Problem
The login to the Nextcloud app is not reliable. Sometimes it is very fast but very often it takes up to three or four minutes.
Investigation
Nextcloud was installed as a container on the UCS host.
Step 1: Server usage
top
did not show any high load on the server:
top - 17:07:49 up 8:57, 1 user, load average: 0,02, 0,05, 0,01
Tasks: 164 total, 1 running, 163 sleeping, 0 stopped, 0 zombie
%Cpu(s): 0,7 us, 1,0 sy, 0,0 ni, 97,7 id, 0,7 wa, 0,0 hi, 0,0 si, 0,0 st
KiB Mem : 4050972 total, 2568596 free, 691516 used, 790860 buff/cache
KiB Swap: 2097148 total, 2097148 free, 0 used. 3107404 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
7 root 20 0 0 0 0 S 0,3 0,0 0:05.00 rcu_sched
1285 root 20 0 521756 43828 21236 S 0,3 1,1 0:00.28 samba
1926 root 20 0 177952 22240 11148 S 0,3 0,5 0:00.78 dhcpd
30311 root 20 0 139808 10608 9152 S 0,3 0,3 0:00.03 sshd
Step 2: Check network settings
Use ip, route and ucr to get information about network settings:
root@ucs:~# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
link/ether 00:22:19:ba:13:67 brd ff:ff:ff:ff:ff:ff
inet 172.16.100.100/16 brd 172.10.255.255 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::222:19ff:feba:1367/64 scope link
valid_lft forever preferred_lft forever
3: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default
link/ether 02:42:26:c8:b9:ab brd ff:ff:ff:ff:ff:ff
inet 172.17.42.1/16 scope global docker0
valid_lft forever preferred_lft forever
inet6 fe80::42:26ff:fec8:b9ab/64 scope link
valid_lft forever preferred_lft forever
root@ucs:~# route -n
Kernel-IP-Routentabelle
Ziel Router Genmask Flags Metric Ref Use Iface
0.0.0.0 172.16.100.1 0.0.0.0 UG 0 0 0 eth0
172.16.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0
172.17.0.0 0.0.0.0 255.255.0.0 U 0 0 0 docker0
root@ucs:~# ucr search --brief --value 172.
appcenter/apps/nextcloud/ip: 172.17.0.2
dns/allow/query/cache: localhost; 10.0.0.0/8; 169.254.0.0/16; 172.16.0.0/12; 192.168.0.0/16; fc00::/7; fe80::/10; localnets
dns/forwarder1: 172.16.100.1
docker/daemon/default/opts/bip: 172.17.42.1/16
gateway: 172.16.100.1
interfaces/eth0/address: 172.16.100.100
interfaces/eth0/broadcast: 172.16.255.255
interfaces/eth0/network: 172.16.0.0
nameserver1: 172.16.100.100
[...]
Step 3: Check consistency of DNS entries
Repeat DNS queries to leverage cacheing:
root@ucs:~# for i in {0..3}; do host ucs.multi.ucs; sleep 3; echo ---; done
ucs.multi.ucs has address 192.168.1.9
ucs.multi.ucs has address 172.16.200.100
---
ucs.multi.ucs has address 192.168.1.9
ucs.multi.ucs has address 172.16.200.100
---
ucs.multi.ucs has address 172.16.200.100
ucs.multi.ucs has address 192.168.1.9
Above shows a second IP address for the host named “ucs.multi.ucs” but this IP address is not configured (see above steps).
Step 4:
Check DNS entry of the host in UMC.
In UMC the host had as additional IP the address 192.168.1.9 which was removed then.
Solution
In DNS settings the UCS server had an non existing IP address attached. Removing this IP led brought a fast login back.