Andy Kurth created VCL-879:
------------------------------
Summary: Add semaphore to iptables commands
Key: VCL-879
URL: https://issues.apache.org/jira/browse/VCL-879
Project: VCL
Issue Type: Improvement
Components: vcld (backend)
Affects Versions: 2.4.2
Reporter: Andy Kurth
A command to configure iptables on a particular host may fail if another
iptables command is being executed at the same time.
This is a problem for the iptables commands executed on NAT hosts. Multiple
vcld processes may be running at the same time which attempt to modify a NAT
host's iptables firewall. The following warning will appear in _vcld.log_ when
this problem occurs:
{noformat}
2015-06-25 12:45:09|13308|5183|5206|timeout|iptables.pm:flush_chain|588|flushed
'vcld-5206' chain in 'nat' table on nat-01
|13288|5182|5205|timeout|iptables.pm:flush_chain|584| ---- WARNING ----
|13288|5182|5205|timeout|iptables.pm:flush_chain|584| 2015-06-25
12:45:09|13288|5182|5205|timeout|iptables.pm:flush_chain|584|failed to flush
'vcld-5205' chain in 'nat' table on nat-01, exit status: 4, command:
|13288|5182|5205|timeout|iptables.pm:flush_chain|584| /sbin/iptables --flush
vcld-5205 --table nat
|13288|5182|5205|timeout|iptables.pm:flush_chain|584| output:
|13288|5182|5205|timeout|iptables.pm:flush_chain|584| iptables: Resource
temporarily unavailable.
|13288|5182|5205|timeout|iptables.pm:flush_chain|584| ( 0) iptables.pm,
flush_chain (line: 584)
|13288|5182|5205|timeout|iptables.pm:flush_chain|584| (-1) iptables.pm,
delete_chain (line: 433)
|13288|5182|5205|timeout|iptables.pm:flush_chain|584| (-2) iptables.pm,
sanitize_reservation (line: 485)
|13288|5182|5205|timeout|iptables.pm:flush_chain|584| (-3) reclaim.pm, process
(line: 136)
|13288|5182|5205|timeout|iptables.pm:flush_chain|584| (-4) vcld, make_new_child
(line: 587)
|13288|5182|5205|timeout|iptables.pm:flush_chain|584| (-5) vcld, main (line:
348)
{noformat}
This is not a problem for commands which configure iptables on a compute node
because only a single vcld process is acting on the node at a time, which means
a single iptables command is executed at a time.
A semaphore should be optained before executing iptables commands which may
encounter this problem. There are several iptables commands which are executed
on compute nodes and NAT hosts. Care should be taken to limit the use of a
semaphore to only the commands which require it, otherwise performance will
suffer.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
