Reduce public interface of this package. Later each result will contain
an additional status, so it makes more sense to use the same functions
and result processing everywhere.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
Do not check that a node indeed belongs to the container, because the
synchronization will fail in this case anyway.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
1. Modifying operations are not expected to fail, unless the shard is
read-only.
2. `Get*` operations should increase error counter too, unless the
error is `ErrTreeNotFound`.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
Do not return backend type from the service for now, because memory
backend is expected to vanish.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
The tricky part here is the engine itself: we stop iteration on
`ErrReadOnly` because it is better to synchronize the shard later than
to have partial trees stored in 2 shards.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
Current implementation prevents invalid operations to become valid at
some later point (consider adding a child to the non-existent parent and
then adding the parent). This seems to diverge from the paper algorithm
and complicates implementation. Make it simpler.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
In case node is down or failing for some reason, we can expect `Dial` to
fail. In case we actively try to replicate and `Dial` always takes 2
seconds, replication-related channels quickly become full. That affects
latency of all other write operations.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
Before this commit the replication channel was quickly filled under
heavy load. This lead to the continuously increasing latency for all
write operations. Now it looks better.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
Also fix a bug with replicator using the multiaddress instead of
<host>:<port> format expected by gRPC library.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
Currently to find a node by path we iterate over all the children on
each level. This is far from optimal and scales badly with the number of
nodes on a single level. Thus we introduce "indexed attributes" for
which an additional information is stored and which can be use in
`*ByPath` operations. Currently this set only includes `FileName`
attribute but this may change in future.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
Consider a node `{FileName: "dir", Attribute: "xxx"}`. In case we add
a new node by path `["dir", "file.txt"]`, create a new intermediate node
with a single attribute.
`GetByPath` now also considers only nodes with a single attribute while building a path.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
In this commit we implement algorithm for CRDT trees from
https://martin.klepmann.com/papers/move-op.pdf
Each tree is identified by the ID of a container it belongs to
and the tree name itself. Essentially, it is a sequence of operations
which should be applied in chronological order to get a usual tree
representation.
There are 2 backends for now: bbolt database and in-memory.
In-memory backend is here for debugging and will eventually act
as a memory-cache for the on-disk database.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
