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stability enhancement during overload conditions #20492

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stability enhancement during overload conditions #20492

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8 changes: 4 additions & 4 deletions server/etcdserver/server_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1167,7 +1167,7 @@ func TestPublishV3(t *testing.T) {
lgMu: new(sync.RWMutex),
lg: lg,
readych: make(chan struct{}),
Cfg: config.ServerConfig{Logger: lg, TickMs: 1, SnapshotCatchUpEntries: DefaultSnapshotCatchUpEntries, MaxRequestBytes: 1000},
Cfg: config.ServerConfig{Logger: lg, TickMs: 1, SnapshotCatchUpEntries: DefaultSnapshotCatchUpEntries, MaxRequestBytes: 1000, ServerFeatureGate: features.NewDefaultServerFeatureGate("test", lg)},
memberID: 1,
r: *newRaftNode(raftNodeConfig{lg: lg, Node: n}),
attributes: membership.Attributes{Name: "node1", ClientURLs: []string{"http://a", "http://b"}},
Expand Down Expand Up @@ -1209,7 +1209,7 @@ func TestPublishV3Stopped(t *testing.T) {
srv := &EtcdServer{
lgMu: new(sync.RWMutex),
lg: zaptest.NewLogger(t),
Cfg: config.ServerConfig{Logger: zaptest.NewLogger(t), TickMs: 1, SnapshotCatchUpEntries: DefaultSnapshotCatchUpEntries},
Cfg: config.ServerConfig{Logger: zaptest.NewLogger(t), TickMs: 1, SnapshotCatchUpEntries: DefaultSnapshotCatchUpEntries, ServerFeatureGate: features.NewDefaultServerFeatureGate("test", nil)},
r: *r,
cluster: &membership.RaftCluster{},
w: mockwait.NewNop(),
Expand Down Expand Up @@ -1237,7 +1237,7 @@ func TestPublishV3Retry(t *testing.T) {
lgMu: new(sync.RWMutex),
lg: lg,
readych: make(chan struct{}),
Cfg: config.ServerConfig{Logger: lg, TickMs: 1, SnapshotCatchUpEntries: DefaultSnapshotCatchUpEntries, MaxRequestBytes: 1000},
Cfg: config.ServerConfig{Logger: lg, TickMs: 1, SnapshotCatchUpEntries: DefaultSnapshotCatchUpEntries, MaxRequestBytes: 1000, ServerFeatureGate: features.NewDefaultServerFeatureGate("test", lg)},
memberID: 1,
r: *newRaftNode(raftNodeConfig{lg: lg, Node: n}),
w: mockwait.NewNop(),
Expand Down Expand Up @@ -1288,7 +1288,7 @@ func TestUpdateVersionV3(t *testing.T) {
lgMu: new(sync.RWMutex),
lg: zaptest.NewLogger(t),
memberID: 1,
Cfg: config.ServerConfig{Logger: lg, TickMs: 1, SnapshotCatchUpEntries: DefaultSnapshotCatchUpEntries, MaxRequestBytes: 1000},
Cfg: config.ServerConfig{Logger: lg, TickMs: 1, SnapshotCatchUpEntries: DefaultSnapshotCatchUpEntries, MaxRequestBytes: 1000, ServerFeatureGate: features.NewDefaultServerFeatureGate("test", lg)},
r: *newRaftNode(raftNodeConfig{lg: zaptest.NewLogger(t), Node: n}),
attributes: membership.Attributes{Name: "node1", ClientURLs: []string{"http://node1.com"}},
cluster: &membership.RaftCluster{},
Expand Down
20 changes: 20 additions & 0 deletions server/etcdserver/util.go
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ import (
"fmt"
"time"

pb "go.etcd.io/etcd/api/v3/etcdserverpb"
"go.etcd.io/etcd/client/pkg/v3/types"
"go.etcd.io/etcd/server/v3/etcdserver/api/membership"
"go.etcd.io/etcd/server/v3/etcdserver/api/rafthttp"
Expand All @@ -42,6 +43,25 @@ func isConnectedFullySince(transport rafthttp.Transporter, since time.Time, self
return numConnectedSince(transport, since, self, members) == len(members)
}

// exceedsRequestLimit checks if the committed index is too far ahead of
// the applied index. Priority requests are allowed up to 10% extra gap.
func exceedsRequestLimit(ai, ci uint64, r *pb.InternalRaftRequest, enablePriority bool) bool {
if ci <= ai+maxGapBetweenApplyAndCommitIndex {
return false
}
// allow up to 100% extra gap for priority requests
if enablePriority && isPriorityRequest(r) {
if ci <= ai+maxGapBetweenApplyAndCommitIndex*200/100 {
return false
}
}
return true
}

func isPriorityRequest(r *pb.InternalRaftRequest) bool {
return r != nil && r.LeaseRevoke != nil
}

// numConnectedSince counts how many members are connected to the local member
// since the given time.
func numConnectedSince(transport rafthttp.Transporter, since time.Time, self types.ID, members []*membership.Member) int {
Expand Down
65 changes: 65 additions & 0 deletions server/etcdserver/util_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -19,8 +19,10 @@ import (
"testing"
"time"

"github.com/stretchr/testify/assert"
"go.uber.org/zap/zaptest"

pb "go.etcd.io/etcd/api/v3/etcdserverpb"
"go.etcd.io/etcd/client/pkg/v3/types"
"go.etcd.io/etcd/server/v3/etcdserver/api/membership"
"go.etcd.io/etcd/server/v3/etcdserver/api/rafthttp"
Expand Down Expand Up @@ -110,3 +112,66 @@ type testStringerFunc func() string
func (s testStringerFunc) String() string {
return s()
}

func TestExceedsRequestLimit(t *testing.T) {
tests := []struct {
name string
ci uint64
ai uint64
expectedResult bool
req *pb.InternalRaftRequest
enablePriority bool
}{
{
ci: 1 + maxGapBetweenApplyAndCommitIndex,
ai: 1,
expectedResult: false,
req: nil,
name: "Test nil InternalRaftRequest",
},
{
ci: 1 + maxGapBetweenApplyAndCommitIndex,
ai: 1,
expectedResult: false,
req: &pb.InternalRaftRequest{},
name: "Test non-critical request and gap is not larger than maxGapBetweenApplyAndCommitIndex",
},
{
ci: 1 + maxGapBetweenApplyAndCommitIndex + 1,
ai: 1,
expectedResult: true,
req: &pb.InternalRaftRequest{},
name: "Test non-critical request and gap is larger than maxGapBetweenApplyAndCommitIndex",
},
{
ci: 1 + maxGapBetweenApplyAndCommitIndex + 1,
ai: 1,
expectedResult: false,
req: &pb.InternalRaftRequest{LeaseRevoke: &pb.LeaseRevokeRequest{}},
name: "Test critical request and gap is larger than maxGapBetweenApplyAndCommitIndex with priority check",
enablePriority: true,
},
{
ci: 1 + maxGapBetweenApplyAndCommitIndex + 1,
ai: 1,
expectedResult: true,
req: &pb.InternalRaftRequest{LeaseRevoke: &pb.LeaseRevokeRequest{}},
name: "Test critical request and gap is larger than maxGapBetweenApplyAndCommitIndex without priority check",
enablePriority: false,
},
{
ci: 1 + 2*maxGapBetweenApplyAndCommitIndex + 1,
ai: 1,
expectedResult: true,
req: &pb.InternalRaftRequest{LeaseRevoke: &pb.LeaseRevokeRequest{}},
name: "Test critical request and gap is larger than 200% maxGapBetweenApplyAndCommitIndex with priority check",
enablePriority: true,
},
}

for _, tc := range tests {
t.Run(tc.name, func(t *testing.T) {
assert.Equal(t, tc.expectedResult, exceedsRequestLimit(tc.ai, tc.ci, tc.req, tc.enablePriority))
})
}
}
3 changes: 2 additions & 1 deletion server/etcdserver/v3_server.go
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Original file line number Diff line number Diff line change
Expand Up @@ -817,7 +817,8 @@ func (s *EtcdServer) doSerialize(ctx context.Context, chk func(*auth.AuthInfo) e
func (s *EtcdServer) processInternalRaftRequestOnce(ctx context.Context, r pb.InternalRaftRequest) (*apply2.Result, error) {
ai := s.getAppliedIndex()
ci := s.getCommittedIndex()
if ci > ai+maxGapBetweenApplyAndCommitIndex {

if exceedsRequestLimit(ai, ci, &r, s.FeatureEnabled(features.PriorityRequest)) {
return nil, errors.ErrTooManyRequests
}

Expand Down
6 changes: 6 additions & 0 deletions server/features/etcd_features.go
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Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,11 @@ const (
// beta: v3.7
// main PR: https://github.com/etcd-io/etcd/pull/20589
FastLeaseKeepAlive featuregate.Feature = "FastLeaseKeepAlive"
// PriorityRequest enables certain kinds of requests(e.g. LreaeRevoke) having higher priority to be applied under overload conditions.
// owner: @silentred
// alpha: v3.7
// main PR: https://github.com/etcd-io/etcd/pull/20492
PriorityRequest featuregate.Feature = "PriorityRequest"
)

var DefaultEtcdServerFeatureGates = map[featuregate.Feature]featuregate.FeatureSpec{
Expand All @@ -90,6 +95,7 @@ var DefaultEtcdServerFeatureGates = map[featuregate.Feature]featuregate.FeatureS
LeaseCheckpointPersist: {Default: false, PreRelease: featuregate.Alpha},
SetMemberLocalAddr: {Default: false, PreRelease: featuregate.Alpha},
FastLeaseKeepAlive: {Default: true, PreRelease: featuregate.Beta},
PriorityRequest: {Default: false, PreRelease: featuregate.Alpha},
}

func NewDefaultServerFeatureGate(name string, lg *zap.Logger) featuregate.FeatureGate {
Expand Down