Elasticsearch version : 6.7.0
Three servers, all servers are node.master and node.data. config like this：
cluster.name: ismartv-elk
node.name: node1
path.data: /opt/elkdata
path.logs: /var/log/elasticsearch
node.master: true
node.data: true
bootstrap.memory_lock: false
bootstrap.system_call_filter: false
network.host: 192.168.2.123
http.port: 9200
discovery.zen.ping.unicast.hosts: ["192.168.2.123", "192.168.2.124", "192.168.2.125"]
discovery.zen.minimum_master_nodes: 2
LOG：
[2019-05-15T09:42:50,824][DEBUG][o.e.a.a.c.n.s.TransportNodesStatsAction] [node1] failed to execute on node [LSmq2wVeTVKroGwqg4jcZw]
org.elasticsearch.transport.RemoteTransportException: [node3][192.168.2.125:9300][cluster:monitor/nodes/stats[n]]
Caused by: org.apache.lucene.store.AlreadyClosedException: Underlying file changed by an external force at 2019-05-15T01:32:07Z, (lock=NativeFSLock(path=/opt/elkdata/nodes/0/node.lock,impl=sun.nio.ch.FileLockImpl[0:9223372036854775807 exclusive valid],creationTime=2019-05-15T01:32:55Z))
at org.apache.lucene.store.NativeFSLockFactory$NativeFSLock.ensureValid(NativeFSLockFactory.java:191) ~[lucene-core-7.7.0.jar:7.7.0 8c831daf4eb41153c25ddb152501ab5bae3ea3d5 - jimczi - 2019-02-04 23:16:28]
at org.elasticsearch.env.NodeEnvironment.assertEnvIsLocked(NodeEnvironment.java:1022) ~[elasticsearch-6.7.0.jar:6.7.0]
I don't know what this log means？ And what do I need to do?
THANKS!