vendor/go.etcd.io/etcd/raft/tracker/progress.go - voltha-openolt-adapter - Gitiles

 // Copyright 2019 The etcd Authors
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.

 package tracker

 import (
 	"fmt"
 	"sort"
 	"strings"
 )

 // Progress represents a follower’s progress in the view of the leader. Leader
 // maintains progresses of all followers, and sends entries to the follower
 // based on its progress.
 //
 // NB(tbg): Progress is basically a state machine whose transitions are mostly
 // strewn around `*raft.raft`. Additionally, some fields are only used when in a
 // certain State. All of this isn't ideal.
 type Progress struct {
 	Match, Next uint64
 	// State defines how the leader should interact with the follower.
 	//
 	// When in StateProbe, leader sends at most one replication message
 	// per heartbeat interval. It also probes actual progress of the follower.
 	//
 	// When in StateReplicate, leader optimistically increases next
 	// to the latest entry sent after sending replication message. This is
 	// an optimized state for fast replicating log entries to the follower.
 	//
 	// When in StateSnapshot, leader should have sent out snapshot
 	// before and stops sending any replication message.
 	State StateType

 	// PendingSnapshot is used in StateSnapshot.
 	// If there is a pending snapshot, the pendingSnapshot will be set to the
 	// index of the snapshot. If pendingSnapshot is set, the replication process of
 	// this Progress will be paused. raft will not resend snapshot until the pending one
 	// is reported to be failed.
 	PendingSnapshot uint64

 	// RecentActive is true if the progress is recently active. Receiving any messages
 	// from the corresponding follower indicates the progress is active.
 	// RecentActive can be reset to false after an election timeout.
 	//
 	// TODO(tbg): the leader should always have this set to true.
 	RecentActive bool

 	// ProbeSent is used while this follower is in StateProbe. When ProbeSent is
 	// true, raft should pause sending replication message to this peer until
 	// ProbeSent is reset. See ProbeAcked() and IsPaused().
 	ProbeSent bool

 	// Inflights is a sliding window for the inflight messages.
 	// Each inflight message contains one or more log entries.
 	// The max number of entries per message is defined in raft config as MaxSizePerMsg.
 	// Thus inflight effectively limits both the number of inflight messages
 	// and the bandwidth each Progress can use.
 	// When inflights is Full, no more message should be sent.
 	// When a leader sends out a message, the index of the last
 	// entry should be added to inflights. The index MUST be added
 	// into inflights in order.
 	// When a leader receives a reply, the previous inflights should
 	// be freed by calling inflights.FreeLE with the index of the last
 	// received entry.
 	Inflights *Inflights

 	// IsLearner is true if this progress is tracked for a learner.
 	IsLearner bool
 }

 // ResetState moves the Progress into the specified State, resetting ProbeSent,
 // PendingSnapshot, and Inflights.
 func (pr *Progress) ResetState(state StateType) {
 	pr.ProbeSent = false
 	pr.PendingSnapshot = 0
 	pr.State = state
 	pr.Inflights.reset()
 }

 func max(a, b uint64) uint64 {
 	if a > b {
 		return a
 	}
 	return b
 }

 func min(a, b uint64) uint64 {
 	if a > b {
 		return b
 	}
 	return a
 }

 // ProbeAcked is called when this peer has accepted an append. It resets
 // ProbeSent to signal that additional append messages should be sent without
 // further delay.
 func (pr *Progress) ProbeAcked() {
 	pr.ProbeSent = false
 }

 // BecomeProbe transitions into StateProbe. Next is reset to Match+1 or,
 // optionally and if larger, the index of the pending snapshot.
 func (pr *Progress) BecomeProbe() {
 	// If the original state is StateSnapshot, progress knows that
 	// the pending snapshot has been sent to this peer successfully, then
 	// probes from pendingSnapshot + 1.
 	if pr.State == StateSnapshot {
 		pendingSnapshot := pr.PendingSnapshot
 		pr.ResetState(StateProbe)
 		pr.Next = max(pr.Match+1, pendingSnapshot+1)
 	} else {
 		pr.ResetState(StateProbe)
 		pr.Next = pr.Match + 1
 	}
 }

 // BecomeReplicate transitions into StateReplicate, resetting Next to Match+1.
 func (pr *Progress) BecomeReplicate() {
 	pr.ResetState(StateReplicate)
 	pr.Next = pr.Match + 1
 }

 // BecomeSnapshot moves the Progress to StateSnapshot with the specified pending
 // snapshot index.
 func (pr *Progress) BecomeSnapshot(snapshoti uint64) {
 	pr.ResetState(StateSnapshot)
 	pr.PendingSnapshot = snapshoti
 }

 // MaybeUpdate is called when an MsgAppResp arrives from the follower, with the
 // index acked by it. The method returns false if the given n index comes from
 // an outdated message. Otherwise it updates the progress and returns true.
 func (pr *Progress) MaybeUpdate(n uint64) bool {
 	var updated bool
 	if pr.Match < n {
 		pr.Match = n
 		updated = true
 		pr.ProbeAcked()
 	}
 	if pr.Next < n+1 {
 		pr.Next = n + 1
 	}
 	return updated
 }

 // OptimisticUpdate signals that appends all the way up to and including index n
 // are in-flight. As a result, Next is increased to n+1.
 func (pr *Progress) OptimisticUpdate(n uint64) { pr.Next = n + 1 }

 // MaybeDecrTo adjusts the Progress to the receipt of a MsgApp rejection. The
 // arguments are the index the follower rejected to append to its log, and its
 // last index.
 //
 // Rejections can happen spuriously as messages are sent out of order or
 // duplicated. In such cases, the rejection pertains to an index that the
 // Progress already knows were previously acknowledged, and false is returned
 // without changing the Progress.
 //
 // If the rejection is genuine, Next is lowered sensibly, and the Progress is
 // cleared for sending log entries.
 func (pr *Progress) MaybeDecrTo(rejected, last uint64) bool {
 	if pr.State == StateReplicate {
 		// The rejection must be stale if the progress has matched and "rejected"
 		// is smaller than "match".
 		if rejected <= pr.Match {
 			return false
 		}
 		// Directly decrease next to match + 1.
 		//
 		// TODO(tbg): why not use last if it's larger?
 		pr.Next = pr.Match + 1
 		return true
 	}

 	// The rejection must be stale if "rejected" does not match next - 1. This
 	// is because non-replicating followers are probed one entry at a time.
 	if pr.Next-1 != rejected {
 		return false
 	}

 	if pr.Next = min(rejected, last+1); pr.Next < 1 {
 		pr.Next = 1
 	}
 	pr.ProbeSent = false
 	return true
 }

 // IsPaused returns whether sending log entries to this node has been throttled.
 // This is done when a node has rejected recent MsgApps, is currently waiting
 // for a snapshot, or has reached the MaxInflightMsgs limit. In normal
 // operation, this is false. A throttled node will be contacted less frequently
 // until it has reached a state in which it's able to accept a steady stream of
 // log entries again.
 func (pr *Progress) IsPaused() bool {
 	switch pr.State {
 	case StateProbe:
 		return pr.ProbeSent
 	case StateReplicate:
 		return pr.Inflights.Full()
 	case StateSnapshot:
 		return true
 	default:
 		panic("unexpected state")
 	}
 }

 func (pr *Progress) String() string {
 	var buf strings.Builder
 	fmt.Fprintf(&buf, "%s match=%d next=%d", pr.State, pr.Match, pr.Next)
 	if pr.IsLearner {
 		fmt.Fprint(&buf, " learner")
 	}
 	if pr.IsPaused() {
 		fmt.Fprint(&buf, " paused")
 	}
 	if pr.PendingSnapshot > 0 {
 		fmt.Fprintf(&buf, " pendingSnap=%d", pr.PendingSnapshot)
 	}
 	if !pr.RecentActive {
 		fmt.Fprintf(&buf, " inactive")
 	}
 	if n := pr.Inflights.Count(); n > 0 {
 		fmt.Fprintf(&buf, " inflight=%d", n)
 		if pr.Inflights.Full() {
 			fmt.Fprint(&buf, "[full]")
 		}
 	}
 	return buf.String()
 }

 // ProgressMap is a map of *Progress.
 type ProgressMap map[uint64]*Progress

 // String prints the ProgressMap in sorted key order, one Progress per line.
 func (m ProgressMap) String() string {
 	ids := make([]uint64, 0, len(m))
 	for k := range m {
 		ids = append(ids, k)
 	}
 	sort.Slice(ids, func(i, j int) bool {
 		return ids[i] < ids[j]
 	})
 	var buf strings.Builder
 	for _, id := range ids {
 		fmt.Fprintf(&buf, "%d: %s\n", id, m[id])
 	}
 	return buf.String()
 }
	// Copyright 2019 The etcd Authors
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.

	package tracker

	import (
	"fmt"
	"sort"
	"strings"
	)

	// Progress represents a follower’s progress in the view of the leader. Leader
	// maintains progresses of all followers, and sends entries to the follower
	// based on its progress.
	//
	// NB(tbg): Progress is basically a state machine whose transitions are mostly
	// strewn around `*raft.raft`. Additionally, some fields are only used when in a
	// certain State. All of this isn't ideal.
	type Progress struct {
	Match, Next uint64
	// State defines how the leader should interact with the follower.
	//
	// When in StateProbe, leader sends at most one replication message
	// per heartbeat interval. It also probes actual progress of the follower.
	//
	// When in StateReplicate, leader optimistically increases next
	// to the latest entry sent after sending replication message. This is
	// an optimized state for fast replicating log entries to the follower.
	//
	// When in StateSnapshot, leader should have sent out snapshot
	// before and stops sending any replication message.
	State StateType

	// PendingSnapshot is used in StateSnapshot.
	// If there is a pending snapshot, the pendingSnapshot will be set to the
	// index of the snapshot. If pendingSnapshot is set, the replication process of
	// this Progress will be paused. raft will not resend snapshot until the pending one
	// is reported to be failed.
	PendingSnapshot uint64

	// RecentActive is true if the progress is recently active. Receiving any messages
	// from the corresponding follower indicates the progress is active.
	// RecentActive can be reset to false after an election timeout.
	//
	// TODO(tbg): the leader should always have this set to true.
	RecentActive bool

	// ProbeSent is used while this follower is in StateProbe. When ProbeSent is
	// true, raft should pause sending replication message to this peer until
	// ProbeSent is reset. See ProbeAcked() and IsPaused().
	ProbeSent bool

	// Inflights is a sliding window for the inflight messages.
	// Each inflight message contains one or more log entries.
	// The max number of entries per message is defined in raft config as MaxSizePerMsg.
	// Thus inflight effectively limits both the number of inflight messages
	// and the bandwidth each Progress can use.
	// When inflights is Full, no more message should be sent.
	// When a leader sends out a message, the index of the last
	// entry should be added to inflights. The index MUST be added
	// into inflights in order.
	// When a leader receives a reply, the previous inflights should
	// be freed by calling inflights.FreeLE with the index of the last
	// received entry.
	Inflights *Inflights

	// IsLearner is true if this progress is tracked for a learner.
	IsLearner bool
	}

	// ResetState moves the Progress into the specified State, resetting ProbeSent,
	// PendingSnapshot, and Inflights.
	func (pr *Progress) ResetState(state StateType) {
	pr.ProbeSent = false
	pr.PendingSnapshot = 0
	pr.State = state
	pr.Inflights.reset()
	}

	func max(a, b uint64) uint64 {
	if a > b {
	return a
	}
	return b
	}

	func min(a, b uint64) uint64 {
	if a > b {
	return b
	}
	return a
	}

	// ProbeAcked is called when this peer has accepted an append. It resets
	// ProbeSent to signal that additional append messages should be sent without
	// further delay.
	func (pr *Progress) ProbeAcked() {
	pr.ProbeSent = false
	}

	// BecomeProbe transitions into StateProbe. Next is reset to Match+1 or,
	// optionally and if larger, the index of the pending snapshot.
	func (pr *Progress) BecomeProbe() {
	// If the original state is StateSnapshot, progress knows that
	// the pending snapshot has been sent to this peer successfully, then
	// probes from pendingSnapshot + 1.
	if pr.State == StateSnapshot {
	pendingSnapshot := pr.PendingSnapshot
	pr.ResetState(StateProbe)
	pr.Next = max(pr.Match+1, pendingSnapshot+1)
	} else {
	pr.ResetState(StateProbe)
	pr.Next = pr.Match + 1
	}
	}

	// BecomeReplicate transitions into StateReplicate, resetting Next to Match+1.
	func (pr *Progress) BecomeReplicate() {
	pr.ResetState(StateReplicate)
	pr.Next = pr.Match + 1
	}

	// BecomeSnapshot moves the Progress to StateSnapshot with the specified pending
	// snapshot index.
	func (pr *Progress) BecomeSnapshot(snapshoti uint64) {
	pr.ResetState(StateSnapshot)
	pr.PendingSnapshot = snapshoti
	}

	// MaybeUpdate is called when an MsgAppResp arrives from the follower, with the
	// index acked by it. The method returns false if the given n index comes from
	// an outdated message. Otherwise it updates the progress and returns true.
	func (pr *Progress) MaybeUpdate(n uint64) bool {
	var updated bool
	if pr.Match < n {
	pr.Match = n
	updated = true
	pr.ProbeAcked()
	}
	if pr.Next < n+1 {
	pr.Next = n + 1
	}
	return updated
	}

	// OptimisticUpdate signals that appends all the way up to and including index n
	// are in-flight. As a result, Next is increased to n+1.
	func (pr *Progress) OptimisticUpdate(n uint64) { pr.Next = n + 1 }

	// MaybeDecrTo adjusts the Progress to the receipt of a MsgApp rejection. The
	// arguments are the index the follower rejected to append to its log, and its
	// last index.
	//
	// Rejections can happen spuriously as messages are sent out of order or
	// duplicated. In such cases, the rejection pertains to an index that the
	// Progress already knows were previously acknowledged, and false is returned
	// without changing the Progress.
	//
	// If the rejection is genuine, Next is lowered sensibly, and the Progress is
	// cleared for sending log entries.
	func (pr *Progress) MaybeDecrTo(rejected, last uint64) bool {
	if pr.State == StateReplicate {
	// The rejection must be stale if the progress has matched and "rejected"
	// is smaller than "match".
	if rejected <= pr.Match {
	return false
	}
	// Directly decrease next to match + 1.
	//
	// TODO(tbg): why not use last if it's larger?
	pr.Next = pr.Match + 1
	return true
	}

	// The rejection must be stale if "rejected" does not match next - 1. This
	// is because non-replicating followers are probed one entry at a time.
	if pr.Next-1 != rejected {
	return false
	}

	if pr.Next = min(rejected, last+1); pr.Next < 1 {
	pr.Next = 1
	}
	pr.ProbeSent = false
	return true
	}

	// IsPaused returns whether sending log entries to this node has been throttled.
	// This is done when a node has rejected recent MsgApps, is currently waiting
	// for a snapshot, or has reached the MaxInflightMsgs limit. In normal
	// operation, this is false. A throttled node will be contacted less frequently
	// until it has reached a state in which it's able to accept a steady stream of
	// log entries again.
	func (pr *Progress) IsPaused() bool {
	switch pr.State {
	case StateProbe:
	return pr.ProbeSent
	case StateReplicate:
	return pr.Inflights.Full()
	case StateSnapshot:
	return true
	default:
	panic("unexpected state")
	}
	}

	func (pr *Progress) String() string {
	var buf strings.Builder
	fmt.Fprintf(&buf, "%s match=%d next=%d", pr.State, pr.Match, pr.Next)
	if pr.IsLearner {
	fmt.Fprint(&buf, " learner")
	}
	if pr.IsPaused() {
	fmt.Fprint(&buf, " paused")
	}
	if pr.PendingSnapshot > 0 {
	fmt.Fprintf(&buf, " pendingSnap=%d", pr.PendingSnapshot)
	}
	if !pr.RecentActive {
	fmt.Fprintf(&buf, " inactive")
	}
	if n := pr.Inflights.Count(); n > 0 {
	fmt.Fprintf(&buf, " inflight=%d", n)
	if pr.Inflights.Full() {
	fmt.Fprint(&buf, "[full]")
	}
	}
	return buf.String()
	}

	// ProgressMap is a map of *Progress.
	type ProgressMap map[uint64]*Progress

	// String prints the ProgressMap in sorted key order, one Progress per line.
	func (m ProgressMap) String() string {
	ids := make([]uint64, 0, len(m))
	for k := range m {
	ids = append(ids, k)
	}
	sort.Slice(ids, func(i, j int) bool {
	return ids[i] < ids[j]
	})
	var buf strings.Builder
	for _, id := range ids {
	fmt.Fprintf(&buf, "%d: %s\n", id, m[id])
	}
	return buf.String()
	}