Thanks, Konstantine.
One minor request to clarify the following sentence:
As soon as a worker detects the addition of a topic to a connector's set of
active topics, the worker will cease to post update messages to the
status.storage.topic for that connector.
As it stands, it sounds like the worker will not write *any more active
topic records for this or any connectors* to the topic specified by the
`status.storage.topic` worker configuration once the worker detects (by
reading) a new active topic. I suspect that this is not the intention, and
that instead it is trying to say that no more messages *for this topic and
connector*. IOW, something more like:
As soon as a worker detects the addition of a topic to a connector's set of
active topics, the worker will not post to the status.storage.topic
additional update records for the connector and this newly-detected active
topic.
Otherwise, this KIP looks great!
Best regards,
Randall
On Fri, Jan 17, 2020 at 8:04 PM Konstantine Karantasis <
konstant...@confluent.io> wrote:
> Hi all,
>
> I've updated KIP-558 with the following based on our previous discussion:
>
> * Added timestamp to the metadata (the record value).
> * The KIP now mentions a metric-based implementation in the Rejected
> Alternatives section.
> * The record key format is now using the single character ':' as a
> separator between topic-${topic name} and connector-${connector name}
> * Added a bullet point to mention that the topic storing the new
> information can be a partitioned topic.
> * The KIP mentions that the feature does not require rebuilding connectors
> (no changes in public interfaces/classes).
> * Added a security section.
> * KIP preserves symmetry with respect to reset between both types of
> connectors and keeps reset and config as separate, unrelated endpoints.
>
> Given than we made significant progress these past few days and only a few
> minor improvements in the KIPs text are remaining, I'd like to start the
> vote today, so that we give this KIP the necessary time (72 hours) to have
> a chance to be voted by the KIP deadline next Wednesday, Jan 22nd.
> Let's return here, or the main vote thread for any comments (either minor
> to major).
>
> Best,
> Konstantine
>
>
>
> On Fri, Jan 17, 2020 at 3:51 PM Konstantine Karantasis <
> konstant...@confluent.io> wrote:
>
> >
> > Thanks for the follow up Chris. Replies below:
> >
> > On Fri, Jan 17, 2020 at 3:07 PM Christopher Egerton <chr...@confluent.io
> >
> > wrote:
> >
> >> Thanks, Konstantine. Just a few more questions:
> >>
> >> > > 2. What is the motivation for the `topic.tracking.allow.reset`
> config?
> >> Is
> >> > > there any anticipated case where it would be useful to have topic
> >> tracking
> >> > > enabled but with resets disabled? We could easily add this
> >> configuration
> >> > > later if a use case arises, but if we add it now it'll be difficult
> to
> >> > > remove.
> >> > >
> >>
> >> > The motivation is for operators of a Connect cluster to be able to
> >> disable
> >> > resetting the history of active topics altogether, while allowing at
> the
> >> > same time to view the active sets.
> >>
> >> What I was trying to ask was, is there a use case for enabling the
> latter
> >> but not the former? We should be careful about adding extra worker
> configs
> >> and unless we can anticipate a reasonable scenario in which this would
> >> happen, we should err on the side of caution and avoid adding a config
> >> that
> >> would be difficult to remove later but, comparably, much easier to add.
> >>
> >
> > The application use case is the ability to have immutable histories of
> > topic usage or control when resets are allowed and how they are performed
> > (e.g. resets could be allowed briefly during a maintenance phase and get
> > disabled again).
> > I'm also never thrilled when I add an extra configuration parameter.
> > However namespacing here will help with the extra cognitive burden.
> > Similarly the defaults should cover most use cases too.
> >
> > > > 5. As far as automatic resets for sink connectors go, I agree with
> your
> >> > > reasoning about the inherent asymmetry between sinks and sources,
> and
> >> with
> >> > > the motivation to avoid confusing users by listing
> no-longer-consumed
> >> > > topics in the active topics for a sink connector. I think that this
> >> > > asymmetry is worth avoiding a scenario where a connector is
> >> reconfigured to
> >> > > only consume from topic "foo" but, from a prior configuration, topic
> >> "bar"
> >> > > is still listed in its active topics.
> >> > > I do want to request clarification on the meaning of the phrase "any
> >> topics
> >> > > no longer consumed" as used under the header "Restarting,
> >> reconfiguring
> >> or
> >> > > deleting a connector". Does this mean that the current set of active
> >> topics
> >> > > for the connector will be filtered and any that are longer contained
> >> in
> >> the
> >> > > sink connector's "topics" config or matched by its "topics.regex"
> >> config
> >> > > will be removed, or does it mean that all topics will be removed and
> >> then
> >> > > the active topics list will be repopulated as records are consumed
> >> from
> >> new
> >> > > topics?
> >> > >
> >>
> >> > The intention was to imply the former. But based on Randall's comment
> >> > above, I'm changing the KIP to include a reset parameter in the PUT
> >> > /connectors/{name}/config endpoint
> >> > In this case, the reset will be a complete reset for both source and
> >> sink
> >> > connectors. This will help keeping the behavior symmetric between the
> >> two
> >> > connector types.
> >>
> >> I did see Randall's suggestion, but I was hoping we could retain some
> more
> >> intelligent behavior. Two things I'd like for us to avoid if possible:
> >>
> >> - Sinks consuming from infrequently-written topics unnecessarily
> dropping
> >> those topics, either as part of an explicit reset or an implicit one
> >> - Sinks listing a topic in their active topics list that they are, in
> >> reality, no longer consuming from
> >>
> >> Intelligently filtering out no-longer-consumed topics from a sink
> >> connector's active topics list (instead of blanket resetting, or not
> >> resetting at all) would prevent both of those from happening. We could
> >> expand the proposed reset parameter from a boolean to a three-option
> >> parameter with "none" (don't reset the topics list), "all" (reset the
> >> entire topics list), and "infer" (reset all topics if for a source, or
> >> intelligently filter out no-longer-consumed topics if for a sink).
> >>
> >
> > I don't see significant advantages in the complexity that the three-value
> > query parameter would introduce.
> > Overall resetting is included for convenience and is not essential to the
> > main objective of this KIP which is to track the topics used by a
> connector
> > during its lifetime.
> > I think it's desirable to strike a good balance between the objective of
> > tracking the topics used by connectors and keeping things simple.
> > Given that the general programming model that Kafka Connect supports is
> > that of continuous streams of events, representing active topics as
> either
> > the topics that a connector has used since it was first created or as the
> > topics that have been actively used since the latest reset is sufficient
> to
> > cover a large majority of use cases.
> >
> > Furthermore, I see future KIPs that would add features to topic tracking
> > preferable in comparison to future KIPs that would try to remedy this
> first
> > KIP with adjustments, simplifications and deprecation of features.
> > Therefore, the query parameter, which I'll add to the KIP shortly, can
> > indeed be represented as a boolean. Absence retains all topics and
> presence
> > resets all the topics.
> > Based on the discussion so far, it seems that keeping things simple and
> > symmetric is preferred. I think I agree, even if in the initial draft of
> > the KIP I described how we could inspect the configuration of a sink
> > connector for changes.
> >
> > Best,
> > Konstantine
> >
> >
> > Independent of your thoughts on the above, what will the default value
> for
> >> the newly-proposed parameter be? If resets are performed by default, the
> >> first scenario I outlined would become possible; if not, then the second
> >> would become possible. I'd lean towards performing them by default but
> >> would be interested in others' thoughts. (If the proposed "infer" value
> >> were the default, neither scenario would be an issue).
> >>
> >> Cheers,
> >>
> >> Chris
> >>
> >> On Fri, Jan 17, 2020 at 2:01 PM Konstantine Karantasis <
> >> konstant...@confluent.io> wrote:
> >>
> >> > Hey Chris! Thanks for the comments. Answers inline below:
> >> >
> >> > On Fri, Jan 17, 2020 at 11:47 AM Christopher Egerton <
> >> chr...@confluent.io>
> >> > wrote:
> >> >
> >> > > Hi Konstantine,
> >> > >
> >> > > Thanks for the KIP! There's been a lot of productive discussion so
> >> far so
> >> > > I'll try to keep my remarks brief.
> >> > >
> >> > > 1. As far as resetting the active topics for a connector goes, it's
> >> noted
> >> > > in the KIP that this can be done for a deleted connector. Can this
> >> also
> >> > be
> >> > > done for connectors that were never created to begin with? What
> would
> >> the
> >> > > behavior be in this case? (Can this be clarified in the KIP?)
> >> > >
> >> >
> >> > Indeed, the intention is to keep reset as an independent and
> idempotent
> >> > method.
> >> > Keep in mind that a tombstone will be written to the topic if the
> >> in-memory
> >> > view (of active topics) of the worker that serves the request contains
> >> this
> >> > connector.
> >> > This should at least prevent fake reset requests from filling up the
> >> topic
> >> > with tombstone messages.
> >> >
> >> >
> >> >
> >> > > 2. What is the motivation for the `topic.tracking.allow.reset`
> >> config? Is
> >> > > there any anticipated case where it would be useful to have topic
> >> > tracking
> >> > > enabled but with resets disabled? We could easily add this
> >> configuration
> >> > > later if a use case arises, but if we add it now it'll be difficult
> to
> >> > > remove.
> >> > >
> >> >
> >> > The motivation is for operators of a Connect cluster to be able to
> >> disable
> >> > resetting the history of active topics altogether, while allowing at
> the
> >> > same time to view the active sets.
> >> >
> >> >
> >> > > 3. Nit - the JSON formatting in the value format/value example
> columns
> >> > > under the "Format of the new status record" heading is a little
> >> > confusing.
> >> > > Assuming the top-level value is meant to be an object, it should be
> >> > wrapped
> >> > > in braces ("{" and "}").
> >> > >
> >> >
> >> > Good catch. Fixed.
> >> >
> >> >
> >> > > 4. The KIP focuses heavily on the use of the status topic for
> storage
> >> of
> >> > > connector topic information, but presumably we'd also want this
> >> > information
> >> > > to be available in standalone mode. If this is the case, it'd be
> nice
> >> to
> >> > > tweak the language to refer explicitly to distributed mode when
> >> > discussing
> >> > > the changes to the status topic and note (probably just in once
> place)
> >> > that
> >> > > similar functionality will also be added to the standalone worker's
> >> > > in-memory status store.
> >> > >
> >> >
> >> > It's true that the design is detailed w.r.t. what should happen in the
> >> > KafkaStatusBackingStore which is a Kafka-based implementation of the
> >> > StatusBackingStore interface. This is intentional because this
> >> > implementation influences and informs the semantics of topic tracking.
> >> I'd
> >> > prefer not to make the language too abstract here. A KIP is not
> exactly
> >> a
> >> > standard and KIPs often discuss the impact of implementation in
> behavior
> >> > (this KIP is a good example). But I'm happy to add a note to mention
> >> that
> >> > these semantics will apply to standalone mode too.
> >> >
> >> >
> >> > > 5. As far as automatic resets for sink connectors go, I agree with
> >> your
> >> > > reasoning about the inherent asymmetry between sinks and sources,
> and
> >> > with
> >> > > the motivation to avoid confusing users by listing
> no-longer-consumed
> >> > > topics in the active topics for a sink connector. I think that this
> >> > > asymmetry is worth avoiding a scenario where a connector is
> >> reconfigured
> >> > to
> >> > > only consume from topic "foo" but, from a prior configuration, topic
> >> > "bar"
> >> > > is still listed in its active topics.
> >> > > I do want to request clarification on the meaning of the phrase "any
> >> > topics
> >> > > no longer consumed" as used under the header "Restarting,
> >> reconfiguring
> >> > or
> >> > > deleting a connector". Does this mean that the current set of active
> >> > topics
> >> > > for the connector will be filtered and any that are longer contained
> >> in
> >> > the
> >> > > sink connector's "topics" config or matched by its "topics.regex"
> >> config
> >> > > will be removed, or does it mean that all topics will be removed and
> >> then
> >> > > the active topics list will be repopulated as records are consumed
> >> from
> >> > new
> >> > > topics?
> >> > >
> >> >
> >> > The intention was to imply the former. But based on Randall's comment
> >> > above, I'm changing the KIP to include a reset parameter in the PUT
> >> > /connectors/{name}/config endpoint
> >> > In this case, the reset will be a complete reset for both source and
> >> sink
> >> > connectors. This will help keeping the behavior symmetric between the
> >> two
> >> > connector types.
> >> >
> >> > Best,
> >> > Konstantine
> >> >
> >> >
> >> > > Cheers,
> >> > >
> >> > > Chris
> >> > >
> >> > > On Thu, Jan 16, 2020 at 1:51 PM Konstantine Karantasis <
> >> > > konstant...@confluent.io> wrote:
> >> > >
> >> > > > Thanks for new comments Randall. Following up with my replies
> inline
> >> > > below.
> >> > > > I'll also go ahead and update the KIP with the suggestions that
> are
> >> > > > outstanding right now and post a summary of the changes.
> >> > > >
> >> > > > On Wed, Jan 15, 2020 at 2:37 PM Randall Hauch <rha...@gmail.com>
> >> > wrote:
> >> > > >
> >> > > > > My responses are inline:
> >> > > > >
> >> > > > > On Wed, Jan 15, 2020 at 2:05 PM Konstantine Karantasis <
> >> > > > > konstant...@confluent.io> wrote:
> >> > > > >
> >> > > > > > Hi Randall, Tom and Almog. I'm excited to read your comments.
> >> I'll
> >> > > > reply
> >> > > > > in
> >> > > > > > separate emails, in order.
> >> > > > > >
> >> > > > > > First, to Randall's comments, I'm replying below with a
> >> reference
> >> > to
> >> > > > the
> >> > > > > > comment number:
> >> > > > > >
> >> > > > > > 1. Although I can imagine we'd be interested in adding
> >> additional
> >> > > > > metadata
> >> > > > > > in the record value, I didn't see the need for a timestamp in
> >> this
> >> > > > first
> >> > > > > > draft.
> >> > > > > > Now that you mention, the way I'd interpret a timestamp in the
> >> > > > connector
> >> > > > > > status record value would be as an approximation of since when
> >> this
> >> > > > > > connector has been using this topic.
> >> > > > > > Happy to add this if we think this info is useful. Of course,
> >> > > accuracy
> >> > > > of
> >> > > > > > this information depends on message retention in Kafka and on
> >> how
> >> > > long
> >> > > > > the
> >> > > > > > workers have been running without a restart, so this might
> make
> >> > this
> >> > > > > > approximation less useful if it gets recomputed from time to
> >> time.
> >> > > > > > To your reference in "Recording active topics" I'll reply
> below,
> >> > > > because
> >> > > > > > that's Tom's question too.
> >> > > > > >
> >> > > > >
> >> > > > > Makes sense that the timestamp in the connector is the
> >> (approximate)
> >> > > time
> >> > > > > that the connector has been using the topic. I do think it's
> worth
> >> > > adding
> >> > > > > in the record value (not relying upon Kafka record timestamp).
> >> > > > >
> >> > > > > Regarding "message retention", by default Connect creates the
> >> status
> >> > > > topic
> >> > > > > with compaction but no deletion policy, which means infinite
> >> > retention.
> >> > > > > Don't several things become problematic if finite retention is
> >> used
> >> > on
> >> > > > the
> >> > > > > status topic, or do we need to worry about this for the active
> >> topic
> >> > > > > records. Do we need to periodically rewrite all of the active
> >> topic
> >> > > > > records? If so, we could just write new records using the
> original
> >> > > > > timestamp as originally read by the worker. If the worker does
> >> > > > periodically
> >> > > > > (maybe just on task startup) rewrite the active topic records,
> >> then
> >> > > we'd
> >> > > > > have to be sure about the semantics of and interplay with
> >> concurrent
> >> > > > > explicit "reset" calls.
> >> > > > >
> >> > > >
> >> > > > Good point. These topics are configured to have infinite
> retention.
> >> > I'll
> >> > > > add the timestamp as type 'long'.
> >> > > >
> >> > > >
> >> > > > >
> >> > > > > >
> >> > > > > > 2. I'll explain with an example, that maybe is worth adding to
> >> the
> >> > > KIP
> >> > > > > > because what's expected to happen might not be as obvious as I
> >> > > thought
> >> > > > > when
> >> > > > > > a new topic is recorded.
> >> > > > > > Let's say we have two workers, W1 and W2, each running two
> >> worker
> >> > > tasks
> >> > > > > T11
> >> > > > > > T12 and T21 T22 respectively associated with a connector C1.
> All
> >> > > tasks
> >> > > > > will
> >> > > > > > run producers that will produce records to the same topic,
> >> > > > "test-topic".
> >> > > > > > When the connector starts, both workers track this connector's
> >> set
> >> > of
> >> > > > > > active topics as empty. Given the absence of synchronization
> >> > (that's
> >> > > > > good)
> >> > > > > > in how this information is recorded and persisted in the
> status
> >> > > topic,
> >> > > > > all
> >> > > > > > four tasks might race to record status messages:
> >> > > > > >
> >> > > > > > For example:
> >> > > > > >
> >> > > > > > T11, running at worker W1, will send Kafka records with:
> >> > > > > > key: topic-test-topic-connector-C1
> >> > > > > > value: "topic": { "connector": "some-source", "task":
> >> > > > > "some-source-TT11",
> >> > > > > > "name": "test-topic" }
> >> > > > > >
> >> > > > > > and T22, running at worker W2, will send Kafka records with:
> >> > > > > > key: topic-test-topic-connector-C1
> >> > > > > > value: "topic": { "connector": "some-source", "task":
> >> > > > > "some-source-TT22",
> >> > > > > > "name": "test-topic" }
> >> > > > > >
> >> > > > > > (similarly tasks T12 and T21 might send topic status records).
> >> > > > > >
> >> > > > > > These four records (they might not even be four but there's
> >> going
> >> > to
> >> > > be
> >> > > > > at
> >> > > > > > least one) may be written in any order. Because the topic is
> >> > > compacted
> >> > > > > and
> >> > > > > > these records have the same key, eventually only one message
> >> will
> >> > be
> >> > > > > > retained.
> >> > > > > > The task ID of that message will be the ID of the task that
> >> wrote
> >> > > > last. I
> >> > > > > > can see this being used mostly for troubleshooting.
> >> > > > > >
> >> > > > >
> >> > > > > Thanks for the clarification. Might be good to clarify the
> >> language a
> >> > > bit
> >> > > > > more, though I'm not convinced an example is really needed.
> >> > > > >
> >> > > >
> >> > > > I'll try to see how they both fit. Sure.
> >> > > >
> >> > > >
> >> > > > >
> >> > > > >
> >> > > > > >
> >> > > > > > 3. I believe across the whole KIP, when I'm referring to the
> >> task
> >> > > > > entity, I
> >> > > > > > imply the worker task. Not the user code that is running as
> >> > > > > implementation
> >> > > > > > of the SourceTask or SinkTask abstract classes. Didn't want to
> >> > > increase
> >> > > > > > complexity by referring to a task as worker task.
> >> > > > > > But I see your point and I'm going to prefer the terms
> "worker"
> >> and
> >> > > > > "worker
> >> > > > > > task" to highlight that it's the framework that is aware of
> this
> >> > > > feature
> >> > > > > > and not the user code.
> >> > > > > >
> >> > > > >
> >> > > > > Thank you.
> >> > > > >
> >> > > >
> >> > > > +1
> >> > > >
> >> > > >
> >> > > > >
> >> > > > >
> >> > > > > >
> >> > > > > > 4. I assumed that absence of changes to the public API would
> >> > indicate
> >> > > > > that
> >> > > > > > these interfaces/abstract classes remain unchanged. But
> >> definitely
> >> > > it's
> >> > > > > > worth to explicitly mention that.
> >> > > > > >
> >> > > > >
> >> > > > > Thanks!
> >> > > > >
> >> > > > > +1
> >> > > >
> >> > > >
> >> > > > >
> >> > > > > >
> >> > > > > > 5. That is correct. My intention is to make reset work well
> with
> >> > the
> >> > > > > > streaming programming model. Resetting (which btw is not
> >> mandatory)
> >> > > > means
> >> > > > > > that you are cleaning the slate for a connector that is
> >> currently
> >> > > > > running,
> >> > > > > > and its currently active topics will soon be populated from
> >> scratch
> >> > > > > because
> >> > > > > > new records will be produced or consumed.
> >> > > > > > But resetting is not required. I see it more like a useful
> >> > operation,
> >> > > > in
> >> > > > > > case users want to clean the active topics history, without
> >> having
> >> > to
> >> > > > > > delete a connector, since delete has further implications in
> the
> >> > > > > > connector's progress tracking.
> >> > > > > >
> >> > > > >
> >> > > > > I do think it's worth trying to clarify in the document what
> >> happens
> >> > > when
> >> > > > > active topics are cleared for a connector that is currently
> >> running.
> >> > > > >
> >> > > >
> >> > > > Good point.
> >> > > >
> >> > > >
> >> > > > >
> >> > > > >
> >> > > > > >
> >> > > > > > 6. I fixed the typo - thanks! I'm very much in favor of
> >> preserving
> >> > > > > symmetry
> >> > > > > > between the two connector types. This has definitely more long
> >> term
> >> > > > > > benefits and may help to avoid confusion. However, the
> >> asymmetry is
> >> > > > > > inherited here by the asymmetry that exists today between
> source
> >> > and
> >> > > > sink
> >> > > > > > connectors.
> >> > > > > > Source connector don't list topics in their configurations but
> >> sink
> >> > > > > > connectors do. So, if a user reconfigures a sink connector
> with
> >> a
> >> > > > > different
> >> > > > > > set of topics, if we don't reset the topics based on the new
> >> > configs
> >> > > > (and
> >> > > > > > my thought here was to match the new configuration with the
> set
> >> of
> >> > > > active
> >> > > > > > topics), the old topics, currently not listed in the
> connectors
> >> > > > > > configuration, will keep showing up as active topics. The user
> >> will
> >> > > > have
> >> > > > > to
> >> > > > > > explicitly reset the active topics after reconfiguring to
> avoid
> >> > this.
> >> > > > If
> >> > > > > > there's consensus that preserving this asymmetry is worse than
> >> > having
> >> > > > to
> >> > > > > > reset the active topics, I'm happy to change this in the KIP.
> >> > > > > >
> >> > > > >
> >> > > > > Would it be easier to keep the symmetric approach (the active
> >> topics
> >> > > are
> >> > > > > cleared only explicitly) if the POST connector method supported
> a
> >> new
> >> > > > query
> >> > > > > parameter to reset the topics before starting (but after
> stopping
> >> any
> >> > > > > already running tasks)? That makes it easy to reconfigure a
> >> connector
> >> > > > > (source or sink) and atomically clear the active topics before
> the
> >> > > > > connector is (re)started. Without that feature, I can't just
> >> > > reconfigure
> >> > > > a
> >> > > > > running sink connector and be sure that the active topics are
> >> cleared
> >> > > > > atomically -- unless we adopt the asymmetric behavior currently
> in
> >> > the
> >> > > > KIP.
> >> > > > >
> >> > > > > WDYT?
> >> > > > >
> >> > > >
> >> > > > I like the idea. I'll update the KIP.
> >> > > >
> >> > > >
> >> > > > > > 7. What I try to avoid here is the following situation: For
> some
> >> > > reason
> >> > > > > (a
> >> > > > > > sequence of failures to write tombstones to the status topic),
> >> > stale
> >> > > > > topic
> >> > > > > > status records remain in that topic even after a connector has
> >> been
> >> > > > > > deleted. Requiring to restart a connector with the same name
> >> just
> >> > to
> >> > > > > apply
> >> > > > > > a follow up reset of active topics doesn't seem necessary. I
> >> like
> >> > the
> >> > > > > idea
> >> > > > > > of decoupling connector existence from the maintenance of the
> >> > status
> >> > > > > topic.
> >> > > > > > Of course, a similar clean up is something that the workers
> >> could
> >> > > also
> >> > > > > > perform, but to avoid complexity and potential race
> conditions,
> >> I'm
> >> > > > > leaving
> >> > > > > > this out for the moment (it's also an implementation detail).
> >> > > > > >
> >> > > > > > 8. Indeed, a security section is warranted. I believe the main
> >> > > > > implication
> >> > > > > > is that if you are able to query a connector's status, config,
> >> etc
> >> > > you
> >> > > > > will
> >> > > > > > be able to also see its active topics. Furthermore, if you are
> >> > > > allowing a
> >> > > > > > worker task to create topics as well as produce or consume
> from
> >> > > topics
> >> > > > > only
> >> > > > > > via connector config overrides, leaving the worker configs
> >> without
> >> > > > > > permissions to these topics, meaning that you assign per
> >> connector
> >> > > > > > permissions and not across the board, then this feature should
> >> > > respect
> >> > > > > > this. The topics are still stored in common data structures
> >> within
> >> > > the
> >> > > > > > worker and are persisted in the status topic. But this info
> >> should
> >> > > not
> >> > > > be
> >> > > > > > leaked to anyone who's not supposed to have access to the
> status
> >> > > topic
> >> > > > or
> >> > > > > > the Connect REST API endpoints. To this respect I feel this
> >> feature
> >> > > > > > inherits the assumptions and security guarantees of similar
> >> > > information
> >> > > > > > already stored by the Connect framework. I'm happy to add this
> >> to a
> >> > > > > > security section, if we agree that the above cover the
> subject.
> >> > > > > >
> >> > > > >
> >> > > > > I think that makes sense, and it'd be great to add that in a
> >> Security
> >> > > > > section.
> >> > > > >
> >> > > >
> >> > > > I'll go ahead and add this info to a Security section.
> >> > > >
> >> > > > >
> >> > > > > > 9. I assumed that partitioning is implied by default, because
> >> > there's
> >> > > > no
> >> > > > > > requirement for complete ordering of topic status records. But
> >> I'll
> >> > > add
> >> > > > > > this fact as a separate bullet. The status.storage.topic is
> >> > already a
> >> > > > > > partitioned topic.
> >> > > > > >
> >> > > > >
> >> > > > > Agreed. I think it'd be sufficient to simply mention that
> >> partition
> >> > > will
> >> > > > be
> >> > > > > chosen based upon the active topic records' keys, ensuring that
> >> all
> >> > > > active
> >> > > > > topic records for the same connector will be written to the same
> >> > > > partition
> >> > > > > and will be totally ordered.
> >> > > > >
> >> > > >
> >> > > > I'm adding a bullet point to refer to partitioning for this topic.
> >> > Thanks
> >> > > >
> >> > > > - Konstantine
> >> > > >
> >> > > >
> >> > > > > >
> >> > > > > > I'm following up with the rest of the comments, shortly.
> >> > > > > > Thanks,
> >> > > > > > Konstantine
> >> > > > > >
> >> > > > > >
> >> > > > > > On Wed, Jan 15, 2020 at 9:19 AM Almog Gavra <
> al...@confluent.io
> >> >
> >> > > > wrote:
> >> > > > > >
> >> > > > > > > Hi Konstantine,
> >> > > > > > >
> >> > > > > > > Thanks for the KIP! This is going to make automatic
> >> integration
> >> > > with
> >> > > > > > > Connect much more powerful.
> >> > > > > > >
> >> > > > > > > My thoughts are mostly around freshness of the data and
> being
> >> > able
> >> > > to
> >> > > > > > > expose that to users. Riffing on Randall's timestamp
> question
> >> -
> >> > > have
> >> > > > we
> >> > > > > > > considered adding some interval at which point a connector
> >> will
> >> > > > > republish
> >> > > > > > > any topics that it encounters and update the timestamp? That
> >> way
> >> > we
> >> > > > > have
> >> > > > > > > some refreshing mechanism that isn't as powerful as the
> >> complete
> >> > > > reset
> >> > > > > > > (which may not be practical in many scenarios).
> >> > > > > > >
> >> > > > > > > I also agree with Randall's other point (Would it be better
> to
> >> > not
> >> > > > > > > automatically reset connector's active topics when a sink
> >> > connector
> >> > > > is
> >> > > > > > > restarted?). I think keeping the behavior as symmetrical
> >> between
> >> > > sink
> >> > > > > and
> >> > > > > > > source connectors is a good idea.
> >> > > > > > >
> >> > > > > > > Lastly, with regards to the API, I can imagine it is also
> >> pretty
> >> > > > useful
> >> > > > > > to
> >> > > > > > > answer the inverse question: "which connectors write to
> topic
> >> X".
> >> > > > > Perhaps
> >> > > > > > > we can achieve this by letting the users compute it and just
> >> > expose
> >> > > > an
> >> > > > > > API
> >> > > > > > > that returns the entire mapping at once (instead of needing
> to
> >> > call
> >> > > > the
> >> > > > > > > /connectors/{name}/topics endpoint for each connector).
> >> > > > > > >
> >> > > > > > > Otherwise, looks good to me! Hits the requirements that I
> had
> >> in
> >> > > mind
> >> > > > > on
> >> > > > > > > the nose.
> >> > > > > > > - Almog
> >> > > > > > >
> >> > > > > > > On Wed, Jan 15, 2020 at 1:14 AM Tom Bentley <
> >> tbent...@redhat.com
> >> > >
> >> > > > > wrote:
> >> > > > > > >
> >> > > > > > > > Hi Konstantine,
> >> > > > > > > >
> >> > > > > > > > Thanks for the KIP, I can see how it could be useful.
> >> > > > > > > >
> >> > > > > > > > a) Did you consider using a metric for this? I don't think
> >> it
> >> > > would
> >> > > > > > > satisfy
> >> > > > > > > > all the use cases you have in mind, but you could mention
> >> it in
> >> > > the
> >> > > > > > > > rejected alternatives.
> >> > > > > > > >
> >> > > > > > > > b) If the topic name contains the string "-connector" then
> >> the
> >> > > key
> >> > > > > > format
> >> > > > > > > > is ambiguous. This isn't necessarily fatal because the
> value
> >> > will
> >> > > > > > > > disambiguate, but it could be misleading. Any reason not
> to
> >> > just
> >> > > > use
> >> > > > > a
> >> > > > > > > JSON
> >> > > > > > > > key, and simplify the value?
> >> > > > > > > >
> >> > > > > > > > c) I didn't understand this part: "As soon as a worker
> >> detects
> >> > > the
> >> > > > > > > addition
> >> > > > > > > > of a topic to a connector's set of active topics, the
> worker
> >> > will
> >> > > > > cease
> >> > > > > > > to
> >> > > > > > > > post update messages to the status.storage.topic for that
> >> > > > connector.
> >> > > > > ".
> >> > > > > > > I'm
> >> > > > > > > > sure I've overlooking something but why is this necessary?
> >> Is
> >> > > this
> >> > > > > were
> >> > > > > > > the
> >> > > > > > > > task id in the value is used?
> >> > > > > > > >
> >> > > > > > > > Thanks again,
> >> > > > > > > >
> >> > > > > > > > Tom
> >> > > > > > > >
> >> > > > > > > > On Wed, Jan 15, 2020 at 12:15 AM Randall Hauch <
> >> > rha...@gmail.com
> >> > > >
> >> > > > > > wrote:
> >> > > > > > > >
> >> > > > > > > > > Oh, one more thing:
> >> > > > > > > > >
> >> > > > > > > > > 9. There's no mention of how the status topic is
> >> partitioned,
> >> > > or
> >> > > > > how
> >> > > > > > > > > partitioning will be used by the new topic records. The
> >> KIP
> >> > > > should
> >> > > > > > > > probably
> >> > > > > > > > > outline this for clarity and completeness.
> >> > > > > > > > >
> >> > > > > > > > > Best regards,
> >> > > > > > > > >
> >> > > > > > > > > Randall
> >> > > > > > > > >
> >> > > > > > > > > On Tue, Jan 14, 2020 at 5:25 PM Randall Hauch <
> >> > > rha...@gmail.com>
> >> > > > > > > wrote:
> >> > > > > > > > >
> >> > > > > > > > > > Thanks, Konstantine. Overall, this KIP looks
> interesting
> >> > and
> >> > > > > really
> >> > > > > > > > > > useful, and for the most part is spot on. I do have a
> >> > number
> >> > > of
> >> > > > > > > > > > questions/comments about specifics:
> >> > > > > > > > > >
> >> > > > > > > > > > 1. The topic records have a value that includes the
> >> > > > connector
> >> > > > > > > name,
> >> > > > > > > > > > task number that last reported the topic is used,
> and
> >> > the
> >> > > > > topic
> >> > > > > > > > name.
> >> > > > > > > > > > There's no mention of record timestamps, but I
> >> wonder if
> >> > > > it'd
> >> > > > > be
> >> > > > > > > > > useful to
> >> > > > > > > > > > record this. One challenge might be that a
> connector
> >> > does
> >> > > > not
> >> > > > > > > write
> >> > > > > > > > > to a
> >> > > > > > > > > > topic for a while or the task remains running for
> >> long
> >> > > > periods
> >> > > > > > of
> >> > > > > > > > > time and
> >> > > > > > > > > > therefore the worker doesn't record that this topic
> >> has
> >> > > been
> >> > > > > > newly
> >> > > > > > > > > written
> >> > > > > > > > > > to since it the task was restarted. IOW, the
> >> semantics
> >> > of
> >> > > > the
> >> > > > > > > > > timestamp may
> >> > > > > > > > > > be a bit murky. Have you thought about recording
> the
> >> > > > > timestamp,
> >> > > > > > > and
> >> > > > > > > > > if so
> >> > > > > > > > > > what are the pros and cons?
> >> > > > > > > > > > - The "Recording active topics" section says the
> >> > > following:
> >> > > > > > > > > > "As soon as a worker detects the addition of a
> >> topic
> >> > > to a
> >> > > > > > > > > > connector's set of active topics, all the
> >> connector's
> >> > > > tasks
> >> > > > > > > that
> >> > > > > > > > > inspect
> >> > > > > > > > > > source or sink records will cease to post update
> >> > > messages
> >> > > > > to
> >> > > > > > > the
> >> > > > > > > > > > status.storage.topic."
> >> > > > > > > > > > This probably means the timestamp won't be very
> >> > useful.
> >> > > > > > > > > > 2. The KIP says "the Kafka record value stores the
> >> ID of
> >> > > the
> >> > > > > > task
> >> > > > > > > > that
> >> > > > > > > > > > succeeded to store a topic status record last."
> >> However,
> >> > > > this
> >> > > > > > is a
> >> > > > > > > > bit
> >> > > > > > > > > > unclear: is it really storing the last task that
> >> > > > successfully
> >> > > > > > > wrote
> >> > > > > > > > > to that
> >> > > > > > > > > > topic (as this would require very frequent writes
> to
> >> > this
> >> > > > > > topic),
> >> > > > > > > or
> >> > > > > > > > > is it
> >> > > > > > > > > > more that this is the task that was last *recorded*
> >> as
> >> > > > having
> >> > > > > > > > written
> >> > > > > > > > > > to the topic? (Here, "recorded" could be a bit of a
> >> gray
> >> > > > area,
> >> > > > > > > since
> >> > > > > > > > > this
> >> > > > > > > > > > would depend on the how the worker periodically
> >> records
> >> > > this
> >> > > > > > > > > information.)
> >> > > > > > > > > > Any kind of clarity here might be helpful.
> >> > > > > > > > > > 3. In the "Recording active topics" section (and
> the
> >> > > > > surrounding
> >> > > > > > > > > > sections), the "task" is used ambiguously. For
> >> example,
> >> > > > "when
> >> > > > > > its
> >> > > > > > > > > tasks
> >> > > > > > > > > > start processing their first records ... these
> tasks
> >> > will
> >> > > > > start
> >> > > > > > > > > inspecting
> >> > > > > > > > > > which is the Kafka topic of each of these records".
> >> > IIUC,
> >> > > > the
> >> > > > > > > first
> >> > > > > > > > > "task"
> >> > > > > > > > > > mentioned is the connector's task, and the second
> is
> >> the
> >> > > > > > worker's
> >> > > > > > > > > task. Do
> >> > > > > > > > > > we need to distinguish this more clearly?
> >> > > > > > > > > > 4. Maybe I missed it, but does this KIP explicitly
> >> say
> >> > > that
> >> > > > > the
> >> > > > > > > > > > Connector API is unchanged? It's probably worth
> >> pointing
> >> > > out
> >> > > > > to
> >> > > > > > > help
> >> > > > > > > > > > assuage any concerns that connector implementations
> >> have
> >> > > to
> >> > > > > > change
> >> > > > > > > > to
> >> > > > > > > > > make
> >> > > > > > > > > > use of this feature.
> >> > > > > > > > > > 5. In the "Resetting a connector's set of active
> >> topics"
> >> > > > > section
> >> > > > > > > the
> >> > > > > > > > > > behavior is not exactly clear. Consider a user
> >> running
> >> > > > > connector
> >> > > > > > > > "A",
> >> > > > > > > > > the
> >> > > > > > > > > > connector has been fully started and is processing
> >> > > records,
> >> > > > > and
> >> > > > > > > the
> >> > > > > > > > > worker
> >> > > > > > > > > > has recorded topic usage records. Then the user
> >> resets
> >> > the
> >> > > > > > active
> >> > > > > > > > > topics
> >> > > > > > > > > > for connector A while the connector is still
> >> running? If
> >> > > the
> >> > > > > > > > connector
> >> > > > > > > > > > writes to no new topics, before the tasks are
> >> rebalanced
> >> > > > then
> >> > > > > is
> >> > > > > > > it
> >> > > > > > > > > correct
> >> > > > > > > > > > that Connect would report no active topics? And
> after
> >> > the
> >> > > > > tasks
> >> > > > > > > are
> >> > > > > > > > > > rebalance, will the worker record any topics used
> by
> >> > > > connector
> >> > > > > > A?
> >> > > > > > > > > > 6. In the "Restaring" (misspelled) section:
> >> > > "Reconfiguring a
> >> > > > > > > source
> >> > > > > > > > > > connector has also no altering effect for a source
> >> > > > connector.
> >> > > > > > > > > However, when
> >> > > > > > > > > > reconfiguring a sink connector if the new
> >> configuration
> >> > no
> >> > > > > > longer
> >> > > > > > > > > includes
> >> > > > > > > > > > any of the previously tracked topics, these topics
> >> will
> >> > be
> >> > > > > > removed
> >> > > > > > > > > from the
> >> > > > > > > > > > set of active topics for this sink connector by
> >> > appending
> >> > > > > > > tombstone
> >> > > > > > > > > > messages appropriately after the reconfiguration of
> >> the
> >> > > > > > > connector."
> >> > > > > > > > > Would
> >> > > > > > > > > > it be better to not automatically reset connector's
> >> > active
> >> > > > > > topics
> >> > > > > > > > > when a
> >> > > > > > > > > > sink connector is restarted? Isn't that more
> >> consistent
> >> > > with
> >> > > > > the
> >> > > > > > > > > > "Resetting" behavior and the goals at the top of
> the
> >> > KIP:
> >> > > > > "it'd
> >> > > > > > be
> >> > > > > > > > > useful
> >> > > > > > > > > > for users, operators and applications to know which
> >> are
> >> > > the
> >> > > > > > topics
> >> > > > > > > > > that a
> >> > > > > > > > > > connector has used since it was first created"?
> >> > > > > > > > > > 7. The `PUT /connectors/{name}/topics/reset`
> endpoint
> >> > > "this
> >> > > > > > > request
> >> > > > > > > > > > can be reapplied after the deletion of the
> >> connector".
> >> > > IOW,
> >> > > > > even
> >> > > > > > > > > though
> >> > > > > > > > > > connector with that name doesn't exist, we can
> still
> >> > make
> >> > > > this
> >> > > > > > > > > request? How
> >> > > > > > > > > > does this compare with other methods such as
> >> "status"?
> >> > > > > > > > > > 8. What are the security implications of this
> >> proposal?
> >> > > > > > > > > >
> >> > > > > > > > > > As you can see, most of these can probably be
> addressed
> >> > > without
> >> > > > > > much
> >> > > > > > > > > work.
> >> > > > > > > > > >
> >> > > > > > > > > > Best regards,
> >> > > > > > > > > >
> >> > > > > > > > > > Randall
> >> > > > > > > > > >
> >> > > > > > > > > > On Mon, Jan 13, 2020 at 11:05 PM Konstantine
> Karantasis
> >> <
> >> > > > > > > > > > konstant...@confluent.io> wrote:
> >> > > > > > > > > >
> >> > > > > > > > > >> Hi all.
> >> > > > > > > > > >>
> >> > > > > > > > > >> I just posted KIP-558: Track the set of actively used
> >> > topics
> >> > > > by
> >> > > > > > > > > connectors
> >> > > > > > > > > >> in Kafka Connect
> >> > > > > > > > > >>
> >> > > > > > > > > >> Wiki link here:
> >> > > > > > > > > >>
> >> > > > > > > > > >>
> >> > > > > > > > >
> >> > > > > > > >
> >> > > > > > >
> >> > > > > >
> >> > > > >
> >> > > >
> >> > >
> >> >
> >>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-558%3A+Track+the+set+of+actively+used+topics+by+connectors+in+Kafka+Connect
> >> > > > > > > > > >>
> >> > > > > > > > > >> I think it's a nice extension to follow up on KIP-158
> >> and
> >> > a
> >> > > > > useful
> >> > > > > > > > > feature
> >> > > > > > > > > >> to the ever increasing number of applications that
> are
> >> > built
> >> > > > > > around
> >> > > > > > > > > Kafka
> >> > > > > > > > > >> Connect.
> >> > > > > > > > > >> Would love to hear what you think.
> >> > > > > > > > > >>
> >> > > > > > > > > >> Best,
> >> > > > > > > > > >> Konstantine
> >> > > > > > > > > >>
> >> > > > > > > > > >
> >> > > > > > > > >
> >> > > > > > > >
> >> > > > > > >
> >> > > > > >
> >> > > > >
> >> > > >
> >> > >
> >> >
> >>
> >
>
