Keep getting "Index Lifecycle error"

[Apollyon]

Hello,
I am using ELK 7.5.1.

I keep seeing this error when going on the Index Management page.

illegal_argument_exception: source alias [rollover-index] does not point to a write index

The Lifecycle Policy is pointing to the correct one.
In the Index Template that is in use shows in the settings the index.lifecycle.name and index.lifecycle.rollover_alias. However, when getting to the Aliases section of the template set up. When I go to add the alias with the below config. After saving the template and viewing the alias set up again it only shows the alias name and not the "is_write_index" setting.

"rollover-index": { "is_write_index": true }

Also, when trying to do this, just before saving the template. On going to the Request tab, is displays the full input of the alias setting. Shown below. But this also shows the same behavior as above.

"aliases": {
  "rollover-index": { "is_write_index": true }
}

Would there be a work around with this or is there a particular way to set up this?
Probably me being slow as normal but have been racking my head with this and tried everything I could think of.

Thank you in advance

[bhavyarm]

@alisongoryachev @cjcenizal can we get some help here?

Thanks,
Bhavya

[gbrown (Gordon Brown)]

A couple things:

1. The is_write_index alias config should not be set in the template, it should be set in the create index request used to create the first index. If you leave that in the template, you will experience errors when the second index is created. This is a bit counterintuitive, I'll admit - basically, ILM creates the new index, and then once the index has been fully created, swaps which index is the write index, and having the is_write_index config in the template interferes with this process.
2. It's not clear from your post whether you just changed the template, or updated the index itself. Just changing the template will not retroactively update the index if it's already been created. If you just changed the template, you'll need to update the index that already exists.