Warning on ELK version change and volume data index mismatch between Lucene and volume

[mburaksayici]

Update readme for elasticsearch volume warning during version change in .env ELK_VERSION

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What does this implement/fix? Explain your changes.

Spent too much time experimenting, I've realised that errors caused by ELK version change. When user runs ELK, volume for elastic becomes already created with 8.8.0. Then when you try to switch <8.6.0, required Lucene version for indexing becomes different.

Does this close any currently open issues?

No

Any relevant logs, error output, etc?

java.lang.IllegalArgumentException: Could not load codec 'Lucene95'. Did you forget to add lucene-backward-codecs.jar?

Any other comments?

It's not confusing, however volume attached to docker is not on local, so it took time for me to realise that. I'm newbie to ELK, so I didn't know Lucene, indexing, elastic stores in docker volume not on local etc.

Where has this been tested?

Ubuntu 20.04, on a typical Amazon EC2 server

[mburaksayici]

And may be during the prune inside Makefile, deleting the elastic volume can be an option

[sherifabdlnaby]

@mburaksayici Can we move this to the notes section? I believe it should be reworded that Downgrades are not always
supported, and if you don't care about the data you can remove the volumes.