Can not connect to Elasticsearch server

hi all

I'm using Axon ivy 6.3 on Linux server. Sometime i get this exception (after deployment somehow):

 Caused by: ch.ivyteam.ivy.business.data.store.search.internal.elasticsearch.ElasticsearchException: Cannot reach Elasticsearch server
    at ch.ivyteam.ivy.business.data.store.search.internal.elasticsearch.JestOperation.execute(JestOperation.java:44)
    at ch.ivyteam.ivy.business.data.store.search.internal.elasticsearch.JestSearcher.search(JestSearcher.java:32)
    at ch.ivyteam.ivy.business.data.store.search.internal.ResultImpl.execute(ResultImpl.java:36)
    at ch.ivyteam.ivy.business.data.store.search.internal.QueryImpl.raw(QueryImpl.java:135)
    at ch.ivyteam.ivy.business.data.store.search.internal.QueryImpl.executeQuery(QueryImpl.java:179)
    at ch.ivyteam.ivy.business.data.store.search.internal.ExecutorImpl.execute(ExecutorImpl.java:18)
    at ch.ivyteam.ivy.business.data.store.search.internal.QueryImpl.execute(QueryImpl.java:115)
    at ch.axonivy.fintech.standard.dossier.DossierIdGenerator.initializeSeed(DossierIdGenerator.java:64)
    at ch.axonivy.fintech.standard.dossier.DossierIdGenerator.nextId(DossierIdGenerator.java:43)
    at ch.axonivy.fintech.abs.dossier.AbsDossierService.generateCobId(AbsDossierService.java:57)
    at sun.reflect.GeneratedMethodAccessor9141.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at ch.ivyteam.ivy.scripting.internal.types.IvyJavaMethod.invokeImpl(IvyJavaMethod.java:73)
    ... 211 more
Caused by: io.searchbox.client.config.exception.CouldNotConnectException: Could not connect to http://localhost:19200
    at io.searchbox.client.http.JestHttpClient.execute(JestHttpClient.java:59)
    at ch.ivyteam.ivy.business.data.store.search.internal.elasticsearch.JestOperation.execute(JestOperation.java:37)
    ... 224 more
Caused by: org.apache.http.conn.HttpHostConnectException: Connect to localhost:19200 [localhost/127.0.0.1] failed: Connection refused
    at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.java:158)
    at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.connect(PoolingHttpClientConnectionManager.java:353)
    at org.apache.http.impl.execchain.MainClientExec.establishRoute(MainClientExec.java:380)
    at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:236)
    at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:184)
    at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:88)
    at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110)
    at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:184)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:82)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:107)
    at io.searchbox.client.http.JestHttpClient.executeRequest(JestHttpClient.java:109)
    at io.searchbox.client.http.JestHttpClient.execute(JestHttpClient.java:56)
    ... 225 more
Caused by: java.net.ConnectException: Connection refused
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:589)
    at org.apache.http.conn.socket.PlainConnectionSocketFactory.connectSocket(PlainConnectionSocketFactory.java:74)
    at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.java:141)
    ... 236 more

After restarting server, it's seem to work again.

The exception is clear but we don't know rootcause yet. Does anyone get same issue? and do you have any hints for it?

Updated: i have deployed several ivy engine on same physical server, i think there is some instance of elasticservers as well. Could it be a confliction there?

Thanks in advance