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neigh: enable garbage collection #1068

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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.

@dirkmueller dirkmueller added this to the Cloud 7 Update1 milestone Feb 4, 2017
Itxaka
Itxaka previously approved these changes 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
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ARP?

# 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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The?

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 vuntz left a comment

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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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5 participants