#vulnerable code 
                                void installSnapshot() {
        if (this.state == State.Snapshot) {
            LOG.warn("Replicator {} is installing snapshot, ignore the new request.", this.options.getPeerId());
            this.id.unlock();
            return;
        }
        boolean doUnlock = true;
        try {
            Requires.requireTrue(this.reader == null,
                "Replicator %s already has a snapshot reader, current state is %s", this.options.getPeerId(),
                this.state);
            this.reader = this.options.getSnapshotStorage().open();
            if (this.reader == null) {
                final NodeImpl node = this.options.getNode();
                final RaftException error = new RaftException(EnumOutter.ErrorType.ERROR_TYPE_SNAPSHOT);
                error.setStatus(new Status(RaftError.EIO, "Fail to open snapshot"));
                this.id.unlock();
                doUnlock = false;
                node.onError(error);
                return;
            }
            final String uri = this.reader.generateURIForCopy();
            if (uri == null) {
                final NodeImpl node = this.options.getNode();
                final RaftException error = new RaftException(EnumOutter.ErrorType.ERROR_TYPE_SNAPSHOT);
                error.setStatus(new Status(RaftError.EIO, "Fail to generate uri for snapshot reader"));
                releaseReader();
                this.id.unlock();
                doUnlock = false;
                node.onError(error);
                return;
            }
            final RaftOutter.SnapshotMeta meta = this.reader.load();
            if (meta == null) {
                final String snapshotPath = this.reader.getPath();
                final NodeImpl node = this.options.getNode();
                final RaftException error = new RaftException(EnumOutter.ErrorType.ERROR_TYPE_SNAPSHOT);
                error.setStatus(new Status(RaftError.EIO, "Fail to load meta from %s", snapshotPath));
                releaseReader();
                this.id.unlock();
                doUnlock = false;
                node.onError(error);
                return;
            }
            final InstallSnapshotRequest.Builder rb = InstallSnapshotRequest.newBuilder();
            rb.setTerm(this.options.getTerm());
            rb.setGroupId(this.options.getGroupId());
            rb.setServerId(this.options.getServerId().toString());
            rb.setPeerId(this.options.getPeerId().toString());
            rb.setMeta(meta);
            rb.setUri(uri);

            this.statInfo.runningState = RunningState.INSTALLING_SNAPSHOT;
            this.statInfo.lastLogIncluded = meta.getLastIncludedIndex();
            this.statInfo.lastTermIncluded = meta.getLastIncludedTerm();

            final InstallSnapshotRequest request = rb.build();
            this.state = State.Snapshot;
            // noinspection NonAtomicOperationOnVolatileField
            this.installSnapshotCounter++;
            final long monotonicSendTimeMs = Utils.monotonicMs();
            final int stateVersion = this.version;
            final int seq = getAndIncrementReqSeq();
            final Future<Message> rpcFuture = this.rpcService.installSnapshot(this.options.getPeerId().getEndpoint(),
                request, new RpcResponseClosureAdapter<InstallSnapshotResponse>() {

                    @Override
                    public void run(final Status status) {
                        onRpcReturned(Replicator.this.id, RequestType.Snapshot, status, request, getResponse(), seq,
                            stateVersion, monotonicSendTimeMs);
                    }
                });
            addInflight(RequestType.Snapshot, this.nextIndex, 0, 0, seq, rpcFuture);
        } finally {
            if (doUnlock) {
                this.id.unlock();
            }
        }
    } 
                            #location 19 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                long getNextSendIndex() {
        // Fast path
        if (this.inflights.isEmpty()) {
            return this.nextIndex;
        }
        // Too many in-flight requests.
        if (this.inflights.size() > this.raftOptions.getMaxReplicatorInflightMsgs()) {
            return -1L;
        }
        // Last request should be a AppendEntries request and has some entries.
        if (this.rpcInFly != null && this.rpcInFly.isSendingLogEntries()) {
            return this.rpcInFly.startIndex + this.rpcInFly.count;
        }
        return -1L;
    }