17967: Read from volumes with high-priority storage classes first.

[arvados.git] / services / keepstore / volume.go

diff --git a/services/keepstore/volume.go b/services/keepstore/volume.go
index 26e6b731828f9be0861044cb6a7c4e10d097d05f..9bfc6ca3e5191d2953ceac75f915a07cab19c69f 100644 (file)
--- a/services/keepstore/volume.go
+++ b/services/keepstore/volume.go
@@ -10,6 +10,7 @@ import (
        "fmt"
        "io"
        "math/big"
+       "sort"
        "sync/atomic"
        "time"
 
@@ -343,6 +344,27 @@ func makeRRVolumeManager(logger logrus.FieldLogger, cluster *arvados.Cluster, my
                        vm.writables = append(vm.writables, mnt)
                }
        }
+       // pri(i): return highest priority of any storage class
+       // offered by vm.readables[i]
+       pri := func(i int) int {
+               any, best := false, 0
+               for class := range vm.readables[i].KeepMount.StorageClasses {
+                       if p := cluster.StorageClasses[class].Priority; !any || best < p {
+                               best = p
+                               any = true
+                       }
+               }
+               return best
+       }
+       // sort vm.readables, first by highest priority of any offered
+       // storage class (highest->lowest), then by volume UUID
+       sort.Slice(vm.readables, func(i, j int) bool {
+               if pi, pj := pri(i), pri(j); pi != pj {
+                       return pi > pj
+               } else {
+                       return vm.readables[i].KeepMount.UUID < vm.readables[j].KeepMount.UUID
+               }
+       })
        return vm, nil
 }