# Interpolation in string should be happening but isn't

**URL:** <https://discuss.elastic.co/t/interpolation-in-string-should-be-happening-but-isnt/266275>\
**Category:** Logstash\
**Created:** [March 4, 2021, 6:35pm UTC](https://discuss.elastic.co/t/interpolation-in-string-should-be-happening-but-isnt/266275 "2021-03-04T18:35:00Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Supermathie](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/supermathie/32/44936_2.png) [@Supermathie](https://discuss.elastic.co/u/Supermathie)\
**Post date:** [March 4, 2021, 6:35pm UTC](https://discuss.elastic.co/t/interpolation-in-string-should-be-happening-but-isnt/266275/1 "2021-03-04T18:35:00Z")

</div>

I have the following document that went through logstash (v7.10.2):

 ![image](https://us1.discourse-cdn.com/elastic/original/3X/c/d/cdf54b421253105bcde28346a00ce77c13916983.png)

and `message` was constructed with the snippet:

```nohighlight
    mutate {
      add_field => { "message" => "%{[http][request][method]} %{[url][domain]}%{[url][original]}" }
    }

```

but obviously these values didn't get interpolated - what might cause this?

---

<div class="post-metadata">

**Author:** ![Supermathie](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/supermathie/32/44936_2.png) [@Supermathie](https://discuss.elastic.co/u/Supermathie)\
**Post date:** [March 4, 2021, 6:59pm UTC](https://discuss.elastic.co/t/interpolation-in-string-should-be-happening-but-isnt/266275/2 "2021-03-04T18:59:22Z")

</div>

This appears to be due to having fields in my elastic document as dot-separated:

```auto
…
    "http.request.method": "GET",
    "discourse.time.redis": 0.018657,
    "url.domain": "test.example.net",
…

```

Reading up about this it seems that the Kibana grok debugger behaves _completely differently_ than logstash… which is exactly opposite what you want from a debugging tool?

My patterns are using e.g.:

```auto
%{DATA:url.original}

```

syntax which gives the correct (nested values) result in the grok debugger, but a single dot-separated field name with logstash.

The bracket patterns in kibana:

```auto
%{DATA:[url][original]}

```

give e.g.:

```auto
…
  "[url][domain]": "vdc00ent1.staged-by-discourse.com",
…

```

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [April 1, 2021, 7:00pm UTC](https://discuss.elastic.co/t/interpolation-in-string-should-be-happening-but-isnt/266275/3 "2021-04-01T19:00:13Z")

</div>

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