# Calculate time difference between two logs with unique ID

**URL:** <https://discuss.elastic.co/t/calculate-time-difference-between-two-logs-with-unique-id/82333>\
**Category:** Logstash\
**Created:** [April 13, 2017, 5:16pm UTC](https://discuss.elastic.co/t/calculate-time-difference-between-two-logs-with-unique-id/82333 "2017-04-13T17:16:09Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![michaeleino](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/michaeleino/32/17349_2.png) [@michaeleino](https://discuss.elastic.co/u/michaeleino)\
**Post date:** [April 13, 2017, 5:16pm UTC](https://discuss.elastic.co/t/calculate-time-difference-between-two-logs-with-unique-id/82333/1 "2017-04-13T17:16:09Z")

</div>

hello all,  
I'm in the need to calculate the time difference manually without the elapsed plug-in as my end time varies & may got to 24hour with a very big amount of logs. I managed to get the start time from the old log by:

```
elasticsearch {
                query => "Event:'Sent' AND ID:%{[ID]}"
                index => "mylog*"
                result_size => "1"
                enable_sort => "false"
                fields => { "@timestamp" => "SentTime" }
        }

```

It actually works fine & return the right date in the format "2017-03-29T22:00:03.000Z"

But it's going bad with: return values in this format "January 18th 1970, 08:07:09.056"

```
ruby {
          code => "event.set('[SecondsToDeliver]', event.get('@timestamp').to_f - event.get('SentTime').to_f)"
          add_tag => ["rubyfilter"]
         }

```

I'm sure it is a trivial syntax error but i can't manage to catch it to work with logstash V5.

---

<div class="post-metadata">

**Author:** ![michaeleino](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/michaeleino/32/17349_2.png) [@michaeleino](https://discuss.elastic.co/u/michaeleino)\
**Post date:** [April 16, 2017, 12:30am UTC](https://discuss.elastic.co/t/calculate-time-difference-between-two-logs-with-unique-id/82333/2 "2017-04-16T00:30:31Z")

</div>

this issue is commonly asked in logstash forums, it is really confusing.  
Where is the community help!

I wasted here a lot of time & to save others time, the following syntax works fine with logstash 5.3

```
elasticsearch {
                        hosts => ["Your elastic host"]
                        query => 'Event:"Sent" AND ID:"%{ID}"'
                        fields => { "@timestamp" => "SentTime" }
                        tag_on_failure => ["NoSent_ID"]
                }

             date {
                match => ["[SentTime]", "ISO8601"]
                target => "[SentTime]"
             }
        ruby {
                    init => "require 'time'"
                    code => "duration = (event.get('@timestamp') - event.get('SentTime')) rescue nil; event.set('Log_duration', duration); "
                 }
```

---

<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:** [May 14, 2017, 12:39am UTC](https://discuss.elastic.co/t/calculate-time-difference-between-two-logs-with-unique-id/82333/3 "2017-05-14T00:39:23Z")

</div>

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