This was very old code that was hard to follow and quite fragile, with
failures and infinite loops occurring fairly frequently. These changes
make the code more robust, including the addition of timeouts, some code
cleanup, and some improvements to the logical flow.
Also forces the libvirt migration to occur on the cluster network, which
couples to changes in the libvirtd listen (via pvc-ansible) and in
Daemon.py via the previous commit.
1. Remove a number of time.sleep commands which don't really seem
necessary any longer and which significantly increased the startup
time while parsing the VM list.
2. Handle some variable sets during initialization of the object,
rather than waiting for a management command, enabling...
3. Know when a state change, and the corresponding Libvirt lookup,
is unnecessary due to the target node not matching the current node.
This also removes a number of unremovable errors from Libvirt on the
console which were annoying.
This reduces the total time taken by the VM startup segment (lines
760-762 of Daemon.py) from 17.117s down to 0.976s for 82 VMs.
Implements the ability for a client to watch almost-live domain
console logs from the hypervisors. It does this using a deque-based
"tail -f" mechanism (with a configurable buffer per-VM) that watches
the domain console logfile in the (configurable) directory every
half-second. It then stores the current buffer in Zookeeper when
changed, where a client can then request it, either as a static piece
of text in the `less` pager, or via a similar "tail -f" functionality
implemented using fixed line splitting and comparison to provide a
generally-seamless output.
Enabling this feature requires each guest VM to implement a Libvirt
serial log and write its (text) console to it, for example using the
default logging directory:
```
<serial type='pty'>
<log file='/var/log/libvirt/vmname.log' append='off'/>
<serial>
```
The append mode can be either on or off; on grows files unbounded,
off causes the log (and hence the PVC log data) to be truncated on
initial VM startup from offline. The administrator must choose how
they best want to handle this until Libvirt implements their own
clog-type logging format.
Completely restructure the daemon code to move the 4 discrete daemons
into a single daemon that can be run on every hypervisor. Introduce the
idea of a static list of "coordinator" nodes which are configured at
install time to run Zookeeper and FRR in router mode, and which are
allowed to take on client network management duties (gateway, DHCP, DNS,
etc.) while also allowing them to run VMs (i.e. no dedicated "router"
nodes required).
Joshua Boniface