13647: Use cluster config instead of custom keepstore config.
[arvados.git] / services / keep-balance / balance.go
index 7ad2d484aed2cb4dd933e4909b3c36fe96bf39ed..9f814a20d3572b58ea5c65333a94a6d0136f62c2 100644 (file)
@@ -8,6 +8,8 @@ import (
        "bytes"
        "crypto/md5"
        "fmt"
+       "io"
+       "io/ioutil"
        "log"
        "math"
        "os"
@@ -15,24 +17,14 @@ import (
        "sort"
        "strings"
        "sync"
+       "syscall"
        "time"
 
        "git.curoverse.com/arvados.git/sdk/go/arvados"
        "git.curoverse.com/arvados.git/sdk/go/keepclient"
+       "github.com/sirupsen/logrus"
 )
 
-// CheckConfig returns an error if anything is wrong with the given
-// config and runOptions.
-func CheckConfig(config Config, runOptions RunOptions) error {
-       if len(config.KeepServiceList.Items) > 0 && config.KeepServiceTypes != nil {
-               return fmt.Errorf("cannot specify both KeepServiceList and KeepServiceTypes in config")
-       }
-       if !runOptions.Once && config.RunPeriod == arvados.Duration(0) {
-               return fmt.Errorf("you must either use the -once flag, or specify RunPeriod in config")
-       }
-       return nil
-}
-
 // Balancer compares the contents of keepstore servers with the
 // collections stored in Arvados, and issues pull/trash requests
 // needed to get (closer to) the optimal data layout.
@@ -43,20 +35,26 @@ func CheckConfig(config Config, runOptions RunOptions) error {
 // BlobSignatureTTL; and all N existing replicas of a given data block
 // are in the N best positions in rendezvous probe order.
 type Balancer struct {
+       Logger  logrus.FieldLogger
+       Dumper  logrus.FieldLogger
+       Metrics *metrics
+
+       LostBlocksFile string
+
        *BlockStateMap
        KeepServices       map[string]*KeepService
        DefaultReplication int
-       Logger             *log.Logger
-       Dumper             *log.Logger
        MinMtime           int64
 
        classes       []string
+       mounts        int
        mountsByClass map[string]map[*KeepMount]bool
        collScanned   int
        serviceRoots  map[string]string
        errors        []error
        stats         balancerStats
        mutex         sync.Mutex
+       lostBlocks    io.Writer
 }
 
 // Run performs a balance operation using the given config and
@@ -71,13 +69,31 @@ type Balancer struct {
 func (bal *Balancer) Run(config Config, runOptions RunOptions) (nextRunOptions RunOptions, err error) {
        nextRunOptions = runOptions
 
-       bal.Dumper = runOptions.Dumper
-       bal.Logger = runOptions.Logger
-       if bal.Logger == nil {
-               bal.Logger = log.New(os.Stderr, "", log.LstdFlags)
-       }
+       defer bal.time("sweep", "wall clock time to run one full sweep")()
 
-       defer timeMe(bal.Logger, "Run")()
+       var lbFile *os.File
+       if bal.LostBlocksFile != "" {
+               tmpfn := bal.LostBlocksFile + ".tmp"
+               lbFile, err = os.OpenFile(tmpfn, os.O_CREATE|os.O_WRONLY, 0777)
+               if err != nil {
+                       return
+               }
+               defer lbFile.Close()
+               err = syscall.Flock(int(lbFile.Fd()), syscall.LOCK_EX|syscall.LOCK_NB)
+               if err != nil {
+                       return
+               }
+               defer func() {
+                       // Remove the tempfile only if we didn't get
+                       // as far as successfully renaming it.
+                       if lbFile != nil {
+                               os.Remove(tmpfn)
+                       }
+               }()
+               bal.lostBlocks = lbFile
+       } else {
+               bal.lostBlocks = ioutil.Discard
+       }
 
        if len(config.KeepServiceList.Items) > 0 {
                err = bal.SetKeepServices(config.KeepServiceList)
@@ -94,6 +110,7 @@ func (bal *Balancer) Run(config Config, runOptions RunOptions) (nextRunOptions R
                        return
                }
        }
+       bal.cleanupMounts()
 
        if err = bal.CheckSanityEarly(&config.Client); err != nil {
                return
@@ -121,6 +138,17 @@ func (bal *Balancer) Run(config Config, runOptions RunOptions) (nextRunOptions R
        if err = bal.CheckSanityLate(); err != nil {
                return
        }
+       if lbFile != nil {
+               err = lbFile.Sync()
+               if err != nil {
+                       return
+               }
+               err = os.Rename(bal.LostBlocksFile+".tmp", bal.LostBlocksFile)
+               if err != nil {
+                       return
+               }
+               lbFile = nil
+       }
        if runOptions.CommitPulls {
                err = bal.CommitPulls(&config.Client)
                if err != nil {
@@ -168,6 +196,38 @@ func (bal *Balancer) DiscoverKeepServices(c *arvados.Client, okTypes []string) e
        })
 }
 
+func (bal *Balancer) cleanupMounts() {
+       rwdev := map[string]*KeepService{}
+       for _, srv := range bal.KeepServices {
+               for _, mnt := range srv.mounts {
+                       if !mnt.ReadOnly && mnt.DeviceID != "" {
+                               rwdev[mnt.DeviceID] = srv
+                       }
+               }
+       }
+       // Drop the readonly mounts whose device is mounted RW
+       // elsewhere.
+       for _, srv := range bal.KeepServices {
+               var dedup []*KeepMount
+               for _, mnt := range srv.mounts {
+                       if mnt.ReadOnly && rwdev[mnt.DeviceID] != nil {
+                               bal.logf("skipping srv %s readonly mount %q because same device %q is mounted read-write on srv %s", srv, mnt.UUID, mnt.DeviceID, rwdev[mnt.DeviceID])
+                       } else {
+                               dedup = append(dedup, mnt)
+                       }
+               }
+               srv.mounts = dedup
+       }
+       for _, srv := range bal.KeepServices {
+               for _, mnt := range srv.mounts {
+                       if mnt.Replication <= 0 {
+                               log.Printf("%s: mount %s reports replication=%d, using replication=1", srv, mnt.UUID, mnt.Replication)
+                               mnt.Replication = 1
+                       }
+               }
+       }
+}
+
 // CheckSanityEarly checks for configuration and runtime errors that
 // can be detected before GetCurrentState() and ComputeChangeSets()
 // are called.
@@ -188,6 +248,24 @@ func (bal *Balancer) CheckSanityEarly(c *arvados.Client) error {
                        return fmt.Errorf("config error: %s: proxy servers cannot be balanced", srv)
                }
        }
+
+       var checkPage arvados.CollectionList
+       if err = c.RequestAndDecode(&checkPage, "GET", "arvados/v1/collections", nil, arvados.ResourceListParams{
+               Limit:              new(int),
+               Count:              "exact",
+               IncludeTrash:       true,
+               IncludeOldVersions: true,
+               Filters: []arvados.Filter{{
+                       Attr:     "modified_at",
+                       Operator: "=",
+                       Operand:  nil,
+               }},
+       }); err != nil {
+               return err
+       } else if n := checkPage.ItemsAvailable; n > 0 {
+               return fmt.Errorf("%d collections exist with null modified_at; cannot fetch reliably", n)
+       }
+
        return nil
 }
 
@@ -235,7 +313,7 @@ func (bal *Balancer) ClearTrashLists(c *arvados.Client) error {
 //
 // It encodes the resulting information in BlockStateMap.
 func (bal *Balancer) GetCurrentState(c *arvados.Client, pageSize, bufs int) error {
-       defer timeMe(bal.Logger, "GetCurrentState")()
+       defer bal.time("get_state", "wall clock time to get current state")()
        bal.BlockStateMap = NewBlockStateMap()
 
        dd, err := c.DiscoveryDocument()
@@ -245,35 +323,60 @@ func (bal *Balancer) GetCurrentState(c *arvados.Client, pageSize, bufs int) erro
        bal.DefaultReplication = dd.DefaultCollectionReplication
        bal.MinMtime = time.Now().UnixNano() - dd.BlobSignatureTTL*1e9
 
-       errs := make(chan error, 2+len(bal.KeepServices))
+       errs := make(chan error, 1)
        wg := sync.WaitGroup{}
 
-       // Start one goroutine for each KeepService: retrieve the
-       // index, and add the returned blocks to BlockStateMap.
+       // When a device is mounted more than once, we will get its
+       // index only once, and call AddReplicas on all of the mounts.
+       // equivMount keys are the mounts that will be indexed, and
+       // each value is a list of mounts to apply the received index
+       // to.
+       equivMount := map[*KeepMount][]*KeepMount{}
+       // deviceMount maps each device ID to the one mount that will
+       // be indexed for that device.
+       deviceMount := map[string]*KeepMount{}
        for _, srv := range bal.KeepServices {
+               for _, mnt := range srv.mounts {
+                       equiv := deviceMount[mnt.DeviceID]
+                       if equiv == nil {
+                               equiv = mnt
+                               if mnt.DeviceID != "" {
+                                       deviceMount[mnt.DeviceID] = equiv
+                               }
+                       }
+                       equivMount[equiv] = append(equivMount[equiv], mnt)
+               }
+       }
+
+       // Start one goroutine for each (non-redundant) mount:
+       // retrieve the index, and add the returned blocks to
+       // BlockStateMap.
+       for _, mounts := range equivMount {
                wg.Add(1)
-               go func(srv *KeepService) {
+               go func(mounts []*KeepMount) {
                        defer wg.Done()
-                       bal.logf("%s: retrieve indexes", srv)
-                       for _, mount := range srv.mounts {
-                               bal.logf("%s: retrieve index", mount)
-                               idx, err := srv.IndexMount(c, mount.UUID, "")
-                               if err != nil {
-                                       errs <- fmt.Errorf("%s: retrieve index: %v", mount, err)
-                                       return
-                               }
-                               if len(errs) > 0 {
-                                       // Some other goroutine encountered an
-                                       // error -- any further effort here
-                                       // will be wasted.
-                                       return
+                       bal.logf("mount %s: retrieve index from %s", mounts[0], mounts[0].KeepService)
+                       idx, err := mounts[0].KeepService.IndexMount(c, mounts[0].UUID, "")
+                       if err != nil {
+                               select {
+                               case errs <- fmt.Errorf("%s: retrieve index: %v", mounts[0], err):
+                               default:
                                }
-                               bal.logf("%s: add %d replicas to map", mount, len(idx))
+                               return
+                       }
+                       if len(errs) > 0 {
+                               // Some other goroutine encountered an
+                               // error -- any further effort here
+                               // will be wasted.
+                               return
+                       }
+                       for _, mount := range mounts {
+                               bal.logf("%s: add %d entries to map", mount, len(idx))
                                bal.BlockStateMap.AddReplicas(mount, idx)
-                               bal.logf("%s: done", mount)
+                               bal.logf("%s: added %d entries to map at %dx (%d replicas)", mount, len(idx), mount.Replication, len(idx)*mount.Replication)
                        }
-                       bal.logf("%s: done", srv)
-               }(srv)
+                       bal.logf("mount %s: index done", mounts[0])
+               }(mounts)
        }
 
        // collQ buffers incoming collections so we can start fetching
@@ -289,8 +392,11 @@ func (bal *Balancer) GetCurrentState(c *arvados.Client, pageSize, bufs int) erro
                defer wg.Done()
                for coll := range collQ {
                        err := bal.addCollection(coll)
-                       if err != nil {
-                               errs <- err
+                       if err != nil || len(errs) > 0 {
+                               select {
+                               case errs <- err:
+                               default:
+                               }
                                for range collQ {
                                }
                                return
@@ -320,7 +426,10 @@ func (bal *Balancer) GetCurrentState(c *arvados.Client, pageSize, bufs int) erro
                        })
                close(collQ)
                if err != nil {
-                       errs <- err
+                       select {
+                       case errs <- err:
+                       default:
+                       }
                }
        }()
 
@@ -334,17 +443,20 @@ func (bal *Balancer) GetCurrentState(c *arvados.Client, pageSize, bufs int) erro
 func (bal *Balancer) addCollection(coll arvados.Collection) error {
        blkids, err := coll.SizedDigests()
        if err != nil {
-               bal.mutex.Lock()
-               bal.errors = append(bal.errors, fmt.Errorf("%v: %v", coll.UUID, err))
-               bal.mutex.Unlock()
-               return nil
+               return fmt.Errorf("%v: %v", coll.UUID, err)
        }
        repl := bal.DefaultReplication
        if coll.ReplicationDesired != nil {
                repl = *coll.ReplicationDesired
        }
        debugf("%v: %d block x%d", coll.UUID, len(blkids), repl)
-       bal.BlockStateMap.IncreaseDesired(coll.StorageClassesDesired, repl, blkids)
+       // Pass pdh to IncreaseDesired only if LostBlocksFile is being
+       // written -- otherwise it's just a waste of memory.
+       pdh := ""
+       if bal.LostBlocksFile != "" {
+               pdh = coll.PortableDataHash
+       }
+       bal.BlockStateMap.IncreaseDesired(pdh, coll.StorageClassesDesired, repl, blkids)
        return nil
 }
 
@@ -357,47 +469,52 @@ func (bal *Balancer) addCollection(coll arvados.Collection) error {
 func (bal *Balancer) ComputeChangeSets() {
        // This just calls balanceBlock() once for each block, using a
        // pool of worker goroutines.
-       defer timeMe(bal.Logger, "ComputeChangeSets")()
-       bal.setupCaches()
+       defer bal.time("changeset_compute", "wall clock time to compute changesets")()
+       bal.setupLookupTables()
 
        type balanceTask struct {
                blkid arvados.SizedDigest
                blk   *BlockState
        }
-       nWorkers := 1 + runtime.NumCPU()
-       todo := make(chan balanceTask, nWorkers)
-       results := make(chan balanceResult, 16)
-       var wg sync.WaitGroup
-       for i := 0; i < nWorkers; i++ {
-               wg.Add(1)
-               go func() {
-                       for work := range todo {
-                               results <- bal.balanceBlock(work.blkid, work.blk)
+       workers := runtime.GOMAXPROCS(-1)
+       todo := make(chan balanceTask, workers)
+       go func() {
+               bal.BlockStateMap.Apply(func(blkid arvados.SizedDigest, blk *BlockState) {
+                       todo <- balanceTask{
+                               blkid: blkid,
+                               blk:   blk,
                        }
-                       wg.Done()
-               }()
-       }
-       bal.BlockStateMap.Apply(func(blkid arvados.SizedDigest, blk *BlockState) {
-               todo <- balanceTask{
-                       blkid: blkid,
-                       blk:   blk,
-               }
-       })
-       close(todo)
+               })
+               close(todo)
+       }()
+       results := make(chan balanceResult, workers)
        go func() {
+               var wg sync.WaitGroup
+               for i := 0; i < workers; i++ {
+                       wg.Add(1)
+                       go func() {
+                               for work := range todo {
+                                       results <- bal.balanceBlock(work.blkid, work.blk)
+                               }
+                               wg.Done()
+                       }()
+               }
                wg.Wait()
                close(results)
        }()
        bal.collectStatistics(results)
 }
 
-func (bal *Balancer) setupCaches() {
+func (bal *Balancer) setupLookupTables() {
        bal.serviceRoots = make(map[string]string)
-       bal.classes = []string{"default"}
+       bal.classes = defaultClasses
        bal.mountsByClass = map[string]map[*KeepMount]bool{"default": {}}
+       bal.mounts = 0
        for _, srv := range bal.KeepServices {
                bal.serviceRoots[srv.UUID] = srv.UUID
                for _, mnt := range srv.mounts {
+                       bal.mounts++
+
                        // All mounts on a read-only service are
                        // effectively read-only.
                        mnt.ReadOnly = mnt.ReadOnly || srv.ReadOnly
@@ -406,7 +523,7 @@ func (bal *Balancer) setupCaches() {
                                bal.mountsByClass["default"][mnt] = true
                                continue
                        }
-                       for _, class := range mnt.StorageClasses {
+                       for class := range mnt.StorageClasses {
                                if mbc := bal.mountsByClass[class]; mbc == nil {
                                        bal.classes = append(bal.classes, class)
                                        bal.mountsByClass[class] = map[*KeepMount]bool{mnt: true}
@@ -439,10 +556,11 @@ var changeName = map[int]string{
 }
 
 type balanceResult struct {
-       blk   *BlockState
-       blkid arvados.SizedDigest
-       have  int
-       want  int
+       blk        *BlockState
+       blkid      arvados.SizedDigest
+       have       int
+       want       int
+       classState map[string]balancedBlockState
 }
 
 // balanceBlock compares current state to desired state for a single
@@ -457,7 +575,7 @@ func (bal *Balancer) balanceBlock(blkid arvados.SizedDigest, blk *BlockState) ba
        }
 
        // Build a list of all slots (one per mounted volume).
-       var slots []slot
+       slots := make([]slot, 0, bal.mounts)
        for _, srv := range bal.KeepServices {
                for _, mnt := range srv.mounts {
                        var repl *Replica
@@ -474,7 +592,7 @@ func (bal *Balancer) balanceBlock(blkid arvados.SizedDigest, blk *BlockState) ba
                        slots = append(slots, slot{
                                mnt:  mnt,
                                repl: repl,
-                               want: repl != nil && (mnt.ReadOnly || repl.Mtime >= bal.MinMtime),
+                               want: repl != nil && mnt.ReadOnly,
                        })
                }
        }
@@ -491,12 +609,30 @@ func (bal *Balancer) balanceBlock(blkid arvados.SizedDigest, blk *BlockState) ba
        // won't want to trash any replicas.
        underreplicated := false
 
+       classState := make(map[string]balancedBlockState, len(bal.classes))
        unsafeToDelete := make(map[int64]bool, len(slots))
        for _, class := range bal.classes {
                desired := blk.Desired[class]
+
+               countedDev := map[string]bool{}
+               have := 0
+               for _, slot := range slots {
+                       if slot.repl != nil && bal.mountsByClass[class][slot.mnt] && !countedDev[slot.mnt.DeviceID] {
+                               have += slot.mnt.Replication
+                               if slot.mnt.DeviceID != "" {
+                                       countedDev[slot.mnt.DeviceID] = true
+                               }
+                       }
+               }
+               classState[class] = balancedBlockState{
+                       desired: desired,
+                       surplus: have - desired,
+               }
+
                if desired == 0 {
                        continue
                }
+
                // Sort the slots by desirability.
                sort.Slice(slots, func(i, j int) bool {
                        si, sj := slots[i], slots[j]
@@ -504,14 +640,14 @@ func (bal *Balancer) balanceBlock(blkid arvados.SizedDigest, blk *BlockState) ba
                                // Prefer a mount that satisfies the
                                // desired class.
                                return bal.mountsByClass[class][si.mnt]
-                       } else if wanti, wantj := si.want, si.want; wanti != wantj {
+                       } else if si.want != sj.want {
                                // Prefer a mount that will have a
                                // replica no matter what we do here
                                // -- either because it already has an
                                // untrashable replica, or because we
                                // already need it to satisfy a
                                // different storage class.
-                               return slots[i].want
+                               return si.want
                        } else if orderi, orderj := srvRendezvous[si.mnt.KeepService], srvRendezvous[sj.mnt.KeepService]; orderi != orderj {
                                // Prefer a better rendezvous
                                // position.
@@ -530,32 +666,48 @@ func (bal *Balancer) balanceBlock(blkid arvados.SizedDigest, blk *BlockState) ba
                        }
                })
 
-               // Servers and mounts (with or without existing
+               // Servers/mounts/devices (with or without existing
                // replicas) that are part of the best achievable
                // layout for this storage class.
                wantSrv := map[*KeepService]bool{}
                wantMnt := map[*KeepMount]bool{}
+               wantDev := map[string]bool{}
                // Positions (with existing replicas) that have been
                // protected (via unsafeToDelete) to ensure we don't
                // reduce replication below desired level when
                // trashing replicas that aren't optimal positions for
                // any storage class.
                protMnt := map[*KeepMount]bool{}
+               // Replication planned so far (corresponds to wantMnt).
+               replWant := 0
+               // Protected replication (corresponds to protMnt).
+               replProt := 0
 
                // trySlot tries using a slot to meet requirements,
                // and returns true if all requirements are met.
                trySlot := func(i int) bool {
                        slot := slots[i]
-                       if len(protMnt) < desired && slot.repl != nil {
+                       if wantMnt[slot.mnt] || wantDev[slot.mnt.DeviceID] {
+                               // Already allocated a replica to this
+                               // backend device, possibly on a
+                               // different server.
+                               return false
+                       }
+                       if replProt < desired && slot.repl != nil && !protMnt[slot.mnt] {
                                unsafeToDelete[slot.repl.Mtime] = true
                                protMnt[slot.mnt] = true
+                               replProt += slot.mnt.Replication
                        }
-                       if len(wantMnt) < desired && (slot.repl != nil || !slot.mnt.ReadOnly) {
+                       if replWant < desired && (slot.repl != nil || !slot.mnt.ReadOnly) {
                                slots[i].want = true
                                wantSrv[slot.mnt.KeepService] = true
                                wantMnt[slot.mnt] = true
+                               if slot.mnt.DeviceID != "" {
+                                       wantDev[slot.mnt.DeviceID] = true
+                               }
+                               replWant += slot.mnt.Replication
                        }
-                       return len(protMnt) >= desired && len(wantMnt) >= desired
+                       return replProt >= desired && replWant >= desired
                }
 
                // First try to achieve desired replication without
@@ -582,25 +734,52 @@ func (bal *Balancer) balanceBlock(blkid arvados.SizedDigest, blk *BlockState) ba
                                if slot.repl == nil || !bal.mountsByClass[class][slot.mnt] {
                                        continue
                                }
-                               if safe++; safe >= desired {
+                               if safe += slot.mnt.Replication; safe >= desired {
                                        break
                                }
                        }
                        underreplicated = safe < desired
                }
+
+               // set the unachievable flag if there aren't enough
+               // slots offering the relevant storage class. (This is
+               // as easy as checking slots[desired] because we
+               // already sorted the qualifying slots to the front.)
+               if desired >= len(slots) || !bal.mountsByClass[class][slots[desired].mnt] {
+                       cs := classState[class]
+                       cs.unachievable = true
+                       classState[class] = cs
+               }
+
+               // Avoid deleting wanted replicas from devices that
+               // are mounted on multiple servers -- even if they
+               // haven't already been added to unsafeToDelete
+               // because the servers report different Mtimes.
+               for _, slot := range slots {
+                       if slot.repl != nil && wantDev[slot.mnt.DeviceID] {
+                               unsafeToDelete[slot.repl.Mtime] = true
+                       }
+               }
        }
 
        // TODO: If multiple replicas are trashable, prefer the oldest
        // replica that doesn't have a timestamp collision with
        // others.
 
+       countedDev := map[string]bool{}
        var have, want int
        for _, slot := range slots {
+               if countedDev[slot.mnt.DeviceID] {
+                       continue
+               }
                if slot.want {
-                       want++
+                       want += slot.mnt.Replication
                }
                if slot.repl != nil {
-                       have++
+                       have += slot.mnt.Replication
+               }
+               if slot.mnt.DeviceID != "" {
+                       countedDev[slot.mnt.DeviceID] = true
                }
        }
 
@@ -609,24 +788,24 @@ func (bal *Balancer) balanceBlock(blkid arvados.SizedDigest, blk *BlockState) ba
                // TODO: request a Touch if Mtime is duplicated.
                var change int
                switch {
-               case !underreplicated && slot.repl != nil && !slot.want && !unsafeToDelete[slot.repl.Mtime]:
+               case !underreplicated && !slot.want && slot.repl != nil && slot.repl.Mtime < bal.MinMtime && !unsafeToDelete[slot.repl.Mtime]:
                        slot.mnt.KeepService.AddTrash(Trash{
                                SizedDigest: blkid,
                                Mtime:       slot.repl.Mtime,
                                From:        slot.mnt,
                        })
                        change = changeTrash
-               case len(blk.Replicas) == 0:
-                       change = changeNone
-               case slot.repl == nil && slot.want && !slot.mnt.ReadOnly:
+               case len(blk.Replicas) > 0 && slot.repl == nil && slot.want && !slot.mnt.ReadOnly:
                        slot.mnt.KeepService.AddPull(Pull{
                                SizedDigest: blkid,
                                From:        blk.Replicas[0].KeepMount.KeepService,
                                To:          slot.mnt,
                        })
                        change = changePull
-               default:
+               case slot.repl != nil:
                        change = changeStay
+               default:
+                       change = changeNone
                }
                if bal.Dumper != nil {
                        var mtime int64
@@ -638,13 +817,14 @@ func (bal *Balancer) balanceBlock(blkid arvados.SizedDigest, blk *BlockState) ba
                }
        }
        if bal.Dumper != nil {
-               bal.Dumper.Printf("%s have=%d want=%v %s", blkid, have, want, strings.Join(changes, " "))
+               bal.Dumper.Printf("%s refs=%d have=%d want=%v %v %v", blkid, blk.RefCount, have, want, blk.Desired, changes)
        }
        return balanceResult{
-               blk:   blk,
-               blkid: blkid,
-               have:  have,
-               want:  want,
+               blk:        blk,
+               blkid:      blkid,
+               have:       have,
+               want:       want,
+               classState: classState,
        }
 }
 
@@ -659,23 +839,102 @@ func (bb blocksNBytes) String() string {
 }
 
 type balancerStats struct {
-       lost, overrep, unref, garbage, underrep, justright blocksNBytes
-       desired, current                                   blocksNBytes
-       pulls, trashes                                     int
-       replHistogram                                      []int
+       lost          blocksNBytes
+       overrep       blocksNBytes
+       unref         blocksNBytes
+       garbage       blocksNBytes
+       underrep      blocksNBytes
+       unachievable  blocksNBytes
+       justright     blocksNBytes
+       desired       blocksNBytes
+       current       blocksNBytes
+       pulls         int
+       trashes       int
+       replHistogram []int
+       classStats    map[string]replicationStats
+
+       // collectionBytes / collectionBlockBytes = deduplication ratio
+       collectionBytes      int64 // sum(bytes in referenced blocks) across all collections
+       collectionBlockBytes int64 // sum(block size) across all blocks referenced by collections
+       collectionBlockRefs  int64 // sum(number of blocks referenced) across all collections
+       collectionBlocks     int64 // number of blocks referenced by any collection
+}
+
+func (s *balancerStats) dedupByteRatio() float64 {
+       if s.collectionBlockBytes == 0 {
+               return 0
+       }
+       return float64(s.collectionBytes) / float64(s.collectionBlockBytes)
+}
+
+func (s *balancerStats) dedupBlockRatio() float64 {
+       if s.collectionBlocks == 0 {
+               return 0
+       }
+       return float64(s.collectionBlockRefs) / float64(s.collectionBlocks)
+}
+
+type replicationStats struct {
+       desired      blocksNBytes
+       surplus      blocksNBytes
+       short        blocksNBytes
+       unachievable blocksNBytes
+}
+
+type balancedBlockState struct {
+       desired      int
+       surplus      int
+       unachievable bool
 }
 
 func (bal *Balancer) collectStatistics(results <-chan balanceResult) {
        var s balancerStats
        s.replHistogram = make([]int, 2)
+       s.classStats = make(map[string]replicationStats, len(bal.classes))
        for result := range results {
                surplus := result.have - result.want
                bytes := result.blkid.Size()
+
+               if rc := int64(result.blk.RefCount); rc > 0 {
+                       s.collectionBytes += rc * bytes
+                       s.collectionBlockBytes += bytes
+                       s.collectionBlockRefs += rc
+                       s.collectionBlocks++
+               }
+
+               for class, state := range result.classState {
+                       cs := s.classStats[class]
+                       if state.unachievable {
+                               cs.unachievable.blocks++
+                               cs.unachievable.bytes += bytes
+                       }
+                       if state.desired > 0 {
+                               cs.desired.replicas += state.desired
+                               cs.desired.blocks++
+                               cs.desired.bytes += bytes * int64(state.desired)
+                       }
+                       if state.surplus > 0 {
+                               cs.surplus.replicas += state.surplus
+                               cs.surplus.blocks++
+                               cs.surplus.bytes += bytes * int64(state.surplus)
+                       } else if state.surplus < 0 {
+                               cs.short.replicas += -state.surplus
+                               cs.short.blocks++
+                               cs.short.bytes += bytes * int64(-state.surplus)
+                       }
+                       s.classStats[class] = cs
+               }
+
                switch {
                case result.have == 0 && result.want > 0:
                        s.lost.replicas -= surplus
                        s.lost.blocks++
                        s.lost.bytes += bytes * int64(-surplus)
+                       fmt.Fprintf(bal.lostBlocks, "%s", strings.SplitN(string(result.blkid), "+", 2)[0])
+                       for pdh := range result.blk.Refs {
+                               fmt.Fprintf(bal.lostBlocks, " %s", pdh)
+                       }
+                       fmt.Fprint(bal.lostBlocks, "\n")
                case surplus < 0:
                        s.underrep.replicas -= surplus
                        s.underrep.blocks++
@@ -694,7 +953,7 @@ func (bal *Balancer) collectStatistics(results <-chan balanceResult) {
                case surplus > 0:
                        s.overrep.replicas += surplus
                        s.overrep.blocks++
-                       s.overrep.bytes += bytes * int64(len(result.blk.Replicas)-result.want)
+                       s.overrep.bytes += bytes * int64(result.have-result.want)
                default:
                        s.justright.replicas += result.want
                        s.justright.blocks++
@@ -706,22 +965,23 @@ func (bal *Balancer) collectStatistics(results <-chan balanceResult) {
                        s.desired.blocks++
                        s.desired.bytes += bytes * int64(result.want)
                }
-               if len(result.blk.Replicas) > 0 {
-                       s.current.replicas += len(result.blk.Replicas)
+               if result.have > 0 {
+                       s.current.replicas += result.have
                        s.current.blocks++
-                       s.current.bytes += bytes * int64(len(result.blk.Replicas))
+                       s.current.bytes += bytes * int64(result.have)
                }
 
-               for len(s.replHistogram) <= len(result.blk.Replicas) {
+               for len(s.replHistogram) <= result.have {
                        s.replHistogram = append(s.replHistogram, 0)
                }
-               s.replHistogram[len(result.blk.Replicas)]++
+               s.replHistogram[result.have]++
        }
        for _, srv := range bal.KeepServices {
                s.pulls += len(srv.ChangeSet.Pulls)
                s.trashes += len(srv.ChangeSet.Trashes)
        }
        bal.stats = s
+       bal.Metrics.UpdateStats(s)
 }
 
 // PrintStatistics writes statistics about the computed changes to
@@ -735,6 +995,14 @@ func (bal *Balancer) PrintStatistics() {
        bal.logf("%s overreplicated (have>want>0)", bal.stats.overrep)
        bal.logf("%s unreferenced (have>want=0, new)", bal.stats.unref)
        bal.logf("%s garbage (have>want=0, old)", bal.stats.garbage)
+       for _, class := range bal.classes {
+               cs := bal.stats.classStats[class]
+               bal.logf("===")
+               bal.logf("storage class %q: %s desired", class, cs.desired)
+               bal.logf("storage class %q: %s short", class, cs.short)
+               bal.logf("storage class %q: %s surplus", class, cs.surplus)
+               bal.logf("storage class %q: %s unachievable", class, cs.unachievable)
+       }
        bal.logf("===")
        bal.logf("%s total commitment (excluding unreferenced)", bal.stats.desired)
        bal.logf("%s total usage", bal.stats.current)
@@ -807,6 +1075,7 @@ func (bal *Balancer) CheckSanityLate() error {
 // existing blocks that are either underreplicated or poorly
 // distributed according to rendezvous hashing.
 func (bal *Balancer) CommitPulls(c *arvados.Client) error {
+       defer bal.time("send_pull_lists", "wall clock time to send pull lists")()
        return bal.commitAsync(c, "send pull list",
                func(srv *KeepService) error {
                        return srv.CommitPulls(c)
@@ -817,6 +1086,7 @@ func (bal *Balancer) CommitPulls(c *arvados.Client) error {
 // keepstore servers. This has the effect of deleting blocks that are
 // overreplicated or unreferenced.
 func (bal *Balancer) CommitTrash(c *arvados.Client) error {
+       defer bal.time("send_trash_lists", "wall clock time to send trash lists")()
        return bal.commitAsync(c, "send trash list",
                func(srv *KeepService) error {
                        return srv.CommitTrash(c)
@@ -830,7 +1100,6 @@ func (bal *Balancer) commitAsync(c *arvados.Client, label string, f func(srv *Ke
                        var err error
                        defer func() { errs <- err }()
                        label := fmt.Sprintf("%s: %v", srv, label)
-                       defer timeMe(bal.Logger, label)()
                        err = f(srv)
                        if err != nil {
                                err = fmt.Errorf("%s: %v", label, err)
@@ -854,6 +1123,17 @@ func (bal *Balancer) logf(f string, args ...interface{}) {
        }
 }
 
+func (bal *Balancer) time(name, help string) func() {
+       observer := bal.Metrics.DurationObserver(name+"_seconds", help)
+       t0 := time.Now()
+       bal.Logger.Printf("%s: start", name)
+       return func() {
+               dur := time.Since(t0)
+               observer.Observe(dur.Seconds())
+               bal.Logger.Printf("%s: took %vs", name, dur.Seconds())
+       }
+}
+
 // Rendezvous hash sort function. Less efficient than sorting on
 // precomputed rendezvous hashes, but also rarely used.
 func rendezvousLess(i, j string, blkid arvados.SizedDigest) bool {