14360: Rename keeplocal -> dontupdate, add explanation.

Arvados-DCO-1.1-Signed-off-by: Tom Clegg <tclegg@veritasgenetics.com>

diff --git a/lib/dispatchcloud/container/queue.go b/lib/dispatchcloud/container/queue.go
index 17a38259d31cf7579f479aa460b1461992465615..e0e1cd0cd1ddc7d1d9b1f7891d4ea2ab2c42e280 100644 (file)
--- a/lib/dispatchcloud/container/queue.go
+++ b/lib/dispatchcloud/container/queue.go
@@ -56,11 +56,19 @@ type Queue struct {
        chooseType typeChooser
        client     APIClient
 
-       auth      *arvados.APIClientAuthorization
-       current   map[string]QueueEnt
-       updated   time.Time
-       mtx       sync.Mutex
-       keeplocal map[string]struct{}
+       auth    *arvados.APIClientAuthorization
+       current map[string]QueueEnt
+       updated time.Time
+       mtx     sync.Mutex
+
+       // Methods that modify the Queue (like Lock) add the affected
+       // container UUIDs to dontupdate. When applying a batch of
+       // updates received from the network, anything appearing in
+       // dontupdate is skipped, in case the received update has
+       // already been superseded by the locally initiated change.
+       // When no network update is in progress, this protection is
+       // not needed, and dontupdate is nil.
+       dontupdate map[string]struct{}
 }
 
 // NewQueue returns a new Queue. When a new container appears in the
@@ -126,7 +134,7 @@ func (cq *Queue) Entries() (entries map[string]QueueEnt, threshold time.Time) {
 // containers.
 func (cq *Queue) Update() error {
        cq.mtx.Lock()
-       cq.keeplocal = map[string]struct{}{}
+       cq.dontupdate = map[string]struct{}{}
        updateStarted := time.Now()
        cq.mtx.Unlock()
 
@@ -138,7 +146,7 @@ func (cq *Queue) Update() error {
        cq.mtx.Lock()
        defer cq.mtx.Unlock()
        for uuid, ctr := range next {
-               if _, keep := cq.keeplocal[uuid]; keep {
+               if _, keep := cq.dontupdate[uuid]; keep {
                        continue
                }
                if cur, ok := cq.current[uuid]; !ok {
@@ -149,7 +157,7 @@ func (cq *Queue) Update() error {
                }
        }
        for uuid := range cq.current {
-               if _, keep := cq.keeplocal[uuid]; keep {
+               if _, keep := cq.dontupdate[uuid]; keep {
                        continue
                } else if _, keep = next[uuid]; keep {
                        continue
@@ -157,7 +165,7 @@ func (cq *Queue) Update() error {
                        delete(cq.current, uuid)
                }
        }
-       cq.keeplocal = nil
+       cq.dontupdate = nil
        cq.updated = updateStarted
        return nil
 }
@@ -198,8 +206,8 @@ func (cq *Queue) apiUpdate(uuid, action string) error {
 
        cq.mtx.Lock()
        defer cq.mtx.Unlock()
-       if cq.keeplocal != nil {
-               cq.keeplocal[uuid] = struct{}{}
+       if cq.dontupdate != nil {
+               cq.dontupdate[uuid] = struct{}{}
        }
        if ent, ok := cq.current[uuid]; !ok {
                cq.addEnt(uuid, resp)