The previous method was a "throw it in the sea"-type migration with some
(very arbitrary) sleep statements thrown in for good measure.
Reimplement this with some hard locking. During each phase of the
transition, the nodes acquire read/write shared locks to a Zookeeper key
so that they can tightly coordinate the actions of transferring each
part of the primary state between them. This is done in a subthread to
prevent strange blocking issues that were encountered, likely due to
business in the existing main thread.
Implements the storing of three VM metadata attributes:
1. Node limits - allows specifying a list of hosts on which the VM must
run. This limit influences the migration behaviour of VMs.
2. Per-VM node selectors - allows each VM to have its migration
autoselection method specified, to automatically allow different methods
per VM based on the administrator's preferences.
3. VM autorestart - allows a VM to be automatically restarted from a
stopped state, presumably due to a failure to find a target node (either
due to limits or otherwise) during a flush/fence recovery, on the next
node unflush/ready state of its home hypervisor. Useful mostly in
conjunction with limits to ensure that VMs which were shut down due to
there being no valid migration targets are started back up when their
node becomes ready again.
Includes the full client interaction with these metadata options,
including printing, as well as defining a new function to modify this
metadata. For the CLI it is set/modified either on `vm define` or via the
`vm meta` command. For the API it is set/modified either on a POST to
the `/vm` endpoint (during VM definition) or on POST to the `/vm/<vm>`
endpoint. For the API this replaces the previous reserved word for VM
creation from scratch as this will no longer be implemented in-daemon
(see #22).
Closes#52
Store the flush_thread of a node as a class object. Before starting a
new flush thread (either flush or unflush), stop the existing one if it
exists to prevent further migrations, then start the new thread. Set the
object to None on init and again once the task actually finishes. Remove
the inflush flag as this is not required when using these threads and
functionally does nothing any longer, but add the flush_stopper flag to
trigger cancellation of the current job.
This just seemed like more trouble that it was worth. Flush locks were
originally intended as a way to counteract the weird issues around
flushing that were mostly fixed by the code refactoring, so this will
help test if those issues are truly gone. If not, will look into a
cleaner solution that doesn't result in unchangeable states.
Similar to recent client changes, don't replace the previous node record
of an already-migrated VM. Wait for shutdown if required. Use a
continue statement instead of a needless else block.
Adds a config flag that turns on the API client following the Primary
coordinator. The retcode of the start/stop commands is ignore so this
can fail gracefully if e.g. the client isn't installed.
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.
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
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.
Trying to directly AXFR from dnsmasq is a mess, since their zone is
barely compliant with spec, it doesn't support notifies, and it is
generally really messy.
This implements an advanced "AXFR parser" system, which looks at the
results of an AXFR from the local dnsmasq instances per-network, and
updates the real replicated MariaDB pdns backend cluster with the
changed data. This allows a sensible, transferable zone with its own
SOA that is dynamically reconfigured as hosts come and go from the
dnsmasq zone.
Joshua Boniface