Hi,

in recent versions it works like that:

https://www.elastic.co/guide/en/elasticsearch/reference/current/advanced-configuration.html#set-jvm-options

So in folder jvm.options.d/ add a new file (like "preview.conf") and put "19:--enable-preview" into it. It is basically the same like modifying heap size.

But in general, you can simply use MMapDirectory, the max-map-count setting is only relevant in *huge* (huge means hundreds of huge indexes per node). In that case Java 19's preview features would be recommended.

Uwe

Am 02.01.2023 um 17:41 schrieb S S:
Hi Uwe,

Sorry for the late reply but upgrading the docker image to use OpenJDK was 
easier said that done.

I am not a Java developer/expert so, sorry for the stupid question but, how do 
I specify the --enable-preview flag? ES has got a quite complex way to start so 
I cannot specify the flag on the command line. You suggested to use a 
jvm.properties file but I cannot find anything useful about it when google-ing. 
Where should it be placed? And what should I write in it?

I can see ES recognising OpenJDK 19 while bootstrapping and suggesting to 
enable preview, but it does not suggest how, and I cannot find anything on the 
ES website.

Many thanks.

Seb

On 2 Jan 2023, at 11:48, Uwe Schindler <u...@thetaphi.de> wrote:

Hi,

in general you can still use MMapDirectory. There is no requirement to set 
vm.max_map_count for smaller clusters. The information in Elastics 
documentation is not mandatory and misleading.

If you use newest version of Elasticsearch with Java 19 and you use 
`--enable-preview` in you jvm.properties file, you don't even need to change 
that setting even with larger clusters.

Uwe

Am 02.01.2023 um 11:18 schrieb S S:
We are experimenting with Elastic Search deployed in Azure Container Instances 
(Debian + OpenJDK). The ES indexes are stored into an Azure file share mounted 
via SMB (3.0). The Elastic Search cluster is made up of 4 nodes, each one have 
a separate file share to store the indices.

This configuration has been influenced by some ACIs limitations, specifically:

we cannot set the max_map_count value as we do not have access to the 
underlying host 
(https://www.elastic.co/guide/en/elasticsearch/reference/current/vm-max-map-count.html).
 Unfortunately, this is required to run an ES cluster, therefore we were forced 
to use NIOF
ACI’s storage is ephemera, therefore we had to map volumes to persist the 
indexes. ACIs only allow volume mappings using Azure File Shares, which only 
works with NFS or SMB.

We are experiencing recurring index corruption, specifically a "read past EOF" 
exception. I asked on the Elastic Search forum but the answer I got was a bit generic and 
not really helpful other than confirming that, from ES point of view, ES should work on 
an SMB share as long as it behaves as a local drive. As the underlying exception relates 
to an issue with a Lucene index, I was wondering if you could help out? Specifically, can 
Lucene work on SMB? I can only find sparse information on this configuration and, while 
NFS seems a no-no, for SMB is not that clear. Below is the exception we are getting.

java.io.IOException: read past EOF: 
NIOFSIndexInput(path="/bitnami/elasticsearch/data/indices/mS2bUbLtSeG0FSAMuKX7JQ/0/index/_ldsn_1.fnm")
 buffer: java.nio.HeapByteBuffer[pos=0 lim=1024 cap=1024] chunkLen: 1024 end: 2331: 
NIOFSIndexInput(path="/bitnami/elasticsearch/data/indices/mS2bUbLtSeG0FSAMuKX7JQ/0/index/_ldsn_1.fnm")
               at 
org.apache.lucene.store.NIOFSDirectory$NIOFSIndexInput.readInternal(NIOFSDirectory.java:200)
 ~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.store.BufferedIndexInput.refill(BufferedIndexInput.java:291) 
~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.store.BufferedIndexInput.readByte(BufferedIndexInput.java:55) 
~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.store.BufferedChecksumIndexInput.readByte(BufferedChecksumIndexInput.java:39)
 ~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.codecs.CodecUtil.readBEInt(CodecUtil.java:667) 
~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.codecs.CodecUtil.checkHeader(CodecUtil.java:184) 
~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.codecs.CodecUtil.checkIndexHeader(CodecUtil.java:253) 
~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.codecs.lucene90.Lucene90FieldInfosFormat.read(Lucene90FieldInfosFormat.java:128)
 ~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.index.SegmentReader.initFieldInfos(SegmentReader.java:205) 
~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.index.SegmentReader.<init>(SegmentReader.java:156) 
~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.index.ReadersAndUpdates.createNewReaderWithLatestLiveDocs(ReadersAndUpdates.java:738)
 ~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.index.ReadersAndUpdates.swapNewReaderWithLatestLiveDocs(ReadersAndUpdates.java:754)
 ~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.index.ReadersAndUpdates.writeFieldUpdates(ReadersAndUpdates.java:678)
 ~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.index.ReaderPool.writeAllDocValuesUpdates(ReaderPool.java:251)
 ~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.index.IndexWriter.writeReaderPool(IndexWriter.java:3743) 
~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.index.IndexWriter.getReader(IndexWriter.java:591) 
~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.index.StandardDirectoryReader.doOpenFromWriter(StandardDirectoryReader.java:381)
 ~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.index.StandardDirectoryReader.doOpenIfChanged(StandardDirectoryReader.java:355)
 ~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.index.StandardDirectoryReader.doOpenIfChanged(StandardDirectoryReader.java:345)
 ~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.index.FilterDirectoryReader.doOpenIfChanged(FilterDirectoryReader.java:112)
 ~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.index.DirectoryReader.openIfChanged(DirectoryReader.java:170) 
~[lucene-core-9.3.0.jar:?]
               at 
org.elasticsearch.index.engine.ElasticsearchReaderManager.refreshIfNeeded(ElasticsearchReaderManager.java:48)
 ~[elasticsearch-8.4.1.jar:?]
               at 
org.elasticsearch.index.engine.ElasticsearchReaderManager.refreshIfNeeded(ElasticsearchReaderManager.java:27)
 ~[elasticsearch-8.4.1.jar:?]
               at 
org.apache.lucene.search.ReferenceManager.doMaybeRefresh(ReferenceManager.java:167)
 ~[lucene-core-9.3.0.jar:?]
               at 
org.apache.lucene.search.ReferenceManager.maybeRefreshBlocking(ReferenceManager.java:240)
 ~[lucene-core-9.3.0.jar:?]
               at 
org.elasticsearch.index.engine.InternalEngine$ExternalReaderManager.refreshIfNeeded(InternalEngine.java:355)
 ~[elasticsearch-8.4.1.jar:?]
               at 
org.elasticsearch.index.engine.InternalEngine$ExternalReaderManager.refreshIfNeeded(InternalEngine.java:335)
 ~[elasticsearch-8.4.1.jar:?]
               at 
org.apache.lucene.search.ReferenceManager.doMaybeRefresh(ReferenceManager.java:167)
 ~[lucene-core-9.3.0.jar:?]
Many thanks.

Seb
--
Uwe Schindler
Achterdiek 19, D-28357 Bremen
https://www.thetaphi.de
eMail: u...@thetaphi.de


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