qrilka / kontiki

An implementation of the Raft consensus protocol

kontiki

An implementation of the Raft consensus protocol. Please check original paper for details of the protocol

Hacking

This project is built using cabal. It is recommended that you use cabal >= 1.18 as it introduces an excellent sandboxing capability which deprecates cabal-dev.

Building

If you use the cabal sandboxes first run:

$ cabal sandbox init

This will initialize an empty sandbox under .cabal-sandbox. From this point forward, all dependencies will be installed locally into the sandbox and will not affect your globally installed packages.

First install all the required dependencies:

$ cabal install --only-dependencies --enable-tests --enable-benchmarks --enable-library-coverage

Then you'll need to run the configure command:

$ cabal configure --enable-tests --enable-benchmarks --enable-library-coverage

After that you should be able to build and run the tests:

$ cabal build && cabal test

Code coverage

Running cabal test with --enable-library-coverage should write the test coverage report under dist/hpc.

Haddock

Simply run:

$ cabal haddock

This should generate the documentation under dist/doc.

Available demos

The bin directory contains at least two demos.

udp.hs

This is a demo of an in-memory kontiki cluster running with the use of conduit. You can run up to 3 nodes and you will be able to see the logs output by them.

Simply run the following in separate terminals (once you have built the udp demo executable):

$ kontiki-udp <nodeid>

Where nodeid = ["node0", "node1", "node2", "node3"]. You should be able to follow the logs output by each instance.

Example output:

Reset election timeout: 15324284
Awaiting event
Got event: EMessage "node0" (MRequestVote (RequestVote {rvTerm = Term 1, rvCandidateId = "node0", rvLastLogIndex = Index {unIndex = 0}, rvLastLogTerm = Term 0}))
Input state: WrapState (Follower (FollowerState {_fCurrentTerm = Term 0, _fVotedFor = Nothing}))
Output state: WrapState (Follower (FollowerState {_fCurrentTerm = Term 1, _fVotedFor = Just "node0"}))
Log: Received RequestVote for newer term, bumping
Log: Granting vote
CSend: "node0" -> MRequestVoteResponse (RequestVoteResponse {rvrTerm = Term 1, rvrVoteGranted = True})
Reset election timeout: 14611709
Log: []
Awaiting event
Got event: EMessage "node0" (MAppendEntries (AppendEntries {aeTerm = Term 1, aeLeaderId = "node0", aePrevLogIndex = Index {unIndex = 0}, aePrevLogTerm = Term 0, aeEntries = [], aeCommitIndex = Index {unIndex = 0}}))
Input state: WrapState (Follower (FollowerState {_fCurrentTerm = Term 1, _fVotedFor = Just "node0"}))
Output state: WrapState (Follower (FollowerState {_fCurrentTerm = Term 1, _fVotedFor = Just "node0"}))
Reset election timeout: 18456774
CSend: "node0" -> MAppendEntriesResponse (AppendEntriesResponse {aerTerm = Term 1, aerSuccess = True, aerLastIndex = Index {unIndex = 0}})
Log: []
Awaiting event
Got event: EMessage "node0" (MAppendEntries (AppendEntries {aeTerm = Term 1, aeLeaderId = "node0", aePrevLogIndex = Index {unIndex = 0}, aePrevLogTerm = Term 0, aeEntries = [Entry {eIndex = Index {unIndex = 1}, eTerm = Term 1, eValue = ("node0",0)},Entry {eIndex = Index {unIndex = 2}, eTerm = Term 1, eValue = ("node0",1)}], aeCommitIndex = Index {unIndex = 0}}))
Input state: WrapState (Follower (FollowerState {_fCurrentTerm = Term 1, _fVotedFor = Just "node0"}))
Output state: WrapState (Follower (FollowerState {_fCurrentTerm = Term 1, _fVotedFor = Just "node0"}))
Reset election timeout: 14154414
Truncate: Index {unIndex = 0}
Log entries: [Entry {eIndex = Index {unIndex = 1}, eTerm = Term 1, eValue = ("node0",0)},Entry {eIndex = Index {unIndex = 2}, eTerm = Term 1, eValue = ("node0",1)}]
CSend: "node0" -> MAppendEntriesResponse (AppendEntriesResponse {aerTerm = Term 1, aerSuccess = True, aerLastIndex = Index {unIndex = 2}})
Log: [(1,("node0",0)),(2,("node0",1))]
Awaiting event
Got event: EMessage "node0" (MAppendEntries (AppendEntries {aeTerm = Term 1, aeLeaderId = "node0", aePrevLogIndex = Index {unIndex = 2}, aePrevLogTerm = Term 1, aeEntries = [Entry {eIndex = Index {unIndex = 3}, eTerm = Term 1, eValue = ("node0",2)},Entry {eIndex = Index {unIndex = 4}, eTerm = Term 1, eValue = ("node0",3)}], aeCommitIndex = Index {unIndex = 2}}))
Input state: WrapState (Follower (FollowerState {_fCurrentTerm = Term 1, _fVotedFor = Just "node0"}))
Output state: WrapState (Follower (FollowerState {_fCurrentTerm = Term 1, _fVotedFor = Just "node0"}))
Reset election timeout: 17577659
Truncate: Index {unIndex = 2}
Log entries: [Entry {eIndex = Index {unIndex = 3}, eTerm = Term 1, eValue = ("node0",2)},Entry {eIndex = Index {unIndex = 4}, eTerm = Term 1, eValue = ("node0",3)}]
CSend: "node0" -> MAppendEntriesResponse (AppendEntriesResponse {aerTerm = Term 1, aerSuccess = True, aerLastIndex = Index {unIndex = 4}})
Log: [(1,("node0",0)),(2,("node0",1)),(3,("node0",2)),(4,("node0",3))]
Awaiting event
[snip]

Contributing

Have a look at the issues and try to implement the proposed features.