public void ShouldBecomeFollowerIfAppendEntriesReceivedFromNewLeader()
{
var electionTimeoutInMilliseconds = 1000;
var initialTerm = 0;
var outbox = new ConcurrentBag <object>();
var eventLog = new ConcurrentBag <object>();
var nodeId = Guid.NewGuid();
var numberOfOtherActors = 2;
IEnumerable <Guid> getOtherActors()
{
return(Enumerable.Range(0, numberOfOtherActors).Select(_ => Guid.NewGuid()));
}
_raftNode = new RaftNode(nodeId, outbox.Add, eventLog.Add, getOtherActors, initialTerm,
electionTimeoutInMilliseconds);
void BlockUntilTrue(Func <bool> condition)
{
while (!condition())
{
}
}
// Start the node and let it timeout to trigger an election
_raftNode.Tell(new Initialize());
eventLog.BlockUntilAny(msg => msg is RoleStateChanged rsc && rsc.Term == initialTerm);
// Look for the change in state to a candidate node
Assert.True(eventLog.Count(msg => msg is RoleStateChanged rsc &&
rsc.NewState == RoleState.Candidate &&
rsc.Term == initialTerm) == 1);
// Send a single heartbeat with a higher term so that the node reverts to
// a follower state
var leaderId = Guid.NewGuid();
var requesterId = Guid.NewGuid();
_raftNode.Tell(new Request <AppendEntries>(requesterId,
new AppendEntries(42, leaderId, 0, 0, new object[0], 0)));
// Wait for a response
outbox.BlockUntilAny(msg =>
msg is Response <AppendEntries> response && response.ResponseMessage is AppendEntriesResult ae &&
ae.Term == 42);
var result = outbox.CastAs <Response <AppendEntries> >().First();
Assert.IsType <AppendEntriesResult>(result.ResponseMessage);
var responseMessage = (AppendEntriesResult)result.ResponseMessage;
Assert.True(responseMessage.Success);
// There should also be a state change that shows
// that the candidate node reverted back to a follower state
eventLog.ShouldHaveAtLeastOne(msg => msg is RoleStateChanged rsc && rsc.NewState == RoleState.Follower && rsc.Term > 42);
}