Workaround of race condition between systemd and nginx.

[Gena Makhomed]

On 30.12.2015 16:51, Jim Popovitch wrote:

>> # HG changeset patch
>> # User Gena Makhomed <gmm at csdoc.com>
>> # Date 1451482795 18000
>> #      Wed Dec 30 08:39:55 2015 -0500
>> # Node ID a340d271b3ffa51c0396a5afc5270cb02b701204
>> # Parent  1073d7e4e430ddb53b603d151e1a403d10aa420b
>> Workaround of race condition between systemd and nginx.
>>
>> Just replace network.target with network-online.target in systemd unit
> files.
>> More details:
> http://www.freedesktop.org/wiki/Software/systemd/NetworkTarget/
>
>>From that page, wrt network-online.target:
>
> "It is strongly recommended not to pull in this target too liberally: for
> example network server software should generally not pull this in (since
> server software generally is happy to accept local connections even before
> any routable network interface is up), it's primary purpose is network
> client software that cannot operate without network"

nginx is FreeBSD daemon, ant it is not systemd-aware,
and nginx not follow many strange systemd guidelines.

Current race condition between systemd and nginx follow
to non-working nginx daemon at least under CentOS 7.2
templates under OpenVZ after system reboot.

nginx now requires configured and up network, before starting daemon.
Replace network.target with network-online.target is easy workaround.

P.S.

# cat /var/log/messages

Dec 27 19:08:38 stage-ideil-com systemd: Starting nginx - high 
performance web server...
Dec 27 19:08:39 stage-ideil-com systemd: Starting System Logging Service...
Dec 27 19:08:39 stage-ideil-com systemd: Starting LSB: Bring up/down 
networking...
Dec 27 19:08:39 stage-ideil-com systemd: Starting Postfix Mail Transport 
Agent...
[...]
Dec 27 19:09:24 stage-ideil-com systemd: nginx.service: control process 
exited, code=exited status=1
Dec 27 19:09:24 stage-ideil-com systemd: Failed to start nginx - high 
performance web server.
Dec 27 19:09:24 stage-ideil-com systemd: Unit nginx.service entered 
failed state.
Dec 27 19:09:24 stage-ideil-com systemd: nginx.service failed.
Dec 27 19:09:24 stage-ideil-com systemd-sysctl: Failed to write '16' to 
'/proc/sys/kernel/sysrq': Permission denied
Dec 27 19:09:24 stage-ideil-com systemd-sysctl: Failed to write '1' to 
'/proc/sys/kernel/core_uses_pid': Permission denied
 >Dec 27 19:09:24 stage-ideil-com systemd: Started LSB: Bring up/down 
networking.
 >Dec 27 19:09:24 stage-ideil-com systemd: Reached target Network is Online.
 >Dec 27 19:09:24 stage-ideil-com systemd: Starting Network is Online.
Dec 27 19:09:24 stage-ideil-com systemd: Started The PHP FastCGI Process 
Manager.
 >Dec 27 19:09:24 stage-ideil-com nginx: nginx: the configuration file 
/etc/nginx/nginx.conf syntax is ok
 >Dec 27 19:09:24 stage-ideil-com nginx: nginx: [emerg] bind() to 
172.22.22.202:80 failed (99: Cannot assign requested address)
 >Dec 27 19:09:24 stage-ideil-com nginx: nginx: configuration file 
/etc/nginx/nginx.conf test failed
 >Dec 27 19:09:24 stage-ideil-com network: Bringing up loopback 
interface:  [  OK  ]
 >Dec 27 19:09:25 stage-ideil-com network: Bringing up interface venet0: 
  arping: Device venet0 not available.
 >Dec 27 19:09:25 stage-ideil-com network: [  OK  ]

=====================================================================

# cat /var/log/messages

Dec 24 18:55:14 hroniky-com systemd: Starting Sockets.
Dec 24 18:55:14 hroniky-com systemd: Reached target Basic System.
Dec 24 18:55:14 hroniky-com systemd: Starting Basic System.
Dec 24 18:55:14 hroniky-com systemd: Started D-Bus System Message Bus.
Dec 24 18:55:14 hroniky-com systemd: Starting D-Bus System Message Bus...
Dec 24 18:55:14 hroniky-com systemd: Starting Permit User Sessions...
Dec 24 18:55:14 hroniky-com systemd: Starting Postfix Mail Transport 
Agent...
Dec 24 18:55:14 hroniky-com systemd: Started OpenSSH Server Key Generation.
Dec 24 18:55:14 hroniky-com systemd: Starting /etc/rc.d/rc.local 
Compatibility...
Dec 24 18:55:15 hroniky-com systemd: Starting nginx - high performance 
web server...
Dec 24 18:55:18 hroniky-com systemd: Starting System Logging Service...
Dec 24 18:55:18 hroniky-com systemd: Starting LSB: Bring up/down 
networking...
Dec 24 18:55:18 hroniky-com nginx: nginx: the configuration file 
/etc/nginx/nginx.conf syntax is ok
Dec 24 18:55:18 hroniky-com nginx: nginx: [emerg] bind() to 
172.23.23.161:80 failed (99: Cannot assign requested address)
Dec 24 18:55:18 hroniky-com nginx: nginx: configuration file 
/etc/nginx/nginx.conf test failed
Dec 24 18:55:18 hroniky-com systemd: Starting The PHP FastCGI Process 
Manager...
Dec 24 18:55:18 hroniky-com systemd: Started OpenSSH server daemon.
Dec 24 18:55:18 hroniky-com systemd: Starting OpenSSH server daemon...
Dec 24 18:55:18 hroniky-com systemd: Starting Login Service...
Dec 24 18:55:18 hroniky-com systemd: Starting Dump dmesg to 
/var/log/dmesg...
Dec 24 18:55:18 hroniky-com systemd: Started Permit User Sessions.
Dec 24 18:55:18 hroniky-com systemd: Started /etc/rc.d/rc.local 
Compatibility.
Dec 24 18:55:18 hroniky-com systemd: nginx.service: control process 
exited, code=exited status=1
Dec 24 18:55:18 hroniky-com systemd: Failed to start nginx - high 
performance web server.
Dec 24 18:55:18 hroniky-com systemd: Unit nginx.service entered failed 
state.
Dec 24 18:55:18 hroniky-com systemd: nginx.service failed.

-- 
Best regards,
  Gena