Add a test that drops a table while tablet streaming is running for the
table. The table is dropped after taking the storage snapshot and
initializating streaming sources - after that streaming should be able
to complete or abort correctly if the table is dropped. We want to
verify there is no incorrect access to the destroyed table.
The test tests both types of streaming in stream_blob - sstables
and logstor segments.
Apply filter_errors() to grep_for_errors() results in
test_split_stopped_on_shutdown and
test_group0_apply_while_node_is_being_shutdown. Without filtering,
benign RPC errors like 'connection dropped: Semaphore broken' that
occur during graceful shutdown cause spurious test failures.
The test was failing because the call to:
await log.wait_for('Stopping.*ongoing compactions')
was missing the 'from_mark=log_mark' argument. The log mark was updated
(line: log_mark = await log.mark()) immediately after detecting
'splitting_mutation_writer_switch_wait: waiting', and just before
launching the shutdown task. However, the wait_for call on the following
line was scanning from the beginning of the log, not from that mark.
As a result, the search immediately matched old 'Stopping N tasks for N
ongoing compactions for table system.X due to table removal' messages
emitted during initial server bootstrap (for system.large_partitions,
system.large_rows, system.large_cells), rather than waiting for the
shutdown to actually stop the user-table split compaction.
This caused the test to prematurely send the message to the
'splitting_mutation_writer_switch_wait' injection. The split compaction
was unblocked before the shutdown had aborted it, so it completed
successfully. Since the split succeeded, 'Failed to complete splitting
of table' was never logged.
Meanwhile, 'storage_service_drain_wait' was blocking do_drain() waiting
for a message. With the split already done, the test was stuck waiting
for the expected failure log that would never come (600s timeout). At
the same time, after 60s the 'storage_service_drain_wait' injection
timed out internally, triggering on_internal_error() which -- with
--abort-on-internal-error=1 -- crashed the server (exit code -6).
Fix: pass from_mark=log_mark to the wait_for('Stopping.*ongoing
compactions') call so it only matches messages that appear after the
shutdown has started, ensuring the test correctly synchronizes with the
shutdown aborting the user-table split compaction before releasing the
injection.
Fixes https://scylladb.atlassian.net/browse/SCYLLADB-1319.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Closesscylladb/scylladb#29311
Run keyspace compaction asynchronously in
`test_tombstone_gc_correctness_during_tablet_split` and only await it
after `split_sstable_rewrite` is disabled.
The problem is that `keyspace_compaction()` starts with a flush, and that
flush can take around five seconds. During that window the split
compaction is stopped before major compaction is retried. The stop aborts
the in-flight major compaction attempt, then the split proceeds far enough
to enter the `split_sstable_rewrite` injection point.
At that point the test used to wait synchronously for major compaction to
finish, but major compaction cannot finish yet: when it retries, it needs
the same semaphore that is still effectively tied up behind the blocked
split rewrite. So the test waits for major compaction, while the split
waits for the injection to be released, and the code that would release
that injection never runs.
Starting major compaction as a task breaks that cycle. The test can first
disable `split_sstable_rewrite`, let the split get out of the way, and
only then wait for major compaction to complete.
Fixes https://scylladb.atlassian.net/browse/SCYLLADB-827.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closesscylladb/scylladb#29066
Since commit 509f2af8db, gate_closed_exception can be triggered for ongoing split during shutdown. The commit is correct, but it causes split failure on shutdown to log an error, which causes CI instability. Previously, aborted_exception would be triggered instead which is logged as warning. Let's do the same.
Fixes https://scylladb.atlassian.net/browse/SCYLLADB-951.
Fixes https://github.com/scylladb/scylladb/issues/24850.
Only 2026.1 is affected.
Closesscylladb/scylladb#29032
* github.com:scylladb/scylladb:
replica: Demote log level on split failure during shutdown
service: Demote log level on split failure during shutdown
This test was observed to fail in CI recently but there is not enough information in the logs to figure out what went wrong. This PR makes a few improvements to make the next investigation easier, should it be needed:
* storage-service: add table name to mutation write failure error messages.
* database: the `database_apply` error injection used to cause trouble, catching writes to bystander tables, making tests flaky. To eliminate this, it gained a filter to apply only to non-system keyspaces. Unfortunately, this still allows it to catch writes to the trace tables. While this should not fail the test, it reduces observability, as some traces disappear. Improve this error injection to only apply to selected table. Also merge it with the `database_apply_wait` error injection, to streamline the code a bit.
* test/test_data_resurrection_in_memtable.py: dump data from the datable, before the checks for expected data, so if checks fail, the data in the table is known.
Refs: SCYLLADB-812
Refs: SCYLLADB-870
Fixes: SCYLLADB-1050 (by restricting `database_apply` error injection, so it doesn't affect writes to system traces)
Backport: test related improvement, no backport
Closesscylladb/scylladb#28899
* github.com:scylladb/scylladb:
test/cluster/test_data_resurrection_in_memtable.py: dump rows before check
replica/database: consolidate the two database_apply error injections
service/storage_proxy: add name of table to error message for write errors
Since commit 509f2af8db, gate_closed_exception can be triggered
for ongoing split during shutdown. The commit is correct, but it
causes split failure on shutdown to log an error, which causes
CI instability. Previously, aborted_exception would be triggered
instead which is logged as warning. Let's do the same.
Fixes https://scylladb.atlassian.net/browse/SCYLLADB-951.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
changes in this commit:
1)rename class from 'TestContext' to 'Context' so pytest will not consider this class as a test
2)extend pytest filterwarnings list to ignore warnings from external libs
3) use datetime.datetime.now(datetime.UTC) unstead datetime.datetime.utcnow()
4) use ResultSet.one() instead ResultSet[0]
Fixes SCYLLADB-904
Fixes SCYLLADB-908
Related SCYLLADB-902
Closesscylladb/scylladb#28956
Into a single database_apply one. Add three parameters:
* ks_name and cf_name to filter the tables to be affected
* what - what to do: throw or wait
This leads to smaller footprint in the code and improved filtering for
table names at the cost of some extra error injection params in the
tests.
Add explicit erm-holding variables in all replica-side RPC handlers.
This is required to ensure that tablet migration waits for in-flight
replica requests even if a non-replica coordinator has been fenced out.
Holding erms on the replica side may increase the global-barrier wait
time, since the barrier must drain these requests. We believe this
is acceptable because:
* We already hold erms during replica-side request execution, but in
an ad-hoc, non-systemic way in lower layers of storage_proxy
(e.g. in sp::mutate_locally and do_query_tablets).
* Replica requests are bounded by replica-side timeouts, so the
global-barrier wait time cannot exceed the maximum of these timeouts.
For Paxos verbs, we use token_metadata_guard, which wraps the ERM and
automatically refreshes it when tablet migration does not affect the
current token; see the token_metadata_guard comments for details.
We use this guard only for Paxos verbs because regular reads and writes
already hold raw erms in storage_proxy and on the coordinators.
The erms must be held in all RPC handlers that support fencing — that
is, those with a fencing_token parameter in storage_proxy.idl.
Counter updates already hold erms in
mutate_counter_on_leader_and_replicate.
Fix test_tablets2::test_timed_out_reader_after_cleanup: the tablets
barrier now waits for all nodes. As a result, the replica read
is expected to finish, rather than fail due to the tablet having
moved as it did previously. The test is renamed to
test_tablets_barrier_waits_for_replica_erms to better reflect its
purpose.
Refs scylladb/scylladb#26864
This patch adds a test and reproducer for the issue where the load_stats
refresh procedure throws exceptions if any of the tables have been
dropped since load_stats was produced.
Finishing the deprecation of the skip_mode function in favor of
pytest.mark.skip_mode. This PR is only cleaning and migrating leftover tests
that are still used and old way of skip_mode.
Closesscylladb/scylladb#28299
If a test tries to move a tablet, it assumes the tablets are stable.
This fixes flakiness exposed by size-based load-balancing and a later
change to refresh stats sooner.
Function skip_mode works only on function and only in cluster test. This if OK
when we need to skip one test, but it's not possible to use it with pytestmark
to automatically mark all tests in the file. The goal of this PR is to migrate
skip_mode to be dynamic pytest.mark that can be used as ordinary mark.
Closesscylladb/scylladb#27853
[avi: apply to test/cluster/test_tablets.py::test_table_creation_wakes_up_balancer]
Disable load balancing to avoid the balancer moving the tablet from a
node with less to a node with more available disk space. Otherwise, the
move_tablet API can fail (if the tablet is already in transisiton) or
be a no-op (in case the tablet has already been migrated)
Fixes: #27980Closesscylladb/scylladb#27993
This changes introduces tablet size based load balancing. It is an
extension of capacity based balancing with the addition of actual tablet
sizes.
It computes the difference between the most and least loaded nodes in
the DC and stops further balancing if this difference is bellow the
config option size_based_balance_threshold_percentage.
This config option does not apply to the absolute load, but instead to
the percentage of how much the most loaded node is more loaded than the
least loaded node:
delta = (most_loaded - least_loaded) / most_loaded
If this delta is smaller then the config threshold, the balancer will
consider the nodes balanced.
This is a problem caught after removing split from
add_sstable_and_update_cache(), which was used by
intra node migration when loading new sstables
into the destination shard.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
The test test_truncate_during_topology_change tests TRUNCATE TABLE while
bootstrapping a new node. With tablets enabled TRUNCATE is a global
topology operation which needs to serialize with boostrap.
When TRUNCATE TABLE is issued, it first checks if there is an already
queued truncate for the same table. This can happen if a previous
TRUNCATE operation has timed out, and the client retried. The newly
issued truncate will only join the queued one if it is waiting to be
processed, and will fail immediatelly if the TRUNCATE is already being
processed.
In this test, TRUNCATE will be retried after a timeout (1 minute) due to
the default retry policy, and will be retried up to 3 times, while the
bootstrap is delayed by 2 minutes. This means that the test can validate
the result of a truncate which was started after bootstrap was
completed.
Because of the way truncate joins existing truncate operations, we can
also have the following scenario:
- TRUNCATE times out after one minute because the new node is being
bootstrapped
- the client retries the TRUNCATE command which also times out after 1m
- the third attempt is received during TRUNCATE being processed which
fails the test
This patch changes the retry policy of the TRUNCATE operation to
FallthroughRetryPolicy which guarantees that TRUNCATE will not be
retried on timeout. It also increases the timeout of the TRUNCATE from 1
to 4 minutes. This way the test will actually validate the performance
of the TRUNCATE operation which was issued during bootstrap, instead of
the subsequent, retried TRUNCATEs which could have been issued after the
bootstrap was complete.
Fixes: #26347Closesscylladb/scylladb#27245
This change adds tests for the correctness of tablet size migration
during the end_migrations stage. This size migration can happend for
tablet migrations and for tablet rebuild.
Consider the following:
1) single-key read starts, blocks on replica e.g. waiting for memory.
2) the same replica is migrated away
3) single-key read expires, coordinator abandons it, releases erm.
4) migration advances to cleanup stage, barrier doesn't wait on
timed-out read
5) compaction group of the replica is deallocated on cleanup
6) that single-key resumes, but doesn't find sstable set (post cleanup)
7) with abort-on-internal-error turned on, node crashes
It's fine for abandoned (= timed out) reads to fail, since the
coordinator is gone.
For active reads (non timed out), the barrier will wait for them
since their coordinator holds erm.
This solution consists of failing reads which underlying tablet
replica has been cleaned up, by just converting internal error
to plain exception.
Fixes#26229.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closesscylladb/scylladb#27078
The patch c543059f86 fixed the synchronization issue between tablet
split and load-and-stream. The synchronization worked only with
raft topology, and therefore was disabled with gossip.
To do the check, storage_service::raft_topology_change_enabled()
but the topology kind is only available/set on shard 0, so it caused
the synchronization to be bypassed when load-and-stream runs on
any shard other than 0.
The reason the reproducer didn't catch it is that it was restricted
to single cpu. It will now run with multi cpu and catch the
problem observed.
Fixes#22707
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closesscylladb/scylladb#26730
When streaming SSTables across tablets, a single SSTable may be streamed to multiple tablets. The previous implementation unlinked SSTables immediately after streaming them for the first tablet, potentially making them partially unavailable for subsequent tablets. This patch replaces unlink() with mark_for_deletion() deferring actual unlinking till sstable::close_files.
test_tablets2::test_tablet_load_and_stream was enhanced to also verify that SSTables are removed after being streamed.
Fixes#26606
Backport is not required, although it is a bug fix, but it isn't visible. This is more of a preparatory fix for https://github.com/scylladb/scylladb/pull/26444.
Closesscylladb/scylladb#26622
* github.com:scylladb/scylladb:
test_tablets2: verify SSTable cleanup after tablet load and stream
tablet_sstable_streamer: replace unlink() call with mark_for_deletion()
Load-and-stream is broken when running concurrently to the finalization step of tablet split.
Consider this:
1) split starts
2) split finalization executes barrier and succeed
3) load-and-stream runs now, starts writing sstable (pre-split)
4) split finalization publishes changes to tablet metadata
5) load-and-stream finishes writing sstable
6) sstable cannot be loaded since it spans two tablets
two possible fixes (maybe both):
1) load-and-stream awaits for topology to quiesce
2) perform split compaction on sstable that spans both sibling tablets
This patch implements # 1. By awaiting for topology to quiesce,
we guarantee that load-and-stream only starts when there's no
chance coordinator is handling some topology operation like
split finalization.
Fixes https://github.com/scylladb/scylladb/issues/26455.
Closesscylladb/scylladb#26456
* github.com:scylladb/scylladb:
test: Add reproducer for l-a-s and split synchronization issue
sstables_loader: Synchronize tablet split and load-and-stream
Greatly improves performance of plan making, because we don't consider
candidates in other racks, most of which will fail to be selected due
to replication constraints (no rack overload). Also (but minor)
reduces the overhead of candidate evaluation, as we don't have to
evaluate rack load.
Enabled only for rf_rack_valid_keyspaces because such setups guarantee
that we will not need (because we must not) move tablets across racks,
and we don't need to execute the general algorithm for the whole DC.
Tested with perf-load-balancing, which performs a single scale-out
operation on a cluster which initially has 10 nodes 88 shards each, 2
racks, RF=2, 70 tables, 256 tablets per table. Scale out adds 6 new
nodes (same shard count). Time to rebalance the cluster (plan making
only, sum of all iterations, no streaming):
Before: 16 min 25 s
After: 0 min 25 s
Before, plan making cost (single incremental iteration) alternated
between fast (0.1 [s]) and slow (14.1 [s]):
Rebalance iteration 7 took 14.156 [s]: mig=88, bad=88, first_bad=17741, eval=93874484, skiplist=0, skip: (load=0, rack=17653, node=0)
Rebalance iteration 8 took 0.143 [s]: mig=88, bad=88, first_bad=88, eval=865407, skiplist=0, skip: (load=0, rack=0, node=0)
The slow run chose min and max nodes in different racks, hence the
fast path failed to find any candidates and we switched to exhaustive
search of candidates in other nodes.
After, all iterations are fast (0.1 [s] per rack, 0.2 [s] per plan-making).
The plan is twice as large because it combines the output of two subsequent (pre-patch)
plan-making calls.
Fixes#26016
Consider the following:
1) balancer emits split decision
2) split compaction starts
3) split decision is revoked
4) emits merge decision
5) completes merge, before compaction in step 2 finishes
After last step, split compaction initiated in step 2 can fail
because it works with the global tablet map, rather than the
map when the compaction started. With the global state changing
under its feet, on merge, the mutation splitting writer will
think it's going backwards since sibling tablets are merged.
This problem was also seen when running load-and-stream, where
split initiated by the sstable writer failed, split completed,
and the unsplit sstable is left in the table dir, causing
problems in the restart.
To fix this, let's make split compaction always work with
the state when it started, not a global state.
Fixes#24153.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
In the ScyllaMetrics `get` function, when requesting the value for a
specific shard, it is expected to return the sum of all values of
metrics for that shard that match the labels.
However, it would return the value of the first matching line it finds
instead of summing all matching lines.
For example, if we have two lines for one shard like:
some_metric{scheduling_group_name="compaction",shard="0"} 1
some_metric{scheduling_group_name="sl:default",shard="0"} 2
The result of this call would be 1 instead of 3:
get('some_metric', shard="0")
We fix this to sum all matching lines.
The filtering of lines by labels is fixed to allow specifying only some
of the labels. Previously, for the line to match the filter, either the
filter needs to be empty, or all the labels in the metric line had to be
specified in the filter parameter and match its value, which is
unexpected, and breaks when more labels are added.
We also simplify the function signature and the implementation - instead
of having the shard as a separate parameter, it can be specified as a
label, like any other label.
introduce tiering marks
1 “unstable” - For unstable tests that will be will continue runing every night and generate up-to-date statistics with failures without failing the “Main” verification path(scylla-ci, Next)
2 “nightly” - for tests that are quite old, stable, and test functionality that rather not be changed or affected by other features, are partially covered in other tests, verify non-critical functionality, have not found any issues or regressions, too long to run on every PR, and can be popped out from the CI run.
set 7 long tests(according to statistic in elastic) as nightly(theses 8 tests took 20% of CI run,
about 4 hours without paralelization)
1 test as unstable(as exaple ot marker usage)
Closesscylladb/scylladb#24974
This commits introduces an config option 'tablet_load_stats_refresh_interval_in_seconds'
that allows overriding the default value without using error injection.
Fixesscylladb/scylladb#24641Closesscylladb/scylladb#24746
A tablet repair started with /storage_service/repair_async/ API
bypasses tablet repair scheduler and repairs only the tablets
that are owned by the requested node. Due to that, to safely repair
the whole keyspace, we need to first disable tablet migrations
and then start repair on all nodes.
With the new API - /storage_service/tablets/repair -
tailored to tablet repair requirements, we do not need additional
preparation before repair. We may request it on one node in
a cluster only and, thanks to tablet repair scheduler,
a whole keyspace will be safely repaired.
Both nodetool and Scylla Manager have already started using
the new API to repair tablets.
Refuse repairing tablet keyspaces with /storage_service/repair_async -
403 Forbidden is returned. repair_async should still be used to repair
vnode keyspaces.
Fixes: https://github.com/scylladb/scylladb/issues/23008.
Breaking change; no backport.
Closesscylladb/scylladb#24678
* github.com:scylladb/scylladb:
repair: remove unused code
api: repair_async: forbid repairing tablet keyspaces
The test test_tombstone_gc_disabled_on_pending_replica was added when
we fixed (#20788) the potential problem with data resurrection during
file based streaming. The issue was occurring only in Enterprise, but
we added the fix in OSS to limit code divergence. This test was added
together with the fix in OSS with the idea to guard this change in OSS.
The real reproducer and test for this fix was added later, after the
fix was ported into Enterprise.
It is in: test/cluster/test_resurrection.py
Since Enterprise has been merged into OSS, there is no more need to
keep the test test_tombstone_gc_disabled_on_pending_replica. Also,
it is flaky with very low probability of failure, making it difficult
to investigate the cause of failure.
Fixes: #22182Closesscylladb/scylladb#25134
Some of the tests in the test suite have proven to be more problematic
in adjusting to RF-rack-validity. Since we'd like to run as many tests
as possible with the `rf_rack_valid_keyspaces` configuration option
enabled, let's disable it in those. In the following commit, we'll enable
it by default.
We adjust all of the simple cases of cluster tests so they work
with `rf_rack_valid_keyspaces: true`. It boils down to assigning
nodes to multiple racks. For most of the changes, we do that by:
* Using `pytest.mark.prepare_3_racks_cluster` instead of
`pytest.mark.prepare_3_nodes_cluster`.
* Using an additional argument -- `auto_rack_dc` -- when calling
`ManagerClient::servers_add()`.
In some cases, we need to assign the racks manually, which may be
less obvious, but in every such situation, the tests didn't rely
on that assignment, so that doesn't affect them or what they verify.
When schema is changed, sstable set is updated according to the compaction
strategy of the new schema (no changes to set are actually made, just
the underlying set type is updated), but the problem is that it happens
without a lock, causing a use-after-free when running concurrently to
another set update.
Example:
1) A: sstable set is being updated on compaction completion
2) B: schema change updates the set (it's non deferring, so it
happens in one go) and frees the set used by A.
3) when A resumes, system will likely crash since the set is freed
already.
ASAN screams about it:
SUMMARY: AddressSanitizer: heap-use-after-free sstables/sstable_set.cc ...
Fix is about deferring update of the set on schema change to compaction,
which is triggered after new schema is set. Only strategy state and
backlog tracker are updated immediately, which is fine since strategy
doesn't depend on any particular implementation of sstable set, since
patch "sstables: Implement sstable_set_impl::all_sstable_runs()".
Fixes#22040.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
When running those operations after a tablet replica is migrated away from
a shard, an assert can fail resulting in a crash.
Status quo (around the assert in truncate procedure):
1) Highest RP seen by table is saved in low_mark, and the current time in
low_mark_at.
2) Then compaction is disabled in order to not mix data written before truncate,
and data written later.
3) Then memtable is flushed in order for the data written before truncate to be
available in sstables and then removed.
4) Now, current time is saved in truncated_at, which is supposedly the time of
truncate to decide which sstables to remove.
Note: truncated_at is likely above low_mark_at due to steps 2 and 3.
The interesting part of the assert is:
(truncated_at <= low_mark_at ? rp <= low_mark : low_mark <= rp)
Note: RP in the assert above is the highest RP among all sstables generated
before truncated_at. RP is retrieved by table::discard_sstables().
If truncated_at > low_mark_at, maybe newer data was written during steps 2 and
3, and memtable's RP becomes greater than low_mark, resulting in a SSTable with
RP > low_mark.
So assert's 2nd condition is there to defend against the scenario above.
truncated_at and low_mark_at uses millisecond granularity, so even if
truncated_at == low_mark_at, data could have been written in steps 2 and 3
(during same MS window), failing the assert. This is fragile.
Reproducer:
To reproduce the problem, truncated_at must be > low_mark_at, which can easily
happen with both drop table and truncate due to steps 2 and 3.
If a shard has 2 or more tablets, the table's highest RP refer to just one
tablet in that shard.
If the tablet with the highest RP is migrated away, then the sstables in that
shard will have lower RP than the recorded highest RP (it's a table wide state,
which makes sense since CL is shared among tablets).
So when either drop table or truncate runs, low_mark will be potentially bigger
than highest RP retrieved from sstables.
Proposed solution:
The current assert is hacked to not fail if writes sneak in, during steps 2 and
3, but it's still fragile and seems not to serve its real purpose, since it's
allowing for RP > low_mark.
We should be able to say that low_mark >= RP, as a way of asserting we're not
leaving data targeted by truncate behind (or that we're not removing the wrong
data).
But the problem is that we're saving low_mark in step 1, before preparation
steps (2 and 3). When truncated_at is recorded in step 4, it's a way of saying
all data written so far is targeted for removal. But as of today, low_mark
refers to all data written up to step 1. So low_mark is now only one set
before issuing flush, and also accounts for all potentially flushed data.
Fixes#18059.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closesscylladb/scylladb#23560
The new option deprecates the existing `enable_tablets` option.
It will be extended in the next patch with a 3rd value: "enforced"
while will enable tablets by default for new keyspace but
without the posibility to opt out using the `tablets = {'enabled':
false}` keyspace schema option.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
There are two semaphores in table for synchronizing changes to sstable list:
sstable_set_mutation_sem: used to serialize two concurrent operations updating
the list, to prevent them from racing with each other.
sstable_deletion_sem: A deletion guard, used to serialize deletion and
iteration over the list, to prevent iteration from finding deleted files on
disk.
they're always taken in this order to avoid deadlocks:
sstable_set_mutation_sem -> sstable_deletion_sem.
problem:
A = tablet cleanup
B = take_snapshot()
1) A acquires sstable_set_mutation_sem for updating list
2) A acquires sstable_deletion_sem, then delete sstable before updating list
3) A releases sstable_deletion_sem, then yield
4) B acquires sstable_deletion_sem
5) B iterates through list and bumps sstable deleted in step 2
6) B fails since it cannot find the file on disk
Initial reaction is to say that no procedure must delete sstable before
updating the list, that's true.
But we want a iteration, running concurrently to cleanup, to not find sstables
being removed from the system. Otherwise, e.g. snapshot works with sstables
of a tablet that was just cleaned up. That's achieved by serializing iteration
with list update.
Since sstable_deletion_sem is used within the scope of deletion only, it's
useless for achieving this. Cleanup could acquire the deletion sem when
preparing list updates, and then pass the "permit" to deletion function, but
then sstable_deletion_sem would essentially become sstable_set_mutation_sem,
which was created exactly to protect the list update.
That being said, it makes sense to merge both semaphores. Also things become
easier to reason about, and we don't have to worry about deadlocks anymore.
The deletion goes through sstable_list_builder, which holds a permit throughout
its lifetime, which guarantees that list updates and deletion are atomic to
other concurrent operations. The interface becomes less error prone with that.
It allowed us to find discard_sstables() was doing deletion without any permit,
meaning another race could happen between truncate and snapshot.
So we're fixing race of (truncate|cleanup) with take_snapshot, as far as we
know. It's possible another unknown races are fixed as well.
Fixes#23049.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closesscylladb/scylladb#23117
