5133271154

Committed 31 May 2023 02:03PM UTC coverage: 67.271% (+0.4%) from 66.918%

Build Type

push

Committed by

Commit Message

chore(ci): add workflow for OSS build + unit tests (#8834)

## Problem

Previous commits broke OSS build. Since we didn't have a test for this,
it was undetected by CI.

## Solution

Add a CI job to verify that we can make the dgraph OSS build, and run
all dgraph OSS unit tests. We do this in a separate workflow because
this does not require a separate self-hosted runner (we can use github
hosted runners for this job).

See also: https://github.com/dgraph-io/dgraph/pull/8832

Run Details

58407 of 86823 relevant lines covered (67.27%)

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Source File
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84.44

/conn/node.go

/*
 * Copyright 2017-2023 Dgraph Labs, Inc. and Contributors
 *
 * 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 conn

import (
        "bytes"
        "context"
        "crypto/tls"
        "encoding/binary"
        "fmt"
        "math/rand"
        "strings"
        "sync"
        "sync/atomic"
        "time"

        "github.com/golang/glog"
        "github.com/pkg/errors"
        "go.etcd.io/etcd/raft"
        "go.etcd.io/etcd/raft/raftpb"
        otrace "go.opencensus.io/trace"

        "github.com/dgraph-io/badger/v4/y"
        "github.com/dgraph-io/dgo/v230/protos/api"
        "github.com/dgraph-io/dgraph/protos/pb"
        "github.com/dgraph-io/dgraph/raftwal"
        "github.com/dgraph-io/dgraph/x"
        "github.com/dgraph-io/ristretto/z"
)

var (
        // ErrNoNode is returned when no node has been set up.
        ErrNoNode = errors.Errorf("No node has been set up yet")
)

// Node represents a node participating in the RAFT protocol.
type Node struct {
        x.SafeMutex

        // Applied is used to keep track of the applied RAFT proposals.
        // The stages are proposed -> committed (accepted by cluster) ->
        // applied (to PL) -> synced (to BadgerDB).
        // This needs to be 64 bit aligned for atomics to work on 32 bit machine.
        Applied y.WaterMark

        joinLock sync.Mutex

        // Used to keep track of lin read requests.
        requestCh chan linReadReq

        // SafeMutex is for fields which can be changed after init.
        _confState *raftpb.ConfState
        _raft      raft.Node

        // Fields which are never changed after init.
        StartTime       time.Time
        Cfg             *raft.Config
        MyAddr          string
        Id              uint64
        peers           map[uint64]string
        confChanges     map[uint64]chan error
        messages        chan sendmsg
        RaftContext     *pb.RaftContext
        Store           *raftwal.DiskStorage
        Rand            *rand.Rand
        tlsClientConfig *tls.Config

        Proposals proposals

        heartbeatsOut int64
        heartbeatsIn  int64
}

// NewNode returns a new Node instance.
func NewNode(rc *pb.RaftContext, store *raftwal.DiskStorage, tlsConfig *tls.Config) *Node {
        snap, err := store.Snapshot()
        x.Check(err)

        n := &Node{
                StartTime: time.Now(),
                Id:        rc.Id,
                MyAddr:    rc.Addr,
                Store:     store,
                Cfg: &raft.Config{
                        ID:                       rc.Id,
                        ElectionTick:             20, // 2s if we call Tick() every 100 ms.
                        HeartbeatTick:            1,  // 100ms if we call Tick() every 100 ms.
                        Storage:                  store,
                        MaxInflightMsgs:          256,
                        MaxSizePerMsg:            256 << 10, // 256 KB should allow more batching.
                        MaxCommittedSizePerReady: 64 << 20,  // Avoid loading entire Raft log into memory.
                        // We don't need lease based reads. They cause issues because they
                        // require CheckQuorum to be true, and that causes a lot of issues
                        // for us during cluster bootstrapping and later. A seemingly
                        // healthy cluster would just cause leader to step down due to
                        // "inactive" quorum, and then disallow anyone from becoming leader.
                        // So, let's stick to default options.  Let's achieve correctness,
                        // then we achieve performance. Plus, for the Dgraph alphas, we'll
                        // be soon relying only on Timestamps for blocking reads and
                        // achieving linearizability, than checking quorums (Zero would
                        // still check quorums).
                        ReadOnlyOption: raft.ReadOnlySafe,
                        // When a disconnected node joins back, it forces a leader change,
                        // as it starts with a higher term, as described in Raft thesis (not
                        // the paper) in section 9.6. This setting can avoid that by only
                        // increasing the term, if the node has a good chance of becoming
                        // the leader.
                        PreVote: true,

                        // We can explicitly set Applied to the first index in the Raft log,
                        // so it does not derive it separately, thus avoiding a crash when
                        // the Applied is set to below snapshot index by Raft.
                        // In case this is a new Raft log, first would be 1, and therefore
                        // Applied would be zero, hence meeting the condition by the library
                        // that Applied should only be set during a restart.
                        //
                        // Update: Set the Applied to the latest snapshot, because it seems
                        // like somehow the first index can be out of sync with the latest
                        // snapshot.
                        Applied: snap.Metadata.Index,

                        Logger: &x.ToGlog{},
                },
                // processConfChange etc are not throttled so some extra delta, so that we don't
                // block tick when applyCh is full
                Applied:     y.WaterMark{Name: "Applied watermark"},
                RaftContext: rc,
                //nolint:gosec // random node id generator does not require cryptographic precision
                Rand:            rand.New(&lockedSource{src: rand.NewSource(time.Now().UnixNano())}),
                confChanges:     make(map[uint64]chan error),
                messages:        make(chan sendmsg, 100),
                peers:           make(map[uint64]string),
                requestCh:       make(chan linReadReq, 100),
                tlsClientConfig: tlsConfig,
        }
        n.Applied.Init(nil)
        // This should match up to the Applied index set above.
        n.Applied.SetDoneUntil(n.Cfg.Applied)
        glog.Infof("Setting raft.Config to: %+v", n.Cfg)
        return n
}

// ReportRaftComms periodically prints the state of the node (heartbeats in and out).
func (n *Node) ReportRaftComms() {
        if !glog.V(3) {
                return
        }
        ticker := time.NewTicker(time.Second)
        defer ticker.Stop()

        for range ticker.C {
                out := atomic.SwapInt64(&n.heartbeatsOut, 0)
                in := atomic.SwapInt64(&n.heartbeatsIn, 0)
                glog.Infof("RaftComm: [%#x] Heartbeats out: %d, in: %d", n.Id, out, in)
        }
}

// SetRaft would set the provided raft.Node to this node.
// It would check fail if the node is already set.
func (n *Node) SetRaft(r raft.Node) {
        n.Lock()
        defer n.Unlock()
        x.AssertTrue(n._raft == nil)
        n._raft = r
}

// Raft would return back the raft.Node stored in the node.
func (n *Node) Raft() raft.Node {
        n.RLock()
        defer n.RUnlock()
        return n._raft
}

// SetConfState would store the latest ConfState generated by ApplyConfChange.
func (n *Node) SetConfState(cs *raftpb.ConfState) {
        glog.Infof("Setting conf state to %+v\n", cs)
        n.Lock()
        defer n.Unlock()
        n._confState = cs
}

// DoneConfChange marks a configuration change as done and sends the given error to the
// config channel.
func (n *Node) DoneConfChange(id uint64, err error) {
        n.Lock()
        defer n.Unlock()
        ch, has := n.confChanges[id]
        if !has {
                return
        }
        delete(n.confChanges, id)
        ch <- err
}

//nolint:gosec // random node id generator does not require cryptographic precision
func (n *Node) storeConfChange(che chan error) uint64 {
        n.Lock()
        defer n.Unlock()
        id := rand.Uint64()
        _, has := n.confChanges[id]
        for has {
                id = rand.Uint64()
                _, has = n.confChanges[id]
        }
        n.confChanges[id] = che
        return id
}

// ConfState would return the latest ConfState stored in node.
func (n *Node) ConfState() *raftpb.ConfState {
        n.RLock()
        defer n.RUnlock()
        return n._confState
}

// Peer returns the address of the peer with the given id.
func (n *Node) Peer(pid uint64) (string, bool) {
        n.RLock()
        defer n.RUnlock()
        addr, ok := n.peers[pid]
        return addr, ok
}

// SetPeer sets the address of the peer with the given id. The address must not be empty.
func (n *Node) SetPeer(pid uint64, addr string) {
        x.AssertTruef(addr != "", "SetPeer for peer %d has empty addr.", pid)
        n.Lock()
        defer n.Unlock()
        n.peers[pid] = addr
}

// Send sends the given RAFT message from this node.
func (n *Node) Send(msg *raftpb.Message) {
        x.AssertTruef(n.Id != msg.To, "Sending message to itself")
        data, err := msg.Marshal()
        x.Check(err)

        if glog.V(2) {
                switch msg.Type {
                case raftpb.MsgHeartbeat, raftpb.MsgHeartbeatResp:
                        atomic.AddInt64(&n.heartbeatsOut, 1)
                case raftpb.MsgReadIndex, raftpb.MsgReadIndexResp:
                case raftpb.MsgApp, raftpb.MsgAppResp:
                case raftpb.MsgProp:
                default:
                        glog.Infof("RaftComm: [%#x] Sending message of type %s to %#x", msg.From, msg.Type, msg.To)
                }
        }
        // As long as leadership is stable, any attempted Propose() calls should be reflected in the
        // next raft.Ready.Messages. Leaders will send MsgApps to the followers; followers will send
        // MsgProp to the leader. It is up to the transport layer to get those messages to their
        // destination. If a MsgApp gets dropped by the transport layer, it will get retried by raft
        // (i.e. it will appear in a future Ready.Messages), but MsgProp will only be sent once. During
        // leadership transitions, proposals may get dropped even if the network is reliable.
        //
        // We can't do a select default here. The messages must be sent to the channel, otherwise we
        // should block until the channel can accept these messages. BatchAndSendMessages would take
        // care of dropping messages which can't be sent due to network issues to the corresponding
        // node. But, we shouldn't take the liberty to do that here. It would take us more time to
        // repropose these dropped messages anyway, than to block here a bit waiting for the messages
        // channel to clear out.
        n.messages <- sendmsg{to: msg.To, data: data}
}

// Snapshot returns the current snapshot.
func (n *Node) Snapshot() (raftpb.Snapshot, error) {
        if n == nil || n.Store == nil {
                return raftpb.Snapshot{}, errors.New("Uninitialized node or raft store")
        }
        return n.Store.Snapshot()
}

// SaveToStorage saves the hard state, entries, and snapshot to persistent storage, in that order.
func (n *Node) SaveToStorage(h *raftpb.HardState, es []raftpb.Entry, s *raftpb.Snapshot) {
        for {
                if err := n.Store.Save(h, es, s); err != nil {
                        glog.Errorf("While trying to save Raft update: %v. Retrying...", err)
                } else {
                        return
                }
        }
}

// PastLife returns the index of the snapshot before the restart (if any) and whether there was
// a previous state that should be recovered after a restart.
func (n *Node) PastLife() (uint64, bool, error) {
        var (
                sp      raftpb.Snapshot
                idx     uint64
                restart bool
                rerr    error
        )
        sp, rerr = n.Store.Snapshot()
        if rerr != nil {
                return 0, false, rerr
        }
        if !raft.IsEmptySnap(sp) {
                glog.Infof("Found Snapshot.Metadata: %+v\n", sp.Metadata)
                restart = true
                idx = sp.Metadata.Index
        }

        var hd raftpb.HardState
        hd, rerr = n.Store.HardState()
        if rerr != nil {
                return 0, false, rerr
        }
        if !raft.IsEmptyHardState(hd) {
                glog.Infof("Found hardstate: %+v\n", hd)
                restart = true
        }

        num := n.Store.NumEntries()
        glog.Infof("Group %d found %d entries\n", n.RaftContext.Group, num)
        // We'll always have at least one entry.
        if num > 1 {
                restart = true
        }
        return idx, restart, nil
}

const (
        messageBatchSoftLimit = 10e6
)

type stream struct {
        msgCh chan []byte
        alive int32
}

// BatchAndSendMessages sends messages in batches.
func (n *Node) BatchAndSendMessages() {
        batches := make(map[uint64]*bytes.Buffer)
        streams := make(map[uint64]*stream)

        for {
                totalSize := 0
                sm := <-n.messages
        slurp_loop:
                for {
                        var buf *bytes.Buffer
                        if b, ok := batches[sm.to]; !ok {
                                buf = new(bytes.Buffer)
                                batches[sm.to] = buf
                        } else {
                                buf = b
                        }
                        totalSize += 4 + len(sm.data)
                        x.Check(binary.Write(buf, binary.LittleEndian, uint32(len(sm.data))))
                        x.Check2(buf.Write(sm.data))

                        if totalSize > messageBatchSoftLimit {
                                // We limit the batch size, but we aren't pushing back on
                                // n.messages, because the loop below spawns a goroutine
                                // to do its dirty work.  This is good because right now
                                // (*node).send fails(!) if the channel is full.
                                break
                        }

                        select {
                        case sm = <-n.messages:
                        default:
                                break slurp_loop
                        }
                }

                for to, buf := range batches {
                        if buf.Len() == 0 {
                                continue
                        }
                        s, ok := streams[to]
                        if !ok || atomic.LoadInt32(&s.alive) <= 0 {
                                s = &stream{
                                        msgCh: make(chan []byte, 100),
                                        alive: 1,
                                }
                                go n.streamMessages(to, s)
                                streams[to] = s
                        }
                        data := make([]byte, buf.Len())
                        copy(data, buf.Bytes())
                        buf.Reset()

                        select {
                        case s.msgCh <- data:
                        default:
                        }
                }
        }
}

func (n *Node) streamMessages(to uint64, s *stream) {
        defer atomic.StoreInt32(&s.alive, 0)

        // Exit after this deadline. Let BatchAndSendMessages create another goroutine, if needed.
        // Let's set the deadline to 10s because if we increase it, then it takes longer to recover from
        // a partition and get a new leader.
        deadline := time.Now().Add(10 * time.Second)
        ticker := time.NewTicker(time.Second)
        defer ticker.Stop()

        var logged int
        for range ticker.C { // Don't do this in an busy-wait loop, use a ticker.
                // doSendMessage would block doing a stream. So, time.Now().After is
                // only there to avoid a busy-wait.
                if err := n.doSendMessage(to, s.msgCh); err != nil {
                        // Update lastLog so we print error only a few times if we are not able to connect.
                        // Otherwise, the log is polluted with repeated errors.
                        if logged == 0 {
                                glog.Warningf("Unable to send message to peer: %#x. Error: %v", to, err)
                                logged++
                        }
                }
                if time.Now().After(deadline) {
                        return
                }
        }
}

func (n *Node) doSendMessage(to uint64, msgCh chan []byte) error {
        addr, has := n.Peer(to)
        if !has {
                return errors.Errorf("Do not have address of peer %#x", to)
        }
        pool, err := GetPools().Get(addr)
        if err != nil {
                return err
        }

        c := pb.NewRaftClient(pool.Get())
        ctx, span := otrace.StartSpan(context.Background(),
                fmt.Sprintf("RaftMessage-%d-to-%d", n.Id, to))
        defer span.End()

        mc, err := c.RaftMessage(ctx)
        if err != nil {
                return err
        }

        var packets, lastPackets uint64
        slurp := func(batch *pb.RaftBatch) {
                for {
                        if len(batch.Payload.Data) > messageBatchSoftLimit {
                                return
                        }
                        select {
                        case data := <-msgCh:
                                batch.Payload.Data = append(batch.Payload.Data, data...)
                                packets++
                        default:
                                return
                        }
                }
        }

        ctx = mc.Context()

        fastTick := time.NewTicker(5 * time.Second)
        defer fastTick.Stop()

        ticker := time.NewTicker(3 * time.Minute)
        defer ticker.Stop()

        for {
                select {
                case data := <-msgCh:
                        batch := &pb.RaftBatch{
                                Context: n.RaftContext,
                                Payload: &api.Payload{Data: data},
                        }
                        slurp(batch) // Pick up more entries from msgCh, if present.
                        span.Annotatef(nil, "[to: %x] [Packets: %d] Sending data of length: %d.",
                                to, packets, len(batch.Payload.Data))
                        if packets%10000 == 0 {
                                glog.V(2).Infof("[to: %x] [Packets: %d] Sending data of length: %d.",
                                        to, packets, len(batch.Payload.Data))
                        }
                        packets++
                        if err := mc.Send(batch); err != nil {
                                span.Annotatef(nil, "Error while mc.Send: %v", err)
                                glog.Errorf("[to: %x] Error while mc.Send: %v", to, err)
                                switch {
                                case strings.Contains(err.Error(), "TransientFailure"):
                                        glog.Warningf("Reporting node: %d addr: %s as unreachable.", to, pool.Addr)
                                        n.Raft().ReportUnreachable(to)
                                        pool.SetUnhealthy()
                                default:
                                }
                                // We don't need to do anything if we receive any error while sending message.
                                // RAFT would automatically retry.
                                return err
                        }
                case <-fastTick.C:
                        // We use this ticker, because during network partitions, mc.Send is
                        // unable to actually send packets, and also does not complain about
                        // them. We could have potentially used the separately tracked
                        // heartbeats to check this, but what we have observed is that
                        // incoming traffic might be OK, but outgoing might not be. So, this
                        // is a better way for us to verify whether this particular outbound
                        // connection is valid or not.
                        ctx, cancel := context.WithTimeout(ctx, 3*time.Second)
                        _, err := c.IsPeer(ctx, n.RaftContext)
                        cancel()
                        if err != nil {
                                glog.Errorf("Error while calling IsPeer %v. Reporting %x as unreachable.", err, to)
                                n.Raft().ReportUnreachable(to)
                                pool.SetUnhealthy()
                                return errors.Wrapf(err, "while calling IsPeer %x", to)
                        }
                case <-ticker.C:
                        if lastPackets == packets {
                                span.Annotatef(nil,
                                        "No activity for a while [Packets == %d]. Closing connection.", packets)
                                return mc.CloseSend()
                        }
                        lastPackets = packets
                case <-ctx.Done():
                        return ctx.Err()
                }
        }
}

// Connect connects the node and makes its peerPool refer to the constructed pool and address
// (possibly updating ourselves from the old address.)  (Unless pid is ourselves, in which
// case this does nothing.)
func (n *Node) Connect(pid uint64, addr string) {
        if pid == n.Id {
                return
        }
        if paddr, ok := n.Peer(pid); ok && paddr == addr {
                // Already connected.
                return
        }
        // Here's what we do.  Right now peerPool maps peer node id's to addr values.  If
        // a *pool can be created, good, but if not, we still create a peerPoolEntry with
        // a nil *pool.
        if addr == n.MyAddr {
                // TODO: Note this fact in more general peer health info somehow.
                glog.Infof("Peer %d claims same host as me\n", pid)
                n.SetPeer(pid, addr)
                return
        }
        GetPools().Connect(addr, n.tlsClientConfig)
        n.SetPeer(pid, addr)
}

// DeletePeer deletes the record of the peer with the given id.
func (n *Node) DeletePeer(pid uint64) {
        if pid == n.Id {
                return
        }
        n.Lock()
        defer n.Unlock()
        delete(n.peers, pid)
}

var errInternalRetry = errors.New("Retry proposal again")

func (n *Node) proposeConfChange(ctx context.Context, conf raftpb.ConfChange) error {
        cctx, cancel := context.WithTimeout(ctx, 3*time.Second)
        defer cancel()

        ch := make(chan error, 1)
        id := n.storeConfChange(ch)
        // TODO: Delete id from the map.
        conf.ID = id
        if err := n.Raft().ProposeConfChange(cctx, conf); err != nil {
                if cctx.Err() != nil {
                        return errInternalRetry
                }
                glog.Warningf("Error while proposing conf change: %v", err)
                return err
        }
        select {
        case err := <-ch:
                return err
        case <-ctx.Done():
                return ctx.Err()
        case <-cctx.Done():
                return errInternalRetry
        }
}

func (n *Node) addToCluster(ctx context.Context, rc *pb.RaftContext) error {
        pid := rc.Id
        rc.SnapshotTs = 0
        rcBytes, err := rc.Marshal()
        x.Check(err)

        cc := raftpb.ConfChange{
                Type:    raftpb.ConfChangeAddNode,
                NodeID:  pid,
                Context: rcBytes,
        }
        if rc.IsLearner {
                cc.Type = raftpb.ConfChangeAddLearnerNode
        }

        err = errInternalRetry
        for err == errInternalRetry {
                glog.Infof("Trying to add %#x to cluster. Addr: %v\n", pid, rc.Addr)
                glog.Infof("Current confstate at %#x: %+v\n", n.Id, n.ConfState())
                err = n.proposeConfChange(ctx, cc)
        }
        return err
}

// ProposePeerRemoval proposes a new configuration with the peer with the given id removed.
func (n *Node) ProposePeerRemoval(ctx context.Context, id uint64) error {
        if n.Raft() == nil {
                return ErrNoNode
        }
        if _, ok := n.Peer(id); !ok && id != n.RaftContext.Id {
                return errors.Errorf("Node %#x not part of group", id)
        }
        cc := raftpb.ConfChange{
                Type:   raftpb.ConfChangeRemoveNode,
                NodeID: id,
        }
        err := errInternalRetry
        for err == errInternalRetry {
                err = n.proposeConfChange(ctx, cc)
        }
        return err
}

type linReadReq struct {
        // A one-shot chan which we send a raft index upon.
        indexCh chan<- uint64
}

var errReadIndex = errors.Errorf(
        "Cannot get linearized read (time expired or no configured leader)")

var readIndexOk, readIndexTotal uint64

// WaitLinearizableRead waits until a linearizable read can be performed.
func (n *Node) WaitLinearizableRead(ctx context.Context) error {
        span := otrace.FromContext(ctx)
        span.Annotate(nil, "WaitLinearizableRead")

        if num := atomic.AddUint64(&readIndexTotal, 1); num%1000 == 0 {
                glog.V(2).Infof("ReadIndex Total: %d\n", num)
        }
        indexCh := make(chan uint64, 1)
        select {
        case n.requestCh <- linReadReq{indexCh: indexCh}:
                span.Annotate(nil, "Pushed to requestCh")
        case <-ctx.Done():
                span.Annotate(nil, "Context expired")
                return ctx.Err()
        }

        select {
        case index := <-indexCh:
                span.Annotatef(nil, "Received index: %d", index)
                if index == 0 {
                        return errReadIndex
                } else if num := atomic.AddUint64(&readIndexOk, 1); num%1000 == 0 {
                        glog.V(2).Infof("ReadIndex OK: %d\n", num)
                }
                err := n.Applied.WaitForMark(ctx, index)
                span.Annotatef(nil, "Error from Applied.WaitForMark: %v", err)
                return err
        case <-ctx.Done():
                span.Annotate(nil, "Context expired")
                return ctx.Err()
        }
}

// RunReadIndexLoop runs the RAFT index in a loop.
func (n *Node) RunReadIndexLoop(closer *z.Closer, readStateCh <-chan raft.ReadState) {
        defer closer.Done()
        readIndex := func(activeRctx []byte) (uint64, error) {
                // Read Request can get rejected then we would wait indefinitely on the channel
                // so have a timeout.
                ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
                defer cancel()

                if err := n.Raft().ReadIndex(ctx, activeRctx); err != nil {
                        glog.Errorf("Error while trying to call ReadIndex: %v\n", err)
                        return 0, err
                }

        again:
                select {
                case <-closer.HasBeenClosed():
                        return 0, errors.New("Closer has been called")
                case rs := <-readStateCh:
                        if !bytes.Equal(activeRctx, rs.RequestCtx) {
                                glog.V(3).Infof("Read state: %x != requested %x", rs.RequestCtx, activeRctx)
                                goto again
                        }
                        return rs.Index, nil
                case <-ctx.Done():
                        glog.Warningf("[%#x] Read index context timed out\n", n.Id)
                        return 0, errInternalRetry
                }
        } // end of readIndex func

        // We maintain one linearizable ReadIndex request at a time.  Others wait queued behind
        // requestCh.
        requests := []linReadReq{}
        for {
                select {
                case <-closer.HasBeenClosed():
                        return
                case <-readStateCh:
                        // Do nothing, discard ReadState as we don't have any pending ReadIndex requests.
                case req := <-n.requestCh:
                slurpLoop:
                        for {
                                requests = append(requests, req)
                                select {
                                case req = <-n.requestCh:
                                default:
                                        break slurpLoop
                                }
                        }
                        // Create one activeRctx slice for the read index, even if we have to call readIndex
                        // repeatedly. That way, we can process the requests as soon as we encounter the first
                        // activeRctx. This is better than flooding readIndex with a new activeRctx on each
                        // call, causing more unique traffic and further delays in request processing.
                        activeRctx := make([]byte, 8)
                        x.Check2(n.Rand.Read(activeRctx))
                        glog.V(4).Infof("Request readctx: %#x", activeRctx)
                        for {
                                index, err := readIndex(activeRctx)
                                if err == errInternalRetry {
                                        continue
                                }
                                if err != nil {
                                        index = 0
                                        glog.Errorf("[%#x] While trying to do lin read index: %v", n.Id, err)
                                }
                                for _, req := range requests {
                                        req.indexCh <- index
                                }
                                break
                        }
                        requests = requests[:0]
                }
        }
}

func (n *Node) joinCluster(ctx context.Context, rc *pb.RaftContext) (*api.Payload, error) {
        // Only process one JoinCluster request at a time.
        n.joinLock.Lock()
        defer n.joinLock.Unlock()

        // Check that the new node is from the same group as me.
        if rc.Group != n.RaftContext.Group {
                return nil, errors.Errorf("Raft group mismatch")
        }
        // Also check that the new node is not me.
        if rc.Id == n.RaftContext.Id {
                return nil, errors.Errorf("REUSE_RAFTID: Raft ID duplicates mine: %+v", rc)
        }

        // Check that the new node is not already part of the group.
        if addr, ok := n.Peer(rc.Id); ok && rc.Addr != addr {
                // There exists a healthy connection to server with same id.
                if _, err := GetPools().Get(addr); err == nil {
                        return &api.Payload{}, errors.Errorf(
                                "REUSE_ADDR: IP Address same as existing peer: %s", addr)
                }
        }
        n.Connect(rc.Id, rc.Addr)

        err := n.addToCluster(context.Background(), rc)
        glog.Infof("[%#x] Done joining cluster with err: %v", rc.Id, err)
        return &api.Payload{}, err
}

dgraph-io / dgraph / 5133271154

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