Add rocksdb

[Stumble]

tendermint/tendermint#3831

Using my fork of gorocksdb from https://github.com/tecbot/gorocksdb for two reasons: 1. The upstream repo encourages vendoring for API stability. 2. The default LDFLAGS setting in upstream repo enforces linking unnecessary compression libraries(https://github.com/tecbot/gorocksdb/blob/162552197222a834c6857385ae890e4decdd5049/dynflag.go#L5), so that if the library is not installed, link will fail. IMHO, tendermint should fork this wrapper and use it here.

To run tests:
First, install rocksdb,

homedir="$PWD"
sudo apt-get update
sudo apt-get install -y build-essential gcc g++ make libgflags-dev libsnappy-dev
wget -O rocks.tar.gz https://github.com/facebook/rocksdb/archive/v6.1.2.tar.gz && \
  tar -zxvf rocks.tar.gz && \
  cd rocksdb-6.1.2/ && \
  make static_lib -j4 && \
  sudo cp librocksdb.a /usr/local/lib/ && \
  cd include/ && \
  sudo rm -rf /usr/local/include/rocksdb && \
  sudo cp -r rocksdb /usr/local/include/ && \
  sudo ldconfig
cd "$homedir"
rm rocks.tar.gz
rm -rf rocksdb-6.1.2

Run tests:

GO_LDFLAGS="-lsnappy" go test -v -tags "rocksdb"

[melekes]

👍 looking good. left a few comments. would be great to have more tests!

[melekes]

what this line does?

[Stumble]

Do you mean these variables? read/write options?

[melekes]

I mean woSync.SetSync(true)

[Stumble]

woSync.SetSync(true) prepares a sync write option. https://godoc.org/github.com/tecbot/gorocksdb#WriteOptions.SetSync

[melekes]

why not put this above with defer? that way we'll avoid duplication s.Free() in moveSliceToBytes and here.

[Stumble]

turns out res.Free() when err != nil is not necessary, removed. I would prefer to have a function that moves c bytes to go slice.

[melekes]

Using my fork of gorocksdb from https://github.com/tecbot/gorocksdb for two reasons:

Have you tried to contribute back to original lib?

[Stumble]

Using my fork of gorocksdb from https://github.com/tecbot/gorocksdb for two reasons:

Have you tried to contribute back to original lib?

Nope, as vendoring was suggested for gorocksdb anyway. I just sent an issue in the upstream, let's see how it goes.

[Stumble]

@melekes , the upstream has not respond to the issue yet. tecbot/gorocksdb#167

[Stumble]

Rocksdb's stats does not work with https://github.com/cosmos/cosmos-sdk/blob/e4c8bd72b72b18035ede103cb4a47da5825d330e/server/export.go#L95.

[tac0turtle]

@Stumble it seems gorocksdb has picked up steam could you rebase your fork until your PR get merged?

[Stumble]

@marbar3778 The PR is merged, I suggest we switch to the original branch.