# StackOverflowError in Lucene
**URL:** https://discuss.elastic.co/t/stackoverflowerror-in-lucene/133659
**Category:** Elasticsearch
**Created:** [May 29, 2018, 10:25am UTC](https://discuss.elastic.co/t/stackoverflowerror-in-lucene/133659 "2018-05-29T10:25:53Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@a.korshunov](https://discuss.elastic.co/u/a.korshunov)
#### Post date: [May 29, 2018, 10:25am UTC](https://discuss.elastic.co/t/stackoverflowerror-in-lucene/133659/1 "2018-05-29T10:25:53Z")
Hi!
I have cluster, that includes 4 nodes:
- ubuntu-es5 (rack-1),
- ubuntu-es6 (rack-1),
- ubuntu-es7 (rack-2),
- ubuntu-es8 (rack-2).
In ubuntu-es8 StackOverflowError occured, that broke the whole cluster:
> [2018-05-29T12:46:47,707][ERROR][o.e.b.ElasticsearchUncaughtExceptionHandler] [ubuntu-es8] fatal error in thread [elasticsearch[ubuntu-es8][search][T#8]], exiting
> java.lang.StackOverflowError: null
> at org.apache.lucene.util.graph.GraphTokenStreamFiniteStrings.articulationPointsRecurse(GraphTokenStreamFiniteStrings.java:278) ~[lucene-core-7.2.1.jar:7.2.1 b2b6438b37073bee1fca40374e85bf91aa457c0b - ubuntu - 2018-01-10 00:48:43]
> at org.apache.lucene.util.graph.GraphTokenStreamFiniteStrings.articulationPointsRecurse(GraphTokenStreamFiniteStrings.java:278) ~[lucene-core-7.2.1.jar:7.2.1 b2b6438b37073bee1fca40374e85bf91aa457c0b - ubuntu - 2018-01-10 00:48:43]
> at org.apache.lucene.util.graph.GraphTokenStreamFiniteStrings.articulationPointsRecurse(GraphTokenStreamFiniteStrings.java:278) ~[lucene-core-7.2.1.jar:7.2.1 b2b6438b37073bee1fca40374e85bf91aa457c0b - ubuntu - 2018-01-10 00:48:43]
What was wrong? How to avoid this behavior. As i remember, this error is know, and was prommised to fix in Elastcisearch 6.0
Elasticsearch version:
> ```
> {
> "name" : "ubuntu-es5",
> "cluster_name" : "company-search-cluster-2",
> "cluster_uuid" : "SAwP5j5jSS6bzZGxl6GLaQ",
> "version" : {
> "number" : "6.2.3",
> "build_hash" : "c59ff00",
> "build_date" : "2018-03-13T10:06:29.741383Z",
> "build_snapshot" : false,
> "lucene_version" : "7.2.1",
> "minimum_wire_compatibility_version" : "5.6.0",
> "minimum_index_compatibility_version" : "5.0.0"
> },
> "tagline" : "You Know, for Search"
> }
>
> ```
Thanks!
---
### Author:  [@thiago](https://discuss.elastic.co/u/thiago)
#### Post date: [May 30, 2018, 6:05pm UTC](https://discuss.elastic.co/t/stackoverflowerror-in-lucene/133659/2 "2018-05-30T18:05:41Z")
Do you know that search query that triggered this error?
---
### Author:  [@a.korshunov](https://discuss.elastic.co/u/a.korshunov)
#### Post date: [May 31, 2018, 6:42am UTC](https://discuss.elastic.co/t/stackoverflowerror-in-lucene/133659/3 "2018-05-31T06:42:00Z")
Unfortunately, don't know. We have index with 765 lines of mapping, 10K requests per day. We are using .NET library and message in error-log of our application is not meaningful: "System.NullReferenceException: Object reference not set to an instance of an object.". We don't use regex-queries, but our analyzers use regex. For example:
```
public class DigitCharFilter : PatternReplaceCharFilter
{
public DigitCharFilter()
{
Pattern = "\\D+";
Replacement = "";
}
}
public class WordDigitCharFilter : PatternReplaceCharFilter
{
public WordDigitCharFilter()
{
Pattern = "[^0-9a-zA-Zа-яА-ЯёЁ]";
Replacement = "";
}
}
public class WordDigitTokenizer : PatternTokenizer
{
public WordDigitTokenizer()
{
Pattern = "[^0-9a-zA-Zа-яА-ЯёЁ]";
}
}
```
May be regex in my analyzers are wrong?
Thanks!
---
### Author:  [@thiago](https://discuss.elastic.co/u/thiago)
#### Post date: [May 31, 2018, 12:25pm UTC](https://discuss.elastic.co/t/stackoverflowerror-in-lucene/133659/4 "2018-05-31T12:25:02Z")
These patterns does not seems harmful. Do you have the complete stacktrace? I would like to take a look in how it starts.
---
### Author:  [@a.korshunov](https://discuss.elastic.co/u/a.korshunov)
#### Post date: [May 31, 2018, 3:09pm UTC](https://discuss.elastic.co/t/stackoverflowerror-in-lucene/133659/5 "2018-05-31T15:09:31Z")
The full log of the failed node available on the following link: [https://yadi.sk/d/AdR9wV4\_3WkxHm](https://yadi.sk/d/AdR9wV4_3WkxHm)
---
### Author:  [@thiago](https://discuss.elastic.co/u/thiago)
#### Post date: [June 1, 2018, 12:31pm UTC](https://discuss.elastic.co/t/stackoverflowerror-in-lucene/133659/6 "2018-06-01T12:31:23Z")
Unfortunately this log is not helping much and we would need to see the actual query to understand more. We suspect that the source of this is a really big query with thousands of words may be triggering this problem.
One thing that you can do that could help tracking queries is to enable [slowlogs](https://www.elastic.co/guide/en/elasticsearch/reference/current/index-modules-slowlog.html). This wouldn't allow logging the actual query since it would get killed before getting a chance to be logged, but at least would log the other queries would could be similar.
---
### Author:  [@a.korshunov](https://discuss.elastic.co/u/a.korshunov)
#### Post date: [June 1, 2018, 3:10pm UTC](https://discuss.elastic.co/t/stackoverflowerror-in-lucene/133659/7 "2018-06-01T15:10:10Z")
Thanks for reply!
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [June 29, 2018, 3:10pm UTC](https://discuss.elastic.co/t/stackoverflowerror-in-lucene/133659/8 "2018-06-29T15:10:15Z")
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