zrepl/platformtest/tests/replication.go

package tests

import (
	"context"
	"fmt"
	"io"
	"os"
	"path"
	"sort"

	"github.com/kr/pretty"
	"github.com/stretchr/testify/require"

	"github.com/zrepl/zrepl/daemon/filters"
	"github.com/zrepl/zrepl/endpoint"
	"github.com/zrepl/zrepl/platformtest"
	"github.com/zrepl/zrepl/replication"
	"github.com/zrepl/zrepl/replication/logic"
	"github.com/zrepl/zrepl/replication/logic/pdu"
	"github.com/zrepl/zrepl/replication/report"
	"github.com/zrepl/zrepl/util/limitio"
	"github.com/zrepl/zrepl/zfs"
)

// mimics the replication invocations of an active-side job
// for a single sender-receiver filesystem pair
//
// each invocation of method Do results in the construction
// of a new sender and receiver instance and one blocking invocation
// of the replication engine without encryption
type replicationInvocation struct {
	sjid, rjid        endpoint.JobID
	sfs               string
	sfilter           *filters.DatasetMapFilter
	rfsRoot           string
	interceptSender   func(e *endpoint.Sender) logic.Sender
	interceptReceiver func(e *endpoint.Receiver) logic.Receiver
	guarantee         pdu.ReplicationConfigProtection
}

func (i replicationInvocation) Do(ctx *platformtest.Context) *report.Report {

	if i.interceptSender == nil {
		i.interceptSender = func(e *endpoint.Sender) logic.Sender { return e }
	}
	if i.interceptReceiver == nil {
		i.interceptReceiver = func(e *endpoint.Receiver) logic.Receiver { return e }
	}

	if i.sfs != "" && i.sfilter != nil || i.sfs == "" && i.sfilter == nil {
		panic("either sfs or sfilter must be set")
	}
	if i.sfilter == nil {
		i.sfilter = filters.NewDatasetMapFilter(1, true)
		err := i.sfilter.Add(i.sfs, "ok")
		require.NoError(ctx, err)
	}
	sender := i.interceptSender(endpoint.NewSender(endpoint.SenderConfig{
		FSF:     i.sfilter.AsFilter(),
		Encrypt: &zfs.NilBool{B: false},
		JobID:   i.sjid,
	}))
	receiver := i.interceptReceiver(endpoint.NewReceiver(endpoint.ReceiverConfig{
		JobID:                      i.rjid,
		AppendClientIdentity:       false,
		RootWithoutClientComponent: mustDatasetPath(i.rfsRoot),
	}))
	plannerPolicy := logic.PlannerPolicy{
		EncryptedSend: logic.TriFromBool(false),
		ReplicationConfig: pdu.ReplicationConfig{
			Protection: &i.guarantee,
		},
	}

	report, wait := replication.Do(
		ctx,
		logic.NewPlanner(nil, nil, sender, receiver, plannerPolicy),
	)
	wait(true)
	return report()
}

func (i replicationInvocation) ReceiveSideFilesystem() string {
	return path.Join(i.rfsRoot, i.sfs)
}

func ReplicationIncrementalIsPossibleIfCommonSnapshotIsDestroyed(ctx *platformtest.Context) {

	platformtest.Run(ctx, platformtest.PanicErr, ctx.RootDataset, `
		CREATEROOT
		+  "sender"
		+  "sender@1"
		+  "receiver"
		R  zfs create -p "${ROOTDS}/receiver/${ROOTDS}"
	`)

	sjid := endpoint.MustMakeJobID("sender-job")
	rjid := endpoint.MustMakeJobID("receiver-job")

	sfs := ctx.RootDataset + "/sender"
	rfsRoot := ctx.RootDataset + "/receiver"
	snap1 := fsversion(ctx, sfs, "@1")

	rep := replicationInvocation{
		sjid:      sjid,
		rjid:      rjid,
		sfs:       sfs,
		rfsRoot:   rfsRoot,
		guarantee: *pdu.ReplicationConfigProtectionWithKind(pdu.ReplicationGuaranteeKind_GuaranteeResumability),
	}
	rfs := rep.ReceiveSideFilesystem()

	// first replication
	report := rep.Do(ctx)
	ctx.Logf("\n%s", pretty.Sprint(report))

	// assert @1 exists on receiver
	_ = fsversion(ctx, rfs, "@1")

	// cut off the common base between sender and receiver
	// (replication engine guarantees resumability through bookmarks)
	err := zfs.ZFSDestroy(ctx, snap1.FullPath(sfs))
	require.NoError(ctx, err)

	// assert that the replication cursor has been created
	snap1CursorName, err := endpoint.ReplicationCursorBookmarkName(sfs, snap1.Guid, sjid)
	require.NoError(ctx, err)
	snap1CursorInfo, err := zfs.ZFSGetFilesystemVersion(ctx, sfs+"#"+snap1CursorName)
	require.NoError(ctx, err)
	require.True(ctx, snap1CursorInfo.IsBookmark())

	// second replication of a new snapshot, should use the cursor
	mustSnapshot(ctx, sfs+"@2")
	report = rep.Do(ctx)
	ctx.Logf("\n%s", pretty.Sprint(report))
	_ = fsversion(ctx, rfs, "@2")

}

func ReplicationIncrementalCleansUpStaleAbstractionsWithCacheOnSecondReplication(ctx *platformtest.Context) {
	implReplicationIncrementalCleansUpStaleAbstractions(ctx, true)
}

func ReplicationIncrementalCleansUpStaleAbstractionsWithoutCacheOnSecondReplication(ctx *platformtest.Context) {
	implReplicationIncrementalCleansUpStaleAbstractions(ctx, false)
}

func implReplicationIncrementalCleansUpStaleAbstractions(ctx *platformtest.Context, invalidateCacheBeforeSecondReplication bool) {

	platformtest.Run(ctx, platformtest.PanicErr, ctx.RootDataset, `
		CREATEROOT
		+  "sender"
		+  "sender@1"
		+  "sender@2"
		+  "sender#2" "sender@2"
		+  "sender@3"
		+  "receiver"
		R  zfs create -p "${ROOTDS}/receiver/${ROOTDS}"
	`)

	sjid := endpoint.MustMakeJobID("sender-job")
	ojid := endpoint.MustMakeJobID("other-job")
	rjid := endpoint.MustMakeJobID("receiver-job")

	sfs := ctx.RootDataset + "/sender"
	rfsRoot := ctx.RootDataset + "/receiver"

	rep := replicationInvocation{
		sjid:      sjid,
		rjid:      rjid,
		sfs:       sfs,
		rfsRoot:   rfsRoot,
		guarantee: *pdu.ReplicationConfigProtectionWithKind(pdu.ReplicationGuaranteeKind_GuaranteeResumability),
	}
	rfs := rep.ReceiveSideFilesystem()

	// first replication
	report := rep.Do(ctx)
	ctx.Logf("\n%s", pretty.Sprint(report))

	// assert most recent send-side version @3 exists on receiver (=replication succeeded)
	rSnap3 := fsversion(ctx, rfs, "@3")
	// assert the source-side versions not managed by zrepl still exist
	snap1 := fsversion(ctx, sfs, "@1")
	snap2 := fsversion(ctx, sfs, "@2")
	_ = fsversion(ctx, sfs, "#2") // non-replicationc-cursor bookmarks should not be affected
	snap3 := fsversion(ctx, sfs, "@3")
	// assert a replication cursor is in place
	snap3CursorName, err := endpoint.ReplicationCursorBookmarkName(sfs, snap3.Guid, sjid)
	require.NoError(ctx, err)
	_ = fsversion(ctx, sfs, "#"+snap3CursorName)
	// assert a last-received hold is in place
	expectRjidHoldTag, err := endpoint.LastReceivedHoldTag(rjid)
	require.NoError(ctx, err)
	holds, err := zfs.ZFSHolds(ctx, rfs, rSnap3.Name)
	require.NoError(ctx, err)
	require.Contains(ctx, holds, expectRjidHoldTag)

	// create artifical stale replication cursors & step holds
	createArtificalStaleAbstractions := func(jobId endpoint.JobID) []endpoint.Abstraction {
		snap2Cursor, err := endpoint.CreateReplicationCursor(ctx, sfs, snap2, jobId) // no shadow
		require.NoError(ctx, err)
		// create artifical stale step holds jobId
		snap1Hold, err := endpoint.HoldStep(ctx, sfs, snap1, jobId) // no shadow
		require.NoError(ctx, err)
		snap2Hold, err := endpoint.HoldStep(ctx, sfs, snap2, jobId) // no shadow
		require.NoError(ctx, err)
		return []endpoint.Abstraction{snap2Cursor, snap1Hold, snap2Hold}
	}
	createArtificalStaleAbstractions(sjid)
	ojidSendAbstractions := createArtificalStaleAbstractions(ojid)

	snap3ojidLastReceivedHold, err := endpoint.CreateLastReceivedHold(ctx, rfs, fsversion(ctx, rfs, "@3"), ojid)
	require.NoError(ctx, err)
	require.True(ctx, zfs.FilesystemVersionEqualIdentity(fsversion(ctx, rfs, "@3"), snap3ojidLastReceivedHold.GetFilesystemVersion()))

	// take another 2 snapshots
	mustSnapshot(ctx, sfs+"@4")
	mustSnapshot(ctx, sfs+"@5")
	snap5 := fsversion(ctx, sfs, "@5")

	if invalidateCacheBeforeSecondReplication {
		endpoint.AbstractionsCacheInvalidate(sfs)
	}

	// do another replication
	// - ojid's abstractions should not be affected on either side
	// - stale abstractions of sjid and rjid should be cleaned up
	// - 1 replication cursors and 1 last-received hold should be present

	checkOjidAbstractionsExist := func() {
		var expectedOjidAbstractions []endpoint.Abstraction
		expectedOjidAbstractions = append(expectedOjidAbstractions, ojidSendAbstractions...)
		expectedOjidAbstractions = append(expectedOjidAbstractions, snap3ojidLastReceivedHold)

		sfsAndRfsFilter := filters.NewDatasetMapFilter(2, true)
		require.NoError(ctx, sfsAndRfsFilter.Add(sfs, "ok"))
		require.NoError(ctx, sfsAndRfsFilter.Add(rfs, "ok"))
		rAbs, rAbsErrs, err := endpoint.ListAbstractions(ctx, endpoint.ListZFSHoldsAndBookmarksQuery{
			FS:          endpoint.ListZFSHoldsAndBookmarksQueryFilesystemFilter{Filter: sfsAndRfsFilter},
			JobID:       &ojid,
			What:        endpoint.AbstractionTypesAll,
			Concurrency: 1,
		})
		require.NoError(ctx, err)
		require.Len(ctx, rAbsErrs, 0)
		ctx.Logf("rAbs=%s", rAbs)
		ctx.Logf("expectedOjidAbstractions=%s", expectedOjidAbstractions)
		require.Equal(ctx, len(expectedOjidAbstractions), len(rAbs))
		for _, ea := range expectedOjidAbstractions {
			ctx.Logf("looking for %s %#v", ea, ea.GetFilesystemVersion())
			found := false
			for _, a := range rAbs {
				eq := endpoint.AbstractionEquals(ea, a)
				ctx.Logf("comp=%v for %s %#v", eq, a, a.GetFilesystemVersion())
				found = found || eq
			}
			require.True(ctx, found, "%s", ea)
		}
	}
	checkOjidAbstractionsExist()

	report = rep.Do(ctx)
	ctx.Logf("\n%s", pretty.Sprint(report))

	checkOjidAbstractionsExist()

	_ = fsversion(ctx, sfs, "@1")
	_ = fsversion(ctx, sfs, "@2")
	_ = fsversion(ctx, sfs, "#2")
	_ = fsversion(ctx, sfs, "@3")
	_ = fsversion(ctx, sfs, "@4")
	_ = fsversion(ctx, sfs, "@5")

	_ = fsversion(ctx, rfs, "@3")
	_ = fsversion(ctx, rfs, "@4")
	_ = fsversion(ctx, rfs, "@5")

	// check bookmark situation
	{
		sBms, err := zfs.ZFSListFilesystemVersions(ctx, mustDatasetPath(sfs), zfs.ListFilesystemVersionsOptions{
			Types: zfs.Bookmarks,
		})
		ctx.Logf("sbms=%s", sBms)
		require.NoError(ctx, err)

		snap5SjidCursorName, err := endpoint.ReplicationCursorBookmarkName(sfs, snap5.Guid, sjid)
		require.NoError(ctx, err)
		snap2SjidCursorName, err := endpoint.ReplicationCursorBookmarkName(sfs, snap2.Guid, sjid)
		require.NoError(ctx, err)
		snap2OjidCursorName, err := endpoint.ReplicationCursorBookmarkName(sfs, snap2.Guid, ojid)
		require.NoError(ctx, err)
		var bmNames []string
		for _, bm := range sBms {
			bmNames = append(bmNames, bm.Name)
		}

		if invalidateCacheBeforeSecondReplication {
			require.Len(ctx, sBms, 3)
			require.Contains(ctx, bmNames, snap5SjidCursorName)
			require.Contains(ctx, bmNames, snap2OjidCursorName)
			require.Contains(ctx, bmNames, "2")
		} else {
			require.Len(ctx, sBms, 4)
			require.Contains(ctx, bmNames, snap5SjidCursorName)
			require.Contains(ctx, bmNames, snap2SjidCursorName)
			require.Contains(ctx, bmNames, snap2OjidCursorName)
			require.Contains(ctx, bmNames, "2")
		}
	}

	// check last-received hold moved
	{
		rAbs, rAbsErrs, err := endpoint.ListAbstractions(ctx, endpoint.ListZFSHoldsAndBookmarksQuery{
			FS:          endpoint.ListZFSHoldsAndBookmarksQueryFilesystemFilter{FS: &rfs},
			JobID:       &rjid,
			What:        endpoint.AbstractionTypesAll,
			Concurrency: 1,
		})
		require.NoError(ctx, err)
		require.Len(ctx, rAbsErrs, 0)
		require.Len(ctx, rAbs, 1)
		require.Equal(ctx, rAbs[0].GetType(), endpoint.AbstractionLastReceivedHold)
		require.Equal(ctx, *rAbs[0].GetJobID(), rjid)
		require.Equal(ctx, rAbs[0].GetFilesystemVersion().GetGuid(), snap5.GetGuid())
	}

}

type PartialSender struct {
	*endpoint.Sender
	failAfterByteCount int64
}

var _ logic.Sender = (*PartialSender)(nil)

func (s *PartialSender) Send(ctx context.Context, r *pdu.SendReq) (r1 *pdu.SendRes, r2 io.ReadCloser, r3 error) {
	r1, r2, r3 = s.Sender.Send(ctx, r)
	r2 = limitio.ReadCloser(r2, s.failAfterByteCount)
	return r1, r2, r3
}

func ReplicationIsResumableFullSend__both_GuaranteeResumability(ctx *platformtest.Context) {

	setup := replicationIsResumableFullSendSetup{
		protection: pdu.ReplicationConfigProtection{
			Initial:     pdu.ReplicationGuaranteeKind_GuaranteeResumability,
			Incremental: pdu.ReplicationGuaranteeKind_GuaranteeResumability,
		},
		expectDatasetIsBusyErrorWhenDestroySnapshotWhilePartiallyReplicated: true,
		expectAllThreeSnapshotsToThreeBePresentAfterLoop:                    true,
		expectNoSnapshotsOnReceiverAfterLoop:                                false,
	}

	implReplicationIsResumableFullSend(ctx, setup)
}

func ReplicationIsResumableFullSend__initial_GuaranteeResumability_incremental_GuaranteeIncrementalReplication(ctx *platformtest.Context) {

	setup := replicationIsResumableFullSendSetup{
		protection: pdu.ReplicationConfigProtection{
			Initial:     pdu.ReplicationGuaranteeKind_GuaranteeResumability,
			Incremental: pdu.ReplicationGuaranteeKind_GuaranteeIncrementalReplication,
		},
		expectDatasetIsBusyErrorWhenDestroySnapshotWhilePartiallyReplicated: true,
		expectAllThreeSnapshotsToThreeBePresentAfterLoop:                    true,
		expectNoSnapshotsOnReceiverAfterLoop:                                false,
	}

	implReplicationIsResumableFullSend(ctx, setup)
}

func ReplicationIsResumableFullSend__initial_GuaranteeIncrementalReplication_incremental_GuaranteeIncrementalReplication(ctx *platformtest.Context) {

	setup := replicationIsResumableFullSendSetup{
		protection: pdu.ReplicationConfigProtection{
			Initial:     pdu.ReplicationGuaranteeKind_GuaranteeIncrementalReplication,
			Incremental: pdu.ReplicationGuaranteeKind_GuaranteeIncrementalReplication,
		},
		expectDatasetIsBusyErrorWhenDestroySnapshotWhilePartiallyReplicated: false,
		expectAllThreeSnapshotsToThreeBePresentAfterLoop:                    false,
		expectNoSnapshotsOnReceiverAfterLoop:                                true,
	}

	implReplicationIsResumableFullSend(ctx, setup)
}

type replicationIsResumableFullSendSetup struct {
	protection                                                          pdu.ReplicationConfigProtection
	expectDatasetIsBusyErrorWhenDestroySnapshotWhilePartiallyReplicated bool
	expectAllThreeSnapshotsToThreeBePresentAfterLoop                    bool
	expectNoSnapshotsOnReceiverAfterLoop                                bool
}

func implReplicationIsResumableFullSend(ctx *platformtest.Context, setup replicationIsResumableFullSendSetup) {

	platformtest.Run(ctx, platformtest.PanicErr, ctx.RootDataset, `
		CREATEROOT
		+  "sender"
		+  "receiver"
		R  zfs create -p "${ROOTDS}/receiver/${ROOTDS}"
	`)

	sjid := endpoint.MustMakeJobID("sender-job")
	rjid := endpoint.MustMakeJobID("receiver-job")

	sfs := ctx.RootDataset + "/sender"
	rfsRoot := ctx.RootDataset + "/receiver"

	sfsmp, err := zfs.ZFSGetMountpoint(ctx, sfs)
	require.NoError(ctx, err)
	require.True(ctx, sfsmp.Mounted)

	writeDummyData(path.Join(sfsmp.Mountpoint, "dummy.data"), 1<<22)
	mustSnapshot(ctx, sfs+"@1")
	snap1 := fsversion(ctx, sfs, "@1")

	rep := replicationInvocation{
		sjid:    sjid,
		rjid:    rjid,
		sfs:     sfs,
		rfsRoot: rfsRoot,
		interceptSender: func(e *endpoint.Sender) logic.Sender {
			return &PartialSender{Sender: e, failAfterByteCount: 1 << 20}
		},
		guarantee: setup.protection,
	}

	rfs := rep.ReceiveSideFilesystem()

	for i := 2; i < 10; i++ {
		report := rep.Do(ctx)
		ctx.Logf("\n%s", pretty.Sprint(report))

		// always attempt to destroy the incremental source
		err := zfs.ZFSDestroy(ctx, snap1.FullPath(sfs))
		if i < 4 {
			// we configured the PartialSender to fail after 1<<20 bytes
			// and we wrote dummy data 1<<22 bytes, thus at least
			// for the first 4 times this should not be possible
			// due to step holds
			if setup.expectDatasetIsBusyErrorWhenDestroySnapshotWhilePartiallyReplicated {
				ctx.Logf("i=%v", i)
				require.Error(ctx, err)
				require.Contains(ctx, err.Error(), "dataset is busy")
			}
		}

		// and create some additional snapshots that could
		// confuse a naive implementation that doesn't take into
		// account resume state when planning replication
		if i == 2 || i == 3 {
			// no significant size to avoid making this test run longer than necessary
			mustSnapshot(ctx, fmt.Sprintf("%s@%d", sfs, i))
		}

		require.Len(ctx, report.Attempts, 1)
		require.Nil(ctx, report.Attempts[0].PlanError)
		require.Len(ctx, report.Attempts[0].Filesystems, 1)
		if len(report.Attempts[0].Filesystems[0].Steps) == 0 {
			break
		}
	}

	if setup.expectAllThreeSnapshotsToThreeBePresentAfterLoop {
		// make sure all the filesystem versions we created
		// were replicated by the replication loop
		_ = fsversion(ctx, rfs, "@1")
		_ = fsversion(ctx, rfs, "@2")
		_ = fsversion(ctx, rfs, "@3")
	}

	if setup.expectNoSnapshotsOnReceiverAfterLoop {
		versions, err := zfs.ZFSListFilesystemVersions(ctx, mustDatasetPath(rfs), zfs.ListFilesystemVersionsOptions{})
		require.NoError(ctx, err)
		require.Empty(ctx, versions)
	}

}

func ReplicationIncrementalDestroysStepHoldsIffIncrementalStepHoldsAreDisabledButStepHoldsExist(ctx *platformtest.Context) {

	platformtest.Run(ctx, platformtest.PanicErr, ctx.RootDataset, `
		CREATEROOT
		+  "sender"
		+  "receiver"
		R  zfs create -p "${ROOTDS}/receiver/${ROOTDS}"
	`)

	sjid := endpoint.MustMakeJobID("sender-job")
	rjid := endpoint.MustMakeJobID("receiver-job")

	sfs := ctx.RootDataset + "/sender"
	rfsRoot := ctx.RootDataset + "/receiver"

	// fully replicate snapshots @1
	{
		mustSnapshot(ctx, sfs+"@1")
		rep := replicationInvocation{
			sjid:      sjid,
			rjid:      rjid,
			sfs:       sfs,
			rfsRoot:   rfsRoot,
			guarantee: *pdu.ReplicationConfigProtectionWithKind(pdu.ReplicationGuaranteeKind_GuaranteeResumability),
		}
		rfs := rep.ReceiveSideFilesystem()
		report := rep.Do(ctx)
		ctx.Logf("\n%s", pretty.Sprint(report))
		// assert this worked (not the main subject of the test)
		_ = fsversion(ctx, rfs, "@1")
	}

	// create a large snapshot @2
	{
		sfsmp, err := zfs.ZFSGetMountpoint(ctx, sfs)
		require.NoError(ctx, err)
		require.True(ctx, sfsmp.Mounted)
		writeDummyData(path.Join(sfsmp.Mountpoint, "dummy.data"), 1<<22)
		mustSnapshot(ctx, sfs+"@2")
	}
	snap2sfs := fsversion(ctx, sfs, "@2")

	// partially replicate snapshots @2 with step holds enabled
	// to effect a step-holds situation
	{
		rep := replicationInvocation{
			sjid:      sjid,
			rjid:      rjid,
			sfs:       sfs,
			rfsRoot:   rfsRoot,
			guarantee: *pdu.ReplicationConfigProtectionWithKind(pdu.ReplicationGuaranteeKind_GuaranteeResumability), // !
			interceptSender: func(e *endpoint.Sender) logic.Sender {
				return &PartialSender{Sender: e, failAfterByteCount: 1 << 20}
			},
		}
		rfs := rep.ReceiveSideFilesystem()
		report := rep.Do(ctx)
		ctx.Logf("\n%s", pretty.Sprint(report))
		// assert this partial receive worked
		_, err := zfs.ZFSGetFilesystemVersion(ctx, rfs+"@2")
		ctx.Logf("%T %s", err, err)
		_, notFullyReceived := err.(*zfs.DatasetDoesNotExist)
		require.True(ctx, notFullyReceived)
		// assert step holds are in place
		abs, absErrs, err := endpoint.ListAbstractions(ctx, endpoint.ListZFSHoldsAndBookmarksQuery{
			FS: endpoint.ListZFSHoldsAndBookmarksQueryFilesystemFilter{
				FS: &sfs,
			},
			Concurrency: 1,
			JobID:       &sjid,
			What:        endpoint.AbstractionTypeSet{endpoint.AbstractionStepHold: true},
		})
		require.NoError(ctx, err)
		require.Empty(ctx, absErrs)
		require.Len(ctx, abs, 2)
		sort.Slice(abs, func(i, j int) bool {
			return abs[i].GetCreateTXG() < abs[j].GetCreateTXG()
		})
		require.True(ctx, zfs.FilesystemVersionEqualIdentity(abs[0].GetFilesystemVersion(), fsversion(ctx, sfs, "@1")))
		require.True(ctx, zfs.FilesystemVersionEqualIdentity(abs[1].GetFilesystemVersion(), fsversion(ctx, sfs, "@2")))
	}

	//
	// end of test setup
	//

	// retry replication with incremental step holds disabled (set to bookmarks-only in this case)
	// - replication should not fail due to holds-related stuff
	// - replication should fail intermittently due to partial sender being fully read
	// - the partial sender is 1/4th the length of the stream, thus expect
	//   successful replication after 5 more attempts
	rep := replicationInvocation{
		sjid:      sjid,
		rjid:      rjid,
		sfs:       sfs,
		rfsRoot:   rfsRoot,
		guarantee: *pdu.ReplicationConfigProtectionWithKind(pdu.ReplicationGuaranteeKind_GuaranteeIncrementalReplication), // !
		interceptSender: func(e *endpoint.Sender) logic.Sender {
			return &PartialSender{Sender: e, failAfterByteCount: 1 << 20}
		},
	}
	rfs := rep.ReceiveSideFilesystem()
	for i := 0; ; i++ {
		require.True(ctx, i < 5)
		report := rep.Do(ctx)
		ctx.Logf("retry run=%v\n%s", i, pretty.Sprint(report))
		_, err := zfs.ZFSGetFilesystemVersion(ctx, rfs+"@2")
		if err == nil {
			break
		}
	}

	// assert replication worked
	fsversion(ctx, rfs, "@2")

	// assert no step holds exist
	abs, absErrs, err := endpoint.ListAbstractions(ctx, endpoint.ListZFSHoldsAndBookmarksQuery{
		FS: endpoint.ListZFSHoldsAndBookmarksQueryFilesystemFilter{
			FS: &sfs,
		},
		Concurrency: 1,
		JobID:       &sjid,
		What:        endpoint.AbstractionTypeSet{endpoint.AbstractionStepHold: true},
	})
	require.NoError(ctx, err)
	require.Empty(ctx, absErrs)
	require.Len(ctx, abs, 0)

	// assert that the replication cursor bookmark exists
	abs, absErrs, err = endpoint.ListAbstractions(ctx, endpoint.ListZFSHoldsAndBookmarksQuery{
		FS: endpoint.ListZFSHoldsAndBookmarksQueryFilesystemFilter{
			FS: &sfs,
		},
		Concurrency: 1,
		JobID:       &sjid,
		What:        endpoint.AbstractionTypeSet{endpoint.AbstractionReplicationCursorBookmarkV2: true},
	})
	require.NoError(ctx, err)
	require.Empty(ctx, absErrs)
	require.Len(ctx, abs, 1)
	require.True(ctx, zfs.FilesystemVersionEqualIdentity(abs[0].GetFilesystemVersion(), snap2sfs))
}

func ReplicationStepCompletedLostBehavior__GuaranteeResumability(ctx *platformtest.Context) {
	scenario := replicationStepCompletedLostBehavior_impl(ctx, pdu.ReplicationGuaranteeKind_GuaranteeResumability)

	require.Error(ctx, scenario.deleteSfs1Err, "protected by holds")
	require.Contains(ctx, scenario.deleteSfs1Err.Error(), "dataset is busy")

	require.Error(ctx, scenario.deleteSfs2Err, "protected by holds")
	require.Contains(ctx, scenario.deleteSfs2Err.Error(), "dataset is busy")

	require.Nil(ctx, scenario.finalReport.Error())
	_ = fsversion(ctx, scenario.rfs, "@3") // @3 ade it to the other side
}

func ReplicationStepCompletedLostBehavior__GuaranteeIncrementalReplication(ctx *platformtest.Context) {
	scenario := replicationStepCompletedLostBehavior_impl(ctx, pdu.ReplicationGuaranteeKind_GuaranteeIncrementalReplication)

	require.NoError(ctx, scenario.deleteSfs1Err, "not protected by holds")
	require.NoError(ctx, scenario.deleteSfs2Err, "not protected by holds")

	// step bookmarks should protect against loss of StepCompleted message
	require.Nil(ctx, scenario.finalReport.Error())
	_ = fsversion(ctx, scenario.rfs, "@3") // @3 ade it to the other side
}

type FailSendCompletedSender struct {
	*endpoint.Sender
}

var _ logic.Sender = (*FailSendCompletedSender)(nil)

func (p *FailSendCompletedSender) SendCompleted(ctx context.Context, r *pdu.SendCompletedReq) (*pdu.SendCompletedRes, error) {
	return nil, fmt.Errorf("[mock] SendCompleted not delivered to actual endpoint")
}

type replicationStepCompletedLost_scenario struct {
	rfs                          string
	deleteSfs1Err, deleteSfs2Err error
	finalReport                  *report.FilesystemReport
}

func replicationStepCompletedLostBehavior_impl(ctx *platformtest.Context, guaranteeKind pdu.ReplicationGuaranteeKind) *replicationStepCompletedLost_scenario {

	platformtest.Run(ctx, platformtest.PanicErr, ctx.RootDataset, `
		CREATEROOT
		+  "sender"
		+  "receiver"
		R  zfs create -p "${ROOTDS}/receiver/${ROOTDS}"
	`)

	sjid := endpoint.MustMakeJobID("sender-job")
	rjid := endpoint.MustMakeJobID("receiver-job")

	sfs := ctx.RootDataset + "/sender"
	rfsRoot := ctx.RootDataset + "/receiver"

	// fully replicate snapshots @1
	{
		mustSnapshot(ctx, sfs+"@1")
		rep := replicationInvocation{
			sjid:      sjid,
			rjid:      rjid,
			sfs:       sfs,
			rfsRoot:   rfsRoot,
			guarantee: *pdu.ReplicationConfigProtectionWithKind(guaranteeKind),
		}
		rfs := rep.ReceiveSideFilesystem()
		report := rep.Do(ctx)
		ctx.Logf("\n%s", pretty.Sprint(report))
		// assert this worked (not the main subject of the test)
		_ = fsversion(ctx, rfs, "@1")
	}

	// create a second snapshot @2
	mustSnapshot(ctx, sfs+"@2")

	// fake loss of stepcompleted message
	rep := replicationInvocation{
		sjid:      sjid,
		rjid:      rjid,
		sfs:       sfs,
		rfsRoot:   rfsRoot,
		guarantee: *pdu.ReplicationConfigProtectionWithKind(guaranteeKind),
		interceptSender: func(e *endpoint.Sender) logic.Sender {
			return &FailSendCompletedSender{e}
		},
	}
	rfs := rep.ReceiveSideFilesystem()
	report := rep.Do(ctx)
	ctx.Logf("\n%s", pretty.Sprint(report))

	// assert the replication worked
	_ = fsversion(ctx, rfs, "@2")
	// and that we hold it using a last-received-hold
	abs, absErrs, err := endpoint.ListAbstractions(ctx, endpoint.ListZFSHoldsAndBookmarksQuery{
		FS: endpoint.ListZFSHoldsAndBookmarksQueryFilesystemFilter{
			FS: &rfs,
		},
		Concurrency: 1,
		JobID:       &rjid,
		What:        endpoint.AbstractionTypeSet{endpoint.AbstractionLastReceivedHold: true},
	})
	require.NoError(ctx, err)
	require.Empty(ctx, absErrs)
	require.Len(ctx, abs, 1)
	require.True(ctx, zfs.FilesystemVersionEqualIdentity(abs[0].GetFilesystemVersion(), fsversion(ctx, rfs, "@2")))

	// now try to delete @2 on the sender, this should work because don't have step holds on it
	deleteSfs2Err := zfs.ZFSDestroy(ctx, sfs+"@2")
	// defer check to caller

	// and create a new snapshot on the sender
	mustSnapshot(ctx, sfs+"@3")

	// now we have: sender @1, @3
	//              recver @1, @2

	// delete @1 on both sides to demonstrate that, if we didn't have bookmarks, we would be out of sync
	deleteSfs1Err := zfs.ZFSDestroy(ctx, sfs+"@1")
	// defer check to caller
	err = zfs.ZFSDestroy(ctx, rfs+"@1")
	require.NoError(ctx, err)

	// attempt replication and return the filesystem report report
	{
		rep := replicationInvocation{
			sjid:      sjid,
			rjid:      rjid,
			sfs:       sfs,
			rfsRoot:   rfsRoot,
			guarantee: *pdu.ReplicationConfigProtectionWithKind(guaranteeKind),
		}
		report := rep.Do(ctx)
		ctx.Logf("expecting failure:\n%s", pretty.Sprint(report))
		require.Len(ctx, report.Attempts, 1)
		require.Len(ctx, report.Attempts[0].Filesystems, 1)
		return &replicationStepCompletedLost_scenario{
			rfs:           rfs,
			deleteSfs1Err: deleteSfs1Err,
			deleteSfs2Err: deleteSfs2Err,
			finalReport:   report.Attempts[0].Filesystems[0],
		}
	}

}

type ErroringReceiver struct {
	recvErr error
	*endpoint.Receiver
}

func (r *ErroringReceiver) Receive(ctx context.Context, req *pdu.ReceiveReq, stream io.ReadCloser) (*pdu.ReceiveRes, error) {
	return nil, r.recvErr
}

type NeverEndingSender struct {
	*endpoint.Sender
}

func (s *NeverEndingSender) Send(ctx context.Context, req *pdu.SendReq) (r *pdu.SendRes, stream io.ReadCloser, _ error) {
	stream = nil
	r = &pdu.SendRes{
		UsedResumeToken: false,
		ExpectedSize:    1 << 30,
	}
	if req.DryRun {
		return r, stream, nil
	}
	dz, err := os.Open("/dev/zero")
	if err != nil {
		panic(err)
	}
	return r, dz, nil
}

func ReplicationReceiverErrorWhileStillSending(ctx *platformtest.Context) {

	platformtest.Run(ctx, platformtest.PanicErr, ctx.RootDataset, `
		CREATEROOT
		+  "sender"
		+  "sender@1"
		+  "receiver"
		R  zfs create -p "${ROOTDS}/receiver/${ROOTDS}"
	`)

	sjid := endpoint.MustMakeJobID("sender-job")
	rjid := endpoint.MustMakeJobID("receiver-job")

	sfs := ctx.RootDataset + "/sender"
	rfsRoot := ctx.RootDataset + "/receiver"

	mockRecvErr := fmt.Errorf("YiezahK3thie8ahKiel5sah2uugei2ize1yi8feivuu7musoat")

	rep := replicationInvocation{
		sjid:      sjid,
		rjid:      rjid,
		sfs:       sfs,
		rfsRoot:   rfsRoot,
		guarantee: *pdu.ReplicationConfigProtectionWithKind(pdu.ReplicationGuaranteeKind_GuaranteeNothing),
		interceptReceiver: func(r *endpoint.Receiver) logic.Receiver {
			return &ErroringReceiver{recvErr: mockRecvErr, Receiver: r}
		},
		interceptSender: func(s *endpoint.Sender) logic.Sender {
			return &NeverEndingSender{s}
		},
	}

	// first replication
	report := rep.Do(ctx)
	ctx.Logf("\n%s", pretty.Sprint(report))

	require.Len(ctx, report.Attempts, 1)
	attempt := report.Attempts[0]
	require.Nil(ctx, attempt.PlanError)
	require.Len(ctx, attempt.Filesystems, 1)
	afs := attempt.Filesystems[0]
	require.Nil(ctx, afs.PlanError)
	require.Len(ctx, afs.Steps, 1)
	require.Nil(ctx, afs.PlanError)
	require.NotNil(ctx, afs.StepError)
	require.Contains(ctx, afs.StepError.Err, mockRecvErr.Error())
}

func ReplicationFailingInitialParentProhibitsChildReplication(ctx *platformtest.Context) {

	platformtest.Run(ctx, platformtest.PanicErr, ctx.RootDataset, `
		CREATEROOT
		+  "sender"
		+  "sender/a"
		+  "sender/a/child"
		+  "sender/aa"
		+  "receiver"
		R  zfs create -p "${ROOTDS}/receiver/${ROOTDS}"
		R  zfs snapshot -r ${ROOTDS}/sender@initial
	`)

	sjid := endpoint.MustMakeJobID("sender-job")
	rjid := endpoint.MustMakeJobID("receiver-job")

	fsA := ctx.RootDataset + "/sender/a"
	fsAChild := ctx.RootDataset + "/sender/a/child"
	fsAA := ctx.RootDataset + "/sender/aa"

	sfilter := filters.NewDatasetMapFilter(3, true)
	mustAddToSFilter := func(fs string) {
		err := sfilter.Add(fs, "ok")
		require.NoError(ctx, err)
	}
	mustAddToSFilter(fsA)
	mustAddToSFilter(fsAChild)
	mustAddToSFilter(fsAA)
	rfsRoot := ctx.RootDataset + "/receiver"

	mockRecvErr := fmt.Errorf("yifae4ohPhaquaes0hohghiep9oufie4roo7quoWooluaj2ee8")

	rep := replicationInvocation{
		sjid:      sjid,
		rjid:      rjid,
		sfilter:   sfilter,
		rfsRoot:   rfsRoot,
		guarantee: *pdu.ReplicationConfigProtectionWithKind(pdu.ReplicationGuaranteeKind_GuaranteeNothing),
		interceptReceiver: func(r *endpoint.Receiver) logic.Receiver {
			return &ErroringReceiver{recvErr: mockRecvErr, Receiver: r}
		},
	}

	r := rep.Do(ctx)
	ctx.Logf("\n%s", pretty.Sprint(r))

	require.Len(ctx, r.Attempts, 1)
	attempt := r.Attempts[0]
	require.Nil(ctx, attempt.PlanError)
	require.Len(ctx, attempt.Filesystems, 3)

	fsByName := make(map[string]*report.FilesystemReport, len(attempt.Filesystems))
	for _, fs := range attempt.Filesystems {
		fsByName[fs.Info.Name] = fs
	}

	require.Contains(ctx, fsByName, fsA)
	require.Contains(ctx, fsByName, fsAA)
	require.Contains(ctx, fsByName, fsAA)

	checkFS := func(fs string, expectErrMsg string) {
		rep := fsByName[fs]
		require.Len(ctx, rep.Steps, 1)
		require.Nil(ctx, rep.PlanError)
		require.NotNil(ctx, rep.StepError)
		require.Contains(ctx, rep.StepError.Err, expectErrMsg)
	}

	checkFS(fsA, mockRecvErr.Error())
	checkFS(fsAChild, "parent(s) failed during initial replication")
	checkFS(fsAA, mockRecvErr.Error()) // fsAA is not treated as a child of fsA
}