During EQC testing it was found that snapshots are still usable even
if the bookie process crashes. This change has snapshots monitor the
bookie and close when the bookie process dies.
head_only mode cna be run with_lookup - but there is no L0 index created in this case.
So the L0 index wasn't returning a potition list and the L0 cache wasn't being checked.
Code now checks every position in the L0 cache, when a lookup is attempted in head_only mode.
Interetsingly setting max_pencillercachesize to a non-integer merely had the impact of making the penciller cache size infinite.
So a guard added to make sure it is an integer going forward.
The IMM iterator should not be reused, as it has already been filtered for a query. so if reused for a different query incorrect and unexpected results may occur.
This reuse had been stopped by a previous commit, and this cleans up subsequently unused code.
Initial commit to add head_only mode to leveled. This allows leveled to receive batches of object changes, but where those objects exist only in the Penciller's Ledger (once they have been persisted within the Ledger).
The aim is to reduce significantly the cost of compaction. Also, the objects ar enot directly accessible (they can only be accessed through folds). Again this makes life easier during merging in the LSM trees (as no bloom filters have to be created).
Previouslythe tinybloom was used within the SST file as an extra check to remove false fetches.
However the SST already has a low FPR check in the slot_index. If the newebloom was used (which is no longer per slot, but per sst), this can be shared with the penciller and then the penciller could use it and avoid the message pass.
the message pass may be blocked by a 2i query or a slot fetch request for a merge. So this should make performance within the Penciller snappier.
This is as a result of taking sst_timings within a volume test - where there was an average of + 100microsecs for each level that was dropped down. Given the bloom/slot checks were < 20 microsecs - there seems to be some further delay.
The bloom is a binary of > 64 bytes - so passing it around should not require a copy.
Compression can be switched between LZ4 and zlib (native).
The setting to determine if compression should happen on receipt is now a macro definition in leveled_codec.
Initially with basic tests. If the SlotIndex has been cached, we can now use the slot index as it is based on the Segment hash algortihm.
This looks like it should lead to an order of magnitude improvement in querying for keys/clocks by segment ID.
This also required a slight tweak to the penciller keyfolder. It now caches the next answer from the SSTiter, rather than restart the iterator. When the IMMiter has many more entries than the SSTiter (as the sSTiter is being filtered but not the IMMiter) this could lead to lots of repeated folding.
Discovered a bug with search ranges in leveled_tree - this was uncovered by an intermittently fialing 19.3 test.
Test case added and bug fixed. It was due to a fialure to use end_key passed causing issues with particular manifests and full bucket ranges.
Switch from magic hash to md5 - to hopefully remove the need for some
of the artificial jumps required to get expected fall positive ratios.
Also split the hash into two 16-bit integers. We assume that SegmentID
(from the perspective of AAE merkle/tictac trees) will always be at
least 16 bits. the idea is that hashes should be used in blooms and
indexes such that some advantage can be gained from just knowing the
segmentID - in particular when folding over all the keys in a bucket.
Performance testing has been difficult so far - I think due to “cloud”
mysteries.
Introduce a dedicated module for all the different fold types. Also simplify the list of folders by deprecating those folds that should eb achieveable by fold_heads/fold_objects type folds but with smarter functions.
Makes sure that the fold functiosn also have better spec coverage, and are dialyzer checked.
As descibed in https://github.com/martinsumner/leveled/issues/92
Only the first fix was made.
Just to eb safe - archiving means renaming to another file with a different extension. Assumption is that renamed files cna be manually reaped if necessary.
this required a switch to change the sync strategy based on rebar parameter.
However tests could be slow on macbook with OTP16 and sync - so timeouts added in unit tests, and ct tests sync_startegy changed to not sync for OTP16.
If the clerk updates the manifest - it might not recognise changes to
the manifest made since the clerk took the manifest. So the penciller
must merge its view of the snapshots back in to the updated manifest
fold objects which snaps in the fold was implemented incorrectly - it
took information from the LedgeCache at the point of the request, not
at the point of the fold. So the LedgerCache SQN may have been
surpassed in the Penciller by the time the fold was called.
Increase this to 90 minutes. The first time all the snapshots are
rebuilt it may take a long time, but they all get scheduled together -
and queued until concurrency limits allow it to be completed.
currently the snapshot is made on initialisation, and only released
when completed (which may be after the queue). so the last couple of
snapshots were over-shooting the 1 hour.
The manifest and the logs are bloated by having the full file path for
every filename in there - given the root path is constant.
Could also cause issues if the mount point is ever changed.
