module Mongo::Operation::SessionsSupported

Shared behavior of operations that support a session.

@since 2.5.2 @api private

Constants

READ_COMMANDS
ZERO_TIMESTAMP

Private Instance Methods

add_read_preference(sel, connection) click to toggle source

Adds $readPreference field to the command document.

$readPreference is only sent when the server is a mongos, following the rules described in github.com/mongodb/specifications/blob/master/source/server-selection/server-selection.rst#passing-read-preference-to-mongos. The topology does not matter for figuring out whether to send $readPreference since the decision is always made based on server type.

$readPreference is sent to OP_MSG-grokking replica set members.

@param [ Hash ] sel Existing command document which will be mutated. @param [ Server::Connection ] connection The connection that the

operation will be executed on.
# File lib/mongo/operation/shared/sessions_supported.rb, line 165
def add_read_preference(sel, connection)
  Lint.assert_type(connection, Server::Connection)

  # https://github.com/mongodb/specifications/blob/master/source/server-selection/server-selection.rst#topology-type-single
  if connection.description.standalone?
    # Read preference is never sent to standalones.
  elsif connection.description.mongos?
    # When server is a mongos:
    # - $readPreference is never sent when mode is 'primary'
    # - When mode is 'secondaryPreferred' $readPreference is only sent
    #   when a non-mode field (i.e. tag_sets) is present
    # - Otherwise $readPreference is sent
    if read
      doc = read.to_mongos
      if doc
        sel['$readPreference'] = doc
      end
    end
  elsif connection.server.cluster.single?
    # In Single topology:
    # - If no read preference is specified by the application, the driver
    #   adds mode: primaryPreferred.
    # - If a read preference is specified by the application, the driver
    #   replaces the mode with primaryPreferred.
    read_doc = if read
      BSON::Document.new(read.to_doc)
    else
      BSON::Document.new
    end
    if [nil, 'primary'].include?(read_doc['mode'])
      read_doc['mode'] = 'primaryPreferred'
    end
    sel['$readPreference'] = read_doc
  else
    # In replica sets, read preference is passed to the server if one
    # is specified by the application, and there is no default.
    if read
      sel['$readPreference'] = read.to_doc
    end
  end
end
add_write_concern!(sel) click to toggle source
# File lib/mongo/operation/shared/sessions_supported.rb, line 94
def add_write_concern!(sel)
  sel[:writeConcern] = write_concern.options if write_concern
end
apply_autocommit!(selector) click to toggle source
# File lib/mongo/operation/shared/sessions_supported.rb, line 98
def apply_autocommit!(selector)
  session.add_autocommit!(selector)
end
apply_causal_consistency!(selector, connection) click to toggle source

Adds causal consistency document to the selector, if one can be constructed and the selector is for a startTransaction command.

When operations are performed in a transaction, only the first operation (the one which starts the transaction via startTransaction) is allowed to have a read concern, and with it the causal consistency document, specified.

# File lib/mongo/operation/shared/sessions_supported.rb, line 49
def apply_causal_consistency!(selector, connection)
  return unless selector[:startTransaction]

  apply_causal_consistency_if_possible(selector, connection)
end
apply_causal_consistency_if_possible(selector, connection) click to toggle source

Adds causal consistency document to the selector, if one can be constructed.

In order for the causal consistency document to be constructed, causal consistency must be enabled for the session and the session must have the current operation time. Also, topology must be replica set or sharded cluster.

# File lib/mongo/operation/shared/sessions_supported.rb, line 62
def apply_causal_consistency_if_possible(selector, connection)
  if !connection.description.standalone?
    cc_doc = session.send(:causal_consistency_doc)
    if cc_doc
      rc_doc = (selector[:readConcern] || read_concern || {}).merge(cc_doc)
      selector[:readConcern] = Options::Mapper.transform_values_to_strings(
        rc_doc)
    end
  end
end
apply_cluster_time!(selector, connection) click to toggle source
# File lib/mongo/operation/shared/sessions_supported.rb, line 77
def apply_cluster_time!(selector, connection)
  if !connection.description.standalone?
    cluster_time = [
      connection.cluster_time,
      session&.cluster_time,
    ].compact.max

    if cluster_time
      selector['$clusterTime'] = cluster_time
    end
  end
end
apply_read_pref!(selector) click to toggle source
# File lib/mongo/operation/shared/sessions_supported.rb, line 110
def apply_read_pref!(selector)
  session.apply_read_pref!(selector) if read_command?(selector)
end
apply_session_options(sel, connection) click to toggle source
# File lib/mongo/operation/shared/sessions_supported.rb, line 207
def apply_session_options(sel, connection)
  apply_cluster_time!(sel, connection)
  sel[:txnNumber] = BSON::Int64.new(txn_num) if txn_num
  sel.merge!(lsid: session.session_id)
  apply_start_transaction!(sel)
  apply_causal_consistency!(sel, connection)
  apply_autocommit!(sel)
  apply_txn_opts!(sel)
  suppress_read_write_concern!(sel)
  validate_read_preference!(sel)
  apply_txn_num!(sel)
  if session.recovery_token &&
    (sel[:commitTransaction] || sel[:abortTransaction])
  then
    sel[:recoveryToken] = session.recovery_token
  end
end
apply_start_transaction!(selector) click to toggle source
# File lib/mongo/operation/shared/sessions_supported.rb, line 102
def apply_start_transaction!(selector)
  session.add_start_transaction!(selector)
end
apply_txn_num!(selector) click to toggle source
# File lib/mongo/operation/shared/sessions_supported.rb, line 106
def apply_txn_num!(selector)
  session.add_txn_num!(selector)
end
apply_txn_opts!(selector) click to toggle source
# File lib/mongo/operation/shared/sessions_supported.rb, line 114
def apply_txn_opts!(selector)
  session.add_txn_opts!(selector, read_command?(selector))
end
build_message(connection) click to toggle source
Calls superclass method
# File lib/mongo/operation/shared/sessions_supported.rb, line 225
def build_message(connection)
  super.tap do |message|
    if session
      # Serialize the message to detect client-side problems,
      # such as invalid BSON keys. The message will be serialized again
      # later prior to being sent to the connection.
      message.serialize(BSON::ByteBuffer.new)

      session.update_state!
    end
  end
end
command(connection) click to toggle source
# File lib/mongo/operation/shared/sessions_supported.rb, line 126
def command(connection)
  if Lint.enabled?
    unless connection.is_a?(Server::Connection)
      raise Error::LintError, "Connection is not a Connection instance: #{connection}"
    end
  end

  sel = selector(connection).dup
  add_write_concern!(sel)
  sel[Protocol::Msg::DATABASE_IDENTIFIER] = db_name

  add_read_preference(sel, connection)

  if connection.features.sessions_enabled?
    apply_cluster_time!(sel, connection)
    if session && (acknowledged_write? || session.in_transaction?)
      apply_session_options(sel, connection)
    end
  elsif session && session.explicit?
    apply_session_options(sel, connection)
  end

  sel
end
flags() click to toggle source
# File lib/mongo/operation/shared/sessions_supported.rb, line 73
def flags
  acknowledged_write? ? [] : [:more_to_come]
end
read_command?(sel) click to toggle source
# File lib/mongo/operation/shared/sessions_supported.rb, line 90
def read_command?(sel)
  READ_COMMANDS.any? { |c| sel[c] }
end
suppress_read_write_concern!(selector) click to toggle source
# File lib/mongo/operation/shared/sessions_supported.rb, line 118
def suppress_read_write_concern!(selector)
  session.suppress_read_write_concern!(selector)
end
validate_read_preference!(selector) click to toggle source
# File lib/mongo/operation/shared/sessions_supported.rb, line 122
def validate_read_preference!(selector)
  session.validate_read_preference!(selector) if read_command?(selector)
end