Add Iterator test against expected state to stress test #10538
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| @@ -1,7 +1,5 @@ | |||
| # Rocksdb Change Log | |||
| ## Unreleased | |||
| ### Behavior Change | |||
| * Updated `TestGet()` in `no_batched_op_stress` (default stress test) to check the result of Get() operations against expected state. | |||
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…test` (#10590) Summary: #10538 added `TestIterateAgainstExpected()` in `no_batched_ops_test` to verify iterator correctness against the in memory expected state. It is not compatible when run after some other stress tests, e.g. `TestPut()` in `batched_op_stress`, that either do not set expected state when writing to DB or use keys that cannot be parsed by `GetIntVal()`. The assert [here](https://github.com/facebook/rocksdb/blob/d17be55aab80b856f96f4af89f8d18fef96646b4/db_stress_tool/db_stress_common.h#L520) could fail. This PR fixed this issue by setting iterator upperbound to `max_key` when `destroy_db_initially=0` to avoid the key space that `batched_op_stress` touches. Pull Request resolved: #10590 Test Plan: ``` # set up DB with batched_op_stress ./db_stress --test_batches_snapshots=1 --verify_iterator_with_expected_state_one_in=1 --max_key_len=3 --max_key=100000000 --skip_verifydb=1 --continuous_verification_interval=0 --writepercent=85 --delpercent=3 --delrangepercent=0 --iterpercent=10 --nooverwritepercent=1 --prefixpercent=0 --readpercent=2 --key_len_percent_dist=1,30,69 # Before this PR, the following test will fail the asserts with error msg like the following # Assertion failed: (size_key <= key_gen_ctx.weights.size() * sizeof(uint64_t)), function GetIntVal, file db_stress_common.h, line 524. ./db_stress --verify_iterator_with_expected_state_one_in=1 --max_key_len=3 --max_key=100000000 --skip_verifydb=1 --continuous_verification_interval=0 --writepercent=0 --delpercent=3 --delrangepercent=0 --iterpercent=95 --nooverwritepercent=1 --prefixpercent=0 --readpercent=2 --key_len_percent_dist=1,30,69 --destroy_db_initially=0 ``` Reviewed By: ajkr Differential Revision: D39085243 Pulled By: cbi42 fbshipit-source-id: a7dfee2320c330773b623b442d730fd014ec7056
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… edition) (#10449) Summary: Delete range logic is moved from `DBIter` to `MergingIterator`, and `MergingIterator` will seek to the end of a range deletion if possible instead of scanning through each key and check with `RangeDelAggregator`. With the invariant that a key in level L (consider memtable as the first level, each immutable and L0 as a separate level) has a larger sequence number than all keys in any level >L, a range tombstone `[start, end)` from level L covers all keys in its range in any level >L. This property motivates optimizations in iterator: - in `Seek(target)`, if level L has a range tombstone `[start, end)` that covers `target.UserKey`, then for all levels > L, we can do Seek() on `end` instead of `target` to skip some range tombstone covered keys. - in `Next()/Prev()`, if the current key is covered by a range tombstone `[start, end)` from level L, we can do `Seek` to `end` for all levels > L. This PR implements the above optimizations in `MergingIterator`. As all range tombstone covered keys are now skipped in `MergingIterator`, the range tombstone logic is removed from `DBIter`. The idea in this PR is similar to #7317, but this PR leaves `InternalIterator` interface mostly unchanged. **Credit**: the cascading seek optimization and the sentinel key (discussed below) are inspired by [Pebble](https://github.com/cockroachdb/pebble/blob/master/merging_iter.go) and suggested by ajkr in #7317. The two optimizations are mostly implemented in `SeekImpl()/SeekForPrevImpl()` and `IsNextDeleted()/IsPrevDeleted()` in `merging_iterator.cc`. See comments for each method for more detail. One notable change is that the minHeap/maxHeap used by `MergingIterator` now contains range tombstone end keys besides point key iterators. This helps to reduce the number of key comparisons. For example, for a range tombstone `[start, end)`, a `start` and an `end` `HeapItem` are inserted into the heap. When a `HeapItem` for range tombstone start key is popped from the minHeap, we know this range tombstone becomes "active" in the sense that, before the range tombstone's end key is popped from the minHeap, all the keys popped from this heap is covered by the range tombstone's internal key range `[start, end)`. Another major change, *delete range sentinel key*, is made to `LevelIterator`. Before this PR, when all point keys in an SST file are iterated through in `MergingIterator`, a level iterator would advance to the next SST file in its level. In the case when an SST file has a range tombstone that covers keys beyond the SST file's last point key, advancing to the next SST file would lose this range tombstone. Consequently, `MergingIterator` could return keys that should have been deleted by some range tombstone. We prevent this by pretending that file boundaries in each SST file are sentinel keys. A `LevelIterator` now only advance the file iterator once the sentinel key is processed. Pull Request resolved: #10449 Test Plan: - Added many unit tests in db_range_del_test - Stress test: `./db_stress --readpercent=5 --prefixpercent=19 --writepercent=20 -delpercent=10 --iterpercent=44 --delrangepercent=2` - Additional iterator stress test is added to verify against iterators against expected state: #10538. This is based on ajkr's previous attempt #5506 (comment). ``` python3 ./tools/db_crashtest.py blackbox --simple --write_buffer_size=524288 --target_file_size_base=524288 --max_bytes_for_level_base=2097152 --compression_type=none --max_background_compactions=8 --value_size_mult=33 --max_key=5000000 --interval=10 --duration=7200 --delrangepercent=3 --delpercent=9 --iterpercent=25 --writepercent=60 --readpercent=3 --prefixpercent=0 --num_iterations=1000 --range_deletion_width=100 --verify_iterator_with_expected_state_one_in=1 ``` - Performance benchmark: I used a similar setup as in the blog [post](http://rocksdb.org/blog/2018/11/21/delete-range.html) that introduced DeleteRange, "a database with 5 million data keys, and 10000 range tombstones (ignoring those dropped during compaction) that were written in regular intervals after 4.5 million data keys were written". As expected, the performance with this PR depends on the range tombstone width. ``` # Setup: TEST_TMPDIR=/dev/shm ./db_bench_main --benchmarks=fillrandom --writes=4500000 --num=5000000 TEST_TMPDIR=/dev/shm ./db_bench_main --benchmarks=overwrite --writes=500000 --num=5000000 --use_existing_db=true --writes_per_range_tombstone=50 # Scan entire DB TEST_TMPDIR=/dev/shm ./db_bench_main --benchmarks=readseq[-X5] --use_existing_db=true --num=5000000 --disable_auto_compactions=true # Short range scan (10 Next()) TEST_TMPDIR=/dev/shm/width-100/ ./db_bench_main --benchmarks=seekrandom[-X5] --use_existing_db=true --num=500000 --reads=100000 --seek_nexts=10 --disable_auto_compactions=true # Long range scan(1000 Next()) TEST_TMPDIR=/dev/shm/width-100/ ./db_bench_main --benchmarks=seekrandom[-X5] --use_existing_db=true --num=500000 --reads=2500 --seek_nexts=1000 --disable_auto_compactions=true ``` Avg over of 10 runs (some slower tests had fews runs): For the first column (tombstone), 0 means no range tombstone, 100-10000 means width of the 10k range tombstones, and 1 means there is a single range tombstone in the entire DB (width is 1000). The 1 tombstone case is to test regression when there's very few range tombstones in the DB, as no range tombstone is likely to take a different code path than with range tombstones. - Scan entire DB | tombstone width | Pre-PR ops/sec | Post-PR ops/sec | ±% | | ------------- | ------------- | ------------- | ------------- | | 0 range tombstone |2525600 (± 43564) |2486917 (± 33698) |-1.53% | | 100 |1853835 (± 24736) |2073884 (± 32176) |+11.87% | | 1000 |422415 (± 7466) |1115801 (± 22781) |+164.15% | | 10000 |22384 (± 227) |227919 (± 6647) |+918.22% | | 1 range tombstone |2176540 (± 39050) |2434954 (± 24563) |+11.87% | - Short range scan | tombstone width | Pre-PR ops/sec | Post-PR ops/sec | ±% | | ------------- | ------------- | ------------- | ------------- | | 0 range tombstone |35398 (± 533) |35338 (± 569) |-0.17% | | 100 |28276 (± 664) |31684 (± 331) |+12.05% | | 1000 |7637 (± 77) |25422 (± 277) |+232.88% | | 10000 |1367 |28667 |+1997.07% | | 1 range tombstone |32618 (± 581) |32748 (± 506) |+0.4% | - Long range scan | tombstone width | Pre-PR ops/sec | Post-PR ops/sec | ±% | | ------------- | ------------- | ------------- | ------------- | | 0 range tombstone |2262 (± 33) |2353 (± 20) |+4.02% | | 100 |1696 (± 26) |1926 (± 18) |+13.56% | | 1000 |410 (± 6) |1255 (± 29) |+206.1% | | 10000 |25 |414 |+1556.0% | | 1 range tombstone |1957 (± 30) |2185 (± 44) |+11.65% | - Microbench does not show significant regression: https://gist.github.com/cbi42/59f280f85a59b678e7e5d8561e693b61 Reviewed By: ajkr Differential Revision: D38450331 Pulled By: cbi42 fbshipit-source-id: b5ef12e8d8c289ed2e163ccdf277f5039b511fca
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Summary: As mentioned in #5506 (comment),
db_stressdoes not have much verification for iterator correctness.It has a
TestIterate()function, but that is mainly for comparing resultsbetween two iterators, one with
total_order_seekand the other optionallysets auto_prefix, upper/lower bounds. Commit 49a0581
added a new
TestIterateAgainstExpected()function that compares iterator againstexpected state. It locks a range of keys, creates an iterator, does
a random sequence of
Next/Prevand compares against expected state.This PR is based on that commit, the main changes include some logs
(for easier debugging if a test fails), a forward and backward scan to
cover the entire locked key range, and a flag for optionally turning on
this version of Iterator testing.
Added constraint that the checks against expected state in
TestIterateAgainstExpected()and inTestGet()are only turned onwhen
--skip_verifydbflag is not set.Remove the change log introduced in #10553.
Test plan: Run
db_stresswith--verify_iterator_with_expected_state_one_in=1,and a large
--iterpercentand--num_iterations. Checkedop_logsmanually to ensure expected coverage. Tweaked part of the code in
#10449 and stress test was able to catch it.