package main
import (
- "errors"
- "fmt"
- "os"
- "strings"
+ "sync/atomic"
"time"
)
Get(loc string) ([]byte, error)
Put(loc string, block []byte) error
Touch(loc string) error
+ Mtime(loc string) (time.Time, error)
Index(prefix string) string
Delete(loc string) error
Status() *VolumeStatus
String() string
+ Writable() bool
}
-// MockVolumes are Volumes used to test the Keep front end.
-//
-// If the Bad field is true, this volume should return an error
-// on all writes and puts.
-//
-type MockVolume struct {
- Store map[string][]byte
- Timestamps map[string]time.Time
- Bad bool
-}
-
-func CreateMockVolume() *MockVolume {
- return &MockVolume{
- make(map[string][]byte),
- make(map[string]time.Time),
- false,
- }
+// A VolumeManager tells callers which volumes can read, which volumes
+// can write, and on which volume the next write should be attempted.
+type VolumeManager interface {
+ // AllReadable returns all volumes.
+ AllReadable() []Volume
+ // AllWritable returns all volumes that aren't known to be in
+ // a read-only state. (There is no guarantee that a write to
+ // one will succeed, though.)
+ AllWritable() []Volume
+ // NextWritable returns the volume where the next new block
+ // should be written. A VolumeManager can select a volume in
+ // order to distribute activity across spindles, fill up disks
+ // with more free space, etc.
+ NextWritable() Volume
+ // Close shuts down the volume manager cleanly.
+ Close()
}
-func (v *MockVolume) Get(loc string) ([]byte, error) {
- if v.Bad {
- return nil, errors.New("Bad volume")
- } else if block, ok := v.Store[loc]; ok {
- return block, nil
- }
- return nil, os.ErrNotExist
+type RRVolumeManager struct {
+ readables []Volume
+ writables []Volume
+ counter uint32
}
-func (v *MockVolume) Put(loc string, block []byte) error {
- if v.Bad {
- return errors.New("Bad volume")
+func MakeRRVolumeManager(volumes []Volume) *RRVolumeManager {
+ vm := &RRVolumeManager{}
+ for _, v := range volumes {
+ vm.readables = append(vm.readables, v)
+ if v.Writable() {
+ vm.writables = append(vm.writables, v)
+ }
}
- v.Store[loc] = block
- return Touch(loc)
+ return vm
}
-func (v *MockVolume) Touch(loc string) error {
- if v.Bad {
- return errors.New("Bad volume")
- }
- v.Timestamps[loc] = time.Now()
- return nil
+func (vm *RRVolumeManager) AllReadable() []Volume {
+ return vm.readables
}
-func (v *MockVolume) Index(prefix string) string {
- var result string
- for loc, block := range v.Store {
- if IsValidLocator(loc) && strings.HasPrefix(loc, prefix) {
- result = result + fmt.Sprintf("%s+%d %d\n",
- loc, len(block), 123456789)
- }
- }
- return result
+func (vm *RRVolumeManager) AllWritable() []Volume {
+ return vm.writables
}
-func (v *MockVolume) Delete(loc string) error {
- if _, ok := v.Store[loc]; ok {
- delete(v.Store, loc)
+func (vm *RRVolumeManager) NextWritable() Volume {
+ if len(vm.writables) == 0 {
return nil
}
- return os.ErrNotExist
-}
-
-func (v *MockVolume) Status() *VolumeStatus {
- var used uint64
- for _, block := range v.Store {
- used = used + uint64(len(block))
- }
- return &VolumeStatus{"/bogo", 123, 1000000 - used, used}
-}
-
-func (v *MockVolume) String() string {
- return "[MockVolume]"
-}
-
-// A VolumeManager manages a collection of volumes.
-//
-// - Volumes is a slice of available Volumes.
-// - Choose() returns a Volume suitable for writing to.
-// - Quit() instructs the VolumeManager to shut down gracefully.
-//
-type VolumeManager interface {
- Volumes() []Volume
- Choose() Volume
- Quit()
-}
-
-type RRVolumeManager struct {
- volumes []Volume
- nextwrite chan Volume
- quit chan int
-}
-
-func MakeRRVolumeManager(vols []Volume) *RRVolumeManager {
- // Create a new VolumeManager struct with the specified volumes,
- // and with new Nextwrite and Quit channels.
- // The Quit channel is buffered with a capacity of 1 so that
- // another routine may write to it without blocking.
- vm := &RRVolumeManager{vols, make(chan Volume), make(chan int, 1)}
-
- // This goroutine implements round-robin volume selection.
- // It sends each available Volume in turn to the Nextwrite
- // channel, until receiving a notification on the Quit channel
- // that it should terminate.
- go func() {
- var i int = 0
- for {
- select {
- case <-vm.quit:
- return
- case vm.nextwrite <- vm.volumes[i]:
- i = (i + 1) % len(vm.volumes)
- }
- }
- }()
-
- return vm
-}
-
-func (vm *RRVolumeManager) Volumes() []Volume {
- return vm.volumes
-}
-
-func (vm *RRVolumeManager) Choose() Volume {
- return <-vm.nextwrite
+ i := atomic.AddUint32(&vm.counter, 1)
+ return vm.writables[i % uint32(len(vm.writables))]
}
-func (vm *RRVolumeManager) Quit() {
- vm.quit <- 1
+func (vm *RRVolumeManager) Close() {
}
projects / arvados.git / blobdiff