Commit 601908d0 authored by Iustin Pop's avatar Iustin Pop
Browse files

Rework the node modify for mc-demotion

The current code in LUSetNodeParms regarding the demotion from master
candidate role is complicated and duplicates the code in ConfigWriter,
where such decisions should be made. Furthermore, we still cannot demote
nodes (not even with force), if other regular nodes exist.

This patch adds a new opcode attribute ‘auto_promote’, and changes the
decision tree as follows:

- if the node will be set to offline or drained or explicitly demoted
  from master candidate, and this parameter is set, then we lock all
  nodes in ExpandNames()
- later, in CheckPrereq(), if the node is
  indeed a master candidate, and the future state (as computed via
  GetMasterCandidateStats with the current node in the exception list)
  has fewer nodes than it should, and we didn't lock all nodes, we exit
  with an exception
- in Exec, if we locked all nodes, we do a AdjustCandidatePool() run, to
  ensure nodes are locked as needed (we do it before updating the node
  to remove a warning, and prevent the situation that if the LU fails
  between these, we're not left with an inconsistent state)

Note that in Exec we run the AdjustCP irrespective of any node state
change (just based on lock status), so we might simplify the CheckPrereq
even more by not checking the future state, basically requiring
auto_promote/lock_all for master candidates, since the case where we
have more than needed master candidates is rarer; OTOH, this would prevent
manual promotion ahead of time of another node, which is why I didn't
choose this way.
Signed-off-by: default avatarIustin Pop <>
Reviewed-by: default avatarGuido Trotter <>
Reviewed-by: default avatarMichael Hanselmann <>
parent 89e5ab02
......@@ -3158,6 +3158,7 @@ class LUSetNodeParams(LogicalUnit):
_CheckBooleanOpField(self.op, 'master_candidate')
_CheckBooleanOpField(self.op, 'offline')
_CheckBooleanOpField(self.op, 'drained')
_CheckBooleanOpField(self.op, 'auto_promote')
all_mods = [self.op.offline, self.op.master_candidate, self.op.drained]
if all_mods.count(None) == 3:
raise errors.OpPrereqError("Please pass at least one modification",
......@@ -3167,8 +3168,22 @@ class LUSetNodeParams(LogicalUnit):
" state at the same time",
# Boolean value that tells us whether we're offlining or draining the node
self.offline_or_drain = (self.op.offline == True or
self.op.drained == True)
self.deoffline_or_drain = (self.op.offline == False or
self.op.drained == False)
self.might_demote = (self.op.master_candidate == False or
self.lock_all = self.op.auto_promote and self.might_demote
def ExpandNames(self):
self.needed_locks = {locking.LEVEL_NODE: self.op.node_name}
if self.lock_all:
self.needed_locks = {locking.LEVEL_NODE: locking.ALL_SET}
self.needed_locks = {locking.LEVEL_NODE: self.op.node_name}
def BuildHooksEnv(self):
"""Build hooks env.
......@@ -3203,25 +3218,17 @@ class LUSetNodeParams(LogicalUnit):
" only via masterfailover",
# Boolean value that tells us whether we're offlining or draining the node
offline_or_drain = self.op.offline == True or self.op.drained == True
deoffline_or_drain = self.op.offline == False or self.op.drained == False
if (node.master_candidate and
(self.op.master_candidate == False or offline_or_drain)):
cp_size = self.cfg.GetClusterInfo().candidate_pool_size
mc_now, mc_should, mc_max = self.cfg.GetMasterCandidateStats()
if mc_now <= cp_size:
msg = ("Not enough master candidates (desired"
" %d, new value will be %d)" % (cp_size, mc_now-1))
# Only allow forcing the operation if it's an offline/drain operation,
# and we could not possibly promote more nodes.
# FIXME: this can still lead to issues if in any way another node which
# could be promoted appears in the meantime.
if self.op.force and offline_or_drain and mc_should == mc_max:
raise errors.OpPrereqError(msg, errors.ECODE_INVAL)
if node.master_candidate and self.might_demote and not self.lock_all:
assert not self.op.auto_promote, "auto-promote set but lock_all not"
# check if after removing the current node, we're missing master
# candidates
(mc_remaining, mc_should, _) = \
if mc_remaining != mc_should:
raise errors.OpPrereqError("Not enough master candidates, please"
" pass auto_promote to allow promotion",
if (self.op.master_candidate == True and
((node.offline and not self.op.offline == False) or
......@@ -3231,7 +3238,7 @@ class LUSetNodeParams(LogicalUnit):
# If we're being deofflined/drained, we'll MC ourself if needed
if (deoffline_or_drain and not offline_or_drain and not
if (self.deoffline_or_drain and not self.offline_or_drain and not
self.op.master_candidate == True and not node.master_candidate):
self.op.master_candidate = _DecideSelfPromotion(self)
if self.op.master_candidate:
......@@ -3286,8 +3293,13 @@ class LUSetNodeParams(LogicalUnit):
node.offline = False
result.append(("offline", "clear offline status due to drain"))
# we locked all nodes, we adjust the CP before updating this node
if self.lock_all:
_AdjustCandidatePool(self, [])
# this will trigger configuration file update, if needed
self.cfg.Update(node, feedback_fn)
# this will trigger job queue propagation or cleanup
if changed_mc:
......@@ -413,6 +413,7 @@ class OpSetNodeParams(OpCode):
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