Cluster.conf

######################################
# Akka Cluster Reference Config File #
######################################

# This is the reference config file that contains all the default settings.
# Make your edits/overrides in your application.conf.

akka {

  cluster {
    # Initial contact points of the cluster.
    # The nodes to join automatically at startup.
    # Comma separated full URIs defined by a string on the form of
    # "akka.tcp://system@hostname:port"
    # Leave as empty if the node is supposed to be joined manually.
    seed-nodes = []

    # How long to wait for one of the seed nodes to reply to initial join request.
    # When this is the first seed node and there is no positive reply from the other
    # seed nodes within this timeout it will join itself to bootstrap the cluster.
    # When this is not the first seed node the join attempts will be performed with
    # this interval.
    seed-node-timeout = 5s

    # If a join request fails it will be retried after this period.
    # Disable join retry by specifying "off".
    retry-unsuccessful-join-after = 10s

    # The joining of given seed nodes will by default be retried indefinitely until
    # a successful join. That process can be aborted if unsuccessful by defining this
    # timeout. When aborted it will run CoordinatedShutdown, which by default will
    # terminate the ActorSystem. CoordinatedShutdown can also be configured to exit
    # the JVM. It is useful to define this timeout if the seed-nodes are assembled
    # dynamically and a restart with new seed-nodes should be tried after unsuccessful
    # attempts.
    shutdown-after-unsuccessful-join-seed-nodes = off

    # Should the 'leader' in the cluster be allowed to automatically mark
    # unreachable nodes as DOWN after a configured time of unreachability?
    # Using auto-down implies that two separate clusters will automatically be
    # formed in case of network partition.
    # Disable with "off" or specify a duration to enable auto-down.
	# If a downing-provider-class is configured this setting is ignored.
    auto-down-unreachable-after = off

    # Time margin after which shards or singletons that belonged to a downed/removed
    # partition are created in surviving partition. The purpose of this margin is that
    # in case of a network partition the persistent actors in the non-surviving partitions
    # must be stopped before corresponding persistent actors are started somewhere else.
    # This is useful if you implement downing strategies that handle network partitions,
    # e.g. by keeping the larger side of the partition and shutting down the smaller side.
    # It will not add any extra safety for auto-down-unreachable-after, since that is not
    # handling network partitions.
    # Disable with "off" or specify a duration to enable.
    down-removal-margin = off

	# Pluggable support for downing of nodes in the cluster.
    # If this setting is left empty behaviour will depend on 'auto-down-unreachable' in the following ways:
    # * if it is 'off' the `NoDowning` provider is used and no automatic downing will be performed
    # * if it is set to a duration the `AutoDowning` provider is with the configured downing duration
    #
    # If specified the value must be the fully qualified class name of an implementation of
    # `Akka.Cluster.IDowningProvider` having two argument constructor:
    #   - argument 1: accepting an `ActorSystem`
    #   - argument 2: accepting an `Akka.Cluster.Cluster`
    downing-provider-class = ""

    # If this is set to "off", the leader will not move 'Joining' members to 'Up' during a network
    # split. This feature allows the leader to accept 'Joining' members to be 'WeaklyUp'
    # so they become part of the cluster even during a network split. The leader will
    # move `Joining` members to 'WeaklyUp' after this configured duration without convergence.
    # The leader will move 'WeaklyUp' members to 'Up' status once convergence has been reached.
    allow-weakly-up-members = 7s

    # The roles of this member. List of strings, e.g. roles = ["A", "B"].
    # The roles are part of the membership information and can be used by
    # routers or other services to distribute work to certain member types,
    # e.g. front-end and back-end nodes.
    roles = []

    # Application version of the deployment. Used by rolling update features
    # to distinguish between old and new nodes. The typical convention is to use
    # 3 digit version numbers `major.minor.patch`, but 1 or two digits are also
    # supported.
    #
    # If no `.` is used it is interpreted as a single digit version number or as
    # plain alphanumeric if it couldn't be parsed as a number.
    #
    # It may also have a qualifier at the end for 2 or 3 digit version numbers such
    # as "1.2-RC1".
    # For 1 digit with qualifier, 1-RC1, it is interpreted as plain alphanumeric.
    #
    # It has support for https://github.com/dwijnand/sbt-dynver format with `+` or
    # `-` separator. The number of commits from the tag is handled as a numeric part.
    # For example `1.0.0+3-73475dce26` is less than `1.0.10+10-ed316bd024` (3 < 10).
    #
    # DEFAULT: by default the app-version will default to the entry assembly's version,
    # i.e. the assembly of the executable running `Program.cs`
    #
    # Values can be "assembly-version" or a version string as defined above, i.e.
    # app-version = "1.0.0"
    # app-version = "1.1-beta1"
    # app-version = "1"
    # app-version = "1.1"
    app-version = assembly-version

	# Run the coordinated shutdown from phase 'cluster-shutdown' when the cluster
    # is shutdown for other reasons than when leaving, e.g. when downing. This
    # will terminate the ActorSystem when the cluster extension is shutdown.
    run-coordinated-shutdown-when-down = on

    role {
      # Minimum required number of members of a certain role before the leader
      # changes member status of 'Joining' members to 'Up'. Typically used together
      # with 'Cluster.registerOnMemberUp' to defer some action, such as starting
      # actors, until the cluster has reached a certain size.
      # E.g. to require 2 nodes with role 'frontend' and 3 nodes with role 'backend':
      #   frontend.min-nr-of-members = 2
      #   backend.min-nr-of-members = 3
      #<role-name>.min-nr-of-members = 1
    }

    # Minimum required number of members before the leader changes member status
    # of 'Joining' members to 'Up'. Typically used together with
    # 'Cluster.registerOnMemberUp' to defer some action, such as starting actors,
    # until the cluster has reached a certain size.
    min-nr-of-members = 1

    # Enable/disable info level logging of cluster events
    log-info = on

    # Enable/disable verbose info-level logging of cluster events
    # for temporary troubleshooting. Defaults to 'off'.
    log-info-verbose = off

    # how long should the node wait before starting the periodic tasks
    # maintenance tasks?
    periodic-tasks-initial-delay = 1s

    # how often should the node send out gossip information?
    gossip-interval = 1s

    # discard incoming gossip messages if not handled within this duration
    gossip-time-to-live = 2s

    # how often should the leader perform maintenance tasks?
    leader-actions-interval = 1s

    # how often should the node move nodes, marked as unreachable by the failure
    # detector, out of the membership ring?
    unreachable-nodes-reaper-interval = 1s

    # How often the current internal stats should be published.
    # A value of 0s can be used to always publish the stats, when it happens.
    # Disable with "off".
    publish-stats-interval = off

    # The id of the dispatcher to use for cluster actors.
    # If not specified, the internal dispatcher is used.
    # If specified you need to define the settings of the actual dispatcher.
    use-dispatcher = ""

    # Gossip to random node with newer or older state information, if any with
    # this probability. Otherwise Gossip to any random live node.
    # Probability value is between 0.0 and 1.0. 0.0 means never, 1.0 means always.
    gossip-different-view-probability = 0.8

    # Reduced the above probability when the number of nodes in the cluster
    # greater than this value.
    reduce-gossip-different-view-probability = 400

    # Settings for the Phi accrual failure detector (http://ddg.jaist.ac.jp/pub/HDY+04.pdf
    # [Hayashibara et al]) used by the cluster subsystem to detect unreachable
    # members.
    failure-detector {

      # FQCN of the failure detector implementation.
      # It must implement akka.remote.FailureDetector and have
      # a public constructor with a com.typesafe.config.Config and
      # akka.actor.EventStream parameter.
      implementation-class = "Akka.Remote.PhiAccrualFailureDetector, Akka.Remote"

      # How often keep-alive heartbeat messages should be sent to each connection.
      heartbeat-interval = 1 s

      # Defines the failure detector threshold.
      # A low threshold is prone to generate many wrong suspicions but ensures
      # a quick detection in the event of a real crash. Conversely, a high
      # threshold generates fewer mistakes but needs more time to detect
      # actual crashes.
      threshold = 8.0

      # Number of the samples of inter-heartbeat arrival times to adaptively
      # calculate the failure timeout for connections.
      max-sample-size = 1000

      # Minimum standard deviation to use for the normal distribution in
      # AccrualFailureDetector. Too low standard deviation might result in
      # too much sensitivity for sudden, but normal, deviations in heartbeat
      # inter arrival times.
      min-std-deviation = 100 ms

      # Number of potentially lost/delayed heartbeats that will be
      # accepted before considering it to be an anomaly.
      # This margin is important to be able to survive sudden, occasional,
      # pauses in heartbeat arrivals, due to for example garbage collect or
      # network drop.
      acceptable-heartbeat-pause = 3 s

      # Number of member nodes that each member will send heartbeat messages to,
      # i.e. each node will be monitored by this number of other nodes.
      monitored-by-nr-of-members = 9

      # After the heartbeat request has been sent the first failure detection
      # will start after this period, even though no heartbeat mesage has
      # been received.
      expected-response-after = 1 s

    }

    # If the tick-duration of the default scheduler is longer than the
    # tick-duration configured here a dedicated scheduler will be used for
    # periodic tasks of the cluster, otherwise the default scheduler is used.
    # See akka.scheduler settings for more details.
    scheduler {
      tick-duration = 33ms
      ticks-per-wheel = 512
    }

    debug {
      # log heartbeat events (very verbose, useful mostly when debugging heartbeating issues)
      verbose-heartbeat-logging = off

	  # log gossip merge events (very verbose, useful when debugging convergence issues)
	  verbose-receive-gossip-logging = off
    }
  }

  # Default configuration for routers
  actor.deployment.default {
    # MetricsSelector to use
    # - available: "mix", "heap", "cpu", "load"
    # - or: Fully qualified class name of the MetricsSelector class.
    #       The class must extend akka.cluster.routing.MetricsSelector
    #       and have a public constructor with com.typesafe.config.Config
    #       parameter.
    # - default is "mix"
    metrics-selector = mix
  }
  actor.deployment.default.cluster {
    # enable cluster aware router that deploys to nodes in the cluster
    enabled = off

    # Maximum number of routees that will be deployed on each cluster
    # member node.
    # Note that max-total-nr-of-instances defines total number of routees, but
    # number of routees per node will not be exceeded, i.e. if you
    # define max-total-nr-of-instances = 50 and max-nr-of-instances-per-node = 2
    # it will deploy 2 routees per new member in the cluster, up to
    # 25 members.
    max-nr-of-instances-per-node = 1

    # Maximum number of routees that will be deployed, in total
    # on all nodes. See also description of max-nr-of-instances-per-node.
    # For backwards compatibility reasons, nr-of-instances
    # has the same purpose as max-total-nr-of-instances for cluster
    # aware routers and nr-of-instances (if defined by user) takes
    # precedence over max-total-nr-of-instances.
    max-total-nr-of-instances = 10000

    # Defines if routees are allowed to be located on the same node as
    # the head router actor, or only on remote nodes.
    # Useful for master-worker scenario where all routees are remote.
    allow-local-routees = on

    # Use members with specified role, or all members if undefined or empty.
    use-role = ""

  }

  # Protobuf serializer for cluster messages
  actor {
    serializers {
      akka-cluster = "Akka.Cluster.Serialization.ClusterMessageSerializer, Akka.Cluster"
    }

    serialization-bindings {
      "Akka.Cluster.IClusterMessage, Akka.Cluster" = akka-cluster
	  "Akka.Cluster.Routing.ClusterRouterPool, Akka.Cluster" = akka-cluster
    }

    serialization-identifiers {
	  "Akka.Cluster.Serialization.ClusterMessageSerializer, Akka.Cluster" = 5
    }
  }
}


# split-brain-resolver

# To enable the split brain resolver you first need to enable the provider in your application.conf:
# for old split brain resolver:
# akka.cluster.downing-provider-class = "Akka.Cluster.SplitBrainResolver"
# for new split brain resolver:
# akka.cluster.downing-provider-class = "Akka.Cluster.SBR.SplitBrainResolverProvider"

akka.cluster.split-brain-resolver {
  # Select one of the available strategies (see descriptions below):
  # static-quorum, keep-majority, keep-oldest, down-all, lease-majority, (keep-referee)
  # keep-referee - supported only with the old split brain resolver
  active-strategy = keep-majority

  # 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

  # When reachability observations by the failure detector are changed the SBR decisions
  # are deferred until there are no changes within the 'stable-after' duration.
  # If this continues for too long it might be an indication of an unstable system/network
  # and it could result in delayed or conflicting decisions on separate sides of a network
  # partition.
  # As a precaution for that scenario all nodes are downed if no decision is made within
  # `stable-after + down-all-when-unstable` from the first unreachability event.
  # The measurement is reset if all unreachable have been healed, downed or removed, or
  # if there are no changes within `stable-after * 2`.
  # The value can be on, off, or a duration.
  # By default it is 'on' and then it is derived to be 3/4 of stable-after, but not less than
  # 4 seconds.
  # supported only with the new split brain resolver
  down-all-when-unstable = on
}

# Down the unreachable nodes if the number of remaining nodes are greater than or equal to
# the given 'quorum-size'. Otherwise down the reachable nodes, i.e. it will shut down that
# side of the partition. In other words, the 'size' defines the minimum number of nodes
# that the cluster must have to be operational. If there are unreachable nodes when starting
# up the cluster, before reaching this limit, the cluster may shutdown itself immediately.
# This is not an issue if you start all nodes at approximately the same time.
#
# 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. For example,
# quorum-size configured to 3 in a 6 node cluster may result in a split where each side
# consists of 3 nodes each, i.e. each side thinks it has enough nodes to continue by
# itself. A warning is logged if this recommendation is violated.
akka.cluster.split-brain-resolver.static-quorum {
  # minimum number of nodes that the cluster must have
  quorum-size = undefined

  # if the 'role' is defined the decision is based only on members with that 'role'
  role = ""
}

# Down the unreachable nodes if the current node is in the majority part based the last known
# membership information. Otherwise down the reachable nodes, i.e. the own part. If the
# the parts are of equal size the part containing the node with the lowest address is kept.
# Note that if there are more than two partitions and none is in majority each part
# will shutdown itself, terminating the whole cluster.
akka.cluster.split-brain-resolver.keep-majority {
  # if the 'role' is defined the decision is based only on members with that 'role'
  role = ""
}

# Down the part that does not contain the oldest member (current singleton).
#
# There is one exception to this rule if 'down-if-alone' is defined to 'on'.
# Then, if the oldest node has partitioned from all other nodes the oldest
# will down itself and keep all other nodes running. The strategy will not
# down the single oldest node when it is the only remaining node in the cluster.
#
# Note that if the oldest node crashes the others will remove it from the cluster
# when 'down-if-alone' is 'on', otherwise they will down themselves if the
# oldest node crashes, i.e. shutdown the whole cluster together with the oldest node.
akka.cluster.split-brain-resolver.keep-oldest {
  # Enable downing of the oldest node when it is partitioned from all other nodes
  down-if-alone = on

  # if the 'role' is defined the decision is based only on members with that 'role',
  # i.e. using the oldest member (singleton) within the nodes with that role
  role = ""
}

# Keep the part that can acquire the lease, and down the other part.
# Best effort is to keep the side that has most nodes, i.e. the majority side.
# This is achieved by adding a delay before trying to acquire the lease on the
# minority side.
# supported only with the new split brain resolver
akka.cluster.split-brain-resolver.lease-majority {
  lease-implementation = ""

  # The recommended format for the lease name is "<service-name>-akka-sbr".
  # When lease-name is not defined, the name will be set to "<actor-system-name>-akka-sbr"
  lease-name = ""

  # This delay is used on the minority side before trying to acquire the lease,
  # as an best effort to try to keep the majority side.
  acquire-lease-delay-for-minority = 2s

  # Release the lease after this duration.
  release-after = 40s

  # If the 'role' is defined the majority/minority is based only on members with that 'role'.
  role = ""
}

# supported only with the old split brain resolver
akka.cluster.split-brain-resolver.keep-referee {
  # referee address on the form of "akka.tcp://system@hostname:port"
  address = ""
  down-all-if-less-than-nodes = 1
}