The VM migration code was very old, very spaghettified, and prone to
strange failures.
Improve this by taking cues from the node primary migration. Use
synchronization between the nodes to ensure lockstep completion of the
migration in discrete steps.
A proper queue can be built later to integrate with this code more
cleanly.
References #108
Use the new "provisioned" memory field, instead of the "allocated"
memory field, to determine the optimal node when using the "mem"
migration selector. This will take into account non-running VMs in the
calculation as well as running VMs.
Adds a separate field to the node memory, "provisioned", which totals
the amount of memory provisioned to all VMs on the node, regardless of
state, and in contrast to "allocated" which only counts running VMs.
Allows for the detection of potential overprovisioned states when
factoring in non-running VMs.
Includes the supporting code to get this data, since the original
implementation of VM memory selection was dependent on the VM being
running and getting this from libvirt. Now, if the VM is not active, it
gets this from the domain XML instead.
Prevents any potential leakage due to autoconfigured IPv6 on bridged
interfaces. These are exclusively VM-side bridges, and the PVC host
should not have any IPv6 configuration on them, ever.
Prevents a bug where the thread can crash due to a change in the
d_domain object while running the for loop. By copying and iterating
over the copy, this becomes safer.
The keepalive was getting stuck gathering memoryStats from the
non-running VM, since it was in a paused state. Avoid this by just
skipping past the rest of the stats gathering if the VM isn't running.
Most of these would silently fail if there was e.g. an issue with the ZK
connection. Instead, encase things in try blocks and handle the
exceptions in a more graceful way, returning None or False if
applicable. Except for locks, which should retry 5 times before
aborting.
Using simple print statements was annoying (lack of timing info and
formatting), so move to using the debug logger for these instead with a
custom state ('d') with white text to differentiate them. Also indicate
which subthread of the keepalive each task is being executed in for
easier tracing of issues.
Verify our IPMI state on startup, and then warn if fencing will fail.
For now, this is sufficient, but in future (requires refactoring) we
might want to adjust how fencing occurs based on this information.
Using the Ceph library was a disaster here; it had no timeout or way to
force it to continue, so keepalives would become stuck and trigger fence
storms. Go back to the manual osd dump command with a 2s timeout which
is far more reliable and can be adequately terminated if it runs long.
Prevent the main keepalive thread from getting stuck due to a subthread
taking an enormous time. If this happens, the rest of the main keepalive
will continue onward, thus ensuring that the main keepalive does not
fail for a significant number of cycles, which would cause a fence.
The previous saving throw limit (3/15s) seems to have been too low. I
was observing bizarre failures where a node would be fenced while it was
still starting up. Some of this may have been related to Zookeeper
connections taking too long, but this was inconsistent.
Increase this to 6 saving throws (30s). This provides significantly more
time for a node to properly check in on startup before another node
fences it. In the real world, 15s vs 30s isn't that big of a downtime
change, but prevents false-positive fences.
Joshua Boniface