Class: Mongo::Cluster::SdamFlow Private

Inherits:
Object
  • Object
show all
Extended by:
Forwardable
Defined in:
lib/mongo/cluster/sdam_flow.rb

Overview

This class is part of a private API. You should avoid using this class if possible, as it may be removed or be changed in the future.

Handles SDAM flow for a server description changed event.

Updates server descriptions, topology descriptions and publishes SDAM events.

SdamFlow is meant to be instantiated once for every server description changed event that needs to be processed.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(cluster, previous_desc, updated_desc, awaited: false) ⇒ SdamFlow

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns a new instance of SdamFlow.



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# File 'lib/mongo/cluster/sdam_flow.rb', line 30

def initialize(cluster, previous_desc, updated_desc, awaited: false)
  @cluster = cluster
  @topology = cluster.topology
  @original_desc = @previous_desc = previous_desc
  @updated_desc = updated_desc
  @servers_to_disconnect = []
  @awaited = !!awaited
end

Instance Attribute Details

#cluster ⇒ Object (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/mongo/cluster/sdam_flow.rb', line 39

def cluster
  @cluster
end

#original_desc ⇒ Object (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/mongo/cluster/sdam_flow.rb', line 39

def original_desc
  @original_desc
end

#previous_desc ⇒ Object (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/mongo/cluster/sdam_flow.rb', line 39

def previous_desc
  @previous_desc
end

#topology ⇒ Object (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

The topology stored in this attribute can change multiple times throughout a single sdam flow (e.g. unknown -> RS no primary -> RS with primary). Events for topology change get sent at the end of flow processing, such that the above example only publishes an unknown -> RS with primary event to the application.

Returns:

  • Mongo::Cluster::Topology The current topology.



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# File 'lib/mongo/cluster/sdam_flow.rb', line 51

def topology
  @topology
end

#updated_desc ⇒ Object (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/mongo/cluster/sdam_flow.rb', line 39

def updated_desc
  @updated_desc
end

Instance Method Details

#add_servers_from_desc(updated_desc) ⇒ Array<Server>

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Note:

Servers are added unmonitored. Monitoring must be started later

Adds all servers referenced in the given description (which is supposed to have come from a good primary) which are not already in the cluster, to the cluster.

separately.

Returns:

  • (Array<Server>) —

    Servers actually added to the cluster. This is the set of servers on which monitoring should be started.



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# File 'lib/mongo/cluster/sdam_flow.rb', line 385

def add_servers_from_desc(updated_desc)
  added_servers = []
  %w[hosts passives arbiters].each do |m|
    updated_desc.send(m).each do |address_str|
      if server = cluster.add(address_str, monitor: false)
        added_servers << server
      end
    end
  end

  verify_invariants

  added_servers
end

#awaited? ⇒ Boolean

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns:

  • (Boolean) 


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# File 'lib/mongo/cluster/sdam_flow.rb', line 53

def awaited?
  @awaited
end

#became_unknown? ⇒ Boolean

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns whether the server whose description this flow processed was not previously unknown, and is now. Used to decide, in particular, whether to clear the server’s connection pool.

Returns:

  • (Boolean) 


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# File 'lib/mongo/cluster/sdam_flow.rb', line 611

def became_unknown?
  updated_desc.unknown? && !original_desc.unknown?
end

#check_if_has_primary ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Checks if the cluster has a primary, and if not, transitions the topology to ReplicaSetNoPrimary. Topology must be ReplicaSetWithPrimary when invoking this method.



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# File 'lib/mongo/cluster/sdam_flow.rb', line 565

def check_if_has_primary
  unless topology.replica_set?
    raise ArgumentError,
          "check_if_has_primary should only be called when topology is replica set, but it is #{topology.class.name.sub(/.*::/,
                                                                                                                        '')}"
  end

  primary = servers_list.detect do |server|
    # A primary with the wrong set name is not a primary
    server.primary? && server.description.replica_set_name == topology.replica_set_name
  end
  return if primary

  @topology = Topology::ReplicaSetNoPrimary.new(
    topology.options, topology.monitoring, self
  )
end

#commit_changes ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Publishes server description changed events, updates topology on the cluster and publishes topology changed event, as needed based on operations performed during SDAM flow processing.



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# File 'lib/mongo/cluster/sdam_flow.rb', line 499

def commit_changes
  # The application-visible sequence of events should be as follows:
  #
  # 1. Description change for the server which we are processing;
  # 2. Topology change, if any;
  # 3. Description changes for other servers, if any.
  #
  # The tricky part here is that the server description changes are
  # not all processed together.

  publish_description_change_event
  start_pool_if_data_bearing

  topology_changed_event_published = false
  if !topology.equal?(cluster.topology) || @need_topology_changed_event
    # We are about to publish topology changed event.
    # Recreate the topology instance to get its server descriptions
    # up to date.
    @topology = topology.class.new(topology.options, topology.monitoring, cluster)
    # This sends the SDAM event
    cluster.update_topology(topology)
    topology_changed_event_published = true
    @need_topology_changed_event = false
  end

  # If a server description changed, topology description change event
  # must be published with the previous and next topologies being of
  # the same type, unless we already published topology change event
  return if topology_changed_event_published

  return if updated_desc.unknown? && previous_desc.unknown?
  return if updated_desc.equal?(previous_desc)

  return unless topology_effectively_changed?

  # If we are here, there has been a change in the server descriptions
  # in our topology, but topology class has not changed.
  # Publish the topology changed event and recreate the topology to
  # get the new list of server descriptions into it.
  @topology = topology.class.new(topology.options, topology.monitoring, cluster)
  # This sends the SDAM event
  cluster.update_topology(topology)
end

#disconnect_servers ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/mongo/cluster/sdam_flow.rb', line 543

def disconnect_servers
  while server = @servers_to_disconnect.shift
    if server.connected?
      # Do not publish server closed event, as this was already done
      server.disconnect!
    end
  end
end

#do_remove(address_str) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Removes specified server from topology and warns if the topology ends up with an empty server list as a result



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# File 'lib/mongo/cluster/sdam_flow.rb', line 430

def do_remove(address_str)
  servers = cluster.remove(address_str, disconnect: false)
  servers.each do |server|
    # Clear the description so that the server is marked as unknown.
    server.clear_description

    # We need to publish server closed event here, but we cannot close
    # the server because it could be the server owning the monitor in
    # whose thread this flow is presently executing, in which case closing
    # the server can terminate the thread and leave SDAM processing
    # incomplete. Thus we have to remove the server from the cluster,
    # publish the event, but do not call disconnect on the server until
    # the very end when all processing has completed.
    publish_sdam_event(
      Mongo::Monitoring::SERVER_CLOSED,
      Mongo::Monitoring::Event::ServerClosed.new(server.address, cluster.topology)
    )
  end
  @servers_to_disconnect += servers
  return unless servers_list.empty?

  log_warn(
    'Topology now has no servers - this is likely a misconfiguration of the cluster and/or the application'
  )
end

#publish_description_change_event ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/mongo/cluster/sdam_flow.rb', line 456

def publish_description_change_event
  # This method may be invoked when server description definitely changed
  # but prior to the topology getting updated. Therefore we check both
  # server description changes and overall topology changes. When this
  # method is called at the end of SDAM flow as part of "commit changes"
  # step, server description change is incorporated into the topology
  # change.
  return unless @server_description_changed || topology_effectively_changed?

  # updated_desc here may not be the description we received from
  # the server - in case of a stale primary, the server reported itself
  # as being a primary but updated_desc here will be unknown.

  # We used to not notify on Unknown -> Unknown server changes.
  # Technically these are valid state changes (or at least as valid as
  # other server description changes when the description has not
  # changed meaningfully but the events are still published).
  # The current version of the driver notifies on Unknown -> Unknown
  # transitions.

  # Avoid dispatching events when updated description is the same as
  # previous description. This allows this method to be called multiple
  # times in the flow when the events should be published, without
  # worrying about whether there are any unpublished changes.
  return if updated_desc.equal?(previous_desc)

  publish_sdam_event(
    ::Mongo::Monitoring::SERVER_DESCRIPTION_CHANGED,
    ::Mongo::Monitoring::Event::ServerDescriptionChanged.new(
      updated_desc.address,
      topology,
      previous_desc,
      updated_desc,
      awaited: awaited?
    )
  )
  @previous_desc = updated_desc
  @need_topology_changed_event = true
end

#remove ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Removes the server whose description we are processing from the topology.



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# File 'lib/mongo/cluster/sdam_flow.rb', line 423

def remove
  publish_description_change_event
  do_remove(updated_desc.address.to_s)
end

#remove_servers_not_in_desc(updated_desc) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Removes servers from the topology which are not present in the given server description (which is supposed to have come from a good primary).



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# File 'lib/mongo/cluster/sdam_flow.rb', line 403

def remove_servers_not_in_desc(updated_desc)
  updated_desc_address_strs = %w[hosts passives arbiters].map do |m|
    updated_desc.send(m)
  end.flatten
  servers_list.each do |server|
    next if updated_desc_address_strs.include?(address_str = server.address.to_s)

    updated_host = updated_desc.address.to_s
    updated_host += " (self-identified as #{updated_desc.me})" if updated_desc.me && updated_desc.me != updated_host
    log_warn(
      "Removing server #{address_str} because it is not in hosts reported by primary " +
      "#{updated_host}. Reported hosts are: " +
      updated_desc.hosts.join(', ')
    )
    do_remove(address_str)
  end
end

#server_description_changed ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/mongo/cluster/sdam_flow.rb', line 85

def server_description_changed
  @previous_server_descriptions = servers_list.map do |server|
    [ server.address.to_s, server.description ]
  end

  unless update_server_descriptions
    # All of the transitions require that server whose updated_desc we are
    # processing is still in the cluster (i.e., was not removed as a result
    # of processing another response, potentially concurrently).
    # If update_server_descriptions returned false we have no servers
    # in the topology for the description we are processing, stop.
    return
  end

  case topology
  when Topology::LoadBalanced
    @updated_desc = ::Mongo::Server::Description::LoadBalancer.new(
      updated_desc.address
    )
    update_server_descriptions
  when Topology::Single
    if topology.replica_set_name && (updated_desc.replica_set_name != topology.replica_set_name)
      log_warn(
        "Server #{updated_desc.address} has an incorrect replica set name '#{updated_desc.replica_set_name}'; expected '#{topology.replica_set_name}'"
      )
      @updated_desc = ::Mongo::Server::Description.new(
        updated_desc.address,
        {},
        average_round_trip_time: updated_desc.average_round_trip_time,
        minimum_round_trip_time: updated_desc.minimum_round_trip_time
      )
      update_server_descriptions
    end
  when Topology::Unknown
    if updated_desc.standalone?
      update_unknown_with_standalone
    elsif updated_desc.mongos?
      @topology = Topology::Sharded.new(topology.options, topology.monitoring, self)
    elsif updated_desc.primary?
      @topology = Topology::ReplicaSetWithPrimary.new(
        topology.options.merge(replica_set_name: updated_desc.replica_set_name),
        topology.monitoring, self
      )
      update_rs_from_primary
    elsif updated_desc.secondary? || updated_desc.arbiter? || updated_desc.other?
      @topology = Topology::ReplicaSetNoPrimary.new(
        topology.options.merge(replica_set_name: updated_desc.replica_set_name),
        topology.monitoring, self
      )
      update_rs_without_primary
    end
  when Topology::Sharded
    unless updated_desc.unknown? || updated_desc.mongos?
      log_warn(
        "Removing server #{updated_desc.address} because it is of the wrong type (#{updated_desc.server_type.to_s.upcase}) - expected SHARDED"
      )
      remove
    end
  when Topology::ReplicaSetWithPrimary
    if updated_desc.standalone? || updated_desc.mongos?
      log_warn(
        "Removing server #{updated_desc.address} because it is of the wrong type (#{updated_desc.server_type.to_s.upcase}) - expected a replica set member"
      )
      remove
      check_if_has_primary
    elsif updated_desc.primary?
      update_rs_from_primary
    elsif updated_desc.secondary? || updated_desc.arbiter? || updated_desc.other?
      update_rs_with_primary_from_member
    else
      check_if_has_primary
    end
  when Topology::ReplicaSetNoPrimary
    if updated_desc.standalone? || updated_desc.mongos?
      log_warn(
        "Removing server #{updated_desc.address} because it is of the wrong type (#{updated_desc.server_type.to_s.upcase}) - expected a replica set member"
      )
      remove
    elsif updated_desc.primary?
      # Here we change topology type to RS with primary, however
      # while processing updated_desc we may find that its RS name
      # does not match our existing RS name. For this reason
      # is is imperative to NOT pass updated_desc's RS name to
      # topology constructor here.
      # During processing we may remove the server whose updated_desc
      # we are processing (e.g. the RS name mismatch case again),
      # in which case topology type will go back to RS without primary
      # in the check_if_has_primary step.
      @topology = Topology::ReplicaSetWithPrimary.new(
        # Do not pass updated_desc's RS name here
        topology.options,
        topology.monitoring, self
      )
      update_rs_from_primary
    elsif updated_desc.secondary? || updated_desc.arbiter? || updated_desc.other?
      update_rs_without_primary
    end
  else
    raise ArgumentError, "Unknown topology #{topology.class}"
  end

  verify_invariants
  commit_changes
  disconnect_servers
end

#stale_primary? ⇒ Boolean

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Whether updated_desc is for a stale primary.

Returns:

  • (Boolean) 


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# File 'lib/mongo/cluster/sdam_flow.rb', line 584

def stale_primary?
  if updated_desc.max_wire_version >= 17
    return true if updated_desc.election_id.nil? && !topology.max_election_id.nil?
    if updated_desc.election_id && topology.max_election_id && updated_desc.election_id < topology.max_election_id
      return true
    end

    if updated_desc.election_id == topology.max_election_id
      return true if updated_desc.set_version.nil? && !topology.max_set_version.nil?
      if updated_desc.set_version && topology.max_set_version && updated_desc.set_version < topology.max_set_version
        return true
      end
    end
  elsif updated_desc.election_id && updated_desc.set_version
    if topology.max_set_version && topology.max_election_id &&
       (updated_desc.set_version < topology.max_set_version ||
           (updated_desc.set_version == topology.max_set_version &&
               updated_desc.election_id < topology.max_election_id))
      return true
    end
  end
  false
end

#start_pool_if_data_bearing ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

If the server being processed is identified as data bearing, creates the server’s connection pool so it can start populating



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# File 'lib/mongo/cluster/sdam_flow.rb', line 554

def start_pool_if_data_bearing
  return unless updated_desc.data_bearing?

  servers_list.each do |server|
    server.pool if server.address == @updated_desc.address
  end
end

#topology_effectively_changed? ⇒ Boolean

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns whether topology meaningfully changed as a result of running SDAM flow.

The spec defines topology equality through equality of topology types and server descriptions in each topology; this definition is not usable by us because our topology objects do not hold server descriptions and are instead “live”. Thus we have to store the full list of server descriptions at the beginning of SDAM flow and compare them to the current ones.

Returns:

  • (Boolean) 


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# File 'lib/mongo/cluster/sdam_flow.rb', line 624

def topology_effectively_changed?
  return true unless topology.equal?(cluster.topology)

  server_descriptions = servers_list.map do |server|
    [ server.address.to_s, server.description ]
  end

  @previous_server_descriptions != server_descriptions
end

#update_rs_from_primary ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Updates topology which must be a ReplicaSetWithPrimary with information from the primary’s server description.

This method does not change topology type to ReplicaSetWithPrimary - this needs to have been done prior to calling this method.

If the primary whose description is being processed is determined to be stale, this method will change the server description and topology type to unknown.



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# File 'lib/mongo/cluster/sdam_flow.rb', line 215

def update_rs_from_primary
  if topology.replica_set_name.nil?
    @topology = Topology::ReplicaSetWithPrimary.new(
      topology.options.merge(replica_set_name: updated_desc.replica_set_name),
      topology.monitoring, self
    )
  end

  if topology.replica_set_name != updated_desc.replica_set_name
    log_warn(
      "Removing server #{updated_desc.address} because it has an " +
      "incorrect replica set name '#{updated_desc.replica_set_name}'; " +
      "expected '#{topology.replica_set_name}'"
    )
    remove
    check_if_has_primary
    return
  end

  if stale_primary?
    @updated_desc = ::Mongo::Server::Description.new(
      updated_desc.address,
      {},
      average_round_trip_time: updated_desc.average_round_trip_time,
      minimum_round_trip_time: updated_desc.minimum_round_trip_time
    )
    update_server_descriptions
    check_if_has_primary
    return
  end

  if updated_desc.max_wire_version >= 17
    @topology = Topology::ReplicaSetWithPrimary.new(
      topology.options.merge(
        max_election_id: updated_desc.election_id,
        max_set_version: updated_desc.set_version
      ), topology.monitoring, self
    )
  else
    max_election_id = topology.new_max_election_id(updated_desc)
    max_set_version = topology.new_max_set_version(updated_desc)

    if max_election_id != topology.max_election_id ||
       max_set_version != topology.max_set_version
      @topology = Topology::ReplicaSetWithPrimary.new(
        topology.options.merge(
          max_election_id: max_election_id,
          max_set_version: max_set_version
        ), topology.monitoring, self
      )
    end
  end

  # At this point we have accepted the updated server description
  # and the topology (both are primary). Commit these changes so that
  # their respective SDAM events are published before SDAM events for
  # server additions/removals that follow
  publish_description_change_event

  servers_list.each do |server|
    next unless server.address != updated_desc.address

    next unless server.primary?

    server.update_description(
      ::Mongo::Server::Description.new(
        server.address,
        {},
        average_round_trip_time: server.description.average_round_trip_time,
        minimum_round_trip_time: updated_desc.minimum_round_trip_time
      )
    )
  end

  servers = add_servers_from_desc(updated_desc)
  remove_servers_not_in_desc(updated_desc)

  check_if_has_primary

  servers.each do |server|
    server.start_monitoring
  end
end

#update_rs_with_primary_from_member ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Updates a ReplicaSetWithPrimary topology from a non-primary member.



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# File 'lib/mongo/cluster/sdam_flow.rb', line 300

def update_rs_with_primary_from_member
  if topology.replica_set_name != updated_desc.replica_set_name
    log_warn(
      "Removing server #{updated_desc.address} because it has an " +
      "incorrect replica set name (#{updated_desc.replica_set_name}); " +
      "current set name is #{topology.replica_set_name}"
    )
    remove
    check_if_has_primary
    return
  end

  if updated_desc.me_mismatch?
    log_warn(
      "Removing server #{updated_desc.address} because it " +
      "reported itself as #{updated_desc.me}"
    )
    remove
    check_if_has_primary
    return
  end

  have_primary = false
  servers_list.each do |server|
    if server.primary?
      have_primary = true
      break
    end
  end

  return if have_primary

  @topology = Topology::ReplicaSetNoPrimary.new(
    topology.options, topology.monitoring, self
  )
end

#update_rs_without_primary ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Updates a ReplicaSetNoPrimary topology from a non-primary member.



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# File 'lib/mongo/cluster/sdam_flow.rb', line 338

def update_rs_without_primary
  if topology.replica_set_name.nil?
    @topology = Topology::ReplicaSetNoPrimary.new(
      topology.options.merge(replica_set_name: updated_desc.replica_set_name),
      topology.monitoring, self
    )
  end

  if topology.replica_set_name != updated_desc.replica_set_name
    log_warn(
      "Removing server #{updated_desc.address} because it has an " +
      "incorrect replica set name (#{updated_desc.replica_set_name}); " +
      "current set name is #{topology.replica_set_name}"
    )
    remove
    return
  end

  publish_description_change_event

  servers = add_servers_from_desc(updated_desc)

  commit_changes

  servers.each do |server|
    server.start_monitoring
  end

  return unless updated_desc.me_mismatch?

  log_warn(
    "Removing server #{updated_desc.address} because it " +
    "reported itself as #{updated_desc.me}"
  )
  remove
  nil
end

#update_server_descriptions ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Updates descriptions on all servers whose address matches updated_desc’s address.



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# File 'lib/mongo/cluster/sdam_flow.rb', line 61

def update_server_descriptions
  servers_list.each do |server|
    next unless server.address == updated_desc.address
    # SDAM flow must be run when topology version in the new description
    # is equal to the current topology version, per the example in
    # https://github.com/mongodb/specifications/blob/master/source/server-discovery-and-monitoring/server-discovery-and-monitoring.md#what-is-the-purpose-of-topologyversion
    return false unless updated_desc.topology_version_gte?(server.description)

    @server_description_changed = server.description != updated_desc

    # Always update server description, so that fields that do not
    # affect description equality comparisons but are part of the
    # description are updated.
    server.update_description(updated_desc)
    server.update_last_scan

    # If there was no content difference between descriptions, we
    # still need to run sdam flow, but if the flow produces no change
    # in topology we will omit sending events.
    return true
  end
  false
end

#update_unknown_with_standalone ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Transitions from unknown to single topology type, when a standalone server is discovered.



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# File 'lib/mongo/cluster/sdam_flow.rb', line 193

def update_unknown_with_standalone
  if seeds.length == 1
    @topology = Topology::Single.new(
      topology.options, topology.monitoring, self
    )
  else
    log_warn(
      "Removing server #{updated_desc.address} because it is a standalone and we have multiple seeds (#{seeds.length})"
    )
    remove
  end
end

#verify_invariants ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Raises:



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# File 'lib/mongo/cluster/sdam_flow.rb', line 634

def verify_invariants
  return unless Mongo::Lint.enabled?
  return unless cluster.topology.single?
  return unless cluster.servers_list.length > 1

  raise Mongo::Error::LintError,
        "Trying to create a single topology with multiple servers: #{cluster.servers_list}"
end