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[DNM] storage: introduce SST snapshot strategy #25134

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[DNM] storage: introduce SST snapshot strategy #25134

wants to merge 5 commits into from

Commits on Apr 27, 2018

  1. c-deps: pull in rocksdb range deletion ingestion change 

    facebook/rocksdb#3778 adds a DeleteRange method
to SstFileWriter and adds support for ingesting SSTs with range deletion
tombstones.

facebook/rocksdb#3779 adds a virtual Truncate method
to Env, which truncates the named file to the specified size.

Release note: None
    @nvanbenschoten
    nvanbenschoten committed Apr 27, 2018
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  2. engine: implement engine.Writer interface on RocksDBSstFileWriter 

    This change adds the `Merge`, `Clear`, and `ClearRange` methods to
`RocksDBSstFileWriter`. In doing so, it makes the type implement the
`engine.Writer` interface.

Release note: None
    @nvanbenschoten
    nvanbenschoten committed Apr 27, 2018
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  3. engine: add Truncate method to RocksDBSstFileWriter 

    This change adds a `Truncate` method to `RocksDBSstFileWriter`. This
method truncates the current SST file and returns the data that was
deleted. This can be used to chunk the SST into pieces. Because SSTs
are built in an append-only manner, this is safe and the sum of the
resulting chunks is equivalent to an SST built without ever calling
`Truncate`.

Release note: None
    @nvanbenschoten
    nvanbenschoten committed Apr 27, 2018
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  4. storage: include snapshotStrategy directly in IncomingSnapshot 

    Instead of decomposing the results of a received snapshot and inserting
each separate piece of state into an `IncomingSnapshot`, we now store
this state directly on each `snapshotStrategy`. The `snapshotStrategy`
is then attached to a `IncomingSnapshot`. This makes more sense, because
the state is specific to the snapshotStrategy, and different strategies
will receive different types of data in different representations.

Release note: None
    @nvanbenschoten
    nvanbenschoten committed Apr 27, 2018
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  5. [DNM] storage: introduce SST snapshot strategy 

    Fixes cockroachdb#16954.
Related to cockroachdb#25047.

This depends on the following two upstream changes to RockDB:
- facebook/rocksdb#3778
- facebook/rocksdb#3779

The change introduces a new snapshot strategy called "SST". This strategy
stream sst files consisting of all keys in a range from the sender to the
receiver. These sst files are then atomically ingested directly into RocksDB.
An important property of the strategy is that the amount of memory required
for a receiver using the strategy is constant with respect to the size of
a range, instead of linear as it is with the KV_BATCH strategy. This will
be critical for increasing the default range size and potentially for
increasing the number of concurrent snapshots allowed per node. The
strategy also seems to significantly speed up snapshots once ranges are
above a certain size (somewhere in the single digit MBs).

This is a WIP change. Before it can be merged it needs:
- to be cleaned up a bit
- more testing (unit test, testing knobs, maybe some chaos)
- proper version handling
- heuristic tuning
- decisions on questions like compactions after ingestion

Release note: None
    @nvanbenschoten
    nvanbenschoten committed Apr 27, 2018
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