Get Consumer lag using LibrdkafkaHandle.OutQueueLength

Description

Hi!

I found a way to get a consumer’s topic lag by reading the internal property OutQueueLength found in the internal LibrdkafkaHandle Handle property of the consumer. Is this a “safe” hack? @mhowlett, can you please explain me why this property was not publicly exposed in the library? If this version is not safe is there another way to accomplish this? Thank you, Alex

Code:

var propertyLevel1 = _consumer.Handle.GetType().GetProperty("LibrdkafkaHandle", BindingFlags.NonPublic | BindingFlags.Instance);
var valueLevel1 = propertyLevel1.GetValue(_consumer.Handle);

var propertyLevel2 = valueLevel1.GetType().GetProperty("OutQueueLength", BindingFlags.NonPublic | BindingFlags.Instance);
var valueLevel2 = propertyLevel2.GetValue(valueLevel1);
                        
topicLag = Convert.ToInt64(valueLevel2);

Checklist

Please provide the following information:

• A complete (i.e. we can run it), minimal program demonstrating the problem. No need to supply a project file.
• Confluent.Kafka nuget version: 1.3.0
• Apache Kafka version: 2.x
• Client configuration.
• Operating system : Linux
• Provide logs (with “debug” : “…” as necessary in configuration).
• Provide broker log excerpts.
• Critical issue.

[alexandrutatagit]

Thank you @edenhill ! Can you please tell me how I can do this in the C# library? Should I hack the same way I did above?

[dogac00]

@wxlevel You have to Subscribe to your topic for consumer to be assigned to partitions.