#### Problem
The current implementation of get_slots_since() invokes multiple rocksdb::get().
As a result, each get() operation may end up requiring one disk read. This leads
to poor performance of get_slots_since described in #24878.
#### Summary of Changes
This PR makes get_slots_since() use the batched version of multi_get() instead,
which allows multiple get operations to be processed in batch so that they can
be answered with fewer disk reads.
Several of the get() methods return a deserialized object (as opposed to
a Vec<u8>) by first getting a byte array out of Rocks, and then using
bincode::deserialize() to get the underlying type. However,
deserialize() only requires a u8 slice, not an owned Vec<u8>. So, we can
use get_pinned_cf() to reference memory owned by Rocks and avoid an
unnecessary copy.
#### Problem
Previously before #26651, our LedgerCleanupService needs RocksDB background
compactions to reclaim ledger disk space via our custom CompactionFilter.
However, since RocksDB's compaction isn't smart enough to know which file to pick,
we rely on the 1-day compaction period so that each file will be forced to be compacted
once a day so that we can reclaim ledger disk space in time. The downside of this is
each ledger file will be rewritten once per day.
#### Summary of Changes
As #26651 makes LedgerCleanupService actively delete those files whose entire slot-range
is older than both --limit-ledger-size and the current root, we can remove the 1-day compaction
period and get rid of the daily ledger file rewrite.
The results on mainnet-beta shows that this PR reduces ~20% write-bytes-per-second
and reduces ~50% read-bytes-per-second on ledger disk.
#### Problem
Blockstore operations such as get_slots_since() issues multiple rocksdb::get()
at once which is not optimal for performance.
#### Summary of Changes
This PR adds LedgerColumn::multi_get() based on rocksdb::batched_multi_get(),
the optimized version of multi_get() where get requests are processed in batch
to minimize read I/O.
These methods are only used in tests but invoked on a merkle shred they
will always invalidate the shred because the merkle proof will no longer
verify. As a result the shred will not sanitize and blockstore will
avoid inserting them. Their use in tests will result in spurious test
coverage because the shreds will not be ingested.
The commit removes implementation of these methods for merkle shreds.
Follow up commits will entirely remove these methods from shreds api.
Add ledger-tool command print-file-metadata
#### Summary of Changes
This PR adds a ledger tool subcommand print-file-metadata.
```
USAGE:
solana-ledger-tool print-file-metadata [FLAGS] [OPTIONS] [SST_FILE_NAME]
Prints the metadata of the specified ledger-store file.
If no file name is unspecified, then it will print the metadata of all ledger files
```
#### Summary of Changes
Add code comments for lowest_cleanup_slot related functions to improve
the code readability for the consistency between blockstore purge logic
and the read side.
#### Problem
RocksDB's delete_range applies to [from, to) while delete_file_in_range
applies to [from, to] by default, and the rust-rocksdb api does not include
the option to make delete_file_in_range apply to [from, to). Such inconsistency
might cause `blockstore::run_purge` to produce an inconsistent result as it
invokes both delete_range and delete_file_in_range.
#### Summary of Changes
This PR makes all our purge / delete related functions to be inclusive
on both starting and ending slots.
Tenets:
1. Limit thread names to 15 characters
2. Prefix all Solana-controlled threads with "sol"
3. Use Camel case. It's more character dense than Snake or Kebab case
The commit
* Identifies Merkle shreds when recovering from erasure codes and
dispatches specialized code to reconstruct shreds.
* Coding shred headers are added to recovered erasure shards.
* Merkle tree is reconstructed for the erasure batch and added to
recovered shreds.
* The common signature (for the root of Merkle tree) is attached to all
recovered shreds.
#### Problem
get_entries_in_data_block() panics when there's inconsistency between
slot_meta and data_shred.
However, as we don't lock on reads, reading across multiple column families is
not atomic (especially for older slots) and thus does not guarantee consistency
as the background cleanup service could purge the slot in the middle. Such
panic was reported in #26980 when the validator serves a high load of RPC calls.
#### Summary of Changes
This PR makes get_entries_in_data_block() panic only when the inconsistency
between slot-meta and data-shred happens on a slot older than lowest_cleanup_slot.
As a consequence of removing buffering when generating coding shreds:
https://github.com/solana-labs/solana/pull/25807
more coding shreds are generated than data shreds, and so
MAX_CODE_SHREDS_PER_SLOT needs to be adjusted accordingly.
The respective value is tied to ERASURE_BATCH_SIZE.
Given the 32:32 erasure recovery schema, current implementation requires
exactly 32 data shreds to generate coding shreds for the batch (except
for the final erasure batch in each slot).
As a result, when serializing ledger entries to data shreds, if the
number of data shreds is not a multiple of 32, the coding shreds for the
last batch cannot be generated until there are more data shreds to
complete the batch to 32 data shreds. This adds latency in generating
and broadcasting coding shreds.
In addition, with Merkle variants for shreds, data shreds cannot be
signed and broadcasted until coding shreds are also generated. As a
result *both* code and data shreds will be delayed before broadcast if
we still require exactly 32 data shreds for each batch.
This commit instead always generates and broadcast coding shreds as soon
as there any number of data shreds available. When serializing entries
to shreds:
* if the number of resulting data shreds is less than 32, then more
coding shreds will be generated so that the resulting erasure batch
has the same recovery probabilities as a 32:32 batch.
* if the number of data shreds is more than 32, then the data shreds are
split uniformly into erasure batches with _at least_ 32 data shreds in
each batch. Each erasure batch will have the same number of code and
data shreds.
For example:
* If there are 19 data shreds, 27 coding shreds are generated. The
resulting 19(data):27(code) erasure batch has the same recovery
probabilities as a 32:32 batch.
* If there are 107 data shreds, they are split into 3 batches of 36:36,
36:36 and 35:35 data:code shreds each.
A consequence of this change is that code and data shreds indices will
no longer align as there will be more coding shreds than data shreds
(not only in the last batch in each slot but also in the intermediate
ones);
#### Problem
LedgerCleanupService requires compactions to propagate & digest range-delete tombstones
to eventually reclaim disk space.
#### Summary of Changes
This PR makes LedgerCleanupService::cleanup_ledger delete any file whose slot-range is
older than the lowest_cleanup_slot. This allows us to reclaim disk space more often with
fewer IOps. Experimental results on mainnet validators show that the PR can effectively
reduce 33% to 40% ledger disk size.