LogDog: Update to archival V2.

server/internal/logdog/archivist/archivist.go

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package archivist
 
 import (
+        "bytes"
+        "encoding/hex"
         "fmt"
+        "io"
 
         "github.com/golang/protobuf/proto"
         "github.com/luci/luci-go/common/api/logdog_coordinator/services/v1"
         "github.com/luci/luci-go/common/errors"
         "github.com/luci/luci-go/common/gcloud/gs"
         "github.com/luci/luci-go/common/logdog/types"
         log "github.com/luci/luci-go/common/logging"
+        "github.com/luci/luci-go/common/parallel"
         "github.com/luci/luci-go/common/proto/logdog/logpb"
         "github.com/luci/luci-go/server/logdog/archive"
         "github.com/luci/luci-go/server/logdog/storage"
         "golang.org/x/net/context"
 )
 
+// Task is a single archive task.
+type Task interface {
+        // UniqueID returns a task-unique value. Other tasks, and other retries of
+        // this task, should (try to) not reuse this ID.
+        UniqueID() string
+
+        // Task is the archive task to execute.
+        Task() *logdog.ArchiveTask
+
+        // AssertLease asserts that the lease for this Task is still held.
+        //
+        // On failure, it will return an error. If successful, the Archivist may
+        // assume that it holds the lease longer.
+        AssertLease(context.Context) error
+}
+
 // Archivist is a stateless configuration capable of archiving individual log
 // streams.
 type Archivist struct {
         // Service is the client to use to communicate with Coordinator's Services
         // endpoint.
         Service logdog.ServicesClient
 
-        // Storage is the intermediate storage instance to use to pull log entries for
-        // archival.
+        // Storage is the archival source Storage instance.
         Storage storage.Storage
-
         // GSClient is the Google Storage client to for archive generation.
         GSClient gs.Client
 
         // GSBase is the base Google Storage path. This includes the bucket name
         // and any associated path.
         GSBase gs.Path
+        // GSStagingBase is the base Google Storage path for archive staging. This
+        // includes the bucket name and any associated path.
+        GSStagingBase gs.Path
+
         // PrefixIndexRange is the maximum number of stream indexes in between index
         // entries. See archive.Manifest for more information.
         StreamIndexRange int
         // PrefixIndexRange is the maximum number of prefix indexes in between index
         // entries. See archive.Manifest for more information.
         PrefixIndexRange int
         // ByteRange is the maximum number of stream data bytes in between index
         // entries. See archive.Manifest for more information.
         ByteRange int
 }
 
 // storageBufferSize is the size, in bytes, of the LogEntry buffer that is used
 // to during archival. This should be greater than the maximum LogEntry size.
 const storageBufferSize = types.MaxLogEntryDataSize * 64
 
 // ArchiveTask processes and executes a single log stream archive task.
-func (a *Archivist) ArchiveTask(c context.Context, desc []byte) error {
-        var task logdog.ArchiveTask
-        if err := proto.Unmarshal(desc, &task); err != nil {
-                log.WithError(err).Errorf(c, "Failed to decode archive task.")
-                return err
-        }
-        return a.Archive(c, &task)
-}
-
-// Archive archives a single log stream. If unsuccessful, an error is returned.
 //
-// This error may be wrapped in errors.Transient if it is believed to have been
-// caused by a transient failure.
+// It returns true on success (delete the task) and false on failure (don't
+// delete the task). The return value of true should only be used if the task
+// is truly complete and acknowledged by the Coordinator.
 //
 // If the supplied Context is Done, operation may terminate before completion,
 // returning the Context's error.
-func (a *Archivist) Archive(c context.Context, t *logdog.ArchiveTask) error {
+func (a *Archivist) ArchiveTask(c context.Context, task Task) bool {
+        delete, err := a.archiveTaskImpl(c, task)
+        log.Fields{
+                log.ErrorKey: err,
+                "delete":     delete,
+                "path":       task.Task().Path,
+        }.Infof(c, "Finished archive task.")
+        return delete
+}
+
+// archiveTaskImpl returns the same boolean value as ArchiveTask, but includes
+// an error. The error is useful for testing to assert that certain conditions
+// were hit.
+func (a *Archivist) archiveTaskImpl(c context.Context, task Task) (bool, error) {
+        at := task.Task()
+        log.Fields{
+                "path": at.Path,
+        }.Debugf(c, "Received archival task.")
+
         // Load the log stream's current state. If it is already archived, we will
         // return an immediate success.
         ls, err := a.Service.LoadStream(c, &logdog.LoadStreamRequest{
-                Path: t.Path,
+                Path: at.Path,
                 Desc: true,
         })
         switch {
         case err != nil:
                 log.WithError(err).Errorf(c, "Failed to load log stream.")
-                return err
+                return false, err
+
         case ls.State == nil:
-                return errors.New("missing state")
+                log.Errorf(c, "Log stream did not include state.")
+                return false, errors.New("log stream did not include state")
+
+        case ls.State.Purged:
+                log.Warningf(c, "Log stream is purged. Discarding archival request.")
+                return true, errors.New("log stream is purged")
+
+        case ls.State.Archived:
+                log.Infof(c, "Log stream is already archived. Discarding archival request.")
+                return true, errors.New("log stream is archived")
+
+        case !bytes.Equal(ls.ArchivalKey, at.Key):
+                if len(ls.ArchivalKey) == 0 {
+                        // The log stream is not registering as "archive pending" state.
+                        //
+                        // This can happen if the eventually-consistent datastore hasn't updated
+                        // its log stream state by the time this Pub/Sub task is received. In
+                        // this case, we will continue retrying the task until datastore registers
+                        // that some key is associated with it.
+                        log.Fields{
+                                "logStreamArchivalKey": hex.EncodeToString(ls.ArchivalKey),
+                                "requestArchivalKey":   hex.EncodeToString(at.Key),
+                        }.Infof(c, "Archival request received before log stream has its key.")
+                        return false, errors.New("premature archival request")
+                }
+
+                // This can happen if a Pub/Sub message is dispatched during a transaction,
+                // but that specific transaction failed. In this case, the Pub/Sub message
+                // will have a key that doesn't match the key that was transactionally
+                // encoded, and can be discarded.
+                log.Fields{
+                        "logStreamArchivalKey": hex.EncodeToString(ls.ArchivalKey),
+                        "requestArchivalKey":   hex.EncodeToString(at.Key),
+                }.Infof(c, "Superfluous archival request (keys do not match). Discarding.")
+                return true, errors.New("superfluous archival request")
+
         case ls.State.ProtoVersion != logpb.Version:
                 log.Fields{
                         "protoVersion":    ls.State.ProtoVersion,
                         "expectedVersion": logpb.Version,
                 }.Errorf(c, "Unsupported log stream protobuf version.")
-                return errors.New("unsupported protobuf version")
+                return false, errors.New("unsupported log stream protobuf version")
+
         case ls.Desc == nil:
-                return errors.New("missing descriptor")
-
-        case ls.State.Purged:
-                log.Warningf(c, "Log stream is purged.")
-                return nil
-        case ls.State.Archived:
-                log.Infof(c, "Log stream is already archived.")
-                return nil
-        }
-
-        // Deserialize and validate the descriptor protobuf.
-        var desc logpb.LogStreamDescriptor
-        if err := proto.Unmarshal(ls.Desc, &desc); err != nil {
+                log.Errorf(c, "Log stream did not include a descriptor.")
+                return false, errors.New("log stream did not include a descriptor")
+        }
+
+        // If the archival request is younger than the settle delay, kick it back to
+        // retry later.
+        age := ls.Age.Duration()
+        if age < at.SettleDelay.Duration() {
+                log.Fields{
+                        "age":         age,
+                        "settleDelay": at.SettleDelay.Duration(),
+                }.Infof(c, "Log stream is younger than the settle delay. Returning task to queue.")
+                return false, errors.New("log stream is within settle delay")
+        }
+
+        // Are we required to archive a complete log stream?
+        complete := (age <= at.CompletePeriod.Duration())
+        if complete && ls.State.TerminalIndex < 0 {
+                log.Warningf(c, "Cannot archive complete stream with no terminal index.")
+                return false, errors.New("completeness required, but stream has no terminal index")
+        }
+
+        ar := logdog.ArchiveStreamRequest{
+                Path: at.Path,
+        }
+
+        // Archive to staging.
+        //
+        // If a non-transient failure occurs here, we will report it to the Archivist
+        // under the assumption that it will continue occurring.
+        //
+        // We will handle error creating the plan and executing the plan in the same
+        // switch statement below.
+        staged, err := a.makeStagedArchival(c, types.StreamPath(at.Path), ls, task.UniqueID())
+        if err != nil {
+                log.WithError(err).Errorf(c, "Failed to create staged archival plan.")
+        } else {
+                err = staged.stage(c, complete)
+        }
+
+        switch {
+        case errors.IsTransient(err):
+                // If this is a transient error, exit immediately and do not delete the
+                // archival task.
+                log.WithError(err).Warningf(c, "TRANSIENT error during archival operation.")
+                return false, err
+
+        case err != nil:
+                // This is a non-transient error, so we are confident that any future
+                // Archival will also encounter this error. We will mark this archival
+                // as an error and report it to the Coordinator.
+                log.WithError(err).Errorf(c, "Archival failed with non-transient error.")
+                ar.Error = err.Error()
+                if ar.Error == "" {
+                        // This needs to be non-nil, so if our acutal error has an empty string,
+                        // fill in a generic message.
+                        ar.Error = "archival error"
+                }
+
+        default:
+                // In case something fails, clean up our staged archival (best effort).
+                defer staged.cleanup(c)
+
+                // Finalize the archival. First, extend our lease to confirm that we still
+                // hold it.
+                if err := task.AssertLease(c); err != nil {
+                        log.WithError(err).Errorf(c, "Failed to extend task lease before finalizing.")
+                        return false, err
+                }
+
+                // Finalize the archival.
+                if err := staged.finalize(c, a.GSClient, &ar); err != nil {
+                        log.WithError(err).Errorf(c, "Failed to finalize archival.")
+                        return false, err
+                }
+        }
+
+        log.Fields{
+                "streamURL":     ar.StreamUrl,
+                "indexURL":      ar.IndexUrl,
+                "dataURL":       ar.DataUrl,
+                "terminalIndex": ar.TerminalIndex,
+                "logEntryCount": ar.LogEntryCount,
+                "hadError":      ar.Error,
+                "complete":      ar.Complete(),
+        }.Debugf(c, "Finished archival round. Reporting archive state.")
+
+        // Extend the lease again to confirm that we still hold it.
+        if err := task.AssertLease(c); err != nil {
+                log.WithError(err).Errorf(c, "Failed to extend task lease before reporting.")
+                return false, err
+        }
+
+        if _, err := a.Service.ArchiveStream(c, &ar); err != nil {
+                log.WithError(err).Errorf(c, "Failed to report archive state.")
+                return false, err
+        }
+
+        // Archival is complete and acknowledged by Coordinator. Consume the archival
+        // task.
+        return true, nil
+}
+
+func (a *Archivist) makeStagedArchival(c context.Context, path types.StreamPath, ls *logdog.LoadStreamResponse, uid string) (
+        *stagedArchival, error) {
+        sa := stagedArchival{
+                Archivist: a,
+                path:      path,
+
+                terminalIndex: ls.State.TerminalIndex,
+        }
+
+        // Deserialize and validate the descriptor protobuf. If this fails, it is a
+        // non-transient error.
+        if err := proto.Unmarshal(ls.Desc, &sa.desc); err != nil {
                 log.Fields{
                         log.ErrorKey:   err,
                         "protoVersion": ls.State.ProtoVersion,
                 }.Errorf(c, "Failed to unmarshal descriptor protobuf.")
-                return err
-        }
-
-        task := &archiveTask{
-                Archivist:   a,
-                ArchiveTask: t,
-                ls:          ls,
-                desc:        &desc,
-        }
-        if err := task.archive(c); err != nil {
-                log.WithError(err).Errorf(c, "Failed to perform archival operation.")
-                return err
-        }
-        log.Fields{
-                "streamURL":     task.ar.StreamUrl,
-                "indexURL":      task.ar.IndexUrl,
-                "dataURL":       task.ar.DataUrl,
-                "terminalIndex": task.ar.TerminalIndex,
-                "complete":      task.ar.Complete,
-        }.Debugf(c, "Finished archive construction.")
-
-        if _, err := a.Service.ArchiveStream(c, &task.ar); err != nil {
-                log.WithError(err).Errorf(c, "Failed to mark log stream as archived.")
-                return err
-        }
-        return nil
-}
-
-// archiveTask is the set of parameters for a single archival.
-type archiveTask struct {
-        *Archivist
-        *logdog.ArchiveTask
-
-        // ls is the log stream state.
-        ls *logdog.LoadStreamResponse
-        // desc is the unmarshaled log stream descriptor.
-        desc *logpb.LogStreamDescriptor
-
-        // ar will be populated during archive construction.
-        ar logdog.ArchiveStreamRequest
-}
-
-// archiveState performs the archival operation on a stream described by a
-// Coordinator State. Upon success, the State will be updated with the result
-// of the archival operation.
-func (t *archiveTask) archive(c context.Context) (err error) {
-        // Generate our archival object managers.
-        bext := t.desc.BinaryFileExt
+                return nil, err
+        }
+
+        bext := sa.desc.BinaryFileExt
         if bext == "" {
                 bext = "bin"
         }
 
-        path := t.Path
-        var streamO, indexO, dataO *gsObject
-        streamO, err = t.newGSObject(c, path, "logstream.entries")
-        if err != nil {
-                log.WithError(err).Errorf(c, "Failed to create log object.")
-                return
-        }
-
-        indexO, err = t.newGSObject(c, path, "logstream.index")
-        if err != nil {
-                log.WithError(err).Errorf(c, "Failed to create index object.")
-                return
-        }
-
-        dataO, err = t.newGSObject(c, path, fmt.Sprintf("data.%s", bext))
-        if err != nil {
-                log.WithError(err).Errorf(c, "Failed to create data object.")
-                return
-        }
-
-        // Load the URLs into our state.
-        t.ar.StreamUrl = streamO.url
-        t.ar.IndexUrl = indexO.url
-        t.ar.DataUrl = dataO.url
-
+        // Construct our staged archival paths.
+        sa.stream = a.makeStagingPaths(path, "logstream.entries", uid)
+        sa.index = a.makeStagingPaths(path, "logstream.index", uid)
+        sa.data = a.makeStagingPaths(path, fmt.Sprintf("data.%s", bext), uid)
+        return &sa, nil
+}
+
+// makeStagingPaths returns a stagingPaths instance for the given path and
+// file name. It incorporates a unique ID into the staging name to differentiate
+// it from other staging paths for the same path/name.
+func (a *Archivist) makeStagingPaths(path types.StreamPath, name, uid string) stagingPaths {
+        return stagingPaths{
+                staged: a.GSStagingBase.Concat(string(path), uid, name),
+                final:  a.GSBase.Concat(string(path), name),
+        }
+}
+
+type stagedArchival struct {
+        *Archivist
+
+        path types.StreamPath
+        desc logpb.LogStreamDescriptor
+
+        stream     stagingPaths
+        streamSize int64
+
+        index     stagingPaths
+        indexSize int64
+
+        data     stagingPaths
+        dataSize int64
+
+        finalized     bool
+        terminalIndex int64
+        logEntryCount int64
+}
+
+// stage executes the archival process, archiving to the staged storage paths.
+//
+// If stage fails, it may return a transient error.
+func (sa *stagedArchival) stage(c context.Context, complete bool) (err error) {
         log.Fields{
-                "streamURL": t.ar.StreamUrl,
-                "indexURL":  t.ar.IndexUrl,
-                "dataURL":   t.ar.DataUrl,
-        }.Infof(c, "Archiving log stream...")
-
-        // We want to try and delete any GS objects that were created during a failed
-        // archival attempt.
-        deleteOnFail := func(o *gsObject) {
-                if o == nil || err == nil {
-                        return
-                }
-                if ierr := o.delete(); ierr != nil {
+                "streamURL": sa.stream.staged,
+                "indexURL":  sa.index.staged,
+                "dataURL":   sa.data.staged,
+        }.Debugf(c, "Staging log stream...")
+
+        // Group any transient errors that occur during cleanup. If we aren't
+        // returning a non-transient error, return a transient "terr".
+        var terr errors.MultiError
+        defer func() {
+                if err == nil && len(terr) > 0 {
+                        err = errors.WrapTransient(terr)
+                }
+        }()
+
+        // Close our writers on exit. If any of them fail to close, mark the archival
+        // as a transient failure.
+        closeWriter := func(closer io.Closer, path gs.Path) {
+                // Close the Writer. If this results in an error, append it to our transient
+                // error MultiError.
+                if ierr := closer.Close(); ierr != nil {
+                        terr = append(terr, ierr)
+                }
+
+                // If we have an archival error, also delete the path associated with this
+                // stream. This is a non-fatal failure, since we've already hit a fatal
+                // one.
+                if err != nil || len(terr) > 0 {
+                        if ierr := sa.GSClient.Delete(path); ierr != nil {
+                                log.Fields{
+                                        log.ErrorKey: ierr,
+                                        "path":       path,
+                                }.Warningf(c, "Failed to delete stream on error.")
+                        }
+                }
+        }
+
+        // createWriter is a shorthand function for creating a writer to a path and
+        // reporting an error if it failed.
+        createWriter := func(p gs.Path) (gs.Writer, error) {
+                w, ierr := sa.GSClient.NewWriter(p)
+                if ierr != nil {
                         log.Fields{
                                 log.ErrorKey: ierr,
-                                "url":        o.url,
-                        }.Warningf(c, "Failed to clean-up GS object on failure.")
-                }
-        }
-        defer deleteOnFail(streamO)
-        defer deleteOnFail(indexO)
-        defer deleteOnFail(dataO)
-
-        // Close our GS object managers on exit. If any of them fail to close, marh
-        // the archival as a failure.
-        closeOM := func(o *gsObject) {
-                if o == nil {
-                        return
-                }
-                if ierr := o.Close(); ierr != nil {
-                        err = ierr
-                }
-        }
-        defer closeOM(streamO)
-        defer closeOM(indexO)
-        defer closeOM(dataO)
+                                "path":       p,
+                        }.Errorf(c, "Failed to create writer.")
+                        return nil, ierr
+                }
+                return w, nil
+        }
+
+        var streamWriter, indexWriter, dataWriter gs.Writer
+        if streamWriter, err = createWriter(sa.stream.staged); err != nil {
+                return
+        }
+        defer closeWriter(streamWriter, sa.stream.staged)
+
+        if indexWriter, err = createWriter(sa.index.staged); err != nil {
+                return err
+        }
+        defer closeWriter(indexWriter, sa.index.staged)
+
+        if dataWriter, err = createWriter(sa.data.staged); err != nil {
+                return err
+        }
+        defer closeWriter(dataWriter, sa.data.staged)
 
         // Read our log entries from intermediate storage.
         ss := storageSource{
                 Context:       c,
-                st:            t.Storage,
-                path:          types.StreamPath(t.Path),
-                contiguous:    t.Complete,
-                terminalIndex: types.MessageIndex(t.ls.State.TerminalIndex),
+                st:            sa.Storage,
+                path:          sa.path,
+                contiguous:    complete,
+                terminalIndex: types.MessageIndex(sa.terminalIndex),
                 lastIndex:     -1,
         }
 
         m := archive.Manifest{
-                Desc:             t.desc,
+                Desc:             &sa.desc,
                 Source:           &ss,
-                LogWriter:        streamO,
-                IndexWriter:      indexO,
-                DataWriter:       dataO,
-                StreamIndexRange: t.StreamIndexRange,
-                PrefixIndexRange: t.PrefixIndexRange,
-                ByteRange:        t.ByteRange,
+                LogWriter:        streamWriter,
+                IndexWriter:      indexWriter,
+                DataWriter:       dataWriter,
+                StreamIndexRange: sa.StreamIndexRange,
+                PrefixIndexRange: sa.PrefixIndexRange,
+                ByteRange:        sa.ByteRange,
 
                 Logger: log.Get(c),
         }
-        err = archive.Archive(m)
-        if err != nil {
+        if err = archive.Archive(m); err != nil {
                 log.WithError(err).Errorf(c, "Failed to archive log stream.")
                 return
         }
 
-        t.ar.TerminalIndex = int64(ss.lastIndex)
-        if tidx := t.ls.State.TerminalIndex; tidx != t.ar.TerminalIndex {
-                // Fail, if we were requested to archive only the complete log.
-                if t.Complete {
-                        log.Fields{
-                                "terminalIndex": tidx,
-                                "lastIndex":     t.ar.TerminalIndex,
-                        }.Errorf(c, "Log stream archival stopped prior to terminal index.")
-                        return errors.New("stream finished short of terminal index")
-                }
-
-                if t.ar.TerminalIndex < 0 {
+        if tidx := sa.terminalIndex; tidx != int64(ss.lastIndex) {
+                // Fail if we were requested to archive only the complete log. We consider
+                // this a transient error with the expectation that the missing entries will
+                // show up in future retries.
+                switch {
+                case complete && ss.hasMissingEntries:
+                        log.Errorf(c, "Log stream has missing entries, but completeness is required.")
+                        err = errors.WrapTransient(errors.New("stream has missing entries"))
+                        return
+
+                case ss.logEntryCount == 0:
                         // If our last log index was <0, then no logs were archived.
                         log.Warningf(c, "No log entries were archived.")
-                } else {
+
+                default:
                         // Update our terminal index.
                         log.Fields{
-                                "from": tidx,
-                                "to":   t.ar.TerminalIndex,
-                        }.Infof(c, "Updated log stream terminal index.")
+                                "terminalIndex":     ss.lastIndex,
+                                "logEntryCount":     ss.logEntryCount,
+                                "hasMissingEntries": ss.hasMissingEntries,
+                        }.Debugf(c, "Finished archiving log stream.")
                 }
         }
 
         // Update our state with archival results.
-        t.ar.Path = t.Path
-        t.ar.StreamSize = streamO.Count()
-        t.ar.IndexSize = indexO.Count()
-        t.ar.DataSize = dataO.Count()
-        t.ar.Complete = !ss.hasMissingEntries
+        sa.terminalIndex = int64(ss.lastIndex)
+        sa.logEntryCount = ss.logEntryCount
+        sa.stream.count = streamWriter.Count()
+        sa.index.count = indexWriter.Count()
+        sa.data.count = dataWriter.Count()
         return
 }
 
-func (t *archiveTask) newGSObject(c context.Context, path string, name string) (*gsObject, error) {
-        p := t.GSBase.Concat(path, name)
-        o := gsObject{
-                gs:     t.GSClient,
-                bucket: p.Bucket(),
-                path:   p.Filename(),
-        }
-
-        // Build our GS URL. Note that since buildGSPath joins with "/", the initial
-        // token, "gs:/", will become "gs://".
-        o.url = string(p)
-
-        var err error
-        o.Writer, err = t.GSClient.NewWriter(o.bucket, o.path)
+type stagingPaths struct {
+        staged gs.Path
+        final  gs.Path
+        count  int64
+}
+
+func (d *stagingPaths) clearStaged() {
+        d.staged = ""
+}
+
+func (sa *stagedArchival) finalize(c context.Context, client gs.Client, ar *logdog.ArchiveStreamRequest) error {
+        err := parallel.FanOutIn(func(taskC chan<- func() error) {
+                for _, d := range sa.getStagingPaths() {
+                        d := d
+
+                        // Don't copy zero-sized streams.
+                        if d.count == 0 {
+                                continue
+                        }
+
+                        taskC <- func() error {
+                                if err := client.Rename(d.staged, d.final); err != nil {
+                                        log.Fields{
+                                                log.ErrorKey: err,
+                                                "stagedPath": d.staged,
+                                                "finalPath":  d.final,
+                                        }.Errorf(c, "Failed to rename GS object.")
+                                        return err
+                                }
+
+                                // Clear the staged value to indicate that it no longer exists.
+                                d.clearStaged()
+                                return nil
+                        }
+                }
+        })
         if err != nil {
-                log.Fields{
-                        log.ErrorKey: err,
-                        "url":        o.url,
-                }.Errorf(c, "Failed to create Writer.")
-                return nil, err
-        }
-
-        // Delete any existing object at this path.
-        if err := o.delete(); err != nil {
-                closeErr := o.Close()
-
-                log.Fields{
-                        log.ErrorKey: err,
-                        "closeErr":   closeErr,
-                        "url":        o.url,
-                }.Errorf(c, "Could not delete object during creation.")
-                return nil, err
-        }
-        return &o, nil
-}
-
-// gsObjectManger wraps a gsObject instance with metadata.
-type gsObject struct {
-        gs.Writer
-
-        // gs is the Client instance.
-        gs gs.Client
-        // bucket is the name of the object's bucket.
-        bucket string
-        // path is the bucket-relative path of the object.
-        path string
-        // url is the Google Storage URL (gs://) of this object.
-        url string
-}
-
-func (o *gsObject) delete() error {
-        return o.gs.Delete(o.bucket, o.path)
-}
-
-// storageSource is an archive.LogEntrySource that pulls log entries from
-// intermediate storage via its storage.Storage instance.
-type storageSource struct {
-        context.Context
-
-        st            storage.Storage    // the storage instance to read from
-        path          types.StreamPath   // the path of the log stream
-        contiguous    bool               // if true, enforce contiguous entries
-        terminalIndex types.MessageIndex // if >= 0, discard logs beyond this
-
-        buf               []*logpb.LogEntry
-        lastIndex         types.MessageIndex
-        hasMissingEntries bool // true if some log entries were missing.
-}
-
-func (s *storageSource) bufferEntries(start types.MessageIndex) error {
-        bytes := 0
-
-        req := storage.GetRequest{
-                Path:  s.path,
-                Index: start,
-        }
-        return s.st.Get(req, func(idx types.MessageIndex, d []byte) bool {
-                le := logpb.LogEntry{}
-                if err := proto.Unmarshal(d, &le); err != nil {
+                return err
+        }
+
+        ar.TerminalIndex = sa.terminalIndex
+        ar.LogEntryCount = sa.logEntryCount
+        ar.StreamUrl = string(sa.stream.final)
+        ar.StreamSize = sa.stream.count
+        ar.IndexUrl = string(sa.index.final)
+        ar.IndexSize = sa.index.count
+        ar.DataUrl = string(sa.data.final)
+        ar.DataSize = sa.data.count
+        return nil
+}
+
+func (sa *stagedArchival) cleanup(c context.Context) {
+        for _, d := range sa.getStagingPaths() {
+                if d.staged == "" {
+                        continue
+                }
+
+                if err := sa.GSClient.Delete(d.staged); err != nil {
                         log.Fields{
-                                log.ErrorKey:  err,
-                                "streamIndex": idx,
-                        }.Errorf(s, "Failed to unmarshal LogEntry.")
-                        return false
-                }
-                s.buf = append(s.buf, &le)
-
-                // Stop loading if we've reached or exceeded our buffer size.
-                bytes += len(d)
-                return bytes < storageBufferSize
-        })
-}
-
-func (s *storageSource) NextLogEntry() (*logpb.LogEntry, error) {
-        if len(s.buf) == 0 {
-                s.buf = s.buf[:0]
-                if err := s.bufferEntries(s.lastIndex + 1); err != nil {
-                        if err == storage.ErrDoesNotExist {
-                                log.Warningf(s, "Archive target stream does not exist in intermediate storage.")
-                                return nil, archive.ErrEndOfStream
-                        }
-
-                        log.WithError(err).Errorf(s, "Failed to retrieve log stream from storage.")
-                        return nil, err
-                }
-        }
-
-        if len(s.buf) == 0 {
-                log.Fields{
-                        "lastIndex": s.lastIndex,
-                }.Debugf(s, "Encountered end of stream.")
-                return nil, archive.ErrEndOfStream
-        }
-
-        var le *logpb.LogEntry
-        le, s.buf = s.buf[0], s.buf[1:]
-
-        // If we're enforcing a contiguous log stream, error if this LogEntry is not
-        // contiguous.
-        sidx := types.MessageIndex(le.StreamIndex)
-        nidx := (s.lastIndex + 1)
-        if sidx != nidx {
-                s.hasMissingEntries = true
-
-                if s.contiguous {
-                        log.Fields{
-                                "index":     sidx,
-                                "nextIndex": nidx,
-                        }.Errorf(s, "Non-contiguous log stream while enforcing.")
-                        return nil, errors.New("non-contiguous log stream")
-                }
-        }
-
-        // If we're enforcing a maximum terminal index, return end of stream if this
-        // LogEntry exceeds that index.
-        if s.terminalIndex >= 0 && sidx > s.terminalIndex {
-                log.Fields{
-                        "index":         sidx,
-                        "terminalIndex": s.terminalIndex,
-                }.Warningf(s, "Discarding log entries beyond expected terminal index.")
-                return nil, archive.ErrEndOfStream
-        }
-
-        s.lastIndex = sidx
-        return le, nil
-}
+                                log.ErrorKey: err,
+                                "path":       d.staged,
+                        }.Warningf(c, "Failed to clean up staged path.")
+                }
+
+                d.clearStaged()
+        }
+}
+
+func (sa *stagedArchival) getStagingPaths() []*stagingPaths {
+        return []*stagingPaths{
+                &sa.stream,
+                &sa.index,
+                &sa.data,
+        }
+}