C++17 introduced try_emplace for maps to replace a pattern:
if(element not in a map) {
map.emplace(...)
}
try_emplace is more efficient and results in a more concise code.
This commit introduces usage of try_emplace when it's appropriate.
Tests: unit(dev)
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Message-Id: <4970091ed770e233884633bf6d46111369e7d2dd.1597327358.git.piotr@scylladb.com>
C++20 introduced `contains` member functions for maps and sets for
checking whether an element is present in the collection. Previously
`count` function was often used in various ways.
`contains` does not only express the intend of the code better but also
does it in more unified way.
This commit replaces all the occurences of the `count` with the
`contains`.
Tests: unit(dev)
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Message-Id: <b4ef3b4bc24f49abe04a2aba0ddd946009c9fcb2.1597314640.git.piotr@scylladb.com>
Merged pull request https://github.com/scylladb/scylla/pull/7018
by Piotr Sarna:
This series addresses various issues with metrics and semaphores - it mainly adds missing metrics, which makes it possible to see the length of the queues attached to the semaphores. In case of view building and view update generation, metrics was not present in these services at all, so a first, basic implementation is added.
More precise semaphore metrics would ease the testing and development of load shedding and admission control.
view_builder: add metrics
db, view: add view update generator metrics
hints: track resource_manager sending queue length
hints: add drain queue length to metrics
table: add metrics for sstable deletion semaphore
database: remove unused semaphore
C++20 introduced `contains` member functions for maps and sets for
checking whether an element is present in the collection. Previously
the code pattern looked like:
<collection>.find(<element>) != <collection>.end()
In C++20 the same can be expressed with:
<collection>.contains(<element>)
This is not only more concise but also expresses the intend of the code
more clearly.
This commit replaces all the occurences of the old pattern with the new
approach.
Tests: unit(dev)
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Message-Id: <f001bbc356224f0c38f06ee2a90fb60a6e8e1980.1597132302.git.piotr@scylladb.com>
Move the classes representing CQL expressions (and utility functions
on them) from the `restrictions` namespace to a new namespace `expr`.
Most of the restriction.hh content was moved verbatim to
expression.hh. Similarly, all expression-related code was moved from
statement_restrictions.cc verbatim to expression.cc.
As suggested in #5763 feedback
https://github.com/scylladb/scylla/pull/5763#discussion_r443210498
Tests: dev (unit)
Signed-off-by: Dejan Mircevski <dejan@scylladb.com>
"
While working on another patch I was getting odd compiler errors
saying that a call to ::make_shared was ambiguous. The reason was that
seastar has both:
template <typename T, typename... A>
shared_ptr<T> make_shared(A&&... a);
template <typename T>
shared_ptr<T> make_shared(T&& a);
The second variant doesn't exist in std::make_shared.
This series drops the dependency in scylla, so that a future change
can make seastar::make_shared a bit more like std::make_shared.
"
* 'espindola/make_shared' of https://github.com/espindola/scylla:
Everywhere: Explicitly instantiate make_lw_shared
Everywhere: Add a make_shared_schema helper
Everywhere: Explicitly instantiate make_shared
cql3: Add a create_multi_column_relation helper
main: Return a shared_ptr from defer_verbose_shutdown
It is important that all replicas participating in a read use the same
memory limits to avoid artificial differences due to different amount of
results. The coordinator now passes down its own memory limit for reads,
in the form of max_result_size (or max_size). For unpaged or reverse
queries this has to be used now instead of the locally set
max_memory_unlimited_query configuration item.
To avoid the replicas accidentally using the local limit contained in
the `query_class_config` returned from
`database::make_query_class_config()`, we refactor the latter into
`database::get_reader_concurrency_semaphore()`. Most of its callers were
only interested in the semaphore only anyway and those that were
interested in the limit as well should get it from the coordinator
instead, so this refactoring is a win-win.
seastar::make_lw_shared has a constructor taking a T&&. There is no
such constructor in std::make_shared:
https://en.cppreference.com/w/cpp/memory/shared_ptr/make_shared
This means that we have to move from
make_lw_shared(T(...)
to
make_lw_shared<T>(...)
If we don't want to depend on the idiosyncrasies of
seastar::make_lw_shared.
Signed-off-by: Rafael Ávila de Espíndola <espindola@scylladb.com>
So that tests can test the `view_update_consumer` in isolation, without
having to set up the whole database machinery. In addition to less
infrastructure setup, this allows more direct checking of mutations
pushed for view generation.
The view update generation process creates two readers. One is used to
read the staging sstables, the data which needs view updates to be
generated for, and another reader for each processed mutation, which
reads the current value (pre-image) of each row in said mutation. The
staging reader is created first and is kept alive until all staging data
is processed. The pre-image reader is created separately for each
processed mutation. The staging reader is not restricted, meaning it
does not wait for admission on the relevant reader concurrency
semaphore, but it does register its resource usage on it. The pre-image
reader however *is* restricted. This creates a situation, where the
staging reader possibly consumes all resources from the semaphore,
leaving none for the later created pre-image reader, which will not be
able to start reading. This will block the view building process meaning
that the staging reader will not be destroyed, causing a deadlock.
This patch solves this by making the staging reader restricted and
making it evictable. To prevent thrashing -- evicting the staging reader
after reading only a really small partition -- we only make the staging
reader evictable after we have read at least 1MB worth of data from it.
The schema_tables.hh -> migration_manager.hh couple seems to work as one
of "single header for everyhing" creating big blot for many seemingly
unrelated .hh's.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
This patch changes the row locking latencies to use
time_estimated_histogram.
The change consist of changing the histogram definition and changing how
values are inserted to the histogram.
Signed-off-by: Amnon Heiman <amnon@scylladb.com>
"
This is the first stage of replacing the existing restrictions code with a new representation. It adds a new class `expression` to replace the existing class `restriction`. Lots of the old code is deleted, though not all -- that will come in subsequent stages.
Tests: unit (dev, debug restrictions_test), dtest (next-gating)
"
* dekimir-restrictions-rewrite:
cql3/restrictions: Drop dead code
cql3/restrictions: Use free functions instead of methods
cql3/restrictions: Create expression objects
cql3/restrictions: Add free functions over new classes
cql3/restrictions: Add new representation
Instead of `restriction` class methods, use the new free functions.
Specific replacement actions are listed below.
Note that class `restrictions` (plural) remains intact -- both its
methods and its type hierarchy remain intact for now.
Ensure full test coverage of the replacement code with new file
test/boost/restrictions_test.cc and some extra testcases in
test/cql/*.
Drop some existing tests because they codify buggy behaviour
(reference #6369, #6382). Drop others because they forbid relation
combinations that are now allowed (eg, mixing equality and
inequality, comparing to NULL, etc.).
Here are some specific categories of what was replaced:
- restriction::is_foo predicates are replaced by using the free
function find_if; sometimes it is used transitively (see, eg,
has_slice)
- restriction::is_multi_column is replaced by dynamic casts (recall
that the `restrictions` class hierarchy still exists)
- utility methods is_satisfied_by, is_supported_by, to_string, and
uses_function are replaced by eponymous free functions; note that
restrictions::uses_function still exists
- restriction::apply_to is replaced by free function
replace_column_def
- when checking infinite_bound_range_deletions, the has_bound is
replaced by local free function bounded_ck
- restriction::bounds and restriction::value are replaced by the more
general free function possible_lhs_values
- using free functions allows us to simplify the
multi_column_restriction and token_restriction hierarchies; their
methods merge_with and uses_function became identical in all
subclasses, so they were moved to the base class
- single_column_primary_key_restrictions<clustering_key>::needs_filtering
was changed to reuse num_prefix_columns_that_need_not_be_filtered,
which uses free functions
Fixes#5799.
Fixes#6369.
Fixes#6371.
Fixes#6372.
Fixes#6382.
Signed-off-by: Dejan Mircevski <dejan@scylladb.com>
Modified log message in view_builder::calculate_shard_build_step to make it distinct from the one in view_builder::execute, changed their logging level to warning, since we're continuing even if we handle an exception.
Fixes#4600
And pass it to `make_range_sstable_reader()` when creating the reader,
thus allowing the incremental selector created therein to exploit the
fact that staging sstables are disjoint (in the case of repair and
streaming at least). This should reduce the memory consumption of the
staging reader considerably when reading from a lot of sstables.
Streaming is handled by just once group for CPU scheduling, so
separating it into read and write classes for I/O is artificial, and
inflates the resources we allow for streaming if both reads and writes
happen at the same time.
Merge both classes into one class ("streaming") and adjust callers. The
merged class has 200 shares, so it reduces streaming bandwidth if both
directions are active at the same time (which is rare; I think it only
happens in view building).
The seastar api v4 changes the return type of when_all_succeed. This
patch adds discard_result when that is best solution to handle the
change.
This doesn't do the actual update to v4 since there are still a few
issues left to fix in seastar. A patch doing just the update will
follow.
Signed-off-by: Rafael Ávila de Espíndola <espindola@scylladb.com>
Message-Id: <20200617233150.918110-1-espindola@scylladb.com>
Merged pull request https://github.com/scylladb/scylla/pull/6516 from
Piotr Sarna:
This series adds error injection points to materialized view paths:
view update generation from staging sstables;
view building;
generating view updates from user writes.
This series comes with a corresponding dtest pull request which adds some
test cases based on error injection.
Fixes#6488
In current mutate_MV() code it's possible for a local endpoint
to become a target for a network operation. That's the source
of occasional `broken promise` benign error messages appearing,
since the mutation is actually applied locally, so there's no point
in creating a write response handler - the node will not send a response
to itself via network.
While at it, the code is deduplicated a little bit - with the paths
simplified, it's easier to ensure that a local endpoint is never
listed as a target for remote network operations.
Fixes#5459
Tests: unit(dev),
dtest(materialized_views_test.TestMaterializedViews.add_dc_during_mv_insert_test)
"
Currently we classify queries as "system" or "user" based on the table
they target. The class of a query determines how the query is treated,
currently: timeout, limits for reverse queries and the concurrency
semaphore. The catch is that users are also allowed to query system
tables and when doing so they will bypass the limits intended for user
queries. This has caused performance problems in the past, yet the
reason we decided to finally address this is that we want to introduce a
memory limit for unpaged queries. Internal (system) queries are all
unpaged and we don't want to impose the same limit on them.
This series uses scheduling groups to distinguish user and system
workloads, based on the assumption that user workloads will run in the
statement scheduling group, while system workloads will run in the main
(or default) scheduling group, or perhaps something else, but in any
case not in the statement one. Currently the scheduling group of reads
and writes is lost when going through the messaging service, so to be
able to use scheduling groups to distinguish user and system reads this
series refactors the messaging service to retain this distinction across
verb calls. Furthermore, we execute some system reads/writes as part of
user reads/writes, such as auth and schema sync. These processes are
tagged to run in the main group.
This series also centralises query classification on the replica and
moves it to a higher level. More specifically, queries are now
classified -- the scheduling group they run in is translated to the
appropriate query class specific configuration -- on the database level
and the configuration is propagated down to the lower layers.
Currently this query class specific configuration consists of the reader
concurrency semaphore and the max memory limit for otherwise unlimited
queries. A corollary of the semaphore begin selected on the database
level is that the read permit is now created before the read starts. A
valid permit is now available during all stages of the read, enabling
tracking the memory consumption of e.g. the memtable and cache readers.
This change aligns nicely with the needs of more accurate reader memory
tracking, which also wants a valid permit that is available in every layer.
The series can be divided roughly into the following distinct patch
groups:
* 01-02: Give system read concurrency a boost during startup.
* 03-06: Introduce user/system statement isolation to messaging service.
* 07-13: Various infrastructure changes to prepare for using read
permits in all stages of reads.
* 14-19: Propagate the semaphore and the permit from database to the
various table methods that currently create the permit.
* 20-23: Migrate away from using the reader concurrency semaphore for
waiting for admission, use the permit instead.
* 24: Introduce `database::make_query_config()` and switch the database
methods needing such a config to use it.
* 25-31: Get rid of all uses of `no_reader_permit()`.
* 32-33: Ban empty permits for good.
* 34: querier_cache: use the queriers' permits to obtain the semaphore.
Fixes: #5919
Tests: unit(dev, release, debug),
dtest(bootstrap_test.py:TestBootstrap.start_stop_test_node), manual
testing with a 2 node mixed cluster with extra logging.
"
* 'query-class/v6' of https://github.com/denesb/scylla: (34 commits)
querier_cache: get semaphore from querier
reader_permit: forbid empty permits
reader_permit: fix reader_resources::operator bool
treewide: remove all uses of no_reader_permit()
database: make_multishard_streaming_reader: pass valid permit to multi range reader
sstables: pass valid permits to all internal reads
compaction: pass a valid permit to sstable reads
database: add compaction read concurrency semaphore
view: use valid permits for reads from the base table
database: use valid permit for counter read-before-write
database: introduce make_query_class_config()
reader_concurrency_semaphore: remove wait_admission and consume_resources()
test: move away from reader_concurrency_semaphore::wait_admission()
reader_permit: resource_units: introduce add()
mutation_reader: restricted_reader: work in terms of reader_permit
row_cache: pass a valid permit to underlying read
memtable: pass a valid permit to the delegate reader
table: require a valid permit to be passed to most read methods
multishard_mutation_query: pass a valid permit to shard mutation sources
querier: add reader_permit parameter and forward it to the mutation_source
...
Until now, view updates were generated with a bunch of random
time points, because the interface was not adjusted for passing
a single time point. The time points were used to determine
whether cells were alive (e.g. because of TTL), so it's better
to unify the process:
1. when generating view updates from user writes, a single time point
is used for the whole operation
2. when generating view updates via the view building process,
a single time point is used for each build step
NOTE: I don't see any reliable and deterministic way of writing
test scenarios which trigger problems with the old code.
After #6488 is resolved and error injection is integrated
into view.cc, tests can be added.
Fixes#6429
Tests: unit(dev)
Message-Id: <f864e965eb2e27ffc13d50359ad1e228894f7121.1590070130.git.sarna@scylladb.com>
View update generation involves reading existing values from the base
table, which will soon require a valid permit to be passed to it, so
make sure we create and pass a valid permit to these reads.
We use `database::make_query_class_config()` to obtain the semaphore for
the read which selects the appropriate user/system semaphore based on
the scheduling group the base table write is running in.
Now that the most prevalent users (range scan and single partition
reads) all pass valid permits we require all users to do so and
propagate the permit down towards `make_sstable_reader()`. The plan is
to use this permit for restricting the sstable readers, instead of the
semaphore the table is configured with. The various
`make_streaming_*reader()` overloads keep using the internal semaphores
as but they also create the permit before the read starts and pass it to
`make_sstable_reader()`.
In order to add tracing to places where it can be useful,
e.g. materialized view updates and hinted handoff, tracing state
is propagated to all applicable call sites.
When generating view updates, an endpoint can appear both
as a primary paired endpoint for the view update, and as a pending
endpoint (due to range movements). In order not to generate
the same update twice for the same endpoint, the paired endpoint
is removed from the list of pending endpoints if present.
Fixes#5459
Tests: unit(dev),
dtest(TestMaterializedViews.add_dc_during_mv_insert_test)
It is currently not possible to wrap the view_updating_consumer in an
std::optional. I intend to do it to allow for compactions to optionally
generate view updates.
The reason for that is that view_updating_consumer has a reference as a
member, which makes the move assignment constructor not be implicitly
generated.
This patch fixes it by keeping a pointer instead of a reference.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Message-Id: <20200421123648.8328-1-glauber@scylladb.com>
There is no reason to read a single SSTable at a time from the staging
directory. Moving SSTables from staging directory essentially involves
scanning input SSTables and creating new SSTables (albeit in a different
directory).
We have a mechanism that does that: compactions. In a follow up patch, I
will introduce a new specialization of compaction that moves SSTables
from staging (potentially compacting them if there are plenty).
In preparation for that, some signatures have to be changed and the
view_updating_consumer has to be more compaction friendly. Meaning:
- Operating with an sstable vector
- taking a table reference, not a database
Because this code is a bit fragile and the reviewer set is fundamentally
different from anything compaction related, I am sending this separately
Signed-off-by: Glauber Costa <glauber@scylladb.com>
The startup routine performs some bookkeeping operations on views,
and so do these events:
- on_create_view;
- on_drop_view;
- on_update_view.
Since the above events are guarded with a semaphore, the startup
routine should also take the same semaphore - in order to ensure
that all bookkeeping operations are serialized.
Refs #6094
The future was marked with a `FIXME: discarded future`, but there's really
no reason not to wait for it, and it was probably meant to be waited for
since its implementation.
Change CQL parsing routine to return std::unique_ptr
instead of seastar::shared_ptr.
This can help reduce redundant shared_ptr copies even further.
Make some supplementary changes necessary for this transition:
* Remove enabled_shared_from_this base class from the following
classes: truncate_statement, authorization_statement,
authentication_statement: these were previously constructing
prepared_statement instance in `prepare` method using
`shared_from_this`.
Make `prepare` methods implementation of inheriting classes
mirror implementation from other statements (i.e.
create a shallow copy of the object when prepairing into
`prepared_statement`; this could be further refactored
to avoid copies as much as possible).
* Remove unused fields in create_role_statement which led to
error while using compiler-generated copy ctor (copying
uninitialied bool values via ctor).
Signed-off-by: Pavel Solodovnikov <pa.solodovnikov@scylladb.com>
Before this patch, when db/view/view.hh was modified, 89 source files had to
be recompiled. After this patch, this number is down to 5.
Most of the irrelevant source files got view.hh by including database.hh,
which included view.hh just for the definition of statistics. So in this
patch we split the view statistics to a separate header file, view_stats.hh,
and database.hh only includes that. A few source files which included
only database.hh and also needed view.hh (for materialized-view related
functions) now need to include view.hh explicitly.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200319121031.540-1-nyh@scylladb.com>
View updates sent as part of the view building process should never
be ignored, but fd49fd7 introduced a bug which may cause exactly that:
the updates are mistakenly sent to background, so the view builder
will not receive negative feedback if an update failed, which will
in turn not cause a retry. Consequently, view building may report
that it "finished" building a view, while some of the updates were
lost. A simple fix is to restore previous behaviour - all updates
triggered by view building are now waited for.
Fixes#6038
Tests: unit(dev),
dtest: interrupt_build_process_with_resharding_low_to_half_test
While CQL does not allow creation of a materialized view with more than one
base regular column in the view's key, in Alternator we do allow this - both
partition and clustering key may be a base regular column. We had a bug in
the logic handling this case:
If the new base row is missing a value for *one* of the view key columns,
we shouldn't create a view row. Similarly, if the existing base row was
missing a value for *one* of the view key columns, a view row does not
exist and doesn't need to be deleted. This was done incorrectly, and made
decisions based on just one of the key columns, and the logic is now
fixed (and I think, simplified) in this patch.
With this patch, the Alternator test which previously failed because of
this problem now passes. The patch also includes new tests in the existing
C++ unit test test_view_with_two_regular_base_columns_in_key. This tests
was already supposed to be testing various cases of two-new-key-columns
updates, but missed the cases explained above. These new tests failed
badly before this patch - some of them had clean write errors, others
caused crashes. With this patch, they pass.
Fixes#6008.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200312162503.8944-1-nyh@scylladb.com>
Local view updates (updates applied to a local node,
without remote communication) are from now on performed
synchronously - which adds consistency guarantees, as a local
write failure will be returned to the client instead of being
silently ignored.
Currently, launching view updates as an asynchronous background job
is done via not waiting for mutate_MV() future in
table::generate_and_propagate_view_updates. That has a big downside,
since mutate_MV() handles *all* view updates for *all* views of a table,
so it's not possible to wait for each view independently.
Per-view granularity is required in order to implement synchronous
view updates of local views - because then we'll synchronously
wait for all views that write to a local node (due to having a matching
partition key with the base), while remote view updates will still
be sent asynchronously.
In order to do that, instead of not waiting for mutate_MV,
we do wait for it properly, but instead launch the asynchronous,
unwaited-for futures inside mutate_MV.
Effectively that means no changes for view updates so far - all updates
will be fired in the background. Later, another patch will introduce
a way to wait for selected updates to finish.
