[jira] [Created] (KAFKA-13936) Invalid consumer lag when monitoring from a kafka streams application

[Prashanth Joseph Babu (Jira)]

Prashanth Joseph Babu created KAFKA-13936:
---------------------------------------------

             Summary: Invalid consumer lag when monitoring from a kafka streams 
application
                 Key: KAFKA-13936
                 URL: https://issues.apache.org/jira/browse/KAFKA-13936
             Project: Kafka
          Issue Type: Bug
          Components: streams
            Reporter: Prashanth Joseph Babu


I have a kafka streams application and I'm trying to monitor the consumer lag 
via stream metrics.

Here's some code snippet

```
 metrics = streams.metrics();            lag = 0;            for (Metric m : 
metrics.values()) {                tags = m.metricName().tags();                
if ( m.metricName().name().equals(MONITOR_CONSUMER_LAG) && 
tags.containsKey(MONTOR_TAG_TOPIC) &&                     
tags.get(MONTOR_TAG_TOPIC).equals(inputTopic) ) {                    
partitionLag = Float.valueOf(m.metricValue().toString()).floatValue();          
          if ( !partitionLag.isNaN() ) {                        lag += 
partitionLag;                    }                }            }
```

Here MONITOR_CONSUMER_LAG is {{{}records-lag-max{}}}.

However these numbers dont match with the consumer lag we see in the kafka UI . 
is records-lag-max the right metric to track for a kafka streams application 
when the objective is to get consumer lag?



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