ruby - Arel::Table @aliases memory leak when used in Rails 5 -

one sentence summary question: cause arel::table's @aliases array grow in size every search done using activerecord?

i have written simple web application using rails 5. when load tested it, memory usage increased indefinitely. after 2.2 million requests, process 1gb of resident memory size.

i investigated getting heap dumps before, right after, , 10 minutes after executing load test 100,000 requests. analyzed heap dumps using the heap dump diffing tool found here. says there 398,000 leaked objects created arel::table#alias().

this statement seems culprit:

@aliases << node 

i confirmed arel::table's @aliases array source of memory leak adding call uniq! in installed version of arel::table#alias():

def alias name = "#{self.name}_2"   nodes::tablealias.new(self, name).tap |node|     @aliases << node   end   @aliases.uniq! # locally added line end 

with modification arel, app's memory usage remained flat duration of load test.

as far can tell, @aliases grows every request app, , grows identical objects. wondering whether bug in arel or doing bad in app cause array grow without ever being cleared or garbage collected.

the app has 4 models:

models

class devicevendor < applicationrecord end  class group < applicationrecord end  class radiusdevice < applicationrecord   belongs_to :device_vendor   validates :ipv4_address, :ip => {format: :v4} end  class radiusvsa < applicationrecord   belongs_to :group   belongs_to :device_vendor end 

migrations

class creategroups < activerecord::migration[5.0]   def change     create_table :groups |t|       t.string :dn       t.integer :rank        t.timestamps     end   end end  class createdevicevendors < activerecord::migration[5.0]   def change     create_table :device_vendors |t|       t.string :name        t.timestamps     end   end end  class createradiusdevices < activerecord::migration[5.0]   def change     create_table :radius_devices |t|       t.string :ipv4_address       t.string :model_number       t.belongs_to :device_vendor, index: true, foreign_key: true        t.timestamps     end   end end  class createradiusvsas < activerecord::migration[5.0]   def change     create_table :radius_vsas |t|       t.string :radius_attributes       t.belongs_to :device_vendor, index: true, foreign_key: true       t.belongs_to :group, index: true, foreign_key: true        t.timestamps     end    end end 

my http endpoint searches radiusvsa based on input parameters group.dn , radiusdevice.ipv4_address. here activerecord calls involved:

# groups param value like: ['ou=foo,cn=bar', 'ou=baz,cn=qux'] group = group.order(rank: :desc).find_by!(dn: params.require('groups')) # source param value like: '10.0.0.1' radius_device = radiusdevice.find_by!(ipv4_address: params.require('source')) # radiusvsa.find_by! call causes arel::table#alias() invoked vendor_attributes = radiusvsa.find_by!(group: group, device_vendor: radius_device.device_vendor) 

it turns out memory leak bug in arel. after getting no responses here day created an issue in rails has been fixed.