Commit Graph

512 Commits

Author SHA1 Message Date
Botond Dénes
ea29fe579b Merge 'replica: ignore cleanup of deallocated storage group' from Aleksandra Martyniuk
Cleanup of a deallocated tablet throws an exception.
Since failed cleanup is retried, we end up in an infinite loop.

Ignore cleanup of deallocated storage groups.

Fixes:  #19752.

Needs to be backported to all branches with tablets (6.0 and later)

Closes scylladb/scylladb#20584

* github.com:scylladb/scylladb:
  test: check if cleanup of deallocated sg is ignored
  replica: ignore cleanup of deallocated storage group
2024-09-16 09:22:56 +03:00
Aleksandra Martyniuk
20d6cf55f2 replica: ignore cleanup of deallocated storage group
Currently, attempt to cleanup deallocated storage group throws
an exception. Failed tablet cleanup is retried, stucking
in an endless loop.

Ignore cleanup of deallocated storage group.
2024-09-13 13:00:53 +02:00
Botond Dénes
c7c5817808 Merge 'Improve timestamp heuristics for tombstone garbage collection' from Benny Halevy
When purging regular tombstone consult the min_live_timestamp, if available.
This is safe since we don't need to protect dead data from resurrection, as it is already dead.

For shadowable_tombstones, consult the min_memtable_live_row_marker_timestamp,
if available, otherwise fallback to the min_live_timestamp.

If we see in a view table a shadowable tombstone with time T, then in any row where the row marker's timestamp is higher than T the shadowable tombstone is completely ignored and it doesn't hide any data in any column, so the shadowable tombstone can be safely purged without any effect or risk resurrecting any deleted data.

In other words, rows which might cause problems for purging a shadowable tombstone with time T are rows with row markers older or equal T. So to know if a whole sstable can cause problems for shadowable tombstone of time T, we need to check if the sstable's oldest row marker (and not oldest column) is older or equal T. And the same check applies similarly to the memtable.

If both extended timestamp statistics are missing, fallback to the legacy (and inaccurate) min_timestamp.

Fixes scylladb/scylladb#20423
Fixes scylladb/scylladb#20424

> [!NOTE]
> no backport needed at this time
> We may consider backport later on after given some soak time in master/enterprise
> since we do see tombstone accumulation in the field under some materialized views workloads

Closes scylladb/scylladb#20446

* github.com:scylladb/scylladb:
  cql-pytest: add test_compaction_tombstone_gc
  sstable_compaction_test: add mv_tombstone_purge_test
  sstable_compaction_test: tombstone_purge_test: test that old deleted data do not inhibit tombstone garbage collection
  sstable_compaction_test: tombstone_purge_test: add testlog debugging
  sstable_compaction_test: tombstone_purge_test: make_expiring: use next_timestamp
  sstable, compaction: add debug logging for extended min timestamp stats
  compaction: get_max_purgeable_timestamp: use memtable and sstable extended timestamp stats
  compaction: define max_purgeable_fn
  tombstone: can_gc_fn: move declaration to compaction_garbage_collector.hh
  sstables: scylla_metadata: add ext_timestamp_stats
  compaction_group, storage_group, table_state: add extended timestamp stats getters
  sstables, memtable: track live timestamps
  memtable_encoding_stats_collector: update row_marker: do nothing if missing
2024-09-13 08:56:51 +03:00
Benny Halevy
57e9e9c369 compaction: define max_purgeable_fn
Before we add a new, is_shadowable, parameter to it.

And define global `can_always_purge` and `can_never_purge`
functions, a-la `always_gc` and `never_gc`.

Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
2024-09-10 19:05:57 +03:00
Benny Halevy
6f202cf48b compaction_group, storage_group, table_state: add extended timestamp stats getters
To return the minimum live timestamp and live row-marker
timestamp across a compaction_group, storage_group, or
table_state.

Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
2024-09-10 19:05:57 +03:00
Pavel Emelyanov
b6f662417c table: Remove unused database& argument from take_snapshot() method
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>

Closes scylladb/scylladb#20496
2024-09-10 14:53:06 +03:00
Lakshmi Narayanan Sreethar
84d06a13c7 api: compaction: add consider_only_existing_data option
Added a new parameter `consider_only_existing_data` to major compaction
API endpoints. When enabled, major compaction will:

- Force-flush all tables.
- Force a new active segment in the commit log.
- Compact all existing SSTables and garbage-collect tombstones by only
  checking the SSTables being compacted. Memtables, commit logs, and
  other SSTables not part of the compaction will not be checked, as they
  will only contain newer data that arrived after the compaction
  started.

The `consider_only_existing_data` is passed down to the compaction
descriptor's `gc_check_only_compacting_sstables` option to ensure that
only the existing data is considered for garbage collection.

The option is also passed to the `maybe_flush_commitlog` method to make
sure all the tables are flushed and a new active segment is created in
the commit log.

Fixes #19728

Signed-off-by: Lakshmi Narayanan Sreethar <lakshmi.sreethar@scylladb.com>
2024-09-05 17:25:45 +05:30
Botond Dénes
b2c07c9b6f Merge 'compaction: change compaction stop reason ' from Aleksandra Martyniuk
Currently "table removal" is logged as a reason of compaction stop for table drop,
tablet cleanup and tablet split. Modify log to reflect the reason.

Closes scylladb/scylladb#20042

* github.com:scylladb/scylladb:
  test: add test to check compaction stop log
  compaction: fix compaction group stop reason
2024-08-26 13:40:07 +03:00
Aleksandra Martyniuk
5005e19de7 compaction: fix compaction group stop reason
compaction_manager::remove passes "table removal" as a reason
of stopping ongoing compactions, but currently remove method
is also called when a tablet is migrated or split.

Pass the actual reason of compaction stop, so that logs aren't
misleading.
2024-08-21 12:42:09 +02:00
Benny Halevy
f40d06b766 table: calculate_tablet_count: use sg_manager storage_groups size
Now, when each shard storage_group_manager keeps
only the storage_groups for the tablet replica it owns,
we can simple return the storage_group map size
instead of counting the number of tablet replicas
mapped to this shard.

Add a unit test that sums the tablet count
on all shards and tests that the sum is equal
to the configured default `initial_tablets.

Fixes #18909

Signed-off-by: Benny Halevy <bhalevy@scylladb.com>

Closes scylladb/scylladb#20223
2024-08-21 11:01:58 +02:00
Tomasz Grabiec
c1de4859d8 Merge 'tablets: Fix race between repair and split' from Raphael "Raph" Carvalho
Consider the following:

```
T
0   split prepare starts
1                               repair starts
2   split prepare finishes
3                               repair adds unsplit sstables
4                               repair ends
5   split executes
```

If repair produces sstable after split prepare phase, the replica will not split that sstable later, as prepare phase is considered completed already. That causes split execution to fail as replicas weren't really prepared. This also can be triggered with load-and-stream which shares the same write (consumer) path.

The approach to fix this is the same employed to prevent a race between split and migration. If migration happens during prepare phase, it can happen source misses the split request, but the tablet will still be split on the destination (if needed). Similarly, the repair writer becomes responsible for splitting the data if underlying table is in split mode. That's implemented in replica::table for correctness, so if node crashes, the new sstable missing split is still split before added to the set.

Fixes #19378.
Fixes #19416.

**Please replace this line with justification for the backport/\* labels added to this PR**

Closes scylladb/scylladb#19427

* github.com:scylladb/scylladb:
  tablets: Fix race between repair and split
  compaction: Allow "offline" sstable to be split
2024-08-19 14:44:28 +02:00
Łukasz Paszkowski
da95f44adc readers: Use reversed schema and native reversed slices
The reconcilable_result is built as it would be constructed for
forward read queries for tables with reversed order.

Mutations constructed for reversed queries are consumed forward.

Drop overloaded reversed functions that reverse read_command and
reconcilable_result directly and keep only those requiring smart
pointers. They are not used any more.
2024-08-13 10:03:46 +02:00
Łukasz Paszkowski
faa62310d9 database: accept reversed schema for reversed queries
Remove schema reversing in query() and query_mutations() methods.
Instead, a reversed schema shall be passed for reversed queries.
Rename a schema variable from s into query_schema for readability.
2024-08-13 10:03:46 +02:00
Łukasz Paszkowski
b270097f1f config: drop reversed_reads_auto_bypass_cache
Reverse reads have already been with us for a while, thus this back
door option to bypass in-memory data cache for reversed queries can
be retired.
2024-08-13 10:02:42 +02:00
Łukasz Paszkowski
80df313f49 config: drop enable_optimized_reversed_reads
Reverse reads have already been with us for a while, thus this back
door option to read entire paritions forward and reversing them after
can be retired.
2024-08-13 10:02:42 +02:00
Raphael S. Carvalho
74612ad358 tablets: Fix race between repair and split
Consider the following:

T
0   split prepare starts
1                               repair starts
2   split prepare finishes
3                               repair adds unsplit sstables
4                               repair ends
5   split executes

If repair produces sstable after split prepare phase, the replica
will not split that sstable later, as prepare phase is considered
completed already. That causes split execution to fail as replicas
weren't really prepared. This also can be triggered with
load-and-stream which shares the same write (consumer) path.

The approach to fix this is the same employed to prevent a race
between split and migration. If migration happens during prepare
phase, it can happen source misses the split request, but the
tablet will still be split on the destination (if needed).
Similarly, the repair writer becomes responsible for splitting
the data if underlying table is in split mode. That's implemented
in replica::table for correctness, so if node crashes, the new
sstable missing split is still split before added to the set.

Fixes #19378.
Fixes #19416.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
2024-08-12 17:28:51 -03:00
Calle Wilund
e18a855abe extensions: Add exception types for IO extensions and handle in memtable write path
Fixes #19960

Write path for sstables/commitlog need to handle the fact that IO extensions can
generate errors, some of which should be considered retry-able, and some that should,
similar to system IO errors, cause the node to go into isolate mode.

One option would of course be for extensions to simply generate std::system_errors,
with system_category and appropriate codes. But this is probably a bad idea, since
it makes it more muddy at which level an error happened, as well as limits the
expressibility of the error.

This adds three distinct types (sharing base) distinguishing permission, availabilty
and configuration errors. These are treated akin to EACCESS, ENOENT and EINVAL in
disk error handler and memtable write loop.

Tests updated to use and verify behaviour.

Closes scylladb/scylladb#19961
2024-08-11 13:52:35 +03:00
Raphael S. Carvalho
75829d75ec replica: Fix race between split compaction and migration
After removal of rwlock (53a6ec05ed), the race was introduced because the order that
compaction groups of a tablet are closed, is no longer deterministic.

Some background first:
Split compaction runs in main (unsplit) group, and adds sstable to left and right groups
on completion.

The race works as follow:
1) split compaction starts on main group of tablet X
2) tablet X reaches cleanup stage, so its compaction groups are closed in parallel
3) left or right group are closed before main (more likely when only main has flush work to do)
4) split compaction completes, and adds sstable to left and right
5) if e.g left is closed, adjusting backlog tracker will trigger an exception, and since that
happens in row cache update's execute(), node crashes.

The problem manifested as follow:
[shard 0: gms] raft_topology - Initiating tablet cleanup of 5739b9b0-49d4-11ef-828f-770894013415:15 on 102a904a-0b15-4661-ba3f-f9085a5ad03c:0
...
[shard 0:strm] compaction - [Split keyspace1.standard1 009e2f80-49e5-11ef-85e3-7161200fb137] Splitting [/var/lib/scylla/data/keyspace1/...]
...
[shard 0:strm] cache - Fatal error during cache update: std::out_of_range (Compaction state for table [0x600007772740] not found),
at: ...
   --------
   seastar::continuation<seastar::internal::promise_base_with_type<void>, row_cache::do_update(...
   --------
   seastar::internal::do_with_state<std::tuple<row_cache::external_updater, std::function<seastar::future<void> ()> >, seastar::future<void> >
   --------
   seastar::internal::coroutine_traits_base<void>::promise_type
   --------
   seastar::internal::coroutine_traits_base<void>::promise_type
   --------
   seastar::(anonymous namespace)::thread_wake_task
   --------
   seastar::continuation<seastar::internal::promise_base_with_type<sstables::compaction_result>, seastar::async<sstables::compaction::run(...
   seastar::continuation<seastar::internal::promise_base_with_type<sstables::compaction_result>, seastar::future<sstables::compaction_resu...

From the log above, it can be seen cache update failure happens under streaming sched group and
during compaction completion, which was good evidence to the cause.
Problem was reproduced locally with the help of tablet shuffling.

Fixes: #19873.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>

Closes scylladb/scylladb#19987
2024-08-11 11:00:19 +03:00
Botond Dénes
1f4b9a5300 Merge 'compaction: drop compaction executors' possibility to bypass task manager' from Aleksandra Martyniuk
If parent_info argument of compaction_manager::perform_compaction
is std::nullopt, then created compaction executor isn't tracked by task
manager. Currently, all compaction operations should by visible in task
manager.

Modify split methods to keep split executor in task manager. Get rid of
the option to bypass task manager.

Closes scylladb/scylladb#19995

* github.com:scylladb/scylladb:
  compaction: replace optional<task_info> with task_info param
  compaction: keep split executor in task manager
2024-08-11 10:26:43 +03:00
Avi Kivity
aa1270a00c treewide: change assert() to SCYLLA_ASSERT()
assert() is traditionally disabled in release builds, but not in
scylladb. This hasn't caused problems so far, but the latest abseil
release includes a commit [1] that causes a 1000 insn/op regression when
NDEBUG is not defined.

Clearly, we must move towards a build system where NDEBUG is defined in
release builds. But we can't just define it blindly without vetting
all the assert() calls, as some were written with the expectation that
they are enabled in release mode.

To solve the conundrum, change all assert() calls to a new SCYLLA_ASSERT()
macro in utils/assert.hh. This macro is always defined and is not conditional
on NDEBUG, so we can later (after vetting Seastar) enable NDEBUG in release
mode.

[1] 66ef711d68

Closes scylladb/scylladb#20006
2024-08-05 08:23:35 +03:00
Aleksandra Martyniuk
c456a43173 compaction: replace optional<task_info> with task_info param
compaction_manager::perform_compaction does not create task manager
task for compaction if parent_info is set to std::nullopt. Currently,
we always want to create task manager task for compaction.

Remove optional from task info parameters which start compaction.
Track all compactions with task manager.
2024-08-02 14:38:46 +02:00
Aleksandra Martyniuk
108d0344b8 compaction: keep split executor in task manager
If perform_compaction gets std::nullopt as a parent info then
the executor won't be tracked by task manager.

Modify storage_group::split call so that it passes empty task_info
instead of nullopt to track split.
2024-08-02 12:45:32 +02:00
Raphael S. Carvalho
8df7f78969 replica: rename for_each_const_compaction_group()
use same name as non-const-qualified variant, by relying on
overloading.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
2024-07-12 16:33:34 -03:00
Botond Dénes
53a6ec05ed Merge 'replica: remove rwlock for protecting iteration over storage group map' from Raphael "Raph" Carvalho
rwlock was added to protect iterations against concurrent updates to the map.

the updates can happen when allocating a new tablet replica or removing an old one (tablet cleanup).

the rwlock is very problematic because it can result in topology changes blocked, as updating token metadata takes the exclusive lock, which is serialized with table wide ops like split / major / explicit flush (and those can take a long time).

to get rid of the lock, we can copy the storage group map and guard individual groups with a gate (not a problem since map is expected to have a maximum of ~100 elements). so cleanup can close that gate (carefully closed after stopping individual groups such that migrations aren't blocked by long-running ops like major), and ongoing iterations (e.g. triggered by nodetool flush) can skip a group that was closed, as such a group is being migrated out.

Fixes #18821.

```
WRITE
=====

./build/release/scylla perf-simple-query --smp 1 --memory 2G --initial-tablets 10 --tablets --write

- BEFORE

65559.52 tps ( 59.6 allocs/op,  16.4 logallocs/op,  14.3 tasks/op,   52841 insns/op,   30946 cycles/op,        0 errors)
67408.05 tps ( 59.3 allocs/op,  16.0 logallocs/op,  14.3 tasks/op,   53018 insns/op,   30874 cycles/op,        0 errors)
67714.72 tps ( 59.3 allocs/op,  16.0 logallocs/op,  14.3 tasks/op,   53026 insns/op,   30881 cycles/op,        0 errors)
67825.57 tps ( 59.3 allocs/op,  16.0 logallocs/op,  14.3 tasks/op,   53015 insns/op,   30821 cycles/op,        0 errors)
67810.74 tps ( 59.3 allocs/op,  16.0 logallocs/op,  14.3 tasks/op,   53009 insns/op,   30828 cycles/op,        0 errors)

         throughput: mean=67263.72 standard-deviation=967.40 median=67714.72 median-absolute-deviation=547.02 maximum=67825.57 minimum=65559.52
instructions_per_op: mean=52981.61 standard-deviation=79.09 median=53014.96 median-absolute-deviation=36.54 maximum=53025.79 minimum=52840.56
  cpu_cycles_per_op: mean=30869.90 standard-deviation=50.23 median=30874.06 median-absolute-deviation=42.11 maximum=30945.94 minimum=30820.89

- AFTER
65448.76 tps ( 59.5 allocs/op,  16.4 logallocs/op,  14.3 tasks/op,   52788 insns/op,   31013 cycles/op,        0 errors)
67290.83 tps ( 59.3 allocs/op,  16.0 logallocs/op,  14.3 tasks/op,   53025 insns/op,   30950 cycles/op,        0 errors)
67646.81 tps ( 59.3 allocs/op,  16.0 logallocs/op,  14.3 tasks/op,   53025 insns/op,   30909 cycles/op,        0 errors)
67565.90 tps ( 59.3 allocs/op,  16.0 logallocs/op,  14.3 tasks/op,   53058 insns/op,   30951 cycles/op,        0 errors)
67537.32 tps ( 59.3 allocs/op,  16.0 logallocs/op,  14.3 tasks/op,   52983 insns/op,   30963 cycles/op,        0 errors)

         throughput: mean=67097.93 standard-deviation=931.44 median=67537.32 median-absolute-deviation=467.97 maximum=67646.81 minimum=65448.76
instructions_per_op: mean=52975.85 standard-deviation=108.07 median=53024.55 median-absolute-deviation=49.45 maximum=53057.99 minimum=52788.49
  cpu_cycles_per_op: mean=30957.17 standard-deviation=37.43 median=30951.31 median-absolute-deviation=7.51 maximum=31013.01 minimum=30908.62

READ
=====

./build/release/scylla perf-simple-query --smp 1 --memory 2G --initial-tablets 10 --tablets

- BEFORE

79423.36 tps ( 63.1 allocs/op,   0.0 logallocs/op,  14.2 tasks/op,   41840 insns/op,   26820 cycles/op,        0 errors)
81076.70 tps ( 63.1 allocs/op,   0.0 logallocs/op,  14.2 tasks/op,   41837 insns/op,   26583 cycles/op,        0 errors)
80927.36 tps ( 63.1 allocs/op,   0.0 logallocs/op,  14.2 tasks/op,   41829 insns/op,   26629 cycles/op,        0 errors)
80539.44 tps ( 63.1 allocs/op,   0.0 logallocs/op,  14.2 tasks/op,   41841 insns/op,   26735 cycles/op,        0 errors)
80793.10 tps ( 63.1 allocs/op,   0.0 logallocs/op,  14.2 tasks/op,   41864 insns/op,   26662 cycles/op,        0 errors)

         throughput: mean=80551.99 standard-deviation=661.12 median=80793.10 median-absolute-deviation=375.37 maximum=81076.70 minimum=79423.36
instructions_per_op: mean=41842.20 standard-deviation=13.26 median=41840.14 median-absolute-deviation=5.68 maximum=41864.50 minimum=41829.29
  cpu_cycles_per_op: mean=26685.88 standard-deviation=93.31 median=26662.18 median-absolute-deviation=56.47 maximum=26820.08 minimum=26582.68

- AFTER
79464.70 tps ( 63.1 allocs/op,   0.0 logallocs/op,  14.2 tasks/op,   41799 insns/op,   26761 cycles/op,        0 errors)
80954.58 tps ( 63.1 allocs/op,   0.0 logallocs/op,  14.2 tasks/op,   41803 insns/op,   26605 cycles/op,        0 errors)
81160.90 tps ( 63.1 allocs/op,   0.0 logallocs/op,  14.2 tasks/op,   41811 insns/op,   26555 cycles/op,        0 errors)
81263.10 tps ( 63.1 allocs/op,   0.0 logallocs/op,  14.2 tasks/op,   41814 insns/op,   26527 cycles/op,        0 errors)
81162.97 tps ( 63.1 allocs/op,   0.0 logallocs/op,  14.2 tasks/op,   41806 insns/op,   26549 cycles/op,        0 errors)

         throughput: mean=80801.25 standard-deviation=755.54 median=81160.90 median-absolute-deviation=361.72 maximum=81263.10 minimum=79464.70
instructions_per_op: mean=41806.47 standard-deviation=5.85 median=41806.05 median-absolute-deviation=4.05 maximum=41813.86 minimum=41799.36
  cpu_cycles_per_op: mean=26599.22 standard-deviation=94.84 median=26554.54 median-absolute-deviation=50.51 maximum=26761.06 minimum=26527.05
```

Closes scylladb/scylladb#19469

* github.com:scylladb/scylladb:
  replica: remove rwlock for protecting iteration over storage group map
  replica: get rid of fragile compaction group intrusive list
2024-07-12 15:45:36 +03:00
Raphael S. Carvalho
c539b7c861 replica: remove rwlock for protecting iteration over storage group map
rwlock was added to protect iterations against concurrent updates to the map.

the updates can happen when allocating a new tablet replica or removing an old one (tablet cleanup).

the rwlock is very problematic because it can result in topology changes blocked, as updating
token metadata takes the exclusive lock, which is serialized with table wide ops like
split / major / explicit flush (and those can take a long time).

to get rid of the lock, we can copy the storage group map and guard individual groups with a gate
(not a problem since map is expected to have a maximum of ~100 elements).
so cleanup can close that gate (carefully closed after stopping individual groups such that
migrations aren't blocked by long-running ops like major), and ongoing iterations (e.g. triggered
by nodetool flush) can skip a group that was closed, as such a group is being migrated out.

Check documentation added to compaction_group.hh to understand how
concurrent iterations and updates to the map work without the rwlock.

Yielding variants that iterate over groups are no longer returning group
id since id stability can no longer be guaranteed without serializing split
finalization and iteration.

Fixes #18821.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
2024-07-09 16:59:24 -03:00
Raphael S. Carvalho
ad5c5bca5f replica: get rid of fragile compaction group intrusive list
It was added to make integration of storage groups easier, but it's
complicated since it's another source of truth and we could have
problems if it becomes inconsistent with the group map.

Fixes #18506.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
2024-07-09 16:53:35 -03:00
Avi Kivity
f31d5e3204 Merge 'repair/streaming: enable toggling tombstone gc with a config item' from Botond Dénes
We currently disable tombstone GC for compaction done on the read path of streaming and repair, because those expired tombstones can still prevent data resurrection. With time-based tombstone GC, missing a repair for long enough can cause data resurrection because a tombstone is potentially GC'd before it could be spread to every node by repair. So repair disseminating these expired tombstones helps clusters which missed repair for long enough. It is not a guarantee because compaction could have done the GC itself, but it is better than nothing.
This last resort is getting less important with repair-based tombstone GC. Furthermore, we have seen this cause huge repair amplification in a cluster, where expired tombstones triggered repair replicating otherwise identical rows.

This series makes tombstone GC on the streaming/repair compaction path configurable with a config item. This new config item defaults to `false` (current behaviour), setting it to `true`, will enable tombstone GC.

Fixes: https://github.com/scylladb/scylladb/issues/19015

Not a regression, no backport needed

Closes scylladb/scylladb#19016

* github.com:scylladb/scylladb:
  test/topology_custom/test_repair: add test for enable_tombstone_gc_for_streaming_and_repair
  replica/table: maybe_compact_for_streaming(): toggle tombstone GC based on the control flag
  replica: propagate enable_tombstone_gc_for_streaming_and_repair to maybe_compact_for_streaming()
  db/config: introduce enable_tombstone_gc_for_streaming_and_repair
2024-07-09 19:04:11 +03:00
Michael Litvak
08b29460fc mv: skip building view updates on a pending replica
Currently, a pending replica that applies a write on a table that has
materialized views, will build all the view updates as a normal replica,
only to realize at a late point, in db::view::get_view_natural_endpoint(),
that it doesn't have a paired view replica to send the updates to. It will
then either drop the view updates, or send them to a pending view
replica, if such exists.

This work is unnecessary since it may be dropped, and even if there is a
pending view replica to send the updates to, the updates that are built
by the pending replica may be wrong since it may have incomplete
information.

This commit fixes the inefficiency by skipping the view update building
step when applying an update on a pending replica.

The metric total_view_updates_on_wrong_node is added to count the cases
that a view update is determined to be unnecessary.

The test reproduces the scenario of writing to a table and applying
the update on a pending replica, and verifies that the pending replica
doesn't try to build view updates.

Fixes scylladb/scylladb#19152

Closes scylladb/scylladb#19488
2024-07-02 13:10:18 +02:00
Avi Kivity
d5ba0b4041 compaction: define compaction_group::table_state earlier
C++23 made std::unique_ptr constexpr. A side effect of this (presumably)
is that the compiler compiles it more eagerly, requiring the full definition
of the class in std::make_unique, while it previously was content with
finding the definition later.

One victim of this change is compaction_group::table_state; define
it earlier to build with C++23.
2024-06-27 17:54:12 +03:00
Avi Kivity
9ecf4ada49 compaction: compaction_group: define destructor out-of-line
Define compaction_group::~compaction_group() out-of-line to prevent
problems instantiating compaction_group::_table_state, which is an
std::unique_ptr. In C++23, std::unique_ptr is constexpr, which means
its methods (in this case the destructor) require seeing the definition
of the class at the point of instantiation.
2024-06-27 17:54:12 +03:00
Botond Dénes
1fca341514 test/topology_custom/test_repair: add test for enable_tombstone_gc_for_streaming_and_repair 2024-06-26 04:05:17 -04:00
Botond Dénes
d3b1ccd03a replica/table: maybe_compact_for_streaming(): toggle tombstone GC based on the control flag
Now enable_tombstone_gc_for_streaming_and_repair is wired in all the way
to maybe_compact_for_streaming(), so we can implement the toggling of
tombstone GC based on it.
2024-06-26 04:05:17 -04:00
Botond Dénes
415457be2b replica: propagate enable_tombstone_gc_for_streaming_and_repair to maybe_compact_for_streaming()
Just wiring, the new flag will be used in the next patch.
2024-06-26 04:05:17 -04:00
Avi Kivity
fdc1449392 treewide: rename flat_mutation_reader_v2 to mutation_reader
flat_mutation_reader_v2 was introduced in a pair of commits in 2021:

  e3309322c3 "Clone flat_mutation_reader related classes into v2 variants"
  08b5773c12 "Adapt flat_mutation_reader_v2 to the new version of the API"

as a replacement for flat_mutation_reader, using range_tombstone_change
instead of range_tombstone to represent represent range tombstones. See
those commits for more information.

The transition was incremental; the last use of the original
flat_mutation_reader was removed in 2022 in commit

  026f8cc1e7 "db: Use mutation_partition_v2 in mvcc"

In turn, flat_mutation_reader was introduced in 2017 in commit

  748205ca75 "Introduce flat_mutation_reader"

To transition from a mutation_reader that nested rows within
a partition in a separate stream, to a flat reader that streamed
partitions and rows in the same stream.

Here, we reclaim the original name and rename the awkward
flat_mutation_reader_v2 to mutation_reader.

Note that mutation_fragment_v2 remains since we still use the original
for compatibilty, sometimes.

Some notes about the transition:

 - files were also renamed. In one case (flat_mutation_reader_test.cc), the
   rename target already existed, so we rename to
    mutation_reader_another_test.cc.

 - a namespace 'mutation_reader' with two definitions existed (in
   mutation_reader_fwd.hh). Its contents was folded into the mutation_reader
   class. As a result, a few #includes had to be adjusted.

Closes scylladb/scylladb#19356
2024-06-21 07:12:06 +03:00
Botond Dénes
ea40567bbc Merge 'Some cleanups for replica table' from Raphael "Raph" Carvalho
backport not needed, these are just cleanups.

Closes scylladb/scylladb#19260

* github.com:scylladb/scylladb:
  replica: simplify perform_cleanup_compaction()
  replica: return storage_group by reference on storage_group_for*()
  replica: devirtualize storage_group_of()
2024-06-14 08:14:58 +03:00
Raphael S. Carvalho
f143f5b90d replica: remove linear search when picking memtable_list for range scan with tablets
with tablets, we're expected to have a worst of ~100 tablets in a given
table and shard, so let's avoid linear search when looking for the
memtable_list in a range scan. we're bounded by ~100 elements, so
shouldn't be a big problem, but it's an inefficiency we can easily
get rid of.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>

Closes scylladb/scylladb#19286
2024-06-14 08:00:17 +03:00
Raphael S. Carvalho
f3a1f5df83 replica: simplify perform_cleanup_compaction()
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
2024-06-12 12:44:21 -03:00
Raphael S. Carvalho
6214dda506 replica: return storage_group by reference on storage_group_for*()
those functions cannot return nullptr, will throw when group is not
found, so better return ref instead.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
2024-06-12 11:53:06 -03:00
Raphael S. Carvalho
9c1d3bcc02 replica: devirtualize storage_group_of()
can be made private to tablet_storage_group_manager.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
2024-06-12 11:29:49 -03:00
Avi Kivity
6608f49718 Merge 'make enable_compacting_data_for_streaming_and_repair truly live-update' from Botond Dénes
This config item is propagated to the table object via table::config. Although the field in `table::config`, used to propagate the value, was `utils::updateable_value<T>`, it was assigned a constant and so the live-update chain was broken.
This series fixes this and adds a test which fails before the patch and passes after. The test needed new test infrastructure, around the failure injection api, namely the ability to exfiltrate the value of internal variable. This infrastructure is also added in this series.

Fixes: https://github.com/scylladb/scylladb/issues/18674

- [x] This patch has to be backported because it fixes broken functionality

Closes scylladb/scylladb#18705

* github.com:scylladb/scylladb:
  test/topology_custom: add test for enable_compacting_data_for_streaming_and_repair live-update
  test/pylib: rest_client: add get_injection()
  api/error_injection: add getter for error_injection
  utils/error_injection: add set_parameter()
  replica/database: fix live-update enable_compacting_data_for_streaming_and_repair
2024-06-11 15:53:19 +03:00
Botond Dénes
8ef4fbdb87 test/topology_custom: add test for enable_compacting_data_for_streaming_and_repair live-update
Avoid this the live-update feature of this config item breaking
silently.
2024-06-11 04:17:48 -04:00
Raphael S. Carvalho
7b41630299 replica: Refresh mutation source when allocating tablet replicas
Consider the following:

1) table A has N tablets and views
2) migration starts for a tablet of A from node 1 to 2.
3) migration is at write_both_read_old stage
4) coordinator will push writes to both nodes (pending and leaving)
5) A has view, so writes to it will also result in reads (table::push_view_replica_updates())
6) tablet's update_effective_replication_map() is not refreshing tablet sstable set (for new tablet migrating in)
7) so read on step 5 is not being able to find sstable set for tablet migrating in

Causes the following error:
"tablets - SSTable set wasn't found for tablet 21 of table mview.users"

which means loss of write on pending replica.

The fix will refresh the table's sstable set (tablet_sstable_set) and cache's snapshot.
It's not a problem to refresh the cache snapshot as long as the logical
state of the data hasn't changed, which is true when allocating new
tablet replicas. That's also done in the context of compactions for example.

Fixes #19052.
Fixes #19033.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>

Closes scylladb/scylladb#19099
2024-06-11 06:59:04 +03:00
Raphael S. Carvalho
b396b05e20 replica: Fix race of tablet snapshot with compaction
tablet snapshot, used by migration, can race with compaction and
can find files deleted. That won't cause data loss because the
error is propagated back into the coordinator that decides to
retry streaming stage. So the consequence is delayed migration,
which might in turn reduce node operation throughput (e.g.
when decommissioning a node). It should be rare though, so
shouldn't have drastic consequences.

Fixes #18977.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>

Closes scylladb/scylladb#18979
2024-05-31 09:58:49 +03:00
Raphael S. Carvalho
578a6c1e07 replica: Only consume memtable of the tablet intersecting with range read
storage_proxy is responsible for intersecting the range of the read
with tablets, and calling replica with a single tablet range, therefore
it makes sense to avoid touching memtables of tablets that don't
intersect with a particular range.

Note this is a performance issue, not correctness one, as memtable
readers that don't intersect with current range won't produce any
data, but cpu is wasted until that's realized (they're added to list
of readers in mutation_reader_merger, more allocations, more data
sources to peek into, etc).

That's also important for streaming e.g. after decommission, that
will consume one tablet at a time through a reader, so we don't want
memtables of streamed tablets (that weren't cleaned up yet) to
be consumed.

Refs #18904.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>

Closes scylladb/scylladb#18907
2024-05-29 15:58:33 +03:00
Botond Dénes
2d79b0106c Merge 'storage_service: Fix race between tablet split and stats retrieval' from Raphael "Raph" Carvalho
Retrieval of tablet stats must be serialized with mutation to token metadata, as the former requires tablet id stability.
If tablet split is finalized while retrieving stats, the saved erm, used by all shards, can have a lower tablet count than the one in a particular shard, causing an abort as tablet map requires that any id feeded into it is lower than its current tablet count.

Fixes #18085.

Closes scylladb/scylladb#18287

* github.com:scylladb/scylladb:
  test: Fix flakiness in topology_experimental_raft/test_tablets
  service: Use tablet read selector to determine which replica to account table stats
  storage_service: Fix race between tablet split and stats retrieval
2024-05-27 16:32:54 +03:00
Raphael S. Carvalho
eb8ef38543 replica: Fix tablet's compaction_groups_for_token_range() with unowned range
File-based tablet streaming calls every shard to return data of every
group that intersects with a given range.
After dynamic group allocation, that breaks as the tablet range will
only be present in a single shard, so an exception is thrown causing
migration to halt during streaming phase.
Ideally, only one shard is invoked, but that's out of the scope of this
fix and compaction_groups_for_token_range() should return empty result
if none of the local groups intersect with the range.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>

Closes scylladb/scylladb#18798
2024-05-22 20:15:33 +03:00
Raphael S. Carvalho
abcc68dbe7 storage_service: Fix race between tablet split and stats retrieval
If tablet split is finalized while retrieving stats, the saved erm, used by all
shards, will be invalidated. It can either cause incorrect behavior or
crash if id is not available.

It's worked by feeding local tablet map into the "coordinator"
collecting stats from all shards. We will also no longer have a snapshot
of erm shared between shards to help intra-node migration. This is
simplified by serializing token metadata changes and the retrieval of
the stats (latter should complete pretty fast, so it shouldn't block
the former for any significant time).

Fixes #18085.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
2024-05-22 09:25:29 -03:00
Avi Kivity
52fe351c31 Merge 'Balance tablets within nodes (intra-node migration)' from Tomasz Grabiec
This is needed to avoid severe imbalance between shards which can
happen when some table grows and is split. The inter-node balance can
be equal, so inter-node migration cannot fix the imbalance. Also, if RF=N
then there is not even a possibility of moving tablets around to fix the imbalance.
The only way to bring the system to balance is to move tablets within the nodes.

The system is not prepared for intra-node migration currently. Request coordination
is host-based, while for intra-node migration it should be (also) shard-based.
The solution employed here is to keep the coordination between nodes as-is,
and for intra-node migration storage_proxy-level coordinator is not aware of
the migration (no pending host). The replica-side request handler will be a
second-level coordinator which routes requests to shards, similar to how
the first-level coordinator routes them to hosts.

Tablet sharder is adjusted to handle intra-migration where a tablet
can have two replicas on the same host. For reads, sharder uses the
read selector to resolve the conflict. For writes, the write selector
is used.

The old shard_of() API is kept to represent shard for reads, and new
method is introduced to query the shards for writing:
shard_for_writes(). All writers should be switched to that API, which
is not done in this patch yet.

The request handler on replica side acts as a second-level
coordinator, using sharder to determine routing to shards. A given
sharder has a scope of a single topology version, a single
effective_replication_map_ptr, which should be kept alive during
writes.

perf-simple-query test results show no signs of regression:

Command: perf-simple-query -c1 -m1G --write --tablets --duration=10

Before:

> 83294.81 tps ( 59.5 allocs/op,  14.3 tasks/op,   53725 insns/op,        0 errors)
> 87756.72 tps ( 59.5 allocs/op,  14.3 tasks/op,   54049 insns/op,        0 errors)
> 86428.47 tps ( 59.6 allocs/op,  14.3 tasks/op,   54208 insns/op,        0 errors)
> 86211.38 tps ( 59.7 allocs/op,  14.3 tasks/op,   54219 insns/op,        0 errors)
> 86559.89 tps ( 59.6 allocs/op,  14.3 tasks/op,   54188 insns/op,        0 errors)
> 86609.39 tps ( 59.6 allocs/op,  14.3 tasks/op,   54117 insns/op,        0 errors)
> 87464.06 tps ( 59.5 allocs/op,  14.3 tasks/op,   54039 insns/op,        0 errors)
> 86185.43 tps ( 59.6 allocs/op,  14.3 tasks/op,   54169 insns/op,        0 errors)
> 86254.71 tps ( 59.6 allocs/op,  14.3 tasks/op,   54139 insns/op,        0 errors)
> 83395.35 tps ( 60.2 allocs/op,  14.4 tasks/op,   54693 insns/op,        0 errors)
>
> median 86428.47 tps ( 59.6 allocs/op,  14.3 tasks/op,   54208 insns/op,        0 errors)
> median absolute deviation: 243.04
> maximum: 87756.72
> minimum: 83294.81
>

After:

> 85523.06 tps ( 59.5 allocs/op,  14.3 tasks/op,   53872 insns/op,        0 errors)
> 89362.47 tps ( 59.6 allocs/op,  14.3 tasks/op,   54226 insns/op,        0 errors)
> 88167.55 tps ( 59.7 allocs/op,  14.3 tasks/op,   54400 insns/op,        0 errors)
> 87044.40 tps ( 59.7 allocs/op,  14.3 tasks/op,   54310 insns/op,        0 errors)
> 88344.50 tps ( 59.6 allocs/op,  14.3 tasks/op,   54289 insns/op,        0 errors)
> 88355.06 tps ( 59.6 allocs/op,  14.3 tasks/op,   54242 insns/op,        0 errors)
> 88725.46 tps ( 59.6 allocs/op,  14.3 tasks/op,   54230 insns/op,        0 errors)
> 88640.08 tps ( 59.6 allocs/op,  14.3 tasks/op,   54210 insns/op,        0 errors)
> 90306.31 tps ( 59.4 allocs/op,  14.3 tasks/op,   54043 insns/op,        0 errors)
> 87343.62 tps ( 59.8 allocs/op,  14.3 tasks/op,   54496 insns/op,        0 errors)
>
> median 88355.06 tps ( 59.6 allocs/op,  14.3 tasks/op,   54242 insns/op,        0 errors)
> median absolute deviation: 1007.41
> maximum: 90306.31
> minimum: 85523.06

Command (reads): perf-simple-query -c1 -m1G  --tablets --duration=10

Before:

> 95860.18 tps ( 63.1 allocs/op,  14.1 tasks/op,   42476 insns/op,        0 errors)
> 97537.69 tps ( 63.1 allocs/op,  14.1 tasks/op,   42454 insns/op,        0 errors)
> 97549.23 tps ( 63.1 allocs/op,  14.1 tasks/op,   42470 insns/op,        0 errors)
> 97511.29 tps ( 63.1 allocs/op,  14.1 tasks/op,   42470 insns/op,        0 errors)
> 97227.32 tps ( 63.1 allocs/op,  14.1 tasks/op,   42471 insns/op,        0 errors)
> 94031.94 tps ( 63.1 allocs/op,  14.1 tasks/op,   42441 insns/op,        0 errors)
> 96978.04 tps ( 63.1 allocs/op,  14.1 tasks/op,   42462 insns/op,        0 errors)
> 96401.70 tps ( 63.1 allocs/op,  14.1 tasks/op,   42473 insns/op,        0 errors)
> 96573.77 tps ( 63.1 allocs/op,  14.1 tasks/op,   42440 insns/op,        0 errors)
> 96340.54 tps ( 63.1 allocs/op,  14.1 tasks/op,   42468 insns/op,        0 errors)
>
> median 96978.04 tps ( 63.1 allocs/op,  14.1 tasks/op,   42462 insns/op,        0 errors)
> median absolute deviation: 571.20
> maximum: 97549.23
> minimum: 94031.94
>

After:

> 99794.67 tps ( 63.1 allocs/op,  14.1 tasks/op,   42471 insns/op,        0 errors)
> 101244.99 tps ( 63.1 allocs/op,  14.1 tasks/op,   42472 insns/op,        0 errors)
> 101128.37 tps ( 63.1 allocs/op,  14.1 tasks/op,   42485 insns/op,        0 errors)
> 101065.27 tps ( 63.1 allocs/op,  14.1 tasks/op,   42465 insns/op,        0 errors)
> 101212.98 tps ( 63.1 allocs/op,  14.1 tasks/op,   42456 insns/op,        0 errors)
> 101413.31 tps ( 63.1 allocs/op,  14.1 tasks/op,   42463 insns/op,        0 errors)
> 101464.92 tps ( 63.1 allocs/op,  14.1 tasks/op,   42466 insns/op,        0 errors)
> 101086.74 tps ( 63.1 allocs/op,  14.1 tasks/op,   42488 insns/op,        0 errors)
> 101559.09 tps ( 63.1 allocs/op,  14.1 tasks/op,   42468 insns/op,        0 errors)
> 100742.58 tps ( 63.1 allocs/op,  14.1 tasks/op,   42491 insns/op,        0 errors)
>
> median 101212.98 tps ( 63.1 allocs/op,  14.1 tasks/op,   42456 insns/op,        0 errors)
> median absolute deviation: 200.33
> maximum: 101559.09
> minimum: 99794.67
>

Fixes #16594

Closes scylladb/scylladb#18026

* github.com:scylladb/scylladb:
  Implement fast streaming for intra-node migration
  test: tablets_test: Test sharding during intra-node migration
  test: tablets_test: Check sharding also on the pending host
  test: py: tablets: Test writes concurrent with migration
  test: py: tablets: Test crash during intra-node migration
  api, storage_service: Introduce API to wait for topology to quiesce
  dht, replica: Remove deprecated sharder APIs
  test: Avoid using deprecated sharded API
  db: do_apply_many() avoid deprecated sharded API
  replica: mutation_dump: Avoid deprecated sharder API
  repair: Avoid deprecated sharder API
  table: Remove optimization which returns empty reader when key is not owned by the shard
  dht: is_single_shard: Avoid deprecated sharder API
  dht: split_range_to_single_shard: Work with static_sharder only
  dht: ring_position_range_sharder: Avoid deprecated sharder APIs
  dht: token: Avoid use of deprecated sharder API by switching to static_sharder
  selective_token_sharder: Avoid use of deprecated sharder API
  docs: Document tablet sharding vs tablet replica placement
  readers/multishard.cc: use shard_for_reads() instead of shard_of()
  multishard_mutation_query.cc: use shard_for_reads() instead of shard_of()
  storage_proxy: Extract common code to apply mutations on many shards according to sharder
  storage_proxy: Prepare per-partition rate-limiting for intra-node migration
  storage_proxy: Avoid shard_of() use in mutate_counter_on_leader_and_replicate()
  storage_proxy: Prepare mutate_hint() for intra-node tablet migration
  commitlog_replayer: Avoid deprecated sharder::shard_of()
  lwt: Avoid deprecated sharder::shard_of()
  compaction: Avoid deprecated sharder::shard_of()
  dht: Extract dht::static_sharder
  replica: Deprecate table::shard_of()
  locator: Deprecate effective_replication_map::shard_of()
  dht: Deprecate old sharder API: shard_of/next_shard/token_for_next_shard
  tests: tablets: py: Add intra-node migration test
  tests: tablets: Test that drained nodes are not balanced internally
  tests: tablets: Add checks of replica set validity to test_load_balancing_with_random_load
  tests: tablets: Verify that disabling balancing results in no intra-node migrations
  tests: tablets: Check that nodes are internally balanced
  tests: tablets: Improve debuggability by showing which rows are missing
  tablets, storage_service: Support intra-node migration in move_tablet() API
  tablet_allocator: Generate intra-node migration plan
  tablet_allocator: Extract make_internode_plan()
  tablet_allocator: Maintain candidate list and shard tablet count for target nodes
  tablet_allocator: Lift apply_load/can_accept_load lambdas to member functions
  tablets, streaming: Implement tablet streaming for intra-node migration
  dht, auto_refreshing_sharder: Allow overriding write selector
  multishard_writer: Handle intra-node migration
  storage_proxy: Handle intra-node tablet migration for writes
  tablets: Get rid of tablet_map::get_shard()
  tablets: Avoid tablet_map::get_shard in cleanup
  tablets: test: Use sharder instead of tablet_map::get_shard()
  tablets: tablet_sharder: Allow working with non-local host
  sharding: Prepare for intra-node-migration
  docs: Document sharder use for tablets
  tablets: Introduce tablet transition kind for intra-node migration
  tests: tablets: Fix use-after-move of skiplist in rebalance_tablets()
  sstables, gdb: Track readers in a linked list
  raft topology: Fix global token metadata barrier to not fence ahead of what is drained
2024-05-20 16:13:01 +03:00
Piotr Dulikowski
68eca3778c Merge 'mv: throttle view update generation for large queries' from Wojciech Mitros
This series is a reupload of #13792 with a few modifications, namely a test is added and the conflicts with recent tablet related changes are fixed.

See https://github.com/scylladb/scylladb/issues/12379 and https://github.com/scylladb/scylladb/pull/13583 for a detailed description of the problem and discussions.

This PR aims to extend the existing throttling mechanism to work with requests that internally generate a large amount of view updates, as suggested by @nyh.

The existing mechanism works in the following way:

* Client sends a request, we generate the view updates corresponding to the request and spawn background tasks which will send these updates to remote nodes
* Each background task consumes some units from the `view_update_concurrency_semaphore`, but doesn't wait for these units, it's just for tracking
* We keep track of the percent of consumed units on each node, this is called `view update backlog`.
* Before sending a response to the client we sleep for a short amount of time. The amount of time to sleep for is based on the fullness of this `view update backlog`. For a well behaved client with limited concurrency this will limit the amount of incoming requests to a manageable level.

This mechanism doesn't handle large DELETE queries. Deleting a partition is fast for the base table, but it requires us to generate a view update for every single deleted row. The number of deleted rows per single client request can be in the millions. Delaying response to the request doesn't help when a single request can generate millions of updates.

To deal with this we could treat the view update generator just like any other client and force it to wait a bit of time before sending the next batch of updates. The amount of time to wait for is calculated just like in the existing throttling code, it's based on the fullness of `view update backlogs`.

The new algorithm of view update generation looks something like this:
```c++
for(;;) {
    auto updates = generate_updates_batch_with_max_100_rows();
    co_await seastar::sleep(calculate_sleep_time_from_backlogs());
    spawn_background_tasks_for_updates(updates);
}
```
Fixes: https://github.com/scylladb/scylladb/issues/12379

Closes scylladb/scylladb#16819

* github.com:scylladb/scylladb:
  test: add test for bad_allocs during large mv queries
  mv: throttle view update generation for large queries
  exceptions: add read_write_timeout_exception, a subclass of request_timeout_exception
  db/view: extract view throttling delay calculation to a global function
  view_update_generator: add get_storage_proxy()
  storage_proxy: make view backlog getters public
2024-05-16 08:22:54 +02:00
Raphael S. Carvalho
715ae689c0 Implement fast streaming for intra-node migration
With intra-node migration, all the movement is local, so we can make
streaming faster by just cloning the sstable set of leaving replica
and loading it into the pending one.

This cloning is underlying storage specific, but s3 doesn't support
snapshot() yet (th sstables::storage procedure which clone is built
upon). It's only supported by file system, with help of hard links.
A new generation is picked for new cloned sstable, and it will
live in the same directory as the original.

A challenge I bumped into was to understand why table refused to
load the sstable at pending replica, as it considered them foreign.
Later I realized that sharder (for reads) at this stage of migration
will point only to leaving replica. It didn't fail with mutation
based streaming, because the sstable writer considers the shard --
that the sstable was written into -- as its owner, regardless of what
sharder says. That was fixed by mimicking this behavior during
loading at pending.

test:
./test.py --mode=dev intranode --repeat=100 passes.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
2024-05-16 00:28:47 +02:00