Lag is always 0

Nobody has claimed this yet.

Burrow: Latest
Kafka: 0.10.1.1

Configuration:
`
[general]
pidfile="burrow.pid"
stdout-logfile="log/burrow.out"

[logging]
filename="log/burrow.log"
level="info"
maxsize=100
maxbackups=30
maxage=10
use-localtime=false
use-compression=true

[zookeeper]
servers=[ "{{ zookeeper_elb.dns }}:{{ zookeeper_elb.port }}" ]
timeout=6

[client-profile.prod]
client-id="burrow-prod"
kafka-version="0.10.1.0"

[cluster.kafka-prod]
class-name="kafka"
servers=[ "{{ kafka_elb.dns }}:{{ kafka_elb.port }}" ]
client-profile="prod"
topic-refresh=120
offset-refresh=30

[consumer.kafka-consumer]
class-name="kafka"
cluster="kafka-prod"
servers=[ "{{ kafka_elb.dns }}:{{ kafka_elb.port }}" ]
client-profile="prod"
offsets-topic="__consumer_offsets"
group-whitelist=".*"
group-blacklist="^(console-consumer-).*$"

[consumer.zookeeper-consumer]
class-name="kafka_zk"
cluster="kafka-prod"
servers=[ "{{ zookeeper_elb.dns }}:{{ zookeeper_elb.port }}" ]
zookeeper-path="/kafka-cluster"
zookeeper-timeout=30
group-whitelist=".*"
group-blacklist="^(console-consumer-).*$"

[httpserver.default]
address=":{{ http_server_port }}"

[storage.default]
class-name="inmemory"
workers=20
intervals=15
expire-group=604800
min-distance=1

[notifier.default]
class-name="http"
interval=60
threshold=1
send-close=true
timeout=5
keepalive=30
url-open="{{ sumologic_http_source_url }}"
template-open="config/http-post-custom.tmpl"
method-open="POST"
url-close="{{ sumologic_http_source_url }}"
template-close="config/http-delete-custom.tmpl"
method-close="POST"
`

Kafka Consumer Group Output
`
[root@ip-y-y-y-y kafka]# kafka-consumer-groups --bootstrap-server x.x.x.x:9092 --describe --group archiver-group-eu-2
GROUP TOPIC PARTITION CURRENT-OFFSET LOG-END-OFFSET LAG OWNER
archiver-group-eu-2 arc-input-eu 67 58154679 59262873 1108194 rdkafka_/a.b.c.d
archiver-group-eu-2 arc-input-eu 68 57150062 58211293 1061231 rdkafka_/a.b.c.d
archiver-group-eu-2 arc-input-eu 69 56387569 57447652 1060083 rdkafka_/a.b.c.d
archiver-group-eu-2 arc-input-eu 70 57199741 58310522 1110781 rdkafka_/10.1.1.225
archiver-group-eu-2 arc-input-eu 71 57227260 58271607 1044347 rdkafka_/10.1.1.225
archiver-group-eu-2 arc-input-eu 72 57894468 58973368 1078900 rdkafka_/a.b.c.d
archiver-group-eu-2 arc-input-eu 73 57977392 59050067 1072675 rdkafka_/a.b.c.d
archiver-group-eu-2 arc-input-eu 74 57802459 58907578 1105119 rdkafka_/a.b.c.d
archiver-group-eu-2 arc-input-eu 75 57465529 58565517 1099988 rdkafka_/a.b.c.d
archiver-group-eu-2 arc-input-eu 76 57072730 58154291 1081561 rdkafka_/a.b.c.d
archiver-group-eu-2 arc-input-eu 77 56688968 57751350 1062382 rdkafka_/a.b.c.d
archiver-group-eu-2 arc-input-eu 78 56192362 57238975 1046613 rdkafka_/a.b.c.d
archiver-group-eu-2 arc-input-eu 79 56371493 57397344 1025851 rdkafka_/a.b.c.d
archiver-group-eu-2 arc-input-eu 80 57794793 58859253 1064460 rdkafka_/a.b.c.d
archiver-group-eu-2 arc-input-eu 81 57720150 58816640 1096490 rdkafka_/a.b.c.d
archiver-group-eu-2 arc-input-eu 82 56583883 57644924 1061041 rdkafka_/a.b.c.d
...
`

Burrow Output
{{server}}/v3/kafka/{{cluster}}/consumer/archiver-group-eu-2
`
{
"error": false,
"message": "consumer detail returned",
"topics": {
"arc-input-eu": [
{
"offsets": [
{
"offset": 59866282,
"timestamp": 1521761057456,
"lag": 0
},
{
"offset": 59866404,
"timestamp": 1521761059578,
"lag": 0
},
{
"offset": 59866405,
"timestamp": 1521761061599,
"lag": 0
},
{
"offset": 59866459,
"timestamp": 1521761063129,
"lag": 0
},
{
"offset": 59866475,
"timestamp": 1521761064522,
"lag": 0
},
{
"offset": 59866483,
"timestamp": 1521761068155,
"lag": 0
},
{
"offset": 59866594,
"timestamp": 1521761069264,
"lag": 0
},
{
"offset": 59866595,
"timestamp": 1521761071166,
"lag": 0
},
{
"offset": 59866609,
"timestamp": 1521761072167,
"lag": 0
},
{
"offset": 59866675,
"timestamp": 1521761073604,
"lag": 0
},
{
"offset": 59866709,
"timestamp": 1521761075370,
"lag": 0
},
{
"offset": 59866712,
"timestamp": 1521761076643,
"lag": 0
},
{
"offset": 59866727,
"timestamp": 1521761078308,
"lag": 0
},
{
"offset": 59866771,
"timestamp": 1521761079632,
"lag": 0
},
{
"offset": 59866816,
"timestamp": 1521761081495,
"lag": 0
}
],
"owner": "/10.1.1.225",
"current-lag": 0
},
...
`

More Info: I noticed, Log-End-Offset is updating (means offsets are getting committed), but lag is also steadily increasing. I would expect Burrow should show lag in this case.

Start by reproducing the reported configuration and comparing the Kafka consumer-group output with the Burrow v3 consumer detail endpoint for the affected group. Trace how committed offsets and log-end offsets become the reported lag; done means Burrow reports the increasing lag shown by Kafka instead of zero.

Written by the indexing model from the issue text.