Akka.NET Split Brain Resolver

Status
	master
	dev
	Stable
	Prerelease

Currently available downing strategies

• Static Quorum
• Keep Referee
• Keep Majority
• Keep Oldest

You can also create your own downing providers.

• Custom Downing Providers Documentation

Configuration

Configure the downing provider class and split-brain-resolver section similar to below

    akka {
        actor.provider = "Akka.Cluster.ClusterActorRefProvider, Akka.Cluster"
        remote {
            dot-netty.tcp {
                hostname = localhost
                port = 8001
            }
        }
        cluster {
            auto-down-unreachable-after = off

            downing-provider-class = "Akka.Cluster.SplitBrainResolver.SplitBrainResolverDowningProvider, Akka.Cluster.SplitBrainResolver"

            split-brain-resolver {
                # Enable one of the available strategies (see descriptions below):
                # static-quorum, keep-majority, keep-oldest, keep-referee 
                active-strategy = off
                
                # Decision is taken by the strategy when there has been no membership or
                # reachability changes for this duration, i.e. the cluster state is stable.
                stable-after = 20s

                # The strategy named static-quorum will down the unreachable nodes if the number 
                # of remaining nodes are greater than or equal to a configured quorum-size. 
                # Otherwise, it will down the reachable nodes
                static-quorum {
                    # if the 'role' is defined the decision is based only on members with that 'role'
                    role = ""
                    # Minimum number of nodes that the cluster must have (not the total size)
                    # Note that you must not add more members to the cluster than quorum-size * 2 - 1, 
                    # because then both sides may down each other and thereby form two separate clusters
                    quorum-size = 3
                }

                # The strategy named keep-majority will down the unreachable nodes if the current node is 
                # in the majority part based on the last known membership information. Otherwise down the 
                # reachable nodes, i.e. the own part. If the parts are of equal size the part containing 
                # the node with the lowest address is kept.
                keep-majority {
                    # if the 'role' is defined the decision is based only on members with that 'role'
                    role = ""
                }

                # The strategy named keep-oldest will down the part that does not contain the oldest member. 
                # The oldest member is interesting because the active Cluster Singleton instance is 
                # running on the oldest member.
                keep-oldest {
                    # if the 'role' is defined the decision is based only on members with that 'role'
                    role = ""
                    # Enable downing of the oldest node when it is partitioned from all other nodes
                    down-if-alone = off
                }

                # The strategy named keep-referee will down the part that does not contain the given referee node.
                keep-referee {
                    # referee address on the form of "akka.tcp://system@hostname:port"
                    address = ""
                    # If the remaining number of nodes are less than the configured down-all-if-less-than-nodes 
                    # all nodes will be downed. If the referee node itself is removed all nodes will be downed.
                    down-all-if-less-than-nodes = 1
                }
            }

            seed-nodes = ["akka.tcp://test-system@localhost:8001"]
        }
    }

Building

Pre-requsites

1. Nuget on your path
2. Dotnet core sdk 2.0+
3. Visual studio 2017.3+ (Potentially optional, but untested)

Building via dotnet has several alternatives

• dotnet build from the repository root
• build.ps1 from the repository root (used via CI)