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# frozen_string_literal: true
module Gitlab
module Database
module LoadBalancing
# A host that wraps the primary database connection.
#
# This class is used to always enable load balancing as if replicas exist,
# without the need for extra database connections. This ensures that code
# using the load balancer doesn't have to handle the case where load
# balancing is enabled, but no replicas have been configured (= the
# default case).
class PrimaryHost
def initialize(load_balancer)
@load_balancer = load_balancer
end
def release_connection
# no-op as releasing primary connections isn't needed.
nil
end
def enable_query_cache!
# This could mess up the primary connection, so we make this a no-op
nil
end
def disable_query_cache!
# This could mess up the primary connection, so we make this a no-op
nil
end
def query_cache_enabled
@load_balancer.pool.query_cache_enabled
end
def connection
@load_balancer.pool.connection
end
def disconnect!(timeout: 120)
nil
end
def offline!
nil
end
def online?
true
end
def primary_write_location
@load_balancer.primary_write_location
end
def database_replica_location
row = query_and_release(<<-SQL.squish)
SELECT pg_last_wal_replay_lsn()::text AS location
SQL
row['location'] if row.any?
rescue *Host::CONNECTION_ERRORS
nil
end
def caught_up?(_location)
true
end
def query_and_release(sql)
connection.select_all(sql).first || {}
rescue StandardError
{}
ensure
release_connection
end
end
end
end
end
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