Is there any way to downgrade elasticsearch from 8.15 to 7.17 ?
We were using elasticsearch version 7.17.
Now, we upgraded to elasticsearch version and using collectors in backward compatibility mode in order to communicate with elasticsearch 8.15.
Elasticsearch does not support downgradesso you would need to either restore a snapshot taken before you upgraded into a 7.17 cluster or reindex your data back into 7.17.
What would be the reason of downgrading?
we are trying ways to upgrade upgrade elasticsearch in production. we have tested in test environments till now.
if something goes wrong, then we need to revert to previous elasticsearch version
also, what is the approach of elasticsearch during upgrade? is it a blue green approach? is there any downtime during the upgrade of a cluster?
This is not possible, Elasticsearch does not support downgrade, so you need to check everything.
If something goes wrong you will need to fix it before continuing to upgrade.
If you will have a downtime depends on how your cluster is configured, how many nodes you have etc.
Did you read the documentation about upgrade? You need to read this before trying to upgrade.
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ok..
can you tell if the elasticsearch upgrade follows a blue-green approach?
The normal way to upgrade Elasticsearch is to do an in-place rolling upgrade. You should make sure you run the upgrade assistant and test it out first in a test cluster as you can not downgrade. If you want to do blue-green that is something you will need to orchestrate and manage yourself.
Did you check the documentation? It explains how the upgrade works.
You can do a rolling-upgrade where you can upgrade your nodes without having a downtime, but this is not a blue-green approach.
Once you start the upgrade you need to finish as having a cluster with nodes with different versions can lead to other issues.
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