Improve "put template" error message and documentation of disallowed characters

[hatharom]

Couldn't find anything in the documentation.
The examples are with *.

I have tried with ? - while PUT-ing a template - which was rejected:
"index_patterns": ["test?"]
response:

"reason": "index_template [temp1] invalid, cause [Validation Failed: 1: template must not contain the following characters [ , ", *, \, <, |, ,, >, /, ?];]"

which is interesting because the error message contains the * as well.

How can I define an index pattern for this?: prefix-anyword-number
right now I am doing this: prefix-- , which is terrible imo.

Or is it only supports the asterisk?

[elasticmachine]

Pinging @elastic/es-core-features (:Core/Features/Indices APIs)

[elasticmachine]

Pinging @elastic/es-docs (>docs)

[cbuescher]

Hi @hatharom,

you can find the code checking the validity of the index patters in MetaDataIndexTemplateService. Looking at this, the following characters seem to be forbidden:
, ,, #, _ and the ones mentioned in Strings, with the notable exception of the asterisk (see https://github.com/elastic/elasticsearch/blob/7.6/server/src/main/java/org/elasticsearch/common/Strings.java#L389). The error message is indeed misleading here, we should correct that and maybe also document the (dis)allowed characters better.

[cbuescher]

@hatharom hope you don't mind me changing the subject of this issue, so its clear its not just a usage question. For pure usage questions we generally prefer asking in the support forums over at https://discuss.elastic.co so we can keep Github issues only for bug reports and feature requests, but since the error message is misleading and the index_patterns documentation probably needs updating I think we should keep this open.

[abprash]

Is someone working on this ? @hatharom , @cbuescher . If not, can i work on this?

[cbuescher]

@abprash sorry, I think this was adressed by #56170 and this issue can be closed.