):
  > Merge "iotune: gracefully exit on predictable exceptions" (Fixes #1623)
  > core/semaphore: Add semaphore_units::release()
  > Merge "rometheus API with grafana uses labels" from Amnon
  > core/thread: Fix stack alloc-dealloc mismatch
  > core/thread: Make jmp_buf_link::yield_at use the same time point as thread_scheduling_group
  > file: support for XFS on older kernels
  > reactor: fix bug when handling EBADF in flush_pending_aio()
  > prometheus CPU should start in 0
  > Collectd: bytes ordering depends on the type
  > tests: Check that backtrace() doesn't corrupt signal mask
  > core/thread: Add stack guards to seastar thread stacks
2016-10-12 23:47:12 +03:00
Avi Kivity
63f053e9b7 storage_proxy: fix mutation reordering with wrapping ranges
If we have a range query involving a wrapping range (i.e., from thrift),
and mutations from both halves of the result are involved, then
we will return the results in the wrong order (and potentially the wrong
partitions) since we order by token, so the results from the second half
of the wrapping range end up before the first.

Fix by splitting the two queries, and merging the second half with lower
priority compared to the first half.

Note: this will be fixed in a better way once we have the sharding iterator,
as then we can query sequentially.

Fixes #1761.
Message-Id: <1476262693-30162-1-git-send-email-avi@scylladb.com>
2016-10-12 15:59:16 +02:00
Avi Kivity
1506b06617 Merge "node_exporter service on ubuntu 16" from Amnon
"This series address two issues that interfere with running the node_exporter as a service in ubuntu 16.
1. The service file should be packed in the deb file
2. When setting the node_exporter as a service it doesn't need to run with scylla use"

* 'amnon/node_exporter_ubuntu_v2' of github.com:cloudius-systems/seastar-dev:
  node-exporter service: No need to run as scylla user
  debian package: Include the node_exporter service file
2016-10-12 12:11:18 +03:00
Amnon Heiman
1bd50789e0 node-exporter service: No need to run as scylla user
the node-exporter does not need to run as scylla user.  It can run
without scylla or without the scylla user being configure.

Signed-off-by: Amnon Heiman <amnon@scylladb.com>
2016-10-11 12:44:27 +03:00
Amnon Heiman
d523bf56ed debian package: Include the node_exporter service file
This will include the node_exporter service script for ubuntu
distribution with systemd support.

Signed-off-by: Amnon Heiman <amnon@scylladb.com>
2016-10-11 12:44:14 +03:00
Avi Kivity
f6998bb260 Merge "Implement describe_splits_ex based on Cassandra" from Duarte
"This patch-set re-implements the describe_splits_ex() verb to more closely
follow Cassandra's implementation, on which some clients rely.

Ref #1139
Ref #693"

* 'describe-splits/v2' of github.com:duarten/scylla:
  thrift: Implement describe_splits_ex based on Cassandra
  storage_service: Implement get_splits() function
  sstables: Add function to get key samples
  sstables/key: Add to_partition_key function
  size_estimates_recorder: Increase estimate accuracy
  sstables: Get estimates for a particular range
  sstables/key: Make key::kind public
2016-10-11 11:13:35 +03:00
Takuya ASADA
0007f2d838 dist/common/sbin: add scylla_cpuset_setup and scylla_dev_mode_setup to /usr/sbin
We haven't added symlinks to /usr/sbin for newly created scripts, so add them.

Fixes #1702

Signed-off-by: Takuya ASADA <syuu@scylladb.com>
Message-Id: <1474879711-31793-1-git-send-email-syuu@scylladb.com>
2016-10-11 11:02:14 +03:00
Takuya ASADA
ccad720bb1 dist/common/script/scylla_io_setup: handle comma correctly when parsing cpuset
The script mistakenly split value at "," when cpuset list is separated
by comma. Instead of matching possible patterns of the argument, let's
pass all characters until reach to space delimiter or end of line.

Fixes #1716

Signed-off-by: Takuya ASADA <syuu@scylladb.com>
Message-Id: <1476171037-32373-1-git-send-email-syuu@scylladb.com>
2016-10-11 10:42:32 +03:00
Duarte Nunes
d8cfc56376 thrift: Implement describe_splits_ex based on Cassandra
This patch re-implements the describe_splits_ex() verb to more closely
follow Cassandra's implementation, on which some clients rely.

Ref #1139
Ref #693

Signed-off-by: Duarte Nunes <duarte@scylladb.com>
2016-10-10 22:32:10 +02:00
Duarte Nunes
01ab2081cd storage_service: Implement get_splits() function
This patch implements the get_splits() function in storage_service,
used to split a particular token range in slices of approximately the
specified size, using the sample keys and estimates of the CF's
sstables.

Signed-off-by: Duarte Nunes <duarte@scylladb.com>
2016-10-10 22:32:08 +02:00
Duarte Nunes
c36dbaf0f1 sstables: Add function to get key samples
This patch implements the get_key_samples() function, on which a
future patch will base an implementation of the describe_splits()
thrift verb closer to Cassandra's.

Signed-off-by: Duarte Nunes <duarte@scylladb.com>
2016-10-10 19:50:14 +02:00
Duarte Nunes
fc07b66678 sstables/key: Add to_partition_key function
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
2016-10-10 19:50:11 +02:00
Duarte Nunes
c19c633299 size_estimates_recorder: Increase estimate accuracy
This patch uses the estimated_keys_for_range() function to get better
estimates.

Signed-off-by: Duarte Nunes <duarte@scylladb.com>
2016-10-10 17:52:16 +02:00
Duarte Nunes
ceed09b23e sstables: Get estimates for a particular range
This patch adds the estimated_keys_for_range() function, which
estimates the number of keys present between the specified range.

Signed-off-by: Duarte Nunes <duarte@scylladb.com>
2016-10-10 17:52:15 +02:00
Duarte Nunes
8c223b31c8 sstables/key: Make key::kind public
Needed to create synthetic keys without any value but with ordering
properties.

Signed-off-by: Duarte Nunes <duarte@scylladb.com>
2016-10-10 17:47:24 +02:00
Avi Kivity
b305d92a65 Merge "housekeeping: check version during setup" from Amnon
"The version is taken from the installation rather than the API, a mode command
line indicated that this is part of the setup and uuid is used for the
interaction with the checkversion server."

* 'amnon/check_version_on_startup_v3' of github.com:cloudius-systems/seastar-dev:
  scylla_setup: Check and report the scylla version
  scylla-housekeeping: check version during setup
2016-10-10 16:37:14 +03:00
Vlad Zolotarov
ab748e829d docs: tracing.md: initial commit
Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
Message-Id: <1475686745-20383-1-git-send-email-vladz@cloudius-systems.com>
2016-10-10 16:12:02 +03:00
Tomasz Grabiec
4357d0a6d9 db: Add counter for writes blocked on dirty memory
There is already queue_length-requests_blocked_memory, but it's a
gauge so does not reflect what happened between the sampling points.

total_operations-requests_blocked_memory will allow to see if there
were any (and how many) requests which were blocked by dirty memory.

Message-Id: <1476098616-12682-1-git-send-email-tgrabiec@scylladb.com>
2016-10-10 14:25:22 +03:00
Pekka Enberg
3b75ff1496 docs/docker: Tag --listen-address as 1.4 feature
The Docker Hub documentation is the same for all image versions. Tag
`--listen-address` as 1.4 feature.

Message-Id: <1475819164-7865-1-git-send-email-penberg@scylladb.com>
2016-10-10 13:26:16 +03:00
Vlad Zolotarov
006999f46c api::storage_service::slow_query: don't use duration_cast in GET
The slow_query_record_ttl() and slow_query_threshold() return the duration
of the appropriate type already - no need for an additional cast.
In addition there was a mistake in a cast of ttl.

Fixes #1734

Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
Message-Id: <1475669400-5925-1-git-send-email-vladz@cloudius-systems.com>
2016-10-09 18:09:13 +03:00
Takuya ASADA
469e9af1f4 dist/common/scripts/scylla_setup: use 'swapon -s' instead of 'swapon --show'
Since Ubuntu 14.04 doesn't supported --show option, we need to prevent use it.
Fixes #1740

Signed-off-by: Takuya ASADA <syuu@scylladb.com>
Message-Id: <1475788340-22939-2-git-send-email-syuu@scylladb.com>
2016-10-09 18:05:14 +03:00
Takuya ASADA
8452045b85 dist/ubuntu: add realpath to dependency, requires for scylla_setup
We need dependency to realpath, since scylla_setup using it.

Fixes #1740.

Signed-off-by: Takuya ASADA <syuu@scylladb.com>
Message-Id: <1475788340-22939-1-git-send-email-syuu@scylladb.com>
2016-10-09 18:05:14 +03:00
Tomasz Grabiec
41e66ebce2 gdb: Introduce 'scylla heapprof'
Presents current heap profile recording.

Works in text mode or dumps to collapsed stacks format from which
flame graph can be generated.

To generate a flamegraph:

  (gdb) scylla heapprof --flame
  Wrote heapprof.stacks

  $ flamegraph.pl --colors mem < heapprof.stacks > heapprof.svg

flamegraph.pl comes from:

  https://github.com/brendangregg/FlameGraph.git

Text mode example:

(gdb) scylla heapprof --min 100000000
All (274699676, #10213)
 \-- void* memory::cpu_pages::allocate_large_and_trim<memory::cpu_pages::allocate_large_aligned(unsigned int, unsigned int)::{lambda(unsigned int, unsigned int)#1}>(unsigned int, memory::cpu_pages::allocate_large_aligned(unsigned int, unsigned int)::{lambda(unsigned int, unsigned int)#1}) + 169  (268435456, #1)
     memory::allocate_large_aligned(unsigned long, unsigned long) + 87
     memory::allocate_aligned(unsigned long, unsigned long) + 48
     aligned_alloc + 9
     logalloc::segment_zone::segment_zone() + 304
     logalloc::segment_pool::allocate_segment() + 477
     logalloc::segment_pool::segment_pool() + 304
     __tls_init.part.801 + 72
     logalloc::region_group::release_requests() + 1333
     logalloc::region_group::add(logalloc::region_group*) + 514

The branches are formatted like this:

   -- <symbol> (<size>, #<count>)

Where <size> is total size of live objects and <count> is total
number of live objects, for all objects allocated from paths going
through this node.

Nodes which share the same <size> and <count> are stacked like this:

   -- <symbol_1> (<size>, #<count>)
      <symbol_2>
      <symbol_3>

Message-Id: <1475583334-19524-1-git-send-email-tgrabiec@scylladb.com>
2016-10-09 10:54:08 +03:00
Glauber Costa
33e9c2bbdd memtable: reduce sstable flush concurrency to one
Limiting the concurrency of memtable flushes to 4 was a temporary
workaround for the fact that we lacked good write behind support. Now
that write behind is properly merged we can reduce the concurrency to
what it should be, one.

This means that memtable flushes will now be serialized, and only when
one of them ends will the next one begin. Disk parallelism is obtained
through the write-behind mechanism.

Fixes #1373

Signed-off-by: Glauber Costa <glauber@scylladb.com>

Message-Id: <528f9ef928b5101bed952df600eb8555c275497a.1475881100.git.glauber@scylladb.com>
2016-10-09 10:48:57 +03:00
Tomasz Grabiec
2a5a90f391 db: Do not timeout streaming readers
There is a limit to concurrency of sstable readers on each shard. When
this limit is exhausted (currently 100 readers) readers queue. There
is a timeout after which queued readers are failed, equal to
read_request_timeout_in_ms (5s by default). The reason we have the
timeout here is primarily because the readers created for the purpose
of serving a CQL request no longer need to execute after waiting
longer than read_request_timeout_in_ms. The coordinator no longer
waits for the result so there is no point in proceeding with the read.

This timeout should not apply for readers created for streaming. The
streaming client currently times out after 10 minutes, so we could
wait at least that long. Timing out sooner makes streaming unreliable,
which under high load may prevent streaming from completing.

The change sets no timeout for streaming readers at replica level,
similarly as we do for system tables readers.

Fixes #1741.

Message-Id: <1475840678-25606-1-git-send-email-tgrabiec@scylladb.com>
2016-10-07 15:41:04 +03:00
Raphael S. Carvalho
9175977a9d cql3: fix build failure by defining out unused function
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <cba6207278ea945ee750d78b189320443843a288.1475793747.git.raphaelsc@scylladb.com>
2016-10-07 08:45:18 +03:00
Avi Kivity
9ac441d3b5 range: adjust split_after to allow split_point outside input range
Make split_after() more generic by allowing split_point to be anywhere,
not just within the input range.  If the split_point is before, the entire
range is returned; and if it is after, stdx::nullopt is returned.

"before" and "after" are not well defined for wrap-around ranges, so
but we are phasing them out and soon there will not be
wrapping_range::split_after() users.

This is a prerequisite for converting partition_range and friends to
nonwrapping_range.
Message-Id: <1475765099-10657-1-git-send-email-avi@scylladb.com>
2016-10-06 17:54:44 +02:00
Raphael S. Carvalho
7ea4513595 database: trigger compaction after loading new sstables
Scylla wasn't trying to compact new sstables uploaded via 'nodetool
refresh'. Thus, all new sstables were left uncompacted until user
issued 'nodetool flush' or a new sstable was written which would
trigger compaction too.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <bbdf274c8bb49f4bedeefcb85da78a6fb61a1232.1475535203.git.raphaelsc@scylladb.com>
2016-10-06 18:26:49 +03:00
Raphael S. Carvalho
9c59ccc52a storage_service: improve log message for refresh
'No new SSTables were found for keyspace1.standard1' was printed
if user uploaded new sstables to upload dir instead, and that is
confusing. We should instead print that if new sstables weren't
found in both cf and cf/upload dirs.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <90386f6255407697434213227ae7ff0de7464f99.1475535203.git.raphaelsc@scylladb.com>
2016-10-06 18:26:32 +03:00
Raphael S. Carvalho
76862d0d9c main: start compaction procedure after commit log is replayed
Commit log replay is a synchronous operation in bootstrap, so services
will only be started after it's completed. By starting compaction before,
less bandwidth will be available to both and consequently boot will be
slowed down. Fix is simply about moving compaction, which is an
asynchronous operation after commitlog replay is over.

Fixes #1620.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <d2a173a4ee4d474317b970c6b39530e61067fea9.1475527955.git.raphaelsc@scylladb.com>
2016-10-06 18:25:24 +03:00
Nadav Har'El
ee7ec10b11 CQL parser: "CREATE MATERIALIZED VIEW" statement
This patch adds the parsing for the "CREATE MATERIALIZED VIEW" statement,
following Cassandra 3 syntax. For example:

   CREATE MATERIALIZED VIEW building_by_city
   AS SELECT * FROM buildings
   WHERE city IS NOT NULL
   PRIMARY KEY(city, name);

It also adds the "IS NOT NULL" operator needed for this purpose.
As in Cassandra, "IS NOT NULL" can only be used for materialized
view creation, and not in a normal SELECT. It can only be used with
the NULL operand (i.e., "IS NOT 3" will be a syntax error).

The current implementation of this statement just does some sanity
checking (such as to verify that "city" is a valid column name and that
the "building" base table exists), complains that materialized views are
not yet supported:

SyntaxException: <ErrorMessage code=2000 [Syntax error in CQL query] message="Failed parsing statement: [CREATE MATERIALIZED VIEW building_by_city AS
SELECT * FROM buildings
WHERE city IS NOT NULL
PRIMARY KEY(city, name);] reason: unsupported operation: Materialized views not yet supported">

As mentioned above, the "IS NOT NULL" restriction is not allowed in
ordinary selects not creating a materialized views:

SELECT * FROM buildings WHERE city IS NOT NULL;
InvalidRequest: code=2200 [Invalid query] message="restriction 'city IS NOT null' is only supported in materialized view creation"

Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <1475742927-30695-1-git-send-email-nyh@scylladb.com>
2016-10-06 15:42:37 +03:00
Glauber Costa
7146776d7c fix sstable tests by not using the flush_reader if no region_group
The latest virtual dirty patches broke the SSTable tests. The reason for
this is that those tests will flush synthetic memtables that do not have
a region_group attached to it.

Normally in cases like this we would just give the flush_reader an empty
region group. However, the memtable class constructor takes a
region_group pointer and that can be null according to the interface.
So we must conditionally test it.

If there isn't a region_group involved, the virtual dirty accounting
should be disabled: after all, we won't even have the baseline memory
to begin with.

One of the approaches to fix this could be to just provide null
accounter classes to be used as a surrogate for the accounting classes
in this case. However, since this is mostly used for tests, a much
simpler way is to just revert back to the scanning reader in that case.

The scanning reader is similar enough to the flush_reader, except that
it can handle partial ranges, slices, and delegate accesses to an
sstable post-flush. We don't need any of that, but as argued above,
there is no need to remove it either.

Signed-off-by: Glauber Costa <glommer@scylladb.com>
Message-Id: <1475667271-60806-1-git-send-email-glommer@scylladb.com>
2016-10-05 12:44:21 +01:00
Avi Kivity
c94fb1bf12 build: reduce inclusions of messaging_service.hh
Remove inclusions from header files (primary offender is fb_utilities.hh)
and introduce new messaging_service_fwd.hh to reduce rebuilds when the
messaging service changes.

Message-Id: <1475584615-22836-1-git-send-email-avi@scylladb.com>
2016-10-05 11:46:49 +03:00
Avi Kivity
f8118d9fc2 Merge "Virtual dirty memory management" from Glauber
"Description:
============

Scylla currently suffers from a brick wall behavior of the request throttler.
Requests pile up until we reach the dirty memory limit, at which point we stop
serving them until we have freed enough memory to allow for more requests.

The problem is that freeing dirty memory means writing an SSTable to completion.
That can take a long time, even if we are blessed with great disks. Those long
waiting times can and will translate into timeouts. That is bad behavior.

What this patch does is introduce one form of virtual dirty memory accounting.
Instead of allowing 100 % of the dirty memory to be filled up until we stop
accepting requests, we will do that when we reach 50 % of memory. However,
instead of releasing requests only when an SSTable is fully written, we start
releasing them when some memory was written.

The practical effect of that, is that once we reach 50 % occupancy in our dirty
memory region, we will bring the system from CPU speed to disk speed, and will
start accepting requests only at the rate we are able to write memory back.

Results
=======

With this patchset running a load big enough to easily saturate the disk,
(commitlog disabled to highlight the effects of the memtable writer), I am able
to run scylla for many minutes, with timeouts occurring only when I run out of
disk space, whereas without this patch a swarm of timeouts would start merely 2
seconds after the load started - and would never get stable.

In V2, I have sent a set of graphs illustrating the performance of this solution.
This version does not have any significant differences in that front.

For details, please refer to
https://groups.google.com/d/msg/scylladb-dev/iCvD-3Z-QqY/EM8KUh_MAQAJ

Accuracy of the accounting:
---------------------------
It is important for us to be as accurate as possible when accounting freed
memory, since every byte we mark as freed may allow one or more requests to be
executed.  I have measured the accuracy of this approach (ignoring padding,
object size for the mutation fragments) to be 99.83 % of used memory in the
test workload I have ran (large, 65k mutations). Memtables under this circumnstance
tend to have a very high occupancy ratio because throttle breeds idle, and idle
breeds compact-on-idle.

Known Issues:
-------------

A lot of time can be elapsed between destroying the flush_reader and actually
releasing memory. The release of memory only happens when the SSTable is fully
sealed, and we have to flush the files, as well as finish writing all SSTable
components at this point. This happened in practice with a buggy kernel that
would result in flushes taking a long time.

After that is fixed, this is just a theoretical problem and in practice it
shouldn't matter given the time we expect those operations to take."

* 'virtual-dirty-v6' of github.com:glommer/scylla:
  database: allow virtual dirty memory management
  streamed_mutation: make _buffer private
  add accounting of memory read to partition_snapshot_reader
  move partition_snapshot_reader code to header file
  LSA: allow a group to query its own region group
  memtables: split scanning reader in two
  sstables: use special reader for writing a memtable
  LSA: export information about object memory footprint
  LSA: export information about size of the throttle queue
  database: export virtual dirty bytes region group
2016-10-04 20:57:52 +03:00
Avi Kivity
cc33c8b4ba Merge seastar upstream
* seastar 18f7bb8...f937fb0 (5):
  > Merge "Fix signal mask corruption" from Tomasz
  > core/memory: Avoid violating strict aliasing when accessing allocation sites
  > core/memory: Avoid indirection when storing allocation sites
  > core/memory: Add a way to disable abort on allocation failure in some scope
  > core/sharded: Allow mapper to take the service by non-const reference
2016-10-04 20:08:57 +03:00
Glauber Costa
f89a67c75c database: allow virtual dirty memory management
Scylla currently suffers from a brick wall behavior of the request throttler.
Requests pile up until we reach the dirty memory limit, at which point we stop
serving them until we have freed enough memory to allow for more requests.

The problem is that freeing dirty memory means writing an SSTable to completion.
That can take a long time, even if we are blessed with great disks. Those long
waiting times can and will translate into timeouts. That is bad behavior.

What this patch does is introduce one form of virtual dirty memory accounting.
Instead of allowing 100 % of the dirty memory to be filled up until we stop
accepting requests, we will do that when we reach 50 % of memory. However,
instead of releasing requests only when an SSTable is fully written, we start
releasing them when some memory was written.

The practical effect of that is that once we reach 50 % occupancy in our dirty
memory region, we will bring the system from CPU speed to disk speed, and will
start accepting requests only at the rate we are able to write memory back.

Signed-off-by: Glauber Costa <glauber@scylladb.com>
2016-10-04 10:39:10 -04:00