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nomad: expand comments on subtle plan apply behaviors

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This commit is contained in:
Michael Schurter 2019-06-26 08:49:24 -07:00
parent e4bc943a68
commit 69ba495f0c
1 changed files with 9 additions and 3 deletions
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12
nomad/plan_apply.go
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@ -104,7 +104,8 @@ func (p *planner) planApply() {
select {
case idx := <-planIndexCh:
// Previous plan committed. Discard snapshot and ensure
// future snapshots include this plan.
// future snapshots include this plan. idx may be 0 if
// plan failed to apply, so use max(prev, idx)
prevPlanResultIndex = max(prevPlanResultIndex, idx)
planIndexCh = nil
snap = nil
@ -112,7 +113,9 @@ func (p *planner) planApply() {
}
if snap != nil {
// If snapshot isn't new enough, discard it
// If snapshot doesn't contain the previous plan
// result's index and the current plan's snapshot it,
// discard it and get a new one below.
minIndex := max(prevPlanResultIndex, pending.plan.SnapshotIndex)
if idx, err := snap.LatestIndex(); err != nil || idx < minIndex {
snap = nil
@ -120,7 +123,10 @@ func (p *planner) planApply() {
}
// Snapshot the state so that we have a consistent view of the world
// if no snapshot is available
// if no snapshot is available.
// - planIndexCh will be nil if the previous plan result applied
// during Dequeue
// - snap will be nil if its index < max(prevIndex, curIndex)
if planIndexCh == nil || snap == nil {
snap, err = p.snapshotMinIndex(prevPlanResultIndex, pending.plan.SnapshotIndex)
if err != nil {