Verified Groovy using [Test Plan]:
# apt-cache policy neutron-common
neutron-common:
Installed: 2:17.1.0-0ubuntu3
Candidate: 2:17.1.0-0ubuntu3
Version table:
*** 2:17.1.0-0ubuntu3 500
500 http://archive.ubuntu.com/ubuntu groovy-proposed/main amd64 Packages
100 /var/lib/dpkg/status
2:17.0.0-0ubuntu3 500
500 http://nova.clouds.archive.ubuntu.com/ubuntu groovy-updates/main
amd64 Packages
2:17.0.0-0ubuntu1 500
500 http://nova.clouds.archive.ubuntu.com/ubuntu groovy/main amd64
Packages
** Description changed:
+ [Impact]
+
When there is a large amount of netdevs registered in the kernel and
debug logging is enabled, neutron-openvswitch-agent and the privsep
daemon spawned by it hang since the RPC call result sent by the privsep
daemon over a unix socket exceeds the message sizes that the msgpack
library can handle.
+
+ The impact of this is that enabling debug logging on the cloud
+ completely stalls neutron-openvswitch-agents and makes them "dead" from
+ the Neutron server perspective.
+
+ The issue is summarized in detail in comment #5
+ https://bugs.launchpad.net/oslo.privsep/+bug/1896734/comments/5
+
+ [Test Plan]
+
+ * deploy Openstack Train/Ussuri/Victoria
+ * need at least one compute host
+ * enable neutron debug logging
+ * create a load of interfaces on your compute host to create a large 'ip
addr show' output
+ * for ((i=0;i<400;i++)); do ip tuntap add mode tap tap-`uuidgen| cut
-c1-11`; done
+ * create a single vm
+ * add floating ip
+ * ping fip
+ * create 20 ports and attach them to the vm
+ * for ((i=0;i<20;i++)); do id=`uuidgen`; openstack port create --network
private --security-group ab698dc1-4b87-4b46-9c38-cd53e3ec7492 X-$id; openstack
server add port X-$id; done
+ * attaching ports should not result in errors
+
+ [Where problems could occur]
+
+ No problems anticipated this patchset.
+
+ ========================================================================
+
+
+ When there is a large amount of netdevs registered in the kernel and debug
logging is enabled, neutron-openvswitch-agent and the privsep daemon spawned by
it hang since the RPC call result sent by the privsep daemon over a unix socket
exceeds the message sizes that the msgpack library can handle.
The impact of this is that enabling debug logging on the cloud
completely stalls neutron-openvswitch-agents and makes them "dead" from
the Neutron server perspective.
The issue is summarized in detail in comment #5
https://bugs.launchpad.net/oslo.privsep/+bug/1896734/comments/5
========================================================================
Old Description
While trying to debug a different issue, I encountered a situation where
privsep hangs in the process of handling a request from neutron-
openvswitch-agent when debug logging is enabled (juju debug-log neutron-
openvswitch=true):
https://bugs.launchpad.net/charm-neutron-openvswitch/+bug/1895652/comments/11
https://bugs.launchpad.net/charm-neutron-openvswitch/+bug/1895652/comments/12
The issue gets reproduced reliably in the environment where I
encountered it on all units. As a result, neutron-openvswitch-agent
services hang while waiting for a response from the privsep daemon and
do not progress past basic initialization. They never post any state
back to the Neutron server and thus are marked dead by it.
The processes though are shown as "active (running)" by systemd which
adds to the confusion since they do indeed start from the systemd's
perspective.
systemctl --no-pager status neutron-openvswitch-agent.service
● neutron-openvswitch-agent.service - Openstack Neutron Open vSwitch Plugin
Agent
Loaded: loaded (/lib/systemd/system/neutron-openvswitch-agent.service;
enabled; vendor preset: enabled)
Active: active (running) since Wed 2020-09-23 08:28:41 UTC; 25min ago
Main PID: 247772 (/usr/bin/python)
Tasks: 4 (limit: 9830)
CGroup: /system.slice/neutron-openvswitch-agent.service
├─247772 /usr/bin/python3 /usr/bin/neutron-openvswitch-agent
--config-file=/etc/neutron/neutron.conf
--config-file=/etc/neutron/plugins/ml2/openvswitch_…og
└─248272 /usr/bin/python3 /usr/bin/privsep-helper --config-file
/etc/neutron/neutron.conf --config-file
/etc/neutron/plugins/ml2/openvswitch_agent.ini -…ck
--------------------------------------------------------
An strace shows that the privsep daemon tries to receive input from fd 3
which is the unix socket it uses to communicate with the client.
However, this is just one tread out of many spawned by the privsep
daemon so it is unlikely to be the root cause (there are 65 threads
there in total, see https://paste.ubuntu.com/p/fbGvN2P8rP/)
# there is one extra neutron-openvvswitch-agent running in a LXD container
which can be ignored here (there is an octavia unit on the node which has a
neutron-openvswitch subordinate)
root@node2:~# ps -eo pid,user,args --sort user | grep -P
'privsep.*openvswitch'
860690 100000 /usr/bin/python3 /usr/bin/privsep-helper --config-file
/etc/neutron/neutron.conf --config-file
/etc/neutron/plugins/ml2/openvswitch_agent.ini --privsep_context
neutron.privileged.default --privsep_sock_path /tmp/tmp910qakfk/privsep.sock
248272 root /usr/bin/python3 /usr/bin/privsep-helper --config-file
/etc/neutron/neutron.conf --config-file
/etc/neutron/plugins/ml2/openvswitch_agent.ini --privsep_context
neutron.privileged.default --privsep_sock_path /tmp/tmpcmwn7vom/privsep.sock
363905 root grep --color=auto -P privsep.*openvswitch
root@node2:~# strace -f -p 248453 2>&1
[pid 248786] futex(0x7f6a6401c1d0,
FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, 0, NULL, 0xffffffff <unfinished
...>
[pid 248475] futex(0x7f6a6c024590,
FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, 0, NULL, 0xffffffff <unfinished
...>
[pid 248473] futex(0x7f6a746d9fd0,
FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, 0, NULL, 0xffffffff <unfinished
...>
[pid 248453] recvfrom(3,
root@node2:~# lsof -p 248453 | grep 3u
privsep-h 248453 root 3u unix 0xffff8e6d8abdec00 0t0 356522977
type=STREAM
root@node2:~# ss -pax | grep 356522977
u_str ESTAB 0 0
/tmp/tmp2afa3enn/privsep.sock 356522978
* 356522977
users:(("/usr/bin/python",pid=247567,fd=16))
u_str ESTAB 0 0
* 356522977
* 356522978
users:(("privsep-helper",pid=248453,fd=3))
root@node2:~# lsof -p 247567 | grep 16u
/usr/bin/ 247567 neutron 16u unix 0xffff8e6d8abdb400 0t0 356522978
/tmp/tmp2afa3enn/privsep.sock type=STREAM
** Tags removed: verification-needed-groovy
** Tags added: verification-done-groovy
--
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https://bugs.launchpad.net/bugs/1896734
Title:
A privsep daemon spawned by neutron-openvswitch-agent hangs when debug
logging is enabled (large number of registered NICs) - an RPC response
is too large for msgpack
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