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From Joe Stein <joe.st...@stealth.ly>
Subject Re: Consumer and offset management support in 0.8.2 and 0.9
Date Tue, 06 Jan 2015 07:39:16 GMT
In addition to the issue you bring up, the functionality as a whole has
changed.. when you call OffsetFetchRequest the version = 0 needs to
preserve the old functionality
https://github.com/apache/kafka/blob/0.8.1/core/src/main/scala/kafka/server/KafkaApis.scala#L678-L700
and version = 1 the new
https://github.com/apache/kafka/blob/0.8.2/core/src/main/scala/kafka/server/KafkaApis.scala#L153-L223.
Also the OffsetFetchRequest functionality even though the wire protocol is
the same after the 0.8.2 upgrade for OffsetFetchRequest if you were using
0.8.1.1 OffsetFetchRequest
https://github.com/apache/kafka/blob/0.8.1/core/src/main/scala/kafka/server/KafkaApis.scala#L705-L728
will stop going to zookeeper and start going to Kafka storage
https://github.com/apache/kafka/blob/0.8.2/core/src/main/scala/kafka/server/KafkaApis.scala#L504-L519
so more errors will happen and things break too.

I think we should treat the version field not just to stop from breaking
the wire protocol calls but also as a "feature flag" preserving upgrades
and multiple pathways.

I updated the JIRA for the feature flag needs for OffsetFetch and
OffsetCommit too.

/*******************************************
 Joe Stein
 Founder, Principal Consultant
 Big Data Open Source Security LLC
 http://www.stealth.ly
 Twitter: @allthingshadoop <http://www.twitter.com/allthingshadoop>
********************************************/

On Mon, Jan 5, 2015 at 3:21 PM, Dana Powers <dana.powers@rd.io> wrote:

> ok, opened KAFKA-1841 .  KAFKA-1634 also related.
>
> -Dana
>
> On Mon, Jan 5, 2015 at 10:55 AM, Gwen Shapira <gshapira@cloudera.com>
> wrote:
>
> > Ooh, I see what you mean - the OffsetAndMetadata (or PartitionData)
> > part of the Map changed, which will modify the wire protocol.
> >
> > This is actually not handled in the Java client either. It will send
> > the timestamp no matter which version is used.
> >
> > This looks like a bug and I'd even mark it as blocker for 0.8.2 since
> > it may prevent rolling upgrades.
> >
> > Are you opening the JIRA?
> >
> > Gwen
> >
> > On Mon, Jan 5, 2015 at 10:28 AM, Dana Powers <dana.powers@rd.io> wrote:
> > > specifically comparing 0.8.1 --
> > >
> > >
> >
> https://github.com/apache/kafka/blob/0.8.1/core/src/main/scala/kafka/api/OffsetCommitRequest.scala#L37-L50
> > > ```
> > > (1 to partitionCount).map(_ => {
> > >   val partitionId = buffer.getInt
> > >   val offset = buffer.getLong
> > >   val metadata = readShortString(buffer)
> > >   (TopicAndPartition(topic, partitionId),
> OffsetMetadataAndError(offset,
> > > metadata))
> > > })
> > > ```
> > >
> > > totrunk --
> > >
> > >
> >
> https://github.com/apache/kafka/blob/trunk/core/src/main/scala/kafka/api/OffsetCommitRequest.scala#L44-L69
> > > ```
> > > (1 to partitionCount).map(_ => {
> > >   val partitionId = buffer.getInt
> > >   val offset = buffer.getLong
> > >   val timestamp = {
> > >     val given = buffer.getLong
> > >     if (given == -1L) now else given
> > >   }
> > >   val metadata = readShortString(buffer)
> > >   (TopicAndPartition(topic, partitionId), OffsetAndMetadata(offset,
> > > metadata, timestamp))
> > > })
> > > ```
> > >
> > > should the `timestamp` buffer read be wrapped in an api version check?
> > >
> > >
> > > Dana Powers
> > > Rdio, Inc.
> > > dana.powers@rd.io
> > > rdio.com/people/dpkp/
> > >
> > > On Mon, Jan 5, 2015 at 9:49 AM, Gwen Shapira <gshapira@cloudera.com>
> > wrote:
> > >
> > >> Ah, I see :)
> > >>
> > >> The readFrom function basically tries to read two extra fields if you
> > >> are on version 1:
> > >>
> > >> if (versionId == 1) {
> > >>       groupGenerationId = buffer.getInt
> > >>       consumerId = readShortString(buffer)
> > >>     }
> > >>
> > >> The rest looks identical in version 0 and 1, and still no timestamp in
> > >> sight...
> > >>
> > >> Gwen
> > >>
> > >> On Mon, Jan 5, 2015 at 9:33 AM, Dana Powers <dana.powers@rd.io>
> wrote:
> > >> > Hi Gwen, I am using/writing kafka-python to construct api requests
> and
> > >> have
> > >> > not dug too deeply into the server source code.  But I believe it
is
> > >> > kafka/api/OffsetCommitRequest.scala and specifically the readFrom
> > method
> > >> > used to decode the wire protocol.
> > >> >
> > >> > -Dana
> > >> > OffsetCommitRequest has two constructors now:
> > >> >
> > >> > For version 0:
> > >> >  OffsetCommitRequest(String groupId, Map<TopicPartition,
> > >> > PartitionData> offsetData)
> > >> >
> > >> > And version 1:
> > >> > OffsetCommitRequest(String groupId, int generationId, String
> > >> > consumerId, Map<TopicPartition, PartitionData> offsetData)
> > >> >
> > >> > None of them seem to require timestamps... so I'm not sure where you
> > >> > see that this is required. Can you share an example?
> > >> >
> > >> > Gwen
> > >> >
> > >> > On Sun, Jan 4, 2015 at 11:15 PM, Dana Powers <dana.powers@rd.io>
> > wrote:
> > >> >> Hi Joel,
> > >> >>
> > >> >> I'm looking more closely at the OffsetCommitRequest wire protocol
> > change
> > >> >> you mentioned below, and I cannot figure out how to explicitly
> > >> construct a
> > >> >> request with the earlier version.  Should the api version be
> > different
> > >> for
> > >> >> requests that do not include it and/or servers that do not support
> > the
> > >> >> timestamp field?  It looks like 0.8.1.1 did not include the
> timestamp
> > >> > field
> > >> >> and used api version 0.  But 0.8.2-beta seems to now require
> > timestamps
> > >> >> even when I explicitly encode OffsetCommitRequest api version
0
> > (server
> > >> >> logs a BufferUnderflowException).
> > >> >>
> > >> >> Is this the expected server behavior?  Can you provide any tips
on
> > how
> > >> >> third-party clients should manage the wire-protocol change for
this
> > api
> > >> >> method (I'm working on kafka-python)?
> > >> >>
> > >> >> Thanks,
> > >> >>
> > >> >> -Dana
> > >> >>
> > >> >> On Tue, Nov 18, 2014 at 1:27 PM, Joel Koshy <jjkoshy.w@gmail.com>
> > >> wrote:
> > >> >>
> > >> >>> Yes it should be backwards compatible. So for e.g., you should
be
> > able
> > >> >>> to use an 0.8.1 client with an 0.8.2 broker. In general, you
> should
> > >> >>> not upgrade your clients until after the brokers have been
> upgraded.
> > >> >>> However, you can point an 0.8.2 client at an 0.8.1 broker.
One
> wire
> > >> >>> protocol change I'm aware of is the OffsetCommitRequest. 
There
> is a
> > >> >>> change in the OffsetCommitRequest format (KAFKA-1634) although
you
> > can
> > >> >>> explicitly construct an OffsetCommitRequest with the earlier
> > version.
> > >> >>>
> > >> >>> Thanks,
> > >> >>>
> > >> >>> Joel
> > >> >>>
> > >> >>> On Tue, Nov 18, 2014 at 03:39:41PM -0500, Marius Bogoevici
wrote:
> > >> >>> > Hi Joel,
> > >> >>> >
> > >> >>> > Thanks for all the clarifications!  Just another question
on
> this:
> > >> will
> > >> >>> > 0.8.2 be backwards compatible with 0.8.1, just as 0.8.1
was with
> > 0.8?
> > >> >>> > Generally speaking, would there be any concerns with
using the
> > 0.8.2
> > >> >>> > consumer with a 0.8.1 broker, for instance?
> > >> >>> >
> > >> >>> > Marius
> > >> >>> >
> > >> >>> > On Tue, Nov 18, 2014 at 2:55 PM, Joel Koshy <
> jjkoshy.w@gmail.com>
> > >> > wrote:
> > >> >>> >
> > >> >>> > > Inline..
> > >> >>> > >
> > >> >>> > > On Tue, Nov 18, 2014 at 04:26:04AM -0500, Marius
Bogoevici
> > wrote:
> > >> >>> > > > Hello everyone,
> > >> >>> > > >
> > >> >>> > > > I have a few questions about the current status
and future
> of
> > the
> > >> >>> Kafka
> > >> >>> > > > consumers.
> > >> >>> > > >
> > >> >>> > > > We have been working to adding Kafka support
in Spring XD
> [1],
> > >> >>> currently
> > >> >>> > > > using the high level consumer via Spring Integration
Kafka
> > [2].
> > >> We
> > >> >>> are
> > >> >>> > > > working on adding features such as:
> > >> >>> > > > - the ability to control offsets/replay topics;
> > >> >>> > > > - the ability to control partition allocation
across
> multiple
> > >> >>> consumers;
> > >> >>> > > >
> > >> >>> > > > We are currently at version 0.8.1.1, so using
the simple
> > consumer
> > >> > is
> > >> >>> a
> > >> >>> > > > pretty straightforward choice right now. However,
in the
> > light of
> > >> > the
> > >> >>> > > > upcoming consumer changes for 0.8.2 and 0.9,
I have a few
> > >> > questions:
> > >> >>> > > >
> > >> >>> > > > 1) With respect to the consumer redesign for
0.9, what is
> the
> > >> > future
> > >> >>> of
> > >> >>> > > the
> > >> >>> > > > Simple Consumer and High Level Consumer? To
my best
> > >> understanding,
> > >> >>> the
> > >> >>> > > > existing high level consumer API will be deprecated
in
> favour
> > of
> > >> > the
> > >> >>> new
> > >> >>> > > > consumer API. What is the future of the Simple
Consumer, in
> > this
> > >> >>> case? it
> > >> >>> > > > will continue to exist as a low-level API implementing
the
> > Kafka
> > >> >>> protocol
> > >> >>> > > > [3] and providing the building blocks for the
new consumer,
> or
> > >> will
> > >> >>> it be
> > >> >>> > > > deprecated as well?
> > >> >>> > >
> > >> >>> > > The new consumer will subsume both use-cases (simple
and
> > >> high-level).
> > >> >>> > > You can still use the old SimpleConsumer if you
wish - i.e.,
> the
> > >> wire
> > >> >>> > > protocol for fetch and other requests will still
be supported.
> > >> >>> > >
> > >> >>> > > >
> > >> >>> > > > 2) Regarding the new consumer: the v0.8.2 codebase
contains
> an
> > >> > early
> > >> >>> > > > implementation of it, but since this a feature
scheduled
> only
> > for
> > >> >>> 0.9,
> > >> >>> > > what
> > >> >>> > > > is its status as well? Is it included only
as a future
> > reference
> > >> > and
> > >> >>> for
> > >> >>> > > > stabilizing the API?
> > >> >>> > >
> > >> >>> > > It is a WIP so you cannot really use it.
> > >> >>> > >
> > >> >>> > > > 3) Obviously, offset management is a concern
if using the
> > simple
> > >> >>> > > consumer,
> > >> >>> > > > so - wondering about the Offset Management
API as well. The
> > Kafka
> > >> >>> > > protocol
> > >> >>> > > > document specifically indicates that it will
be fully
> > functional
> > >> in
> > >> >>> 0.8.2
> > >> >>> > > > [4] - however, a functional implementation
is already
> > available
> > >> in
> > >> >>> > > 0.8.1.1
> > >> >>> > > > (accessible via the SimpleConsumer API but
not documented in
> > >> [5]).
> > >> >>> Again,
> > >> >>> > > > trying to understand the extent of what 0.8.1.1
already
> > supports
> > >> >>> > > > (ostensibly, the offset manager support seems
to have been
> > added
> > >> >>> only in
> > >> >>> > > > 0.8.2 - please correct me if I am wrong), and
whether if it
> is
> > >> >>> > > recommended
> > >> >>> > > > for use in production in any form (with the
caveats that
> > >> accompany
> > >> >>> the
> > >> >>> > > use
> > >> >>> > > > of ZooKeeper).
> > >> >>> > >
> > >> >>> > > In 0.8.2 the OffsetCommitRequest and OffsetFetchRequest
will
> use
> > >> > Kafka
> > >> >>> > > as the offsets storage mechanism (not zookeeper).
High-level
> > Java
> > >> >>> > > consumers can choose to store offsets in ZooKeeper
instead by
> > >> setting
> > >> >>> > > offsets.storage=zookeeper
> > >> >>> > >
> > >> >>> > > However, if you are using the simple consumer and
wish to
> store
> > >> >>> > > offsets in ZooKeeper you will need to commit to
ZooKeeper
> > directly.
> > >> >>> > > You can use ZkUtils in the kafka.utils package for
this.
> > >> >>> > >
> > >> >>> > > If you wish to move to Kafka-based offsets we will
be adding a
> > new
> > >> >>> > > OffsetsClient that can be used to commit/fetch offsets
to/from
> > >> Kafka.
> > >> >>> > > This is currently not listed as a blocker for 0.8.2
but I
> think
> > we
> > >> >>> > > should include it. I will update that ticket.
> > >> >>> > >
> > >> >>> > > > 4) Trying to interpret the existing examples
in [6] and the
> > >> > comments
> > >> >>> on
> > >> >>> > > [7]
> > >> >>> > > > - the version of the Offset Management API
that exists in
> > 0.8.1.1
> > >> > is
> > >> >>> > > using
> > >> >>> > > > ZooKeeper - whereas ZooKeeper will be optional
in 0.8.2 - to
> > be
> > >> >>> replaced
> > >> >>> > > by
> > >> >>> > > > Kafka, and phased out if possible. To my understanding,
the
> > >> switch
> > >> >>> > > between
> > >> >>> > > > the two will be controlled by the broker configuration
> (along
> > >> with
> > >> >>> other
> > >> >>> > > > parameters that control the performance of
offset queues. Is
> > that
> > >> >>> > > correct?
> > >> >>> > >
> > >> >>> > > The switch is a client-side configuration. That
wiki is not
> > >> >>> > > up-to-date. The most current documentation is available
as a
> > patch
> > >> in
> > >> >>> > > https://issues.apache.org/jira/browse/KAFKA-1729
> > >> >>> > >
> > >> >>> > > > 5) Also, wondering about the timeline of 0.8.2
- according
> to
> > the
> > >> >>> > > roadmaps
> > >> >>> > > > it should be released relatively shortly. Is
that correct?
> > >> >>> > >
> > >> >>> > > Yes - once the blockers are ironed out.
> > >> >>> > >
> > >> >>> > > >
> > >> >>> > > > Thanks,
> > >> >>> > > > Marius
> > >> >>> > > >
> > >> >>> > > > [1] http://projects.spring.io/spring-xd/
> > >> >>> > > > [2]
> > https://github.com/spring-projects/spring-integration-kafka
> > >> >>> > > > [3]
> > >> >>> > > >
> > >> >>> > >
> > >> >>>
> > >> >
> > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/A+Guide+To+The+Kafka+Protocol
> > >> >>> > > > [4]
> > >> >>> > > >
> > >> >>> > >
> > >> >>>
> > >> >
> > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/A+Guide+To+The+Kafka+Protocol#AGuideToTheKafkaProtocol-OffsetCommit/FetchAPI
> > >> >>> > > > [5]
> > >> > http://kafka.apache.org/082/documentation.html#simpleconsumerapi
> > >> >>> > > > [6]
> > >> >>> > > >
> > >> >>> > >
> > >> >>>
> > >> >
> > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/Committing+and+fetching+consumer+offsets+in+Kafka
> > >> >>> > > > [7] https://issues.apache.org/jira/browse/KAFKA-1729
> > >> >>> > >
> > >> >>> > >
> > >> >>>
> > >> >>>
> > >>
> >
>

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