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cli: remove debug unsafe-remove-dead-replicas
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This command has been replaced by `debug recover`, and was deprecated in
22.2.

Release note (cli change): The deprecated CLI command
`debug unsafe-remove-dead-replicas` has been removed, users should use
`debug recover` instead.
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@erikgrinaker
erikgrinaker committed Oct 1, 2022
1 parent e786cba commit c4dc46f
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Showing 6 changed files with 24 additions and 669 deletions.
349 changes: 0 additions & 349 deletions pkg/cli/debug.go
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,6 @@
package cli

import (
"bufio"
"bytes"
"context"
"encoding/base64"
Expand Down Expand Up @@ -41,7 +40,6 @@ import (
"github.com/cockroachdb/cockroach/pkg/kv/kvserver/gc"
"github.com/cockroachdb/cockroach/pkg/kv/kvserver/liveness/livenesspb"
"github.com/cockroachdb/cockroach/pkg/kv/kvserver/rditer"
"github.com/cockroachdb/cockroach/pkg/kv/kvserver/stateloader"
"github.com/cockroachdb/cockroach/pkg/roachpb"
"github.com/cockroachdb/cockroach/pkg/server"
"github.com/cockroachdb/cockroach/pkg/server/serverpb"
Expand Down Expand Up @@ -1100,347 +1098,6 @@ func runDebugSyncBench(cmd *cobra.Command, args []string) error {
return syncbench.Run(syncBenchOpts)
}

var debugUnsafeRemoveDeadReplicasCmd = &cobra.Command{
Use: "unsafe-remove-dead-replicas --dead-store-ids=[store ID,...] [path]",
Short: "Unsafely attempt to recover a range that has lost quorum (deprecated)",
Long: `
DEPRECATED: use 'debug recover' instead. unsafe-remove-dead-replicas will be
removed in CockroachDB v23.1.
This command is UNSAFE and should only be used with the supervision of
a Cockroach Labs engineer. It is a last-resort option to recover data
after multiple node failures. The recovered data is not guaranteed to
be consistent. If a suitable backup exists, restore it instead of
using this tool.
The --dead-store-ids flag takes a comma-separated list of dead store IDs and
scans this store for any ranges unable to make progress (as indicated by the
remaining replicas not marked as dead). For each such replica in which the local
store is the voter with the highest StoreID, the range descriptors will be (only
when run on that store) rewritten in-place to reflect a replication
configuration in which the local store is the sole voter (and thus able to make
progress).
The intention is for the tool to be run against all stores in the cluster, which
will attempt to recover all ranges in the system for which such an operation is
necessary. This is the safest and most straightforward option, but incurs global
downtime. When availability problems are isolated to a small number of ranges,
it is also possible to restrict the set of nodes to be restarted (all nodes that
have a store that has the highest voting StoreID in one of the ranges that need
to be recovered), and to perform the restarts one-by-one (assuming system ranges
are not affected). With this latter strategy, restarts of additional replicas
may still be necessary, owing to the fact that the former leaseholder's epoch
may still be live, even though that leaseholder may now be on the "unrecovered"
side of the range and thus still unavailable. This case can be detected via the
range status of the affected range(s) and by restarting the listed leaseholder.
This command will prompt for confirmation before committing its changes.
WARNINGS
This tool may cause previously committed data to be lost. It does not preserve
atomicity of transactions, so further inconsistencies and undefined behavior may
result. In the worst case, a corruption of the cluster-internal metadata may
occur, which would complicate the recovery further. It is recommended to take a
filesystem-level backup or snapshot of the nodes to be affected before running
this command (it is not safe to take a filesystem-level backup of a running
node, but it is possible while the node is stopped). A cluster that had this
tool used against it is no longer fit for production use. It must be
re-initialized from a backup.
Before proceeding at the yes/no prompt, review the ranges that are affected to
consider the possible impact of inconsistencies. Further remediation may be
necessary after running this tool, including dropping and recreating affected
indexes, or in the worst case creating a new backup or export of this cluster's
data for restoration into a brand new cluster. Because of the latter
possibilities, this tool is a slower means of disaster recovery than restoring
from a backup.
Must only be used when the dead stores are lost and unrecoverable. If the dead
stores were to rejoin the cluster after this command was used, data may be
corrupted.
After this command is used, the node should not be restarted until at least 10
seconds have passed since it was stopped. Restarting it too early may lead to
things getting stuck (if it happens, it can be fixed by restarting a second
time).
`,
Args: cobra.ExactArgs(1),
RunE: clierrorplus.MaybeDecorateError(runDebugUnsafeRemoveDeadReplicas),
}

var removeDeadReplicasOpts struct {
deadStoreIDs []int
}

func runDebugUnsafeRemoveDeadReplicas(cmd *cobra.Command, args []string) error {
stopper := stop.NewStopper()
defer stopper.Stop(context.Background())

db, err := OpenEngine(args[0], stopper, storage.MustExist)
if err != nil {
return err
}

deadStoreIDs := map[roachpb.StoreID]struct{}{}
for _, id := range removeDeadReplicasOpts.deadStoreIDs {
deadStoreIDs[roachpb.StoreID(id)] = struct{}{}
}
batch, err := removeDeadReplicas(db, deadStoreIDs)
if err != nil {
return err
} else if batch == nil {
fmt.Printf("Nothing to do\n")
return nil
}
defer batch.Close()

fmt.Printf("Proceed with the above rewrites? [y/N] ")

reader := bufio.NewReader(os.Stdin)
line, err := reader.ReadString('\n')
if err != nil {
return err
}
fmt.Printf("\n")
if line[0] == 'y' || line[0] == 'Y' {
fmt.Printf("Committing\n")
if err := batch.Commit(true); err != nil {
return err
}
} else {
fmt.Printf("Aborting\n")
}
return nil
}

func removeDeadReplicas(
db storage.Engine, deadStoreIDs map[roachpb.StoreID]struct{},
) (storage.Batch, error) {
clock := hlc.NewClockWithSystemTimeSource(0 /* maxOffset */)

ctx := context.Background()

storeIdent, err := kvserver.ReadStoreIdent(ctx, db)
if err != nil {
return nil, err
}
fmt.Printf("Scanning replicas on store %s for dead peers %v\n", storeIdent.String(),
removeDeadReplicasOpts.deadStoreIDs)

if _, ok := deadStoreIDs[storeIdent.StoreID]; ok {
return nil, errors.Errorf("this store's ID (%s) marked as dead, aborting", storeIdent.StoreID)
}

var newDescs []roachpb.RangeDescriptor

err = kvserver.IterateRangeDescriptorsFromDisk(ctx, db, func(desc roachpb.RangeDescriptor) error {
numDeadPeers := 0
allReplicas := desc.Replicas().Descriptors()
maxLiveVoter := roachpb.StoreID(-1)
for _, rep := range allReplicas {
if _, ok := deadStoreIDs[rep.StoreID]; ok {
numDeadPeers++
continue
}
// The designated survivor will be the voter with the highest storeID.
// Note that an outgoing voter cannot be designated, as the only
// replication change it could make is to turn itself into a learner, at
// which point the range is completely messed up.
//
// Note: a better heuristic might be to choose the leaseholder store, not
// the largest store, as this avoids the problem of requests still hanging
// after running the tool in a rolling-restart fashion (when the lease-
// holder is under a valid epoch and was ont chosen as designated
// survivor). However, this choice is less deterministic, as leaseholders
// are more likely to change than replication configs. The hanging would
// independently be fixed by the below issue, so staying with largest store
// is likely the right choice. See:
//
// https://github.com/cockroachdb/cockroach/issues/33007
if rep.IsVoterNewConfig() && rep.StoreID > maxLiveVoter {
maxLiveVoter = rep.StoreID
}
}

// If there's no dead peer in this group (so can't hope to fix
// anything by rewriting the descriptor) or the current store is not the
// one we want to turn into the sole voter, don't do anything.
if numDeadPeers == 0 {
return nil
}
if storeIdent.StoreID != maxLiveVoter {
fmt.Printf("not designated survivor, skipping: %s\n", &desc)
return nil
}

// The replica thinks it can make progress anyway, so we leave it alone.
if desc.Replicas().CanMakeProgress(func(rep roachpb.ReplicaDescriptor) bool {
_, ok := deadStoreIDs[rep.StoreID]
return !ok
}) {
fmt.Printf("replica has not lost quorum, skipping: %s\n", &desc)
return nil
}

// We're the designated survivor and the range does not to be recovered.
//
// Rewrite the range as having a single replica. The winning replica is
// picked arbitrarily: the one with the highest store ID. This is not always
// the best option: it may lose writes that were committed on another
// surviving replica that had applied more of the raft log. However, in
// practice when we have multiple surviving replicas but still need this
// tool (because the replication factor was 4 or higher), we see that the
// logs are nearly always in sync and the choice doesn't matter. Correctly
// picking the replica with the longer log would complicate the use of this
// tool.
newDesc := desc
// Rewrite the replicas list. Bump the replica ID so that in case there are
// other surviving nodes that were members of the old incarnation of the
// range, they no longer recognize this revived replica (because they are
// not in sync with it).
replicas := []roachpb.ReplicaDescriptor{{
NodeID: storeIdent.NodeID,
StoreID: storeIdent.StoreID,
ReplicaID: desc.NextReplicaID,
}}
newDesc.SetReplicas(roachpb.MakeReplicaSet(replicas))
newDesc.NextReplicaID++
fmt.Printf("replica has lost quorum, recovering: %s -> %s\n", &desc, &newDesc)
newDescs = append(newDescs, newDesc)
return nil
})
if err != nil {
return nil, err
}

if len(newDescs) == 0 {
return nil, nil
}

batch := db.NewBatch()
for _, desc := range newDescs {
// Write the rewritten descriptor to the range-local descriptor
// key. We do not update the meta copies of the descriptor.
// Instead, we leave them in a temporarily inconsistent state and
// they will be overwritten when the cluster recovers and
// up-replicates this range from its single copy to multiple
// copies. We rely on the fact that all range descriptor updates
// start with a CPut on the range-local copy followed by a blind
// Put to the meta copy.
//
// For example, if we have replicas on s1-s4 but s3 and s4 are
// dead, we will rewrite the replica on s2 to have s2 as its only
// member only. When the cluster is restarted (and the dead nodes
// remain dead), the rewritten replica will be the only one able
// to make progress. It will elect itself leader and upreplicate.
//
// The old replica on s1 is untouched by this process. It will
// eventually either be overwritten by a new replica when s2
// upreplicates, or it will be destroyed by the replica GC queue
// after upreplication has happened and s1 is no longer a member.
// (Note that in the latter case, consistency between s1 and s2 no
// longer matters; the consistency checker will only run on nodes
// that the new leader believes are members of the range).
//
// Note that this tool does not guarantee fully consistent
// results; the most recent writes to the raft log may have been
// lost. In the most unfortunate cases, this means that we would
// be "winding back" a split or a merge, which is almost certainly
// to result in irrecoverable corruption (for example, not only
// will individual values stored in the meta ranges diverge, but
// there will be keys not represented by any ranges or vice
// versa).
key := keys.RangeDescriptorKey(desc.StartKey)
sl := stateloader.Make(desc.RangeID)
ms, err := sl.LoadMVCCStats(ctx, batch)
if err != nil {
return nil, errors.Wrap(err, "loading MVCCStats")
}
err = storage.MVCCPutProto(ctx, batch, &ms, key, clock.Now(), hlc.ClockTimestamp{}, nil, &desc)
if wiErr := (*roachpb.WriteIntentError)(nil); errors.As(err, &wiErr) {
if len(wiErr.Intents) != 1 {
return nil, errors.Errorf("expected 1 intent, found %d: %s", len(wiErr.Intents), wiErr)
}
intent := wiErr.Intents[0]
// We rely on the property that transactions involving the range
// descriptor always start on the range-local descriptor's key. When there
// is an intent, this means that it is likely that the transaction did not
// commit, so we abort the intent.
//
// However, this is not guaranteed. For one, applying a command is not
// synced to disk, so in theory whichever store becomes the designated
// survivor may temporarily have "forgotten" that the transaction
// committed in its applied state (it would still have the committed log
// entry, as this is durable state, so it would come back once the node
// was running, but we don't see that materialized state in
// unsafe-remove-dead-replicas). This is unlikely to be a problem in
// practice, since we assume that the store was shut down gracefully and
// besides, the write likely had plenty of time to make it to durable
// storage. More troubling is the fact that the designated survivor may
// simply not yet have learned that the transaction committed; it may not
// have been in the quorum and could've been slow to catch up on the log.
// It may not even have the intent; in theory the remaining replica could
// have missed any number of transactions on the range descriptor (even if
// they are in the log, they may not yet be applied, and the replica may
// not yet have learned that they are committed). This is particularly
// troubling when we miss a split, as the right-hand side of the split
// will exist in the meta ranges and could even be able to make progress.
// For yet another thing to worry about, note that the determinism (across
// different nodes) assumed in this tool can easily break down in similar
// ways (not all stores are going to have the same view of what the
// descriptors are), and so multiple replicas of a range may declare
// themselves the designated survivor. Long story short, use of this tool
// with or without the presence of an intent can - in theory - really
// tear the cluster apart.
//
// A solution to this would require a global view, where in a first step
// we collect from each store in the cluster the replicas present and
// compute from that a "recovery plan", i.e. set of replicas that will
// form the recovered keyspace. We may then find that no such recovery
// plan is trivially achievable, due to any of the above problems. But
// in the common case, we do expect one to exist.
fmt.Printf("aborting intent: %s (txn %s)\n", key, intent.Txn.ID)

// A crude form of the intent resolution process: abort the
// transaction by deleting its record.
txnKey := keys.TransactionKey(intent.Txn.Key, intent.Txn.ID)
if _, err := storage.MVCCDelete(ctx, batch, &ms, txnKey, hlc.Timestamp{}, hlc.ClockTimestamp{}, nil); err != nil {
return nil, err
}
update := roachpb.LockUpdate{
Span: roachpb.Span{Key: intent.Key},
Txn: intent.Txn,
Status: roachpb.ABORTED,
}
if _, err := storage.MVCCResolveWriteIntent(ctx, batch, &ms, update); err != nil {
return nil, err
}
// With the intent resolved, we can try again.
if err := storage.MVCCPutProto(ctx, batch, &ms, key, clock.Now(), hlc.ClockTimestamp{}, nil, &desc); err != nil {
return nil, err
}
} else if err != nil {
batch.Close()
return nil, err
}
// Write the new replica ID to RaftReplicaIDKey.
replicas := desc.Replicas().Descriptors()
if len(replicas) != 1 {
return nil, errors.Errorf("expected 1 replica, got %v", replicas)
}
if err := sl.SetRaftReplicaID(ctx, batch, replicas[0].ReplicaID); err != nil {
return nil, errors.Wrapf(err, "failed to write new replica ID for range %d", desc.RangeID)
}
// Update MVCC stats.
if err := sl.SetMVCCStats(ctx, batch, &ms); err != nil {
return nil, errors.Wrap(err, "updating MVCCStats")
}
}

return batch, nil
}

var debugMergeLogsCmd = &cobra.Command{
Use: "merge-logs <log file globs>",
Short: "merge multiple log files from different machines into a single stream",
Expand Down Expand Up @@ -1635,7 +1292,6 @@ var DebugCommandsRequiringEncryption = []*cobra.Command{
debugRaftLogCmd,
debugRangeDataCmd,
debugRangeDescriptorsCmd,
debugUnsafeRemoveDeadReplicasCmd,
debugRecoverCollectInfoCmd,
debugRecoverExecuteCmd,
}
Expand All @@ -1650,7 +1306,6 @@ var debugCmds = []*cobra.Command{
debugRaftLogCmd,
debugRangeDataCmd,
debugRangeDescriptorsCmd,
debugUnsafeRemoveDeadReplicasCmd,
debugBallastCmd,
debugCheckLogConfigCmd,
debugDecodeKeyCmd,
Expand Down Expand Up @@ -1767,10 +1422,6 @@ func init() {
f.IntVarP(&debugCompactOpts.maxConcurrency, "max-concurrency", "c", debugCompactOpts.maxConcurrency,
"maximum number of concurrent compactions")

f = debugUnsafeRemoveDeadReplicasCmd.Flags()
f.IntSliceVar(&removeDeadReplicasOpts.deadStoreIDs, "dead-store-ids", nil,
"list of dead store IDs")

f = debugRecoverCollectInfoCmd.Flags()
f.VarP(&debugRecoverCollectInfoOpts.Stores, cliflags.RecoverStore.Name, cliflags.RecoverStore.Shorthand, cliflags.RecoverStore.Usage())

Expand Down
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