Maxscale 2.2.6 memory leak

Good day! Our maxscale after upgrade from 2.1 to 2.2.6 started suffering from an extremely high memory consumption, that after some time makes system unusable.

Using limits.conf (systemd resource control https://www.freedesktop.org/software/systemd/man/systemd.resource-control.html) to limit memory usage of process leads process to backtracing and re-starting.

Here is our MaxScale config:

[maxscale]

threads=4

[server0]

type=server

address=192.168.34.34

port=3306

protocol=MySQLBackend

serversize=0

priority=6

[server1]

type=server

address=192.168.34.35

port=3306

protocol=MySQLBackend

serversize=100

priority=1

[server2]

type=server

address=192.168.34.36

port=3306

protocol=MySQLBackend

serversize=100

priority=2

[server3]

type=server

address=192.168.34.37

port=3306

protocol=MySQLBackend

serversize=100

priority=5

[server4]

type=server

address=192.168.34.38

port=3306

protocol=MySQLBackend

serversize=100

priority=3

[MySQL Monitor]

type=monitor

module=galeramon

#module=mmmon

servers=server0, server1, server2, server3, server4

user=maxscale

passwd=maxscale

monitor_interval=5000

use_priority=true

[Read-Write-Master Service]

type=service

router=readconnroute

servers=server0, server1, server2, server3, server4

user=maxscale

passwd=maxscale

router_options=master

[Read-Write Service]

type=service

router=readwritesplit

servers=server0, server1, server2, server3, server4

user=maxscale

passwd=maxscale

max_slave_connections=1

router_options=slave_selection_criteria=LEAST_GLOBAL_CONNECTIONS,master_accept_reads=true,strict_multi_stmt=true

[Read-Only Service]

type=service

router=readconnroute

servers=server0, server1, server2, server3, server4

user=maxscale

passwd=maxscale

router_options=slave

weightby=serversize

[MaxAdmin Service]

type=service

router=cli

[Read-Write-Master Listener]

type=listener

service=Read-Write-Master Service

protocol=MySQLClient

port=4007

[Read-Write Listener]

type=listener

service=Read-Write Service

protocol=MySQLClient

port=4006

[Read-Only Listener]

type=listener

service=Read-Only Service

protocol=MySQLClient

port=4005

[MaxAdmin Listener]

type=listener

service=MaxAdmin Service

protocol=maxscaled

socket=default

Here is backtrace of out of memory maxscale:

2018-07-13 20:19:49 alert : (1049629) Fatal: MaxScale 2.2.6 received fatal signal 6. Attempting backtrace.
2018-07-13 20:19:49 alert : (1049629) Commit ID: b72a7a89262eeacac3f3fda3041b6607a57655b7 System name: Linux Release string: undefined
2018-07-13 20:19:49 alert : (1049629) /usr/bin/maxscale() [0x407a60]: ??:0
2018-07-13 20:19:49 alert : (1049629) /lib/x86_64-linux-gnu/libpthread.so.0(+0xf890) [0x7f5ed56bd890]: ??:?
2018-07-13 20:19:49 alert : (1049629) /lib/x86_64-linux-gnu/libc.so.6(gsignal+0x37) [0x7f5ed35f2067]: ??:0
2018-07-13 20:19:49 alert : (1049629) /lib/x86_64-linux-gnu/libc.so.6(abort+0x148) [0x7f5ed35f3448]: ??:0
2018-07-13 20:19:49 alert : (1049629) /usr/lib/x86_64-linux-gnu/libstdc++.so.6(ZN9gnu_cxx27_verbose_terminate_handlerEv+0x15d) [0x7f5ed46e3b3d]: ??:0
2018-07-13 20:19:49 alert : (1049629) /usr/lib/x86_64-linux-gnu/libstdc++.so.6(+0x5ebb6) [0x7f5ed46e1bb6]: ??:?
2018-07-13 20:19:49 alert : (1049629) /usr/lib/x86_64-linux-gnu/libstdc++.so.6(+0x5ec01) [0x7f5ed46e1c01]: ??:?
2018-07-13 20:19:49 alert : (1049629) /usr/lib/x86_64-linux-gnu/libstdc++.so.6(__cxa_rethrow+0x49) [0x7f5ed46e1e69]: ??:0
2018-07-13 20:19:49 alert : (1049629) /usr/lib/x86_64-linux-gnu/maxscale/libreadwritesplit.so(ZNSt3tr110_HashtableIjSt4pairIKjjESaIS3_ESt10_Select1stIS3_ESt8equal_toIjENS_4hashIjEENS_8_detail18_Mod_range_hashingENSB_20_Default_ranged_hashENSB_20_Prime_rehash_policyELb0ELb0ELb1EE16_M_insert_bucketERKS3_mm+0x342) [0x7f5ed100fc02]: /usr/include/c++/4.9/tr1/hashtable.h:874
2018-07-13 20:19:49 alert : (1049629) /usr/lib/x86_64-linux-gnu/maxscale/libreadwritesplit.so(_ZN9PSManager5storeEP5gwbufj+0x129) [0x7f5ed100f679]: /usr/include/c++/4.9/tr1/hashtable_policy.h:531
2018-07-13 20:19:49 alert : (1049629) /usr/lib/x86_64-linux-gnu/maxscale/libreadwritesplit.so(_Z19route_session_writeP14RWSplitSessionP5gwbufhj+0x322) [0x7f5ed100b2c2]: /home/vagrant/MaxScale/server/modules/routing/readwritesplit/rwsplit_route_stmt.cc:345
2018-07-13 20:19:49 alert : (1049629) /usr/lib/x86_64-linux-gnu/maxscale/libreadwritesplit.so(_Z20handle_target_is_all14route_target_tP7RWSplitP14RWSplitSessionP5gwbufij+0x105) [0x7f5ed1006bf5]: /home/vagrant/MaxScale/server/modules/routing/readwritesplit/rwsplit_mysql.cc:252
2018-07-13 20:19:49 alert : (1049629) /usr/lib/x86_64-linux-gnu/maxscale/libreadwritesplit.so(_Z17route_single_stmtP7RWSplitP14RWSplitSessionP5gwbufRK9RouteInfo+0x111) [0x7f5ed100a3e1]: /home/vagrant/MaxScale/server/modules/routing/readwritesplit/rwsplit_route_stmt.cc:283
2018-07-13 20:19:49 alert : (1049629) /usr/lib/x86_64-linux-gnu/maxscale/libreadwritesplit.so(+0x815c) [0x7f5ed100215c]: /home/vagrant/MaxScale/server/modules/routing/readwritesplit/readwritesplit.cc:946
2018-07-13 20:19:49 alert : (1049629) /usr/lib/x86_64-linux-gnu/maxscale/libmariadbclient.so(+0x41b3) [0x7f5ecffcc1b3]: /home/vagrant/MaxScale/server/modules/protocol/MySQL/mariadbclient/mysql_client.cc:1711
2018-07-13 20:19:49 alert : (1049629) /usr/lib/x86_64-linux-gnu/maxscale/libmaxscale-common.so.1.0.0(+0x5ae02) [0x7f5ed5b86e02]: /home/vagrant/MaxScale/server/core/dcb.cc:3108
2018-07-13 20:19:49 alert : (1049629) /usr/lib/x86_64-linux-gnu/maxscale/libmaxscale-common.so.1.0.0(+0x5afd8) [0x7f5ed5b86fd8]: /home/vagrant/MaxScale/server/core/dcb.cc:3200
2018-07-13 20:19:49 alert : (1049629) /usr/lib/x86_64-linux-gnu/maxscale/libmaxscale-common.so.1.0.0(_ZN8maxscale6Worker15poll_waiteventsEv+0x1c1) [0x7f5ed5bc0611]: /home/vagrant/MaxScale/server/core/worker.cc:1207
2018-07-13 20:19:50 alert : (1049629) /usr/lib/x86_64-linux-gnu/maxscale/libmaxscale-common.so.1.0.0(_ZN8maxscale6Worker3runEv+0x10f) [0x7f5ed5bc091f]: /home/vagrant/MaxScale/include/maxscale/log_manager.h:116
2018-07-13 20:19:50 alert : (1049629) /usr/bin/maxscale(main+0x1d92) [0x406112]: /home/vagrant/MaxScale/server/core/gateway.cc:2254
2018-07-13 20:19:50 alert : (1049629) /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf5) [0x7f5ed35deb45]: ??:0
2018-07-13 20:19:50 alert : (1049629) /usr/bin/maxscale() [0x406a85]: ??:0

I read the next minor releases notes of 2.2.x and haven't found any fixes of such leaks described.

Hope someone can assist or help to dig into the root cause of such memory leaking.

Here is our memory usage statistics from one of not very busy production servers. 11GB of memory for proxy is very strange operating.

root@wifidb3:~# cat /proc/7481/status
Name: maxscale
State: S (sleeping)
...
VmPeak: 25622988 kB
VmSize: 25561088 kB
VmLck: 0 kB
VmPin: 0 kB
VmHWM: 11341768 kB
VmRSS: 11341768 kB
VmData: 25465648 kB
VmStk: 2180 kB
VmExe: 52 kB
VmLib: 14736 kB
VmPTE: 49332 kB
VmPMD: 108 kB
VmSwap: 13789792 kB
...