# Writing Filebeat Multiline Pattern for Unusual Log Format

**URL:** <https://discuss.elastic.co/t/writing-filebeat-multiline-pattern-for-unusual-log-format/185695>\
**Category:** Beats\
**Tags:** filebeat\
**Created:** [June 13, 2019, 3:47pm UTC](https://discuss.elastic.co/t/writing-filebeat-multiline-pattern-for-unusual-log-format/185695 "2019-06-13T15:47:10Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![DougR](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dougr/32/48095_2.png) [@DougR](https://discuss.elastic.co/u/DougR)\
**Post date:** [June 13, 2019, 3:47pm UTC](https://discuss.elastic.co/t/writing-filebeat-multiline-pattern-for-unusual-log-format/185695/1 "2019-06-13T15:47:10Z")

</div>

As I'm instrumenting a new application for log monitoring via `filebeat`, I came across a log format I've never seen before.

It's a multiline log format, but instead of just continuing, each continuing line contains a copy of the header for the log entry, as follows:

```
[Thread |2640|D] 2019-06-13 00:00:00.021-05:00 Line 1 of message:
[Thread |2640|H] 2019-06-13 00:00:00.021-05:00 Line 2 of message:
[Thread |2640|H] 2019-06-13 00:00:00.021-05:00 Line 3 of message
[Thread |2640|H] 2019-06-13 00:00:00.021-05:00 Line 4 of message
[Thread |2640|H] 2019-06-13 00:00:00.021-05:00 Line 5 of message

```

Taking the following example of a line header:

```
[Thread |2640|D]

```

- `Thread` is obvious - It represents the thread name.
- `2640` - This is actually a 2-byte hex number that appears to be a message ID. However there are some duplicates of this between consecutive messages, so I'm not certain about this.
- `D` - This is a single-character code, that appears to be message severity, i.e., `DEBUG`, in this case. However, subsequent entries that are clearly part of the same message have a code of `H`, which appears to indicate a continuing line.

My questions are:

- Is it possible to write a filebeat multi-line pattern to concatenate these lines? What would that pattern look like?
- Assuming that I can write a filebeat multi-line rule to concatenate these lines, how would I write a logstash rule to clean up the subsequent lines, if possible?

---

<div class="post-metadata">

**Author:** ![DougR](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dougr/32/48095_2.png) [@DougR](https://discuss.elastic.co/u/DougR)\
**Post date:** [June 13, 2019, 3:59pm UTC](https://discuss.elastic.co/t/writing-filebeat-multiline-pattern-for-unusual-log-format/185695/2 "2019-06-13T15:59:11Z")

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It turns out I was incorrect regarding `H` designating a continuing entry (I haven't figured out what it designates yet).

However, continuing entries are indented, after the line header, so the following multiline pattern works in the `filebeat.yml`:

```
^\[.*\|[0-9a-fA-F]{4}\|[A-Z]\] +[0-9]{4}-[0-9]{2}-[0-9]{2} +[0-9]{2}:[0-9]{2}:[0-9]{2}.[0-9]{3}-[0-9]{2}:[0-9]{2} [^]

```

Additionally, in Logstash, I wrote the following `mutate` rule to remove subsequent line headers from the multiline entry. This is placed **before** the `grok`, which parses the entry, but I'm not certain that the location matters:

```
if "multiline" in [log][flags] {
    mutate {
      # Clean up headers on subsequent multilines.
      gsub => ["message",

               # Match 4 spaces at end to avoid replacing timestamp at beginning of log message.
               "\[\S*\s*\|[0-9a-fA-F]{4}\|[\S]\]\s+[0-9]{4}-[0-9]{2}-[0-9]{2}\s+[0-9]{2}:[0-9]{2}:[0-9]{2}\.[0-9]{3}-[0-9]{2}:[0-9]{2}\s{4}",
               " "]
    }
}
```

---

<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:** [July 11, 2019, 3:59pm UTC](https://discuss.elastic.co/t/writing-filebeat-multiline-pattern-for-unusual-log-format/185695/3 "2019-07-11T15:59:11Z")

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