After this, TWCS reshape procedure can be changed to limit job
to 10% of available space.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
(cherry picked from commit 0ce8ee03f1)
std::optional formatting changed while moving from the home-grown formatter to
the fmt provided formatter; don't rely on it for user visible messages.
Here, the optional formatted is known to be engaged, so just print it.
Closesscylladb/scylladb#18533
since we do not rely on FMT_DEPRECATED_OSTREAM to define the
fmt::formatter for us anymore, let's stop defining `FMT_DEPRECATED_OSTREAM`.
in this change,
* utils: drop the range formatters in to_string.hh and to_string.c, as
we don't use them anymore. and the tests for them in
test/boost/string_format_test.cc are removed accordingly.
* utils: use fmt to print chunk_vector and small_vector. as
we are not able to print the elements using operator<< anymore
after switching to {fmt} formatters.
* test/boost: specialize fmt::details::is_std_string_like<bytes>
due to a bug in {fmt} v9, {fmt} fails to format a range whose
element type is `basic_sstring<uint8_t>`, as it considers it
as a string-like type, but `basic_sstring<uint8_t>`'s char type
is signed char, not char. this issue does not exist in {fmt} v10,
so, in this change, we add a workaround to explicitly specialize
the type trait to assure that {fmt} format this type using its
`fmt::formatter` specialization instead of trying to format it
as a string. also, {fmt}'s generic ranges formatter calls the
pair formatter's `set_brackets()` and `set_separator()` methods
when printing the range, but operator<< based formatter does not
provide these method, we have to include this change in the change
switching to {fmt}, otherwise the change specializing
`fmt::details::is_std_string_like<bytes>` won't compile.
* test/boost: in tests, we use `BOOST_REQUIRE_EQUAL()` and its friends
for comparing values. but without the operator<< based formatters,
Boost.Test would not be able to print them. after removing
the homebrew formatters, we need to use the generic
`boost_test_print_type()` helper to do this job. so we are
including `test_utils.hh` in tests so that we can print
the formattable types.
* treewide: add "#include "utils/to_string.hh" where
`fmt::formatter<optional<>>` is used.
* configure.py: do not define FMT_DEPRECATED_OSTREAM
* cmake: do not define FMT_DEPRECATED_OSTREAM
Refs #13245
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
before this change, we rely on the default-generated fmt::formatter
created from operator<<, but fmt v10 dropped the default-generated
formatter.
in this change, we include `fmt/ranges.h` and/or `fmt/std.h`
for formatting the container types, like vector, map
optional and variant using {fmt} instead of the homebrew
formatter based on operator<<.
with this change, the changes adding fmt::formatter and
the changes using ostream formatter explicitly, we are
allowed to drop `FMT_DEPRECATED_OSTREAM` macro.
Refs scylladb#13245
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
This change adds the missing Cassandra compaction option unchecked_tombstone_compaction.
Setting this option to true causes the compaction to ignore tombstone_threshold,
and decide whether to do a compaction only on the value of tombstone_compaction_interval
The interface is fragile because the user may incorrectly use the
wrong "gc before". Given that sstable knows how to properly calculate
"gc before", let's do it in estimate__d__t__r(), leaving no room
for mistakes.
sstable_run's variant was also changed to conform to new interface,
allowing ICS to properly estimate droppable ratio, using GC before
that is calculated using each sstable's range. That's important for
upcoming tablets, as we want to query only the range that belongs
to a particular tablet in the repair history table.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closesscylladb/scylladb#15931
When off-strategy is disabled, data segregation is not postponed,
meaning that getting partition estimate right is important to
decrease filter's false positives. With streaming, we don't
have min and max timestamps at destination, well, we could have
extended the RPC verb to send them, but turns out we can deduce
easily the amount of windows using default TTL. Given partitioner
random nature, it's not absurd to assume that a given range being
streamed may overlap with all windows, meaning that each range
will yield one sstable for each window when segregating incoming
data. Today, we assume the worst of 100 windows (which is the
max amount of sstables the input data can be segregated into)
due to the lack of metadata for estimating the window count.
But given that users are recommended to target a max of ~20
windows, it means partition estimate is being downsized 5x more
than needed. Let's improve it by using default TTL when
estimating window count, so even on absence of timestamp
metadata, the partition estimation won't be way off.
Fixes#15704.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
After "repair: Get rid of the gc_grace_seconds", the sstable's schema (mode,
gc period if applicable, etc) is used to estimate the amount of droppable
data (or determine full expiration = max_deletion_time < gc_before).
It could happen that the user switched from timeout to repair mode, but
sstables will still use the old mode, despite the user asked for a new one.
Another example is when you play with value of grace period, to prevent
data resurrection if repair won't be able to run in a timely manner.
The problem persists until all sstables using old GC settings are recompacted
or node is restarted.
To fix this, we have to feed latest schema into sstable procedures used
for expiration purposes.
Fixes#15643.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closesscylladb/scylladb#15746
Now everything is prepared for the switch, let's do it.
Now let's wait for ICS to enjoy the set of changes.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Split compaction_strategy_impl constructor into methods that will
be reused for validation.
Add additional checks providing that options' values are legal.
Add compaction_strategy_impl::validate_min_max_threshold method
that will be used to validate min and max threshold values
for different compaction methods.
This is the first phase of providing strong exception safety guarantees by the generic `compaction_backlog_tracker::replace_sstables`.
Once all compaction strategies backlog trackers' replace_sstables provide strong exception safety guarantees (i.e. they may throw an exception but must revert on error any intermediate changes they made to restore the tracker to the pre-update state).
Once this series is merged and ICS replace_sstables is also made strongly exception safe (using infrastructure from size_tiered_backlog_tracker introduced here), `compaction_backlog_tracker::replace_sstables` may allow exceptions to propagate back to the caller rather than disabling the backlog tracker on errors.
Closes#14104
* github.com:scylladb/scylladb:
leveled_compaction_backlog_tracker: replace_sstables: provide strong exception safety guarantees
time_window_backlog_tracker: replace_sstables: provide strong exception safety guarantees
size_tiered_backlog_tracker: replace_sstables: provide strong exception safety guarantees
size_tiered_backlog_tracker: provide static calculate_sstables_backlog_contribution
size_tiered_backlog_tracker: make log4 helper static
size_tiered_backlog_tracker: define struct sstables_backlog_contribution
size_tiered_backlog_tracker: update_sstables: update total_bytes only if set changed
compaction_backlog_tracker: replace_sstables: pass old and new sstables vectors by ref
compaction_backlog_tracker: replace_sstables: add FIXME comments about strong exception safety
This is the last step of deprecation dance of DTCS.
In Scylla 5.1, users were warned that DTCS was deprecated.
In 5.2, altering or creation of tables with DTCS was forbidden.
5.3 branch was already created, so this is targetting 5.4.
Users that refused to move away from DTCS will have Scylla
falling back to the default strategy, either STCS or ICS.
See:
WARN 2023-07-14 09:49:11,857 [shard 0] schema_tables - Falling back to size-tiered compaction strategy after the problem: Unable to find compaction strategy class 'DateTieredCompactionStrategy
Then user can later switch to a supported strategy with
alter table.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closes#14559
By making all changes on temporary variables
and eventually moving them back into the tracker members
in a noexcept block the function can safely throw
until the changes are committed.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Instead of providing refresh_sstables_backlog_contribution
that updates the tracker in place, provide a static function
calculate_sstables_backlog_contribution that doesn't change
the tracker state to facilitate exception safety in the next patch.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Encapsulate the contribution-related members in
struct contribution, to be used for strong exception safety.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Although replace_sstables is supposed to be called
only once per {old_ssts, new_ssts} it is safer
to update `_total_bytes` with `sst->data_size()`
only if the sst was inserted/erased successfully.
Otherwise _total_bytes may go out of sync with the
contents of _all.
That said, the next step should be to refer to the
compaction_group's main sstable set directly rather
than maintaining a "shadow" set in the tracker.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
In that level no io_priority_class-es exist. Instead, all the IO happens
in the context of current sched-group. File API no longer accepts prio
class argument (and makes io_intent arg mandatory to impls).
So the change consists of
- removing all usage of io_priority_class
- patching file_impl's inheritants to updated API
- priority manager goes away altogether
- IO bandwidth update is performed on respective sched group
- tune-up scylla-gdb.py io_queues command
The first change is huge and was made semi-autimatically by:
- grep io_priority_class | default_priority_class
- remove all calls, found methods' args and class' fields
Patching file_impl-s is smaller, but also mechanical:
- replace io_priority_class& argument with io_intent* one
- pass intent to lower file (if applicatble)
Dropping the priority manager is:
- git-rm .cc and .hh
- sed out all the #include-s
- fix configure.py and cmakefile
The scylla-gdb.py update is a bit hairry -- it needs to use task queues
list for IO classes names and shares, but to detect it should it checks
for the "commitlog" group is present.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Closes#13963
once compaction_strategy is made staless, the state must be retrieved
in notify_completion() through table_state.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Schema related files are moved there. This excludes schema files that
also interact with mutations, because the mutation module depends on
the schema. Those files will have to go into a separate module.
Closes#12858
LCS backlog tracker uses STCS tracker for L0. Turns out LCS tracker
is calling STCS tracker's replace_sstables() with empty arguments
even when higher levels (> 0) *only* had sstables replaced.
This unnecessary call to STCS tracker will cause it to recompute
the L0 backlog, yielding the same value as before.
As LCS has a fragment size of 0.16G on higher levels, we may be
updating the tracker multiple times during incremental compaction,
which operates on SSTables on higher levels.
Inefficiency is fixed by only updating the STCS tracker if any
L0 sstable is being added or removed from the table.
This may be fixing a quadratic behavior during boot or refresh,
as new sstables are loaded one by one.
Higher levels have a substantial higher number of sstables,
therefore updating STCS tracker only when level 0 changes, reduces
significantly the number of times L0 backlog is recomputed.
Refs #12499.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closes#12676
Today, compaction_backlog_tracker is managed in each compaction_strategy
implementation. So every compaction strategy is managing its own
tracker and providing a reference to it through get_backlog_tracker().
But this prevents each group from having its own tracker, because
there's only a single compaction_strategy instance per table.
To remove this limitation, compaction_strategy impl will no longer
manage trackers but will instead provide an interface for trackers
to be created, such that each compaction group will be allowed to
have its own tracker, which will be managed by compaction manager.
On compaction strategy change, table will update each group with
the new tracker, which is created using the previously introduced
ompaction_group_sstable_set_updater.
Now table's backlog will be the sum of all compaction_group backlogs.
The normalization factor is applied on the sum, so we don't have
to adjust each individual backlog to any factor.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Pass the tombstone_gc_state from the compaction_strategy
to sstables get_gc_before_* functions using the table state
to get to the tombstone_gc_state.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
With compaction_manager switching to table_state, we'll need to
introduce a method in table_state to return maintenance set.
So better to have a descriptive name for main set.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
We should separate the scheduling groups used for major compaction
from the the regular compaction scheduling group so that
the latter can be affected by the backlog tracker in case
backlog accumulates during a long running major compaction.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
The backlog definition for leveled is incorrectly built on the assumption that
the world must reach the state of zero amplification, i.e. everything in the
last level. The actual goal is space amplification of 1.1.
In reality, LCS just wants that for every level L, level L is fan_out=10 times
larger than L-1. See more in commit 9de7abdc80 which adjusts LCS to conform
to this goal.
If level 3 = 1000G, level 2 = 100G, level 1 = 10G, level 0 = 1G, that should
return zero backlog as space amplification is (1000+100+10+1)/1000 = ~1.1
But today, LCS calculates high backlog for the layout above, as it will only be
satisfied once everything is promoted to the maximum level. That's completely
disconnected from what the strategy actually wants. Therefore, a mismatch.
With today's definition, the backlog for any SSTable is:
sizeof(sstable) * (Lmax - levelof(sstable)) * fan_out
where Lmax = maximum level,
and fan_out = LCS' fan out which is 10 by default
That's essentially calculating the total cost for data in the SSTable to climb
up to the maximum level. Of course, if a SSTable is at the maximum level,
(Lmax - levelof(sstable)) returns zero, therefore backlog for it is zero.
Take a look at this example:
If L0 sstable is 0.16G, then its backlog = 0.16G * (3 - 0) * 10 = 4.8G
0.16G = LCS' default fragment size
Maximum level (Lmax in formula) can be easily 3 as:
log10 of (30G/0.16G=~187 sstables)) = ~2.27
~2.27 means that data has exceeded level 2 capacity and so needs 3 levels.
So 3 L0 sstables could add ~15G of backlog. With 1G memory per shard (30:1 disk
memory ratio), that's normalized backlog of ~15, which translates into
additional ~500 shares. That's halfway to full compaction speed.
With more files in higher levels, we can easily get to a normalized backlog
above 30, resulting in 1k shares.
The suboptimal backlog definition causes either table using LCS or coexisting
tables to run with more shares than needed, causing compaction to steal
resources, resulting in higher latency and reduced throughput.
To solve this problem, a new formula is used which will basically calculate
the amount of work needed to achieve the layout goal. We no longer want to
promote everything to the last level, but instead we'll incrementally calculate
the backlog in each level L, which is the amount of work needed such that the
next level L + 1 is at least fan_out times bigger.
Fixes#10583.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
No functional changes intended - this series is quite verbose,
but after it's in, it should be considerably easier to change
the type of SSTable generations to something else - e.g. a string
or timeUUID.
Closes#10533
Then caller can decide whether to copy or move candidate set into the
function. cleanup_sstables_compaction_task can move candidates as
it's no longer needed once it retrieves all descriptors.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Today, all compaction strategies will clean up their files using the
incremental approach of one sstable being rewritten at a time.
Turns out that's not the best approach performance wise. Let's take
STCS for example. As cleanup finishes rewriting one file, the output
file is placed into the sstable set. Regular now can compact that
file with another that was already there (e.g. produced by flush after
cleanup started). Inefficient compactions like this can keep happening
as cleanup incrementally places output file into the candidate list
for regular.
This method will allow strategies to clean up their files in batches.
For example, STCS can clean up all files in smallest tiers in single
round, allowing the output data to be added at once. So next compaction
rounds can be more efficient in terms of writeamp. Another benefit is
that deduplication and GC can happen more efficiently.
The drawback is the space requirement, as we no longer compact one file
a a time. However, the impact is minimized by cleaning up the smallest
tier first. With leveled strategy for example, even though 90% of data
is in highest level, the space requirement is not a problem because
we can apply the incremental compaction on its behalf. The same applies
to ICS. With STCS, the requirement is the size of the tier being
compacted, but that's already expected by its users anyway.
By the time being, all strategies have it unimplemented. so they still
use the old behavior where files are rewritten on at a time.
This will allow us to incrementally implement the cleanup method for
all compaction strategies.
Refs #10097.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
For compaction to be able to purge expired data, like tombstones, a
sstable set snapshot is set in the compaction descriptor.
That's a decision that belongs to task type. For example, all regular
compaction enable GC, whereas scrub for example doesn't for safety
reasons.
The problem is that the decision is being made by every instantiation
of compaction_descriptor in the strategies, which is both unnecessary
and also adds lots of boilerplate to the code, making it hard to
understand and work with.
As sstable set snapshot is an implementation detail, a new method
is being added to compaction_descriptor to make the intention
clearer, making the interface easier to understand.
can_purge_tombstones, used previously by rewrite task only, is being
reused for communicating GC intention into task::compact_sstables().
The boilerplate was a pain when adding a new strategy method for
the ongoing work on cleanup, described by issue #10097.
Another benefit is that we'll now only create a set snapshot when
compaction will really run. Before, it could happen that the snapshot
would be discarded if the compaction attempt had to be postponed,
which is a waste of cpu cycles.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Introduced in commit: ddd693c6d7
We're not emplacing newer windows in the tracker, causing
std::out_of_range when replacing sstables for windows.
Let's fix the logic and add an unit test to cover this.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20220301194944.95096-1-raphaelsc@scylladb.com>
Today, compaction can act much more aggressive than it really has to, because
the strategy and its definition of backlog are completely decoupled.
The backlog definition for size-tiered, which is inherited by all
strategies (e.g.: LCS L0, TWCS' windows), is built on the assumption that the
world must reach the state of zero amplification. But that's unrealistic and
goes against the intent amplification defined by the compaction strategy.
For example, size tiered is a write oriented strategy which allows for extra
space amplification for compaction to keep up with the high write rate.
It can be seen today, in many deployments, that compaction shares is either
close to 1000, or even stuck at 1000, even though there's nothing to be done,
i.e. the compaction strategy is completely satisfied.
When there's a single sstable per tier, for example.
This means that whenever a new compaction job kicks in, it will act much more
aggressive because of the high shares, caused by false backlog of the existing
tables. This translates into higher P99 latencies and reduced throughput.
Solution
========
This problem can be fixed, as proposed in the document "Fixing compaction
aggressiveness due to suboptimal definition of zero backlog by controller" [1],
by removing backlog of tiers that don't have to be compacted now, like a tier
that has a single file. That's about coupling the strategy goal with the
backlog definition. So once strategy becomes satisfied, so will the controller.
Low-efficiency compaction, like compacting 2 files only or cross-tier, only
happens when system is under little load and can proceed at a slower pace.
Once efficient jobs show up, ongoing compactions, even if inefficient, will get
more shares (as efficient jobs add to the backlog) so compaction won't fall
behind.
With this approach, throughput and latency is improved as cpu time is no longer
stolen (unnecessarily) from the foreground requests.
[1]: https://docs.google.com/document/d/1EQnXXGWg6z7VAwI4u8AaUX1vFduClaf6WOMt2wem5oQFixes#4588.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
This new interface allows table to communicate multiple changes in the
SSTable set with a single call, which is useful on compaction completion
for example.
With this new interface, the size tiered backlog tracker will be able to
know when compaction completed, which will allow it to recompute tiers
and their backlog contribution, if any. Without it, tiered tracker
would have to recompute tiers for every change, which would be terribly
expensive.
The old remove/add interface are being removed in favor of the new one.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Instead of lengthy blurbs, switch to single-line, machine-readable
standardized (https://spdx.dev) license identifiers. The Linux kernel
switched long ago, so there is strong precedent.
Three cases are handled: AGPL-only, Apache-only, and dual licensed.
For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0),
reasoning that our changes are extensive enough to apply our license.
The changes we applied mechanically with a script, except to
licenses/README.md.
Closes#9937
