问题
I have a producer in java and consumer in nodeJS. I want to know in java what is the consumer lag, so i know if i can produce more data to the topic.
What is the API in java to get the consumer lag?
回答1:
Why do you need to know the consumer lag ? The aim of a broker is to produce messages asynchronously. If you need to have a synchronous processing, use a basic rest processing.
回答2:
The actual class you can call from Java is the kafka.admin.ConsumerGroupCommand. It's Scala code, but it's easy to call directly from Java.
Here's a link to the Github code for perusal: https://github.com/apache/kafka/blob/bf237fa7c576bd141d78fdea9f17f65ea269c290/core/src/main/scala/kafka/admin/ConsumerGroupCommand.scala
And here's the help output if you don't pass in any parameters. That should help out with the commands you need to send.
List all consumer groups, describe a consumer group, delete consumer group info, or reset consumer group offsets.
Option Description
------ -----------
--all-topics Consider all topics assigned to a
group in the `reset-offsets` process.
--bootstrap-server
--by-duration Reset offsets to offset by duration
from current timestamp. Format:
'PnDTnHnMnS'
--command-config passed to Admin Client and Consumer.
--delete Pass in groups to delete topic
partition offsets and ownership
information over the entire consumer
group. For instance --group g1 --
group g2
--describe Describe consumer group and list
offset lag (number of messages not
yet processed) related to given
group.
--dry-run Only show results without executing
changes on Consumer Groups.
Supported operations: reset-offsets.
--execute Execute operation. Supported
operations: reset-offsets.
--export Export operation execution to a CSV
file. Supported operations: reset-
offsets.
--from-file Reset offsets to values defined in CSV
file.
--group The consumer group we wish to act on.
--list List all consumer groups.
--members Describe members of the group. This
option may be used with '--describe'
and '--bootstrap-server' options
only.
Example: --bootstrap-server localhost:
9092 --describe --group group1 --
members
--offsets Describe the group and list all topic
partitions in the group along with
their offset lag. This is the
default sub-action of and may be
used with '--describe' and '--
bootstrap-server' options only.
Example: --bootstrap-server localhost:
9092 --describe --group group1 --
offsets
--reset-offsets Reset offsets of consumer group.
Supports one consumer group at the
time, and instances should be
inactive
Has 2 execution options: --dry-run
(the default) to plan which offsets
to reset, and --execute to update
the offsets. Additionally, the --
export option is used to export the
results to a CSV format.
You must choose one of the following
reset specifications: --to-datetime,
--by-period, --to-earliest, --to-
latest, --shift-by, --from-file, --
to-current.
To define the scope use --all-topics
or --topic. One scope must be
specified unless you use '--from-
file'.
--shift-by Reset offsets shifting current offset
by 'n', where 'n' can be positive or
negative.
--state Describe the group state. This option
may be used with '--describe' and '--
bootstrap-server' options only.
Example: --bootstrap-server localhost:
9092 --describe --group group1 --
state
--timeout The timeout that can be set for some
use cases. For example, it can be
used when describing the group to
specify the maximum amount of time
in milliseconds to wait before the
group stabilizes (when the group is
just created, or is going through
some changes). (default: 5000)
--to-current Reset offsets to current offset.
--to-datetime Reset offsets to offset from datetime.
Format: 'YYYY-MM-DDTHH:mm:SS.sss'
--to-earliest Reset offsets to earliest offset.
--to-latest Reset offsets to latest offset.
--to-offset Reset offsets to a specific offset.
--topic The topic whose consumer group
information should be deleted or
topic whose should be included in
the reset offset process. In `reset-
offsets` case, partitions can be
specified using this format: `topic1:
0,1,2`, where 0,1,2 are the
partition to be included in the
process. Reset-offsets also supports
multiple topic inputs.
--verbose Provide additional information, if
any, when describing the group. This
option may be used with '--
offsets'/'--members'/'--state' and
'--bootstrap-server' options only.
Example: --bootstrap-server localhost:
9092 --describe --group group1 --
members --verbose
来源：https://stackoverflow.com/questions/51703045/how-to-get-consumer-kafka-lag-in-java