# Can we add field in \_grokparsefailure if block?

**URL:** <https://discuss.elastic.co/t/can-we-add-field-in--grokparsefailure-if-block/100101>\
**Category:** Logstash\
**Created:** [September 11, 2017, 4:53pm UTC](https://discuss.elastic.co/t/can-we-add-field-in--grokparsefailure-if-block/100101 "2017-09-11T16:53:40Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![kant.gaurav](https://avatars.discourse-cdn.com/v4/letter/k/e47c2d/32.png) [@kant.gaurav](https://discuss.elastic.co/u/kant.gaurav)\
**Post date:** [September 11, 2017, 4:53pm UTC](https://discuss.elastic.co/t/can-we-add-field-in--grokparsefailure-if-block/100101/1 "2017-09-11T16:53:40Z")

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is it possible like below?

if "\_grokparsefailure" in [tags] {  
add\_field =\> ["exceptionClass", "other"]  
drop {}  
}

right now it is throwing error.

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**Author:** ![magnusbaeck](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/magnusbaeck/32/44943_2.png) [@magnusbaeck](https://discuss.elastic.co/u/magnusbaeck)\
**Post date:** [September 11, 2017, 6:23pm UTC](https://discuss.elastic.co/t/can-we-add-field-in--grokparsefailure-if-block/100101/2 "2017-09-11T18:23:16Z")

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Put the `add_field` line inside a mutate filter.

But what's the point of adding a tag to an event if you're deleting it on the next line?

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<div class="post-metadata">

**Author:** ![kant.gaurav](https://avatars.discourse-cdn.com/v4/letter/k/e47c2d/32.png) [@kant.gaurav](https://discuss.elastic.co/u/kant.gaurav)\
**Post date:** [September 11, 2017, 6:53pm UTC](https://discuss.elastic.co/t/can-we-add-field-in--grokparsefailure-if-block/100101/3 "2017-09-11T18:53:50Z")

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sorry i mentioned drop by mistake. i dont wanna drop that line, just add a new field in case match fails.

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**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [October 9, 2017, 6:54pm UTC](https://discuss.elastic.co/t/can-we-add-field-in--grokparsefailure-if-block/100101/4 "2017-10-09T18:54:02Z")

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