Thanks. I got it to work if I use KafkaConsumer. I doesn't yet work with
SimpleConsumer, and that includes seeking to 0,0. I'm curious what that isn't
getting it going. It's frustrating because SimpleConsumer supports seek while
KafkaConsumer doesn't offer a seek function, but at the same time, I can reset
KafkaConsumer to the beginning with auto_offset_reset while SimpleConsumer has
yet to work for me any way at all, including with a seek. So far, neither
class is optimal for me (SimpleConsumer doesn't work at all yet and
KafkaConsumer has no seek function).
I'm using kafka-python 0.9.4 btw, just whatever version came up when pip
installed it.
Keith Wiley
Senior Software Engineer, Atigeo
keith.wi...@atigeo.com
________________________________________
From: Steve Miller <st...@idrathernotsay.com>
Sent: Wednesday, July 29, 2015 09:33 AM
To: users@kafka.apache.org
Subject: Re: kafka-python message offset?
Are you using mumrah/kafka-python? I think so from context but I know
there's at least one other implementation rattling around these days. (-:
If that's what you're using, I can see two potential problems you might be
having. You can set the offset to some approximation of wherever you want, by
using :
s_consumer.seek(offset, whence)
"pydoc kafka.consumer" says:
| seek(self, offset, whence)
| Alter the current offset in the consumer, similar to fseek
|
| offset: how much to modify the offset
| whence: where to modify it from
| 0 is relative to the earliest available offset (head)
| 1 is relative to the current offset
| 2 is relative to the latest known offset (tail)
So if you want to go to the beginning, do seek(0, 0).
Seeking to the beginning or the end should be pretty reliable. You can seek
(say) 100K messages relative to the beginning or the end or to the current
offset, but with partitions and message arrival order and the like it's a bit
of a crapshoot where you'll end up. The API will divide your offset by the
number of partitions, then (I believe) apply that delta to each partition.
Hoping that the input stream is relatively well balanced.
But again, seek(0, 0) or seek(0, 2) has always worked reasonably for me, so
much so that I don't remember the default.
The other thing you might be running into is that if you are setting the
partitions parameter to an array containing only zero, and your topic has more
partitions than just partition #0, the producer might be publishing to a
different partition. But you've told the client to read only from partition 0,
so in that case you'd see no data. If you want to consume from every
partition, don't pass in a partitions parameter.
-Steve
On Wed, Jul 29, 2015 at 04:07:33PM +0000, Keith Wiley wrote:
> I'm still not getting the necessary behavior. If I run on the command line,
> I get a series of messages:
>
> --------
> $ ./kafka-console-consumer.sh --zookeeper w.x.y.z:p --topic test
> --from-beginning
> Test
> test
> tests
> asdf
> --------
>
> If I exclude the --from-beginning argument then it hangs, which indicates to
> me that the offset is currently at the end and awaiting new messages. If I
> run through python, it also hangs, which is why I suspect it is insistently
> reading from the end. See below:
>
> --------
> print "Begin constructing SimpleConsumer"
> client = KafkaClient(servers)
> s_consumer = SimpleConsumer(client,
> topic,
> group_id,
> partitions=[0], #Not sure I need this
> auto_commit=False, #Tried with and without,
> doesn't fix the problem
> auto_offset_reset='smallest' #Tried with and
> without, doesn't fix the problem
> )
> print "End constructing SimpleConsumer\n"
>
> print "Begin reading messages"
> try:
> for message in s_consumer:
> print " New message"
> print " " + message.topic
> print " " + message.partition
> print " " + message.offset
> print " " + message.key
> print " " + message.value
> except Exception as e:
> print "Exception: ", e
> print "End reading messages\n"
>
> print "End all"
> --------
>
> Output:
>
> Begin all
>
> Begin constructing SimpleConsumer
> End constructing SimpleConsumer
>
> Begin reading messages
>
> --------
> It just hangs after that. I also tried with a KafkaConsumer instead of a
> SimpleConsumer and it does exactly the same thing. I'm not sure what to do.
>
> ----------------------------------------------------------------------------------------
> Keith Wiley
> Senior Software Engineer, Atigeo
> keith.wi...@atigeo.com
>
>
>
>
>
> ________________________________________
> From: Dana Powers <dana.pow...@rd.io>
> Sent: Tuesday, July 28, 2015 09:58 PM
> To: users@kafka.apache.org
> Subject: Re: kafka-python message offset?
>
> Hi Keith,
>
> you can use the `auto_offset_reset` parameter to kafka-python's
> KafkaConsumer. It behaves the same as the java consumer configuration of
> the same name. See
> http://kafka-python.readthedocs.org/en/latest/apidoc/kafka.consumer.html#kafka.consumer.KafkaConsumer.configure
> for more details on how to configure a KafkaConsumer instance.
>
> For fine-grained control wrt configuring topic/partition offsets, use
> KafkaConsumer.set_topic_partitions() . For the most control, pass a
> dictionary of {(topic, partition): offset, ...} .
> see
> http://kafka-python.readthedocs.org/en/latest/apidoc/kafka.consumer.html#kafka.consumer.kafka.KafkaConsumer.set_topic_partitions
>
> -Dana
>
> On Tue, Jul 28, 2015 at 8:47 PM, Keith Wiley <keith.wi...@atigeo.com> wrote:
>
> > I haven?t found a way to specify that a consumer should read from the
> > beginning, or from any other explicit offset, or that the offset should be
> > ?reset? in any way. The command-line shell scripts (which I believe simply
> > wrap the Scala tools) have flags for this sort of thing. Is there any way
> > to do this through the python library?
> >
> > Thanks.
