ELK upgrade from 6.6 to 7.4.2

HI,

I am currently planning an upgrade from ELK 6.6 to 7.4.2 but I would like to do this as rolling upgrade because having the entire cluster restart or down is not an option. According to the documentation, full cluster restart seems to be the only possible way of upgrading directly from 6.6 to 7.4.2:
https://www.elastic.co/guide/en/elasticsearch/reference/current/restart-upgrade.html

I would like to know if a rolling upgrade is possible and if yes:

  • What are some of the things I might need to keep in mind for this procedure
  • Is there any documentation for the best possible practices to be followed for such an rolling upgrade between major versions?
  • How should the data migration be taken care of when upgrading between 6.6 to 7.4? Can we just follow normal rolling upgrade steps or do we need reindexing or some procedure like that to be followed?

Thanks,
Radhika

No, a rolling upgrade is not possible from 6.6 all the way to 7.4 in one step. The docs list the permitted rolling upgrade paths.

The best practices are documented at the link you shared.

Hi David,
Thank you for confirming regarding the rolling upgrade. So the only possible way is to either:

  • Do a rolling upgrade of the 6.6 cluster to 6.7 or 6.8 prior to beginning the rolling up grade to 7.4.2
  • Full cluster restart to directly upgrade it from 6.6 to 7.4 as according to the doc

Is re-indexing required for 6.6 indices, if we move it to 7.4 or is that only required for indexes prior to 6.x like 5.x or so on?

This is also answered in the very same page of the docs:

Elasticsearch can read indices created in the previous major version. If you have indices created in 5.x or before, you must reindex or delete them before upgrading to 7.4.2.