# How can I compare current value in my stream with previous value in tickscript?

**URL:** <https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006>\
**Category:** InfluxDB 2\
**Tags:** influxdb, telegraf, kapacitor, chronograf, influxql\
**Created:** [March 13, 2019, 9:43pm UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006 "2019-03-13T21:43:19Z")\
**Posts on this page:** 20\
**Page:** 1

<div class="post-metadata">

**Author:** ![gvkarthik93](https://avatars.discourse-cdn.com/v4/letter/g/49beb7/32.png) [@gvkarthik93](https://community.influxdata.com/u/gvkarthik93)\
**Post date:** [March 13, 2019, 9:43pm UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/1 "2019-03-13T21:43:19Z")

</div>

I am working on kapacitor alerts to generate alerts on data in influxDB. I am receiving a new value from the stream when a request has been made. I want to compare the current value in my stream I received with the previous value I received just before it to see if current value is greater than previous value or not. If it is greater than previous value, then I want to generate an alert on chronograf using kapacitor and tickscript.

How do I achieve this in tickscript? Any help is highly appreciated. I am new to tickscript.

---

<div class="post-metadata">

**Author:** ![MarcV](https://sea1.discourse-cdn.com/flex023/user_avatar/community.influxdata.com/marcv/32/7676_2.png) [@MarcV](https://community.influxdata.com/u/MarcV)\
**Post date:** [March 13, 2019, 11:35pm UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/2 "2019-03-13T23:35:42Z")

</div>

Hi ,  
maybe the derivativenode can be used ,  
If the current value is greater than the previous value the derivative will be \> 0 ,

[DerivativeNode](https://docs.influxdata.com/kapacitor/v1.5/nodes/derivative_node/)

Computes the derivative via: (current - previous ) / ( time\_difference / unit)

Update : maybe this is also an option … [InfluxQLNode | Kapacitor 1.5 Documentation](https://docs.influxdata.com/kapacitor/v1.5/nodes/influx_q_l_node/#difference)

---

<div class="post-metadata">

**Author:** ![gvkarthik93](https://avatars.discourse-cdn.com/v4/letter/g/49beb7/32.png) [@gvkarthik93](https://community.influxdata.com/u/gvkarthik93)\
**Post date:** [March 14, 2019, 4:36am UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/3 "2019-03-14T04:36:20Z")

</div>

@MarcV Can you give the tickscript? I am new to it. I need the tickscript for fetching the current and previous values and computing this derivative.

---

<div class="post-metadata">

**Author:** ![MarcV](https://sea1.discourse-cdn.com/flex023/user_avatar/community.influxdata.com/marcv/32/7676_2.png) [@MarcV](https://community.influxdata.com/u/MarcV)\
**Post date:** [March 14, 2019, 6:53am UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/4 "2019-03-14T06:53:37Z")

</div>

Hi the link I posted earlier contains a part of the script you need.  
Does it help you to create the script ?

> **[DerivativeNode | Kapacitor 1.6 Documentation](https://docs.influxdata.com/kapacitor/v1.5/nodes/derivative_node/)**
>
> DerivativeNode computes the derivative of a stream or batch. The derivative is computed on a single field and behaves similarly to the InfluxQL derivative function.

---

<div class="post-metadata">

**Author:** ![MarcV](https://sea1.discourse-cdn.com/flex023/user_avatar/community.influxdata.com/marcv/32/7676_2.png) [@MarcV](https://community.influxdata.com/u/MarcV)\
**Post date:** [March 14, 2019, 10:47am UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/5 "2019-03-14T10:47:25Z")

</div>

Hi here is an example , best regards ,

create a script task1.tick with the following content

```
dbrp "telegraf"."autogen"

stream

 |from()
   .measurement('numbers')

 |derivative('value')

 |alert()
  .info(lambda:"value" > 0 )

```

to create the task in kapacitor

```
kapacitor define task1 -tick task1.tick

```

to enable the task in kapacitor

```
kapacitor enable task1

```

And to test the alert , you can start the influx command line interface and insert some points …

```
influx -database telegraf

insert numbers value=1
insert numbers value=1
insert numbers value=2

```

and to monitor the task

you can use

```
kapacitor watch task1   

```

good luck 🙂

2019-03-14T11:01:00Z

---

<div class="post-metadata">

**Author:** ![gvkarthik93](https://avatars.discourse-cdn.com/v4/letter/g/49beb7/32.png) [@gvkarthik93](https://community.influxdata.com/u/gvkarthik93)\
**Post date:** [March 14, 2019, 6:51pm UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/6 "2019-03-14T18:51:44Z")

</div>

Hey @MarcV I’ve been using this code and it’s not sending an alert. It’s the same as what you did. I am not sure why. Could you please give your feedback?

```
var data = stream
    |from()
        .database(db)
        .retentionPolicy(rp)
        .measurement(measurement)
        .groupBy(groupBy)
        .where(whereFilter)
    |derivative('QCOUNT')
        .as('value')

var trigger = data
    |alert()
        .crit(lambda: "value" > crit)
        .message(message)
        .id(idVar)
        .idTag(idTag)
        .levelTag(levelTag)
        .messageField(messageField)
        .durationField(durationField)
        .details('''
        <b>QCOUNT</b> [{{ index .Fields "QCOUNT" }}]</br>
        ''')
        .email()
        .to('karthik@gmail.com')
```

---

<div class="post-metadata">

**Author:** ![gvkarthik93](https://avatars.discourse-cdn.com/v4/letter/g/49beb7/32.png) [@gvkarthik93](https://community.influxdata.com/u/gvkarthik93)\
**Post date:** [March 14, 2019, 7:01pm UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/7 "2019-03-14T19:01:28Z")

</div>

So I am sending data every 5 minutes. And I wanted the derivative to work on this for every 5 minutes. That is check the value at the end of 5th minute with the one before 5 minutes and if it’s non-negative, which means the value at the end of 5th minute is greater than the before value, send an email alert.

But this seems to be not working. Any help appreciated. I am going through documentation. Thanks for sharing. I am totally new to this. So I am looking for help.

---

<div class="post-metadata">

**Author:** ![MarcV](https://sea1.discourse-cdn.com/flex023/user_avatar/community.influxdata.com/marcv/32/7676_2.png) [@MarcV](https://community.influxdata.com/u/MarcV)\
**Post date:** [March 14, 2019, 7:08pm UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/8 "2019-03-14T19:08:05Z")

</div>

> [@gvkarthik93](#):
>
> |alert() .crit(lambda: “value” \> crit)

Hi ,

do you see alerts triggerd in the Kapacitor logfile ?

Can you try with “value” \> 0 in your lambda expression ?

---

<div class="post-metadata">

**Author:** ![gvkarthik93](https://avatars.discourse-cdn.com/v4/letter/g/49beb7/32.png) [@gvkarthik93](https://community.influxdata.com/u/gvkarthik93)\
**Post date:** [March 14, 2019, 8:30pm UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/9 "2019-03-14T20:30:07Z")

</div>

@MarcV I changed it to “value” \> 0 in lambda expression and it’s still not working.

I don’t see alerts triggered in Kapacitor logfile either. Any idea why?

---

<div class="post-metadata">

**Author:** ![gvkarthik93](https://avatars.discourse-cdn.com/v4/letter/g/49beb7/32.png) [@gvkarthik93](https://community.influxdata.com/u/gvkarthik93)\
**Post date:** [March 14, 2019, 8:34pm UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/10 "2019-03-14T20:34:19Z")

</div>

This is my whole script right now.

```
var data = stream
    |from()
        .database(db)
        .retentionPolicy(rp)
        .measurement(measurement)
        .groupBy(groupBy)
        .where(whereFilter)
    |derivative('QCOUNT')
        .unit(10s)
        .nonNegative()
        .as('value')

var trigger = data
    |alert()
        .crit(lambda: "value" > 0)
        .message(message)
        .id(idVar)
        .idTag(idTag)
        .levelTag(levelTag)
        .messageField(messageField)
        .durationField(durationField)
        .details(details)
        .email()
        .to('karthik@gmail.com')

trigger
    |eval(lambda: float("value"))
        .as('value')
        .keep()
    |influxDBOut()
        .create()
        .database(outputDB)
        .retentionPolicy(outputRP)
        .measurement(outputMeasurement)
        .tag('alertName', name)
        .tag('triggerType', triggerType)

trigger
    |httpOut('output')
```

---

<div class="post-metadata">

**Author:** ![gvkarthik93](https://avatars.discourse-cdn.com/v4/letter/g/49beb7/32.png) [@gvkarthik93](https://community.influxdata.com/u/gvkarthik93)\
**Post date:** [March 14, 2019, 8:37pm UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/11 "2019-03-14T20:37:33Z")

</div>

I am sending the QCOUNT variable through REST call into my influxDb and this REST call runs every 5 minutes. So I want to compare the values at these 5 minutes interval and above is the script I wrote for it. Any help is greatly appreciated.

---

<div class="post-metadata">

**Author:** ![MarcV](https://sea1.discourse-cdn.com/flex023/user_avatar/community.influxdata.com/marcv/32/7676_2.png) [@MarcV](https://community.influxdata.com/u/MarcV)\
**Post date:** [March 14, 2019, 10:51pm UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/12 "2019-03-14T22:51:01Z")

</div>

Hi it is hard to tell but  
Can you check with

```
   kapacitor show yourtask

```

To see if the task processes data  
And

```
  kapacitor stats ingress

```

To see if Kapacitor is getting data from the measurement ?  
Is the value of QCOUNT higher than the  
Previous value ?

---

<div class="post-metadata">

**Author:** ![MarcV](https://sea1.discourse-cdn.com/flex023/user_avatar/community.influxdata.com/marcv/32/7676_2.png) [@MarcV](https://community.influxdata.com/u/MarcV)\
**Post date:** [March 15, 2019, 8:21am UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/13 "2019-03-15T08:21:45Z")

</div>

Hi ,  
@[adarsh\_hatwar](https://community.influxdata.com/u/adarsh_hatwar)  
talks about these relative alerts in chronograf in this post ,  
[https://community.influxdata.com/t/alerting-if-mean-of-a-value-is-above-a-threshold-value-for-a-certain-period-of-time/8969](https://community.influxdata.com/t/alerting-if-mean-of-a-value-is-above-a-threshold-value-for-a-certain-period-of-time/8969)

I have tried it out for your script and chronograf came up with this …

```
var db = 'dbcpu'
var rp = 'autogen'
var measurement = 'cpu'
var groupBy = []
var whereFilter = lambda: ("cpu" == 'cpu-total')
var name = 'compare'
var idVar = name
var message = ''
var idTag = 'alertID'
var levelTag = 'level'
var messageField = 'message'
var durationField = 'duration'
var outputDB = 'chronograf'
var outputRP = 'autogen'
var outputMeasurement = 'alerts'
var triggerType = 'relative'
var shift = 5m
var crit = 0
var data = stream
    |from()
        .database(db)
        .retentionPolicy(rp)
        .measurement(measurement)
        .groupBy(groupBy)
        .where(whereFilter)
    |eval(lambda: "usage_idle")
        .as('value')

var past = data
    |shift(shift)

var current = data

var trigger = past
    |join(current)
        .as('past', 'current')
    |eval(lambda: float("current.value" - "past.value"))
        .keep()
        .as('value')
    |alert()
        .crit(lambda: "value" > crit)
        .message(message)
        .id(idVar)
        .idTag(idTag)
        .levelTag(levelTag)
        .messageField(messageField)
        .durationField(durationField)
        .stateChangesOnly()

trigger
    |eval(lambda: float("value"))
        .as('value')
        .keep()
    |influxDBOut()
        .create()
        .database(outputDB)
        .retentionPolicy(outputRP)
        .measurement(outputMeasurement)
        .tag('alertName', name)
        .tag('triggerType', triggerType)

trigger
    |httpOut('output')

```

---

<div class="post-metadata">

**Author:** ![gvkarthik93](https://avatars.discourse-cdn.com/v4/letter/g/49beb7/32.png) [@gvkarthik93](https://community.influxdata.com/u/gvkarthik93)\
**Post date:** [March 15, 2019, 6:22pm UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/14 "2019-03-15T18:22:19Z")

</div>

@MarcV This won’t work if the data comes continuously right? Say, I have people dumping QCOUNT values at random intervals, unlike every 5 minutes, it won’t work I guess. What I am trying to achieve is that, at any random intervals of data being dumped into influxDB, look at the current value that is being inserted, look at the past value, and if the current value is greater than the past value, then generate an alert. How do I go about this?

And thanks for all your effort. I really appreciated your help.

---

<div class="post-metadata">

**Author:** ![MarcV](https://sea1.discourse-cdn.com/flex023/user_avatar/community.influxdata.com/marcv/32/7676_2.png) [@MarcV](https://community.influxdata.com/u/MarcV)\
**Post date:** [March 17, 2019, 12:05am UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/15 "2019-03-17T00:05:10Z")

</div>

Hi ,  
have you found a solution ?  
what is your task name ?  
Can you share the following information assuming the name of your task is mytask  
and assuming the task is enabled ?

```
 kapacitor show mytask

```

you can also check for errors while the task is executing with :

```
 kapacitor watch mytask
```

---

<div class="post-metadata">

**Author:** ![gvkarthik93](https://avatars.discourse-cdn.com/v4/letter/g/49beb7/32.png) [@gvkarthik93](https://community.influxdata.com/u/gvkarthik93)\
**Post date:** [March 18, 2019, 6:14pm UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/16 "2019-03-18T18:14:54Z")

</div>

@MarcV The task is enabled. It’s still not working. Like I said, the problem I am trying to solve is, to take the previous value and compare with current value in a stream. This QCOUNT variable can be posted in any random interval. Like someone can post that into influxDB whenever they want. When a new value comes in, I want to compare it with previous value. How do I achieve this?

---

<div class="post-metadata">

**Author:** ![adarsh\_hatwar](https://sea1.discourse-cdn.com/flex023/user_avatar/community.influxdata.com/adarsh_hatwar/32/2872_2.png) [@adarsh\_hatwar](https://community.influxdata.com/u/adarsh_hatwar)\
**Post date:** [March 19, 2019, 4:18am UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/17 "2019-03-19T04:18:03Z")

</div>

@gvkarthik93  
Hi, have you looked at [this](https://docs.influxdata.com/kapacitor/v1.5/guides/two-measurement-alert/)?  
Elaborating your use case on your alerts being real time would help a bit.

---

<div class="post-metadata">

**Author:** ![gvkarthik93](https://avatars.discourse-cdn.com/v4/letter/g/49beb7/32.png) [@gvkarthik93](https://community.influxdata.com/u/gvkarthik93)\
**Post date:** [March 19, 2019, 11:08pm UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/18 "2019-03-19T23:08:05Z")

</div>

@adarsh_hatwar I have looked at that example. How do I get the previous value from the same stream of data using that example. Like I mentioned about, I have stream of data coming in. That is I have QCOUNT variable coming in randomly. When a new QCOUNT comes in, how do I get the previous QCOUNT, compare both and generate alert?

---

<div class="post-metadata">

**Author:** ![MarcV](https://sea1.discourse-cdn.com/flex023/user_avatar/community.influxdata.com/marcv/32/7676_2.png) [@MarcV](https://community.influxdata.com/u/MarcV)\
**Post date:** [March 19, 2019, 11:29pm UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/19 "2019-03-19T23:29:13Z")

</div>

Hi can you share your complete script ?

I will test it with exactly the same script.

---

<div class="post-metadata">

**Author:** ![gvkarthik93](https://avatars.discourse-cdn.com/v4/letter/g/49beb7/32.png) [@gvkarthik93](https://community.influxdata.com/u/gvkarthik93)\
**Post date:** [March 20, 2019, 8:40pm UTC](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006/20 "2019-03-20T20:40:59Z")

</div>

@MarcV This is the complete script I am trying.

```
var db = 'telegraf'

var rp = 'autogen'

var measurement = 'E Plus'

var groupBy = []

var whereFilter = lambda: ("domain" == 'gxgame') AND ("statsName" == 'Q Count')

var name = 'qcounttest0318'

var idVar = name

var message = 'subject {{ index .Tags "value" }} {{ index .Fields "value" }}'

var idTag = 'alertID'

var levelTag = 'level'

var messageField = 'message'

var durationField = 'duration'

var outputDB = 'chronograf'

var outputRP = 'autogen'

var outputMeasurement = 'alerts'

var triggerType = 'threshold'

var details = 'message'

var crit = 0

var data = stream
|from()
    .database(db)
    .retentionPolicy(rp)
    .measurement(measurement)
    .groupBy(groupBy)
    .where(whereFilter)
|window()
    .period(10m)
    .every(10m)
    .align()
|derivative('QCOUNT')
    .as('value')

var trigger = data
|alert()
    .crit(lambda: "value" > crit)
    .message(message)
    .id(idVar)
    .idTag(idTag)
    .levelTag(levelTag)
    .messageField(messageField)
    .durationField(durationField)
    .details(details)
    .email()
    .to('karthik@gmail.com')

trigger
|eval(lambda: float("value"))
    .as('value')
    .keep()
|influxDBOut()
    .create()
    .database(outputDB)
    .retentionPolicy(outputRP)
    .measurement(outputMeasurement)
    .tag('alertName', name)
    .tag('triggerType', triggerType)

trigger
|httpOut('output')

```

Any help with the use case I mentioned is appreciated. What I want to achieve is whenever there is a stream of data, look at previous value and compare it with current value and generate alert. This is irregular stream. So people can send data into influxDB anytime.

[Next page](https://community.influxdata.com/t/how-can-i-compare-current-value-in-my-stream-with-previous-value-in-tickscript/9006.md?page=2)