neigh: enable garbage collection #1068
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Itxaka
previously approved these changes
Feb 6, 2017
aplanas
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Feb 6, 2017
| @@ -6,6 +6,14 @@ | |||
| net.ipv4.ip_local_reserved_ports = 35357 | |||
| # Increase system IP port range to allow for more concurrent connections | |||
| net.ipv4.ip_local_port_range = 27018 64999 | |||
| # ensure STALE arp neighbor entries expire from the cache, otherwise | |||
| # VIPs of an OpenStack service or the floating IP of a VM | ||
| # might not become reachable | ||
| # gc_thresh1 is the lower threshold that needs to be reached before | ||
| # stale entries are getting garbage collected. the default of 128 means |
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VIPs and floating ips that move between differnet interfaces might stay for very long times cached incorrectly in the neighbor table until the garbage collection kicks in. by default a STALE (so an entry that used to have an active connection but now doesn't anymore) gets garbage collected after gc_stale_timeout, but *only* if there are more than gc_thresh1 STALE entries in total. The default of 128 means that one has to accumulate 128 stale entries (or trigger a forced cache flush) until this is happening, which for small/low traffic clouds can take an eternity.
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vuntz
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Mar 9, 2017
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openstack-ansible is using a different approach: https://git.openstack.org/cgit/openstack/openstack-ansible-openstack_hosts/tree/defaults/main.yml#n46
Does that make sense? Or is your approach better?
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VIPs and floating ips that move between differnet interfaces might stay
for very long times cached incorrectly in the neighbor table until the
garbage collection kicks in. by default a STALE (so an entry that used
to have an active connection but now doesn't anymore) gets garbage
collected after gc_stale_timeout, but only if there are more than
gc_thresh1 STALE entries in total. The default of 128 means that one has
to accumulate 128 stale entries (or trigger a forced cache flush) until
this is happening, which for small/low traffic clouds can take an
eternity.