Add a systemd service to manage node flush/unflush, useful during
system startup and shutdown to avoid requiring administrator
intervention for this to occur. This is optional and the service is
not enabled by default, and the postinst script informs the
administrator of this.
Also adds a systemd target to collect the two service units together
and provide an easy way to flush+shutdown or startup+unflush the
entire PVC system.
Closes#28
1 second was just slightly too little time to wait and packets would
occasionally be lost on primary switchover. Increase this to 2
seconds to provide more time for arping to run on the new primary.
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.
MariaDB+Galera was terribly unstable, with the cluster failing to
start or dying randomly, and generally seemed incredibly unsuitable
for an HA solution. This commit switches the DNS aggregator SQL
backend to PostgreSQL, implemented via Patroni HA.
It also manages the Patroni state, forcing the primary instance to
follow the PVC coordinator, such that the active DNS Aggregator
instance is always able to communicate read+write with the local
system.
This required some logic changes to how the DNS Aggregator worked,
specifically ensuring that database changes aren't attempted while
the instance isn't actively running - to be honest this was a bug
anyways that had just never been noticed.
Closes#34
Makes an unflush a controlled event like flushing, rather than a
free-for-all. This does slow down unflushing somewhat (disallowing
parallelism from multiple hosts to the current host), but allows
the locking to actually be effective.
Implements a locking mechanism to prevent clobbering of node
flushes. When a flush begins, a global cluster lock is placed
which is freed once the flush completes. While the lock is in place,
other flush events queue waiting for the lock to free before
proceeding.
Modifies the CLI output flow when the `--wait` option is specified.
First, if a lock exists when running the command, the message is
tweaked to indicate this, and the client will wait first for the
lock to free, and then for the flush as normal. Second, the wait
depends on the active lock rather than the domain_status for
consistency purposes.
Closes#32
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.
1. Move to a YAML-based configuration format instead of the original
INI-based configuration to facilitate better organization and
readability.
2. Modify the daemon to be able to operate in several modes based
on configuration flags. Either networking or storage functions
can be disabled using the configuration, allowing the PVC system
to be used only for hypervisor management if required.
Joshua Boniface