Use of field capabilities API can print warnings related to _uid field

[tomcallahan]

Elasticsearch version (bin/elasticsearch --version): 6.2.0 and 6.2.1

Plugins installed: [ x-pack ]

JVM version (java -version): Any

OS version (uname -a if on a Unix-like system): Any

Description of the problem including expected versus actual behavior:

To be able to use the field capabilities without warnings.

Steps to reproduce:

In certain cases, Kibana will trigger warnings in the elasticsearch log through its use of the Field Capabilities API. This happens in particular any time an index pattern is added or refreshed in Kibana. Kibana makes this API call in particular:

[1] Run the following command

GET /*/_field_caps?fields=*&ignore_unavailable=true&allow_no_indices=false

[2] Which will yield the following warnings in the log:

[2018-05-15T16:06:05,154][WARN ][o.e.d.i.m.UidFieldMapper ] Fielddata access on the _uid field is deprecated, use _id instead

This is because in MappedFieldType.java we call fielddataBuilder() to determine whether or not the field can be aggregated on:

    public boolean isAggregatable() {
        try {
            fielddataBuilder("");
            return true;
        } catch (IllegalArgumentException e) {
            return false;
        }
    }

This is likely spewing warnings for a bunch of customers. Kudos to @gmoskovicz for hunting this down.

[jasontedor]

What version of Elasticsearch is this? Please fill out the template when posting an issue.

[elasticmachine]

Pinging @elastic/es-search-aggs

[Constantin07]

I do confirm that this issue is reproducible on ES & Kibana versions 6.2.4.

[Constantin07]

If I run a Refresh field list in Kibana under Management>Index Patterns I'm also getting a lot of below warning messages on all production nodes despite _uid is not used at all.

[2018-05-16T10:55:28,220][WARN ][o.e.d.i.m.UidFieldMapper ] Fielddata access on the _uid field is deprecated, use _id instead
[2018-05-16T10:55:28,220][WARN ][o.e.d.i.m.UidFieldMapper ] Fielddata access on the _uid field is deprecated, use _id instead
[2018-05-16T10:55:28,220][WARN ][o.e.d.i.m.UidFieldMapper ] Fielddata access on the _uid field is deprecated, use _id instead
[2018-05-16T10:55:28,221][WARN ][o.e.d.i.m.UidFieldMapper ] Fielddata access on the _uid field is deprecated, use _id instead
[2018-05-16T10:55:28,222][WARN ][o.e.d.i.m.UidFieldMapper ] Fielddata access on the _uid field is deprecated, use _id instead
[2018-05-16T10:55:28,222][WARN ][o.e.d.i.m.UidFieldMapper ] Fielddata access on the _uid field is deprecated, use _id instead
[2018-05-16T10:55:28,224][WARN ][o.e.d.i.m.UidFieldMapper ] Fielddata access on the _uid field is deprecated, use _id instead
[2018-05-16T11:02:02,818][WARN ][o.e.d.i.m.UidFieldMapper ] Fielddata access on the _uid field is deprecated, use _id instead
[2018-05-16T11:02:02,818][WARN ][o.e.d.i.m.UidFieldMapper ] Fielddata access on the _uid field is deprecated, use _id instead

[gmoskovicz]

@Constantin07 Thanks for the heads up. We are aware of this and to give you some context, the Refresh Index Pattern action is going to end up calling the _field_caps endpoint, which causes this Warning message to be shown.

Keep an eye on this issue as it should be the fix for that as well.

[jimczi]

Thanks for reporting @gmoskovicz @tomcallahan
This is fixed by #30651