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Bug 1787360

Summary: [OVN] ovn-controller: avoid unnecessary recomputes when no SB transaction is available
Product: Red Hat Enterprise Linux Fast Datapath Reporter: Dumitru Ceara <dceara>
Component: ovn2.12Assignee: Dumitru Ceara <dceara>
Status: CLOSED ERRATA QA Contact: Jianlin Shi <jishi>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: FDP 20.ACC: ctrautma, jishi, mmichels, ralongi
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: 1787361 (view as bug list) Environment:
Last Closed: 2020-03-10 10:08:18 UTC Type: Bug
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On:    
Bug Blocks: 1787361    

Description Dumitru Ceara 2020-01-02 14:42:16 UTC 
Description of problem:
If ovn-controller is woken up (e.g., a SB DB update needs to be processed) it will try to run the incremental processing engine. If the current SB DB transaction is still in progress this will fail and trigger a full recompute. However, in some cases processing the changes incrementally doesn't require write operations to the SB DB. To fix this, the engine should try to run even when no SB DB txn is available.

Version-Release number of selected component (if applicable):


How reproducible:
Sometimes, based on how long it takes to process the MAC_Binding row update in ovsdb-server.

Steps to Reproduce:
1. Configure a logical switch attached to a logical router. Configure an IP subnet on the logical router port.
2. Enable debug traces in ovn-controller: ovn-appctl -t ovn-controller vlog/set DBG
2. Send a GARP from a VM attached to the logical switch.
3. This should not trigger a full recompute of the database, i.e., no "engine did not run, force recompute next time" log should be seen in ovn-controller.log.

Actual results:
If the transaction issued by ovn-controller is still in progress when the update is received back from ovsdb-server, ovn-controller will trigger a full recompute.

Expected results:
MAC_Binding updates should be processed incrementally even when SB DB txn is NULL.

Additional info:
Fixed by upstream commit: https://github.com/ovn-org/ovn/commit/e2ab60e3a7c60f3adb8da40e4d1cfeb890d6f80e
Comment 3 Jianlin Shi 2020-02-03 06:48:24 UTC 
tried to reproduce on ovn2.12.0-19 with following steps:

#!/bin/bash                                                                                           

systemctl restart openvswitch                                                                         
systemctl restart ovn-northd
ovn-nbctl set-connection ptcp:6641                                                                    
ovn-sbctl set-connection ptcp:6642                                                                    

ovs-vsctl set open . external-ids:system_id=hv1 external-ids:ovn-remote=tcp:20.0.30.25:6642 external-ids:ovn-encap-type=geneve external-ids:ovn-encap-ip=20.0.30.25
                                                                                                      
systemctl restart ovn-controller                                                                      
                                                                                                      
ovn-nbctl lr-add lr1                                                                                  
ovn-nbctl lrp-add lr1 lrp1 00:01:02:00:02:01 192.168.0.254/24 2001::a/64                              
                                                                                                      
ovn-nbctl ls-add ls1                                                                                  
ovn-nbctl lsp-add ls1 ls1-lr1                                                                         
ovn-nbctl lsp-set-options ls1-lr1 router-port=lrp1                                                    
ovn-nbctl lsp-set-addresses ls1-lr1 "00:01:02:00:02:01 192.168.0.254 2001::a"                         
                                                                                                      
ovn-nbctl lsp-add ls1 lsp1                                                                            
ovn-nbctl  set Logical-Switch ls1 other_config:subnet=192.168.0.0/16                                  
ovn-nbctl set Logical-switch ls1 other_config:ipv6_prefix=2001::0                                     
ovn-nbctl lsp-set-addresses lsp1 "00:01:02:00:02:02 192.168.0.1 2001::1"                              
                                                                                                      
ovs-vsctl add-port br-int vm1 -- set interface vm1 type=internal                                      
ip netns add server0                                                                                  
ip link set vm1 netns server0                                                                         
ip netns exec server0 ip link set lo up                                                               
ip netns exec server0 ip link set vm1 up                                                              
ip netns exec server0 ip link set vm1 address 00:01:02:00:02:02                                       
ip netns exec server0 ip addr add 192.168.0.1/24 dev vm1                                              
ip netns exec server0 ip addr add 2001::1/64 dev vm1                                                  
ovs-vsctl set Interface vm1 external_ids:iface-id=lsp1                                                
                                                                                                      
ovn-nbctl lsp-add ls1 lsp2                                                                            
ovn-nbctl lsp-set-addresses lsp2 "00:01:02:00:02:03 192.168.0.2 2001::2"                              
ovs-vsctl add-port br-int vm2 -- set interface vm2 type=internal                                      
ip netns add server1                                                                                  
ip link set vm2 netns server1                                                                         
ip netns exec server1 ip link set lo up                                                               
ip netns exec server1 ip link set vm2 up                                                              
ip netns exec server1 ip link set vm2 address 00:01:02:00:02:03                                       
ip netns exec server1 ip addr add 192.168.0.2/24 dev vm2                                              
ip netns exec server1 ip addr add 2001::2/64 dev vm2                                                  
ovs-vsctl set Interface vm2 external_ids:iface-id=lsp2                                                
                                                                                                      
                                                                                                      
ovn-appctl -t ovn-controller vlog/set DBG                                                             
ip netns exec server0 python garp.py 

[root@dell-per740-12 bz1787360]# cat garp.py 
from scapy.all import *                                                                               
sendp(Ether(src="00:01:02:00:02:02",dst="ff:ff:ff:ff:ff:ff")/ARP(op=1,hwsrc="00:01:02:00:02:02",hwdst="00:00:00:00:00:00",psrc="192.168.0.1",pdst="192.168.0.1"),iface="vm1")

log on ovn-2.12.0-19:

[root@dell-per740-12 bz1787360]# rpm -qa | grep -E "openvswitch|ovn"
ovn2.12-host-2.12.0-19.el7fdp.x86_64
openvswitch2.12-2.12.0-21.el7fdp.x86_64
ovn2.12-central-2.12.0-19.el7fdp.x86_64
openvswitch-selinux-extra-policy-1.0-14.el7fdp.noarch
ovn2.12-2.12.0-19.el7fdp.x86_64

[root@dell-per740-12 bz1787360]# grep "engine did not run, force recompute next time" /var/log/ovn/ovn-controller.log  -c
479

<==== several lines of "engine did not run, force recompute next time"

then on 2.12.0-26:

[root@dell-per740-12 bz1787360]# grep "engine did not run, force recompute next time" /var/log/ovn/ovn-controller.log  -c
1

<=== only one line of "engine did not run, force recompute next time"

Dumitru, does above result verify the issue?
Comment 4 Dumitru Ceara 2020-02-03 08:28:22 UTC 
(In reply to Jianlin Shi from comment #3)
> [root@dell-per740-12 bz1787360]# grep "engine did not run, force recompute
> next time" /var/log/ovn/ovn-controller.log  -c
> 479
> 
> <==== several lines of "engine did not run, force recompute next time"
> 
> then on 2.12.0-26:
> 
> [root@dell-per740-12 bz1787360]# grep "engine did not run, force recompute
> next time" /var/log/ovn/ovn-controller.log  -c
> 1
> 
> <=== only one line of "engine did not run, force recompute next time"
> 
> Dumitru, does above result verify the issue?

Looks good to me.

Thanks,
Dumitru
Comment 5 Jianlin Shi 2020-02-03 08:29:59 UTC 
set VERIFIED per comment 4
Comment 7 errata-xmlrpc 2020-03-10 10:08:18 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2020:0752