Commit Graph

15 Commits

Author SHA1 Message Date
Joshua Boniface 7c99a7bda7 Safely reset RBD locks on failed VMs
Should correct issues on cold start as well as if a VM crashes
uncleanly, which would prevent the VM from starting due to stale RBD
locks.

This implementation has four parts:
  1. Update how IP addresses are handled, specifically by replacing all
  previous instances of "vni_ipaddr" with "vni_floatingipaddr", and then
  adding the "vni_ipaddr" with the real data for this node's IPs. Also
  include the storage IPs in this where they weren't before, so each
  this_node actually has the local IPs plus floating IPs. This enables
  the next two steps.
  2. Modify flush_locks to take this_node as an argument, and update the
  run_command function to only operate against this node, rather than on
  the primary coordinator.
  3. Have the flush_locks check each lock against the current node, to
  verify that the lock is actually held by the current node. This is the
  only way to do this safely. During fencing, we override this by not
  passing a this_node which bypasses this check.
  4. Have the VM start do the check for VM failure/startup and execute a
  flush_locks before actually starting the VM.
2020-12-14 15:53:18 -05:00
Joshua Boniface 260b39ebf2 Lint: E302 expected 2 blank lines, found X 2020-11-07 14:45:24 -05:00
Joshua Boniface 7932be3948 Lint: E261 at least two spaces before inline comment 2020-11-07 13:11:03 -05:00
Joshua Boniface 3f242cd437 Lint: E202 whitespace before '}' 2020-11-07 12:57:42 -05:00
Joshua Boniface e333f2b935 Lint: E201 whitespace after '{' 2020-11-07 12:38:31 -05:00
Joshua Boniface d9e7b7ec15 Lint: F401 <library> imported but unused 2020-11-06 19:22:49 -05:00
Joshua Boniface 63f4f9aed7 Lint: E722 do not use bare 'except' 2020-11-06 18:55:10 -05:00
Joshua Boniface 224c8082ef Alter text of synchronization messages 2020-10-20 13:08:18 -04:00
Joshua Boniface 726501f4d4 Add additional logging to flush selector
Adds additional debug logging to the flush selector to determine how any
why any given node is selected. Useful for troubleshooting strange
choices.
2020-10-20 12:34:18 -04:00
Joshua Boniface 0e5c681ada Clean up imports
Make several imports more specific to reduce redundant code imports and
improve memory utilization.
2020-08-11 12:09:10 -04:00
Joshua Boniface 95c59ba629 Improve flush handling slightly 2020-05-12 11:04:38 -04:00
Joshua Boniface b413e042a6 Improve handling of primary contention
Previously, contention could occasionally cause a flap/dual primary
contention state due to the lack of checking within this function. This
could cause a state where a node transitions to primary than is almost
immediately shifted away, which could cause undefined behaviour in the
cluster.

The solution includes several elements:
    * Implement an exclusive lock operation in zkhandler
    * Switch the become_primary function to use this exclusive lock
    * Implement exclusive locking during the contention process
    * As a failsafe, check stat versions before setting the node as the
      primary node, in case another node already has
    * Delay the start of takeover/relinquish operations by slightly
      longer than the lock timeout
    * Make the current router_state conditions more explicit (positive
      conditionals rather than negative conditionals)

The new scenario ensures that during contention, only one secondary will
ever succeed at acquiring the lock. Ideally, the other would then grab
the lock and pass, but in testing this does not seem to be the case -
the lock always times out, so the failsafe check is technically not
needed but has been left as an added safety mechanism. With this setup,
the node that fails the contention will never block the switchover nor
will it try to force itself onto the cluster after another node has
successfully won contention.

Timeouts may need to be adjusted in the future, but the base timeout of
0.4 seconds (and transition delay of 0.5 seconds) seems to work reliably
during preliminary tests.
2020-04-12 03:40:17 -04:00
Joshua Boniface 0a367898a0 Don't trigger aggregator fail if fine 2020-03-12 13:22:12 -04:00
Joshua Boniface d2a5fe59c0 Use transitional takeover states for migration
Use a pair of transitional states, "takeover" and "relinquish", when
transitioning between primary and secondary coordinator states. This
provides a clsuter-wide record that the nodes are still working during
their synchronous transition states, and should allow clients to
determine when the node(s) have fully switched over. Also add an
additional 2 seconds of wait at the end of the transition jobs to ensure
everything has had a chance to start before proceeding.

References #72
2020-02-19 14:06:54 -05:00
Joshua Boniface ce985234c3 Use consistent naming of components
Rename "pvcd" to "pvcnoded", and "pvc-api" to "pvcapid" so names for the
daemons are fully consistent. Update the names of the configuration
files as well to match this new formatting.

References #79
2020-02-08 19:34:07 -05:00