First, it is possible for us to end up allocating *or freeing* pages during
a modification of the free list, in a way such that the change to the free list
means that when we finish the modification which caused the allocate or free,
we've overwritten the inner change.
Second, when deallocating trees, we don't actually deallocate the branch nodes
themselves.
The former causes potentially severe data corruption. The latter causes us
to gradually leak pages in a way that we don't notice because we only run those
tests during the RBF tests.
The fix for this is surprisingly intricate, because of the counterintuitive
fact that *allocating* a page means *removing* things from the free list
(and thus potentially deallocating free list pages), while *freeing* a page
means *adding* things to the free list (and thus potentially needing to
allocate pages for the free list).
While modifying the free list, any allocations we need always just come from
the end of the file; we don't try to reuse free pages. If a page becomes
*deallocated* by a free list modification, we don't annotate it in the free
list at the instant that it happens; we stash that information until the
current modification of the free list happens, then iterate through any
such pages.
I am pretty sure there's virtually never more than one, and I don't actually
know that I can create a case wherein we'd end up with the nested case
firing, wherein removing a page from the free list causes us to remove another
page, but I think if the free list got large and cluttered and needed
rebalancing or something it could maybe happen.
These commits are hard to disentagle, and doing them separately means
re-modifying the same chunks of code several times before removing it,
and similar things.
Basically:
(1) Drop the bolt backend storage.
(2) Drop the blue-green wrapper that compares two backends.
(3) Drop unused or barely-used Tx API components from all the
remaining backends.
(4) Minor related cleanup to simplify things related to these.
The boltdb backend existed only to verify RBF. The blue-green wrapper
was mostly used to verify RBF, but in practice we had to do a lot
of working around that, and it introduced a lot of special cases.
Types removed:
IteratorFinder: Used only to implement the roaring iterator
on top of boltdb, and to complicate the way it worked in roaring.
Reverted the complications. Also unexport NewSliceContainers
which is used only for that outside of roaring's internals.
PortMapper from cluster_internal_test.go: Used only for a test
we removed early this year. Never used for anything else.
RawRoaringData: Totally unused.
TxStore: Totally unused.
Functions removed from Tx API, and sometimes corresponding
members were removed from structs:
* Dump: debugging code, I don't think I found any actually reachable
paths to it.
* Group: only used for debugging TxGroup stuff
* IncrementOpN: only used by fragment, fragment can increment its
own opN.
* Options: unused?
* Pointer: debugging only
* Readonly: used only to decide how to handle Tx in a TxGrp,
but we never add a non-readonly Tx to a TxGrp. Removed also all
the corresponding write-aware stuff.
* RoaringBitmapReader: Used exactly once, can just be a bm.WriteTo.
* Sn (and OpenSnList): Unused
* UnionInPlace: unused and conceptually-invalid; it didn't write
to storage and shouldn't have, and was just "create a bitmap
then call union-in-place", which we can do directly.
* UseRowCache: just checked storage.UseRowCache.
Other things removed:
The SetRequiredForAtomicWriteTx and ClearRequiredForAtomicWriteTx
functions go away, since nothing now seems to be using them? Same
for holder_internal_test's `testHasBit` and `testMustNotHaveBit`,
which were unused.
The DBPerShard "DeleteDBPath" and "HasData" functions and related
parts were mostly unused; took out the parts that were never
actually being reached.
Changed the API of one function to simplify special cases and
remove things:
* ImportRoaringBits had a special "data" argument which gave it
subtly different semantics for RBF and roaring (for roaring, it
could produce a roaring bitmap *with ops log*), didn't seem to
be adding much. Removed corresponding "readStorageFromArchive"
which is not otherwise used.
Also took out various debugging/dumping functions that were unused
and may have bitrotted.
Dropped a test from txfactory_internal_test, and the "pjobs"
code, because those two were the only things that needed Barrier
and thus idem, which lets us drop two more dependencies. We already
have errgroup for grouping things which want to terminate as
soon as one of them errors, approximately. To do better we'd have
to have context-threading, really.
Unbroke the WriteFragment test for non-roaring tests and made it
not roaring-only.
This commit fixes an issue where the root record cache is only
built when a write transaction successfully commits. However, if
no write transactions are occurring then the the cache is never
built and saved so it is recomputed on every read tx.
We need to be able to count bits in BitmapPtr containers. This only
comes up if you have a non-container-aligned range count, which we
never do in real production yet, but the API allows it so it should
work. In order to do this, we need to provide the tx to countRange
so it can grab pages as needed. Arguably, we should be able to avoid
actually creating/copying that page since we're only using it
internally, never returning it, but this is a pretty rare case
and probably not performance-critical.
- Previously, on timequantum schemas, we would
create and open a view for the cartesian
product of every possible view and shard.
- This caused us to be very slow on re-open,
and to use lots of memory for views that
held nothing.
- This change makes startup faster, memory
use much lower, and should speed migration.
CountRange for RBF had a subtle bug which wasn't noticed, so, let's
have some CountRange testing and also a benchmark.
We also fix a couple of subtle bugs caught in the process of developing
and testing this.
SliceContainers will allow nil containers, but doesn't return them when
iterating because there's various things that can panic if called on a nil
container. Since countEmptyContainers() has to traverse the whole bitmap
anyway, it doesn't matter which it counts, so we replace it with
countNonEmptyContainers(), and adjust test cases accordingly. This fixes
an issue where if roaring is smart enough to insert a nil container
into a SliceContainers, trying to write it to a file produces an invalid
bitmap with offsets off by 16 and one container fewer than its header predicts.
RBF: don't try to count 0 bits in a container
If we're to the "last container", and we'd be counting all the bits less than
zero, we can skip that. This avoids hitting a bug, which is that c.countRange
doesn't handle BitmapPtr.
This reduces noticably the cost of reading leaf cells, by passing
a single pointer down the stack instead of the entire data structure
up the stack. It's only a few percent overall, but it's noticeable.
This gives RBF an ApplyFilter that can run without instantiating containers
when the filter it's using doesn't need them instantiated. We can also seek
ahead in cases where we know the next key we care about is not just the next
key numerically.
- use short_txkey for rbf
- short_txkey breaks a bunch of bolt_test.go, so leave it on (long) txkey for now.
- remove SliceOfShards method from Tx interface
- the sync.Pool default uses little memory under CI.
- arena approach provides ability to control the maximum memory
used by rbf Cursors.
- cursor caching is adjustable with --rbf-cursor-cache
currently 0 by default (meaning use sync.Pool), and
larger than 0 meaning use an arena of this size.
With the arena, 20 or less is needed to pass CI.
- rbf test suite runs ~ 4x faster
- kitchen sink ingest test runs 16% faster.
- report TotalAlloc in CALLSTATs
fixes#1105
This commit fixes a bug where the root record cache was being
updated in-place causing a race condition with other transactions
using it. The cache implementation has been changed from `rbtree`
to an `immutable.SortedMap`.
- fix a bug in computing leafCell.BitN in a run after a bit Remove
- shrink bitmaps on remove
- util_test.go has Cursor.DebugSlowCheckAllPages to verify;
used by cursor_test.go
- default Tx is once again RBF, changed from bolt.
- document the RBF code review comments that were not addressed
before #1052 was merged, so they don't get lost.
- they should be easily addressed by replaying the entire WAL file
rather than from the DB meta page 0 notion of the last WalID
- cleanup rbf/cfg/cfg.go stale comments, ensure default0 respected.
1 msec checkpoint time, 1MB wal segment defaults.
- return a specific error, ErrNoMetaFound, from findNextWALMetaPage()
rather than io.EOF, since there actually wasn't any file IO involved.
- add http handlers for /cpu-profile/start and /cpu-profile/stop
in http/handler.go enable CPU profiling at specific time points
during an ingest or other operation.
I have a newer staticcheck and golangci-lint on my laptop, and it started
complaining about something. The first comment added disables the check
in staticcheck-as-a-command, the second disables it when it's being done
by golangci-lint, which invokes the analysis passes directly and displays
the output differently, and also doesn't recognize the hints used by
staticcheck.
Newer golangci-lint doesn't find anything else that it wants to complain
about.
Previously, RBF shared a list of WAL segments between the DB & Tx.
However, this increased the need for mutexes to access the data.
WAL segments are effectively immutable on-disk so the list of segments
has been refactored so that changes to the segment list are done via
copy-on-write which allows read transactions to access segment data
without a mutex.
The database checkpointing can remove early, unused segments and
there is an update/add check to make sure that Tx segments pushed back
to the DB do not include removed segments.
This commit fixes an issue where direct writes would overwrite the
source page where data was being copied from because writes are
immediate (instead of going to the WAL first).
- blue_green for doing migration. Called before Holder.Open finishes.
- holdbkg.go added for index lookup. Less wedging between a deadlock and a race.
- fix fault under read-only map under lmdb at
TestExecutor_Execute_Row_Range/RowIDColumnID by doing cow in roaring.
- roaring -tags gofuzz builds again
- roaringparanoia build tag added to make test targets in Makefile
- add rbf.NewDBWithAllocZero for out-of-bounds memory checks
- .circleci/config.yml test-shardwidth-22 with large run container, kept OOM-ing we suspect.
Fixes#819
blake3 code is used in several places on the code. The file was
duplicated on root and rbf package.
To avoid cyclic dependencies, I moved it to hash package. Some methods
must be public to use them in different places.
HashOfDir method was removed. Not used.
Signed-off-by: Antonio Navarro Perez <antnavper@gmail.com>
