Define table_id as a distinct utils::tagged_uuid modeled after raft
tagged_id, so it can be differentiated from other uuid-class types,
in particular from table_schema_version.
Fixes#11207
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Use the common base class for uuid-based types.
tagged_uuid::to_uuid defined here for backward
compatibility, but it will be renamed in the next patch
to uuid().
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
So it can be used for other types in the system outside
of raft, like counter_id, table_id, table_schema_version,
and more.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Now that scylla requries c++20 there's no
need to define our own implementation in utils/bit_cast.hh
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Range tombstones are kept in memory (cache/memtable) in
range_tombstone_list. It keeps them deoverlapped, so applying a range
tombstone which covers many range tombstones will erase existing range
tombstones from the list. This operation needs to be exception-safe,
so range_tombstone_list maintains an undo log. This undo log will
receive a record for each range tombstone which is removed. For
exception safety reasons, before pushing an undo log entry, we reserve
space in the log by calling std::vector::reserve(size() + 1). This is
O(N) where N is the number of undo log entries. Therefore, the whole
application is O(N^2).
This can cause reactor stalls and availability issues when replicas
apply such deletions.
This patch avoids the problem by reserving exponentially increasing
amount of space. Also, to avoid large allocations, switches the
container to chunked_vector.
Fixes#11211Closes#11215
Don't open-code calling the region_impl
_listeners->moved() in region move-constructor
and move-assignment op.
The other._impl->_region might be different then &other
post region::merge so let the region_impl
decide which region* is moved from.
The new_region is also set to region_impl->_region
so need to open-code that either in the said call sites.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
The other _impl is presumed to be engaged already,
so just call other.get_impl() once for both use cases.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
We can't be sure that the other_impl->_region == &other
since it could be a result of a previous merge,
so don't decide for it which region to unlisten to,
let it use its current _region.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Current ~region and region::operator= open-code
region_impl::unlisten. Just call it so it will be
easier to maintain.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
First check if _impl is engaged before accessing it
to set its _region = this in the move constructor and
move assignment operator.
Add unit test for these odd orner cases.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
This series is the first step in the effort to reduce the number of metrics reported by Scylla.
The series focuses on the per-table metrics.
The combination of histograms, per-tables, and per shard makes the number of metrics in a cluster explode.
The following series uses multiple tools to reduce the number of metrics.
1. Multiple metrics should only be reported for the user tables and the condition that checked it was not updated when more non-user keyspaces were added.
2. Second, instead of a histogram, per table, per shard, it will report a summary per table, per shard, and a single histogram per node.
3. Histograms, summaries, and counters will be reported only if they are used (for example, the cas-related metrics will not be reported for tables that are not using cas).
Closes#11058
* github.com:scylladb/scylla:
Add summary_test
database: Reduce the number of per-table metrics
replica/table.cc: Do not register per-table metrics for system
histogram_metrics_helper.hh: Add to_metrics_summary function
Unified histogram, estimated_histogram, rates, and summaries
Split the timed_rate_moving_average into data and timer
utils/histogram.hh: should_sample should use a bitmask
estimated_histogram: add missing getter method
The to_metrics_summary is a helper function that create a metrics type
summary from a timed_rate_moving_average_with_summary object.
Signed-off-by: Amnon Heiman <amnon@scylladb.com>
Currently, there are two metrics reporting mechanisms: the metrics layer
and the API. In most cases, they use the same data sources. The main
difference is around histograms and rate.
The API calculates an exponentially weighted moving average using a
timer that decays the average on each time tick. It calculates a
poor-man histogram by holding the last few entries (typically the last
256 entries). The caller to the API uses those last entries to build a
histogram.
We want to add summaries to Scylla. Similar to the API rate and
histogram, summaries are calculated per time interval.
This patch creates a unified mechanism by introducing an object that
would hold both the old-style histogram and the new
(estimated_histogram). On each time tick, a summary would be calculated.
In the future, we'll replace the API to report summaries instead of the
old-style histogram and deprecate the old style completely.
summary_calculator uses two estimated_histogram to calculate a summary.
timed_rate_moving_average_summary_and_histogram is a unifed class for
ihistogram, rates, summary, and estimated_histogram and will replace
timed_rate_moving_average_and_histogram.
Follow-up patches would move code from using
timed_rate_moving_average_and_histogram to
timed_rate_moving_average_summary_and_histogram. By keeping the API it
would make the transition easy.
Signed-off-by: Amnon Heiman <amnon@scylladb.com>
It was added in d20fae96a2
as a precaution not to invalidate iterators while
traversing _regions. However it is not requried as no allocation
is done on this synchronous path - therefore there is no
point in preventing reclaim.
This will allow making the respective functions const
as they merely return stats and do not modify the tracker impl.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
To make the implementation inline and to prepare
for the next patch that adds a const overload of
this method.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Some methods were also marked inline when declared in the class
definition and in the ir definition site to provide a hint to
the compiler to inline them.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
dynamic_bitset allocates only when constructed.
then on it doesn't throw.
Though not that accessing bits out of range
is undefined behavior.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Maintain the const chain by returning a const segment*
from segment_from_idx() const overload.
And add a respective mutable overload to return a mutable segment*.
This is done for a similar change in idx_from_segment.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Add a const noexcept overload of `find_empty()` so that
can_allocate_more_segments can be const noexcept as well.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
