Hi Andrew and Chris, Firstly, thanks for the input.
To me, the ?type syntax has some pros and cons. On the pros side: * it's pretty succinct * it's flexible enough for the use cases we've identified so far. On the cons side: * it's a bit cryptic; I don't think people who didn't know it already would be able to guess what ?type meant. * it doesn't work so well if there is a whole chain of transformations which need to be applied conditionally (that can still be done, of course, but the user has to duplicate the configuration for each SMT). Nor does it work if you need something akin to a "nested if" (you could fake it using And), but we don't really expect people to need that. Andrew, you didn't give an example of a negated match. Would you use something like !?type for that, or did you have another idea? On balance, I think this is a reasonable trade off. I agree that exposing RecordPredicate as a public API, while providing common implementation(s) would allow most use cases to be covered without coding, but also allow people with specific unaddressed needs to implement their own without having to write a streaming application to do so. Again, I think this is a reasonable trade off. It would be helpful to have a consensus about exactly which condition implementations the KIP should provide. I think we all agree that TopicMatches (or should it be TopicNameMatches?) should be included. HasHeader (or should it be HasHeaderWithName or HasHeaderMatching for a regex version?), And and Or all seem like they could be useful, even though no one has pointed to concrete use cases. It might also be worth considering that it would be natural to add a Filter SMT which filtered records using a RecordPredicate. Perhaps that provides motivation for conditions on the record key as well? If people think the Filter SMT would be useful I'm willing to include it in this KIP, since it seems straightforward. If people are happy with this approach, I'll update the KIP. Kind regards, Tom On Sun, Apr 26, 2020 at 3:00 PM Andrew Schofield <andrew_schofi...@live.com> wrote: > Hi, > I'm suggesting that RecordPredicate be another pluggable interface that > users > could conceivably implement on their own, and that the KIP introduces the > most likely ones as supplied implementations, much as there are SMT > implementations such as HoistField. I don't really see users implementing > their own RecordPredicate, but the supplied ones would probably have a > common > interface and it seems a pity not to expose that as an external API. > > SMT is essentially a toolkit for Kafka Connect and I think RecordPredicate > would be a nice minor enhancement and I'd be happy to contribute code. > > In order to make it simpler to configure, I suggest that the class name > configured > using "?type" would be assumed to be in package > org.apache.kafka.connect.predicates > in the absence of a package name so that shorter names such as > "TopicMatches" > could be used. > > Cheers, > Andrew Schofield > IBM Event Streams > > On 25/04/2020, 21:22, "Christopher Egerton" <chr...@confluent.io> wrote: > > Hi Andrew, > > I know a DSL seems like overkill, and I'm not attached to it by any > means, > but I do think it serves a vital purpose in that it allows people who > don't > know how or have the time to write Java code to act on data being > processed > by connectors. > > Are you proposing that the "RecordPredicate" be another pluggable > interface > that users could then implement on their own? Or, would this be purely > a > syntactic expansion to SMT configuration with some subset of hard-coded > predicates provided by the framework? I think there's value in the > latter, > but the former doesn't seem like it'd bring much to the table as far as > users are concerned, and for developers, it is an improvement, but not > a > major one. > > Cheers, > > Chris > > On Fri, Apr 24, 2020 at 12:04 PM Andrew Schofield < > schofieldandr...@gmail.com> wrote: > > > I wonder whether we're getting a bit overcomplicated with this. I > think all > > that's required here is to add an optional guard predicate for a > > Transformation. > > The predicate cannot end the Transformation chain, but it can allow > or > > prevent a particular > > Transformation from running. > > > > How about this as syntax? > > transforms: extractInt > > transforms.extractInt.?type: > > org.apache.kafka.connect.predicates.TopicMatches > > transforms.extractInt.?regex: my-prefix-.* > > transforms.extractInt.type: > > org.apache.kafka.connect.transforms.ExtractField$Key > > transforms.extractInt.field: c1 > > > > The idea is that a Transformation can have an optional > RecordPredicate. > > The RecordPredicate > > can have configuration items, in a similar way to a Transformation. > The > > syntax of > > using a '?' prefix to separate configuration for the RecordPredicate > from > > the configuration > > for the Transformation could conceivably clash with an existing > > Transformation > > but the chances are minimal. > > > > This syntax doesn't allow for an 'else', but if the KIP offers say a > > TopicMatches predicate > > then that can be configured to return FALSE if the predicate matches. > > > > I feel that a DSL for SMTs is overkill. If you need something that > > complex, it's > > perhaps too complex for a transformation chain and it's really a > streaming > > application. > > > > Andrew Schofield > > IBM Event Streams > > > > On 2020/04/08 21:39:31, Christopher Egerton <chr...@confluent.io> > wrote: > > > Hi Tom, > > > > > > With regards to the potential Transformation::validate method, I > don't > > > quite follow your objections. The AbstractHerder class, > ConnectorConfig > > > class, and embedding of ConfigDefs that happens with the two is all > > > internal logic and we're allowed to modify it however we want, as > long as > > > it doesn't alter any public-facing APIs (and if it does, we just > have to > > > document those changes in a KIP). We don't have to embed the > ConfigDef > > for > > > a transformation chain inside another ConfigDef if the API we want > to > > > present to our users doesn't play well with that part of the code > base. > > > Additionally, beyond aligning with the existing API provided for > > > connectors, another advantage is that it becomes possible to > validate > > > properties for a configuration in the context of all other > properties, so > > > to be clear, it's not just about preserving what may be perceived > as a > > > superficial similarity and comes with real functional benefits > that can't > > > be provided (at least, not as easily) by dynamic construction of a > > > ConfigDef object. > > > > > > As far as the new proposal goes, I hate to say it, but I think > we're > > stuck > > > with the worst of both worlds here. Adding the new RecordPredicate > > > interface seems like it defeats the whole purpose of SMTs, which > is to > > > allow manipulation of a connector's event stream by users who don't > > > necessarily know how or have the time to write Java code of their > own. > > This > > > is also why I'm in favor of adding a lightweight DSL for the > condition; > > > emphasizing readability for people who aren't very familiar with > Connect > > > and just want to get something going quickly should be a priority > for > > SMTs. > > > But if that's not going to happen with this KIP, I'd still choose > the > > > simpler, less-flexible approach initially outlined, in order to > keep > > things > > > simple for people creating connectors and try to let them > accomplish what > > > they want via configuration, not code. > > > > > > With regards to the question about where the line should be drawn > and how > > > much is too much and comparisons to other stream processing > frameworks, I > > > think the nature of SMTs draws the line quite nicely: you can only > > process > > > one message at a time. There's plenty of use cases out there for > > > heavier-duty processing frameworks like Kafka Streams, with > aggregate > > > operations, joining of streams, expanding a single message into > multiple > > > messages, etc. With SMTs, none of this is possible; the general > use case > > is > > > to filter and clean a stream of data. If any of the heavier-weight > logic > > > provided by, e.g., Streams, isn't required for a project, it > should be > > > possible to get along with just a collection of sink connectors, > source > > > connectors, a converter or two, and SMTs that smooth over any > differences > > > in data format between what source connectors produce and what sink > > > connectors expect. This is why I'm comfortable suggesting heavy > expansion > > > of the out-of-the-box SMTs that we provide with Connect; as long as > > they're > > > reasonable to configure, they can greatly reduce the operational > burden > > on > > > anyone running and/or using a Connect cluster since they might > entirely > > > replace additional services that would otherwise be required. > > > > > > All that said--this is a huge ask of someone who just wants to > support > > the > > > SMT equivalent of an "if" statement, and it's totally > understandable if > > > that's too much to ask. The one concern I have left is that if we > expand > > > the SMT in the future, there become compatibility concerns since > SMTs are > > > pretty tightly-coupled with the worker on which they run (although > > > technically, with some classpath/plugin path shuffling, you can run > > > different versions of the out-of-the-box SMTs from the Connect > worker on > > > which they're run). Someone might write a connector config with the > > > If/Conditional/Whatever SMT with a condition type that works on one > > worker, > > > but that doesn't work on another worker that's running an earlier > version > > > of Connect. This is why I'm in favor of adding extra predicates now > > instead > > > of later; if we're going to implement what has the potential to be > a bit > > of > > > a Swiss army knife SMT with room for future expansion of > configuration, > > and > > > we can think of a reasonable way to add that functionality now, it > seems > > > better for users and administrators of Connect to try to do that > now > > > instead of later. > > > > > > Cheers, > > > > > > Chris > > > > > > On Wed, Apr 8, 2020 at 9:45 AM Tom Bentley <tbent...@redhat.com> > wrote: > > > > > > > Since no one objected I've updated the KIP with the revised way > to > > > > configure this transformation. > > > > > > > > On Mon, Apr 6, 2020 at 2:52 PM Tom Bentley <tbent...@redhat.com> > > wrote: > > > > > > > > > To come back about a point Chris made: > > > > > > > > > > 1. Instead of the new "ConfigDef config(Map<String, String> > props)" > > > > method, > > > > >> what would you think about adopting a similar approach as the > > framework > > > > >> uses with connectors, by adding a "Config validate(Map<String, > > String> > > > > >> props)" method that can perform custom validation outside of > what > > can be > > > > >> performed by the ConfigDef's single-property-at-a-time > validation? > > It > > > > may > > > > >> be a little heavyweight for use with this particular SMT, but > it'd > > > > provide > > > > >> more flexibility for other SMT implementations and would > mirror an > > API > > > > >> that > > > > >> developers targeting the framework are likely already > familiar with. > > > > >> > > > > > > > > > > The validate() + config() approach taken for Connectors > doesn't quite > > > > work > > > > > for Transformations. > > > > > > > > > > The default Connector.validate() basically just calls > > > > > `config().validate(connectorConfigs)` and returns a Config. > > Separately > > > > the > > > > > AbstractHeader also calls `config()` and uses the Config and > > ConfigDef to > > > > > build the ConfigInfos. The contract is not really defined well > > enough in > > > > > the javadoc, but this means a connector can use validate() to > build > > the > > > > > ConfigDef which it will return from config(). > > > > > > > > > > For Transformations we don't really want validate() to perform > > validation > > > > > at all since ultimately the transformations config will be > embedded > > in > > > > the > > > > > connector's and will be validated by the connector itself. It > > wouldn't be > > > > > harmful if it _did_ perform validation, just unnecessary. But > having > > a > > > > > validate() method that ought not to validate() seems like a > recipe > > for > > > > > confusion. > > > > > > > > > > Also problematic is that there's no use for the Config > returned from > > > > > Transformations.validate(). > > > > > > > > > > So I'm not convinced that the superficial similarity really > gains > > > > anything. > > > > > > > > > > Kind regards, > > > > > > > > > > Tom > > > > > > > > > > On Mon, Apr 6, 2020 at 2:29 PM Tom Bentley < > tbent...@redhat.com> > > wrote: > > > > > > > > > >> Hi, > > > > >> > > > > >> Hi all, > > > > >> > > > > >> Thanks for the discussion so far. > > > > >> > > > > >> It seems a bit weird to me that when configuring the > Conditional SMT > > > > with > > > > >> a DSL you would use a concise, intuitive DSL for expressing > the > > > > condition, > > > > >> but not for the transforms that it's guarding. It also seems > > natural, if > > > > >> you support this for conditionally applying SMTs, that you'd > soon > > want > > > > to > > > > >> support the same thing for a generic filter transformer. > Then, if > > you > > > > can > > > > >> configure a filter transformation using this DSL, it becomes > odd > > that > > > > you > > > > >> can't do this for mapping transformations. I think it would > be a > > > > mistake to > > > > >> go specifying an expression language for conditions when > really that > > > > might > > > > >> just be part of a language for transformations. > > > > >> > > > > >> I think it would be possible today to write an SMT which > allowed > > you to > > > > >> express the transformation in a DSL. Concretely, it's > possible to > > > > imagine a > > > > >> single transformation taking a DSL something like this: > > > > >> > > > > >> compose( > > > > >> Flatten.Key(delimiter: ':'), > > > > >> If(condition: TopicMatches(pattern: "blah-.*"), > > > > >> then: Flatten.Value(delimiter: '/'))) > > > > >> > > > > >> All I've really done here, beyond what was already proposed, > is > > rename > > > > >> Conditional to If, imagine a couple more bits of syntax > > > > >> (SMTs being constructed by class name and named argument > invocation > > > > >> syntax to support SMT constructors) and add a higher level > compose() > > > > >> function for chaining SMTs (which could easily be replaced > with > > brace > > > > >> delimited blocks). > > > > >> > > > > >> That may be a discussion we should have, but I think in > _this_ KIP > > we > > > > >> should focus on the conditional part, since the above example > > hopefully > > > > >> shows that it would be possible to reuse it in a DSL if there > was > > > > appetite > > > > >> for that. > > > > >> > > > > >> With that in mind, and since my original suggestion for an > > abbreviated > > > > >> config syntax didn't appeal to people, I propose that we > stick with > > the > > > > >> existing norms for configuring this. > > > > >> The previous example would look like this: > > > > >> > > > > >> transformation: flattenKey,if > > > > >> transformation.flattenKey.type: Flatten.Key > > > > >> transformation.flattenKey.delimiter: : > > > > >> transformation.if.type: If > > > > >> transformation.if.condition.type: TopicMatches > > > > >> transformation.if.condition.pattern: blah-.* > > > > >> transformation.if.then: flattenValue > > > > >> transformation.if.then.flattenValue.type: Flatten.Value > > > > >> transformation.if.then.flattenValue.delimiter: / > > > > >> > > > > >> Also, I'm inclined to think we should stick to just supporting > > > > >> TopicMatches and Not, since we've not identified an actual > need for > > > > >> 'has-header', 'or' and 'and'. > > > > >> > > > > >> An example of the usage of Not would look like this: > > > > >> > > > > >> transformation: flattenKey,if > > > > >> transformation.flattenKey.type: Flatten.Key > > > > >> transformation.flattenKey.delimiter: : > > > > >> transformation.if.type: If > > > > >> transformation.if.condition.type: Not > > > > >> transformation.if.condition.operand: startsWithBlah > > > > >> transformation.if.condition.operand.startsWithBlah.type: > > TopicMatches > > > > >> transformation.if.condition.operand.startsWithBlah.pattern: > blah-.* > > > > >> transformation.if.then: flattenValue > > > > >> transformation.if.then.flattenValue.type: Flatten.Value > > > > >> transformation.if.then.flattenValue.delimiter: / > > > > >> > > > > >> Hopefully we can agree that this allows the conditional SMT > part to > > make > > > > >> progress without getting bogged down. > > > > >> > > > > >> Thoughts? If this seems broadly reasonable, I'll update the > KIP. > > > > >> > > > > >> Kind regards, > > > > >> > > > > >> Tom > > > > >> > > > > >> On Fri, Apr 3, 2020 at 5:55 PM Gunnar Morling < > gun...@hibernate.org > > > > > > > >> wrote: > > > > >> > > > > >>> Hi all, > > > > >>> > > > > >>> Thanks a lot for this initiative, Tom! > > > > >>> > > > > >>> To shed some light, the use case where this first came up, > were > > issues > > > > >>> we saw with SMTs being applied to the different topics > produced by > > the > > > > >>> Debezium change data capture connectors. There are different > kinds > > of > > > > >>> topics (for change data, schema history, heartbeats etc.) > and the > > > > >>> record structure to expect may vary between those. Hence we > saw > > issues > > > > >>> with SMTs like ExtractField, which for instance only should > be > > applied > > > > >>> to all change data topics but not the other ones. > > > > >>> > > > > >>> I like the overall approach; for Debezium's purposes, the > simple > > topic > > > > >>> matching and negation operators would be sufficient already. > I > > agree > > > > >>> with Chris and would prefer one single condition attribute, > which > > > > >>> contains a single condition or potentially a logical > expression > > with > > > > >>> not, and, etc. I think it's less ambiguous, in particular > when it > > > > >>> comes to ordering of the different conditions and > determining their > > > > >>> precedence. > > > > >>> > > > > >>> Would love to see this feature in one or another way in > Connect. > > > > >>> > > > > >>> Best, > > > > >>> > > > > >>> --Gunnar > > > > >>> > > > > >>> > > > > >>> > > > > >>> Am Do., 2. Apr. 2020 um 18:48 Uhr schrieb Tom Bentley < > > > > >>> tbent...@redhat.com>: > > > > >>> > > > > > >>> > Hi Chris and Sönke, > > > > >>> > > > > > >>> > Using the numbering from Chris's email... > > > > >>> > > > > > >>> > 1. That's a good point, I'll see what is needed to make > that > > work. > > > > >>> > > > > > >>> > 2. I'm happy enough to add support for "and" and "or" as > part of > > this > > > > >>> KIP > > > > >>> > if people can see a need for it. > > > > >>> > > > > > >>> > In a similar vein, I was wondering about whether it would > be > > > > worthwhile > > > > >>> > having the equivalent of an "else" clause (what's in the > KIP is > > > > >>> basically > > > > >>> > an "if" statement). Without support for "else" I think > people > > would > > > > >>> often > > > > >>> > need two conditionals, with the condition of one being the > > negation > > > > of > > > > >>> the > > > > >>> > condition of another. > > > > >>> > > > > > >>> > 3. I can see the attraction of an expression language. The > pros > > > > include > > > > >>> > being terse and familiar to programmers and potentially > very > > flexible > > > > >>> if > > > > >>> > that's needed in the future. I had a play and implemented > it > > using > > > > >>> ANTLR > > > > >>> > and it's not difficult to write a grammar and implement the > > functions > > > > >>> we've > > > > >>> > already discussed and get decent error messages when the > > expression > > > > is > > > > >>> > malformed. So on the one hand I quite like the idea. On > the other > > > > hand > > > > >>> it > > > > >>> > feels like overkill for the use cases that have actually > been > > > > >>> identified so > > > > >>> > far. > > > > >>> > > > > > >>> > @Sönke what do you make of the expression language idea? > > > > >>> > > > > > >>> > Kind regards, > > > > >>> > > > > > >>> > Tom > > > > >>> > > > > > >>> > On Wed, Apr 1, 2020 at 9:49 PM Christopher Egerton < > > > > >>> chr...@confluent.io> > > > > >>> > wrote: > > > > >>> > > > > > >>> > > Hi Tom, > > > > >>> > > > > > > >>> > > This looks great and I'd love to see the out-of-the-box > SMTs > > become > > > > >>> even > > > > >>> > > more powerful with the improvements you've proposed! Got > a few > > > > >>> remarks and > > > > >>> > > would be interested in your thoughts: > > > > >>> > > > > > > >>> > > 1. Instead of the new "ConfigDef config(Map<String, > String> > > props)" > > > > >>> method, > > > > >>> > > what would you think about adopting a similar approach > as the > > > > >>> framework > > > > >>> > > uses with connectors, by adding a "Config > validate(Map<String, > > > > >>> String> > > > > >>> > > props)" method that can perform custom validation > outside of > > what > > > > >>> can be > > > > >>> > > performed by the ConfigDef's single-property-at-a-time > > validation? > > > > >>> It may > > > > >>> > > be a little heavyweight for use with this particular > SMT, but > > it'd > > > > >>> provide > > > > >>> > > more flexibility for other SMT implementations and would > > mirror an > > > > >>> API that > > > > >>> > > developers targeting the framework are likely already > familiar > > > > with. > > > > >>> > > 2. The possibility for adding the logical operators > "and" and > > "or" > > > > is > > > > >>> > > mentioned, but only as a potential future change and not > one > > > > >>> proposed by > > > > >>> > > this KIP. Why not include those operators sooner rather > than > > later? > > > > >>> > > 3. The syntax for named conditions that are then > referenced in > > > > >>> logical > > > > >>> > > operators is... tricky. It took me a few attempts to > grok the > > > > example > > > > >>> > > provided in the KIP after reading Sönke's question about > the > > > > example > > > > >>> for > > > > >>> > > negation. What about a more sophisticated but less > verbose > > syntax > > > > >>> that > > > > >>> > > supports a single configuration for the condition, even > with > > > > logical > > > > >>> > > operators? I'm thinking something like > > > > >>> > > "transforms.conditionalExtract.condition: > > > > not(has-header:my-header)" > > > > >>> > > instead of the "transforms.conditionalExtract.condition: > > > > >>> not:hasMyHeader" > > > > >>> > > and "transforms.conditionalExtract.condition.hasMyHeader: > > > > >>> > > has-header:my-header" properties. If support for a > logical > > "and" is > > > > >>> added, > > > > >>> > > this could then be expanded to something like > > > > >>> > > "transforms.conditionalExtract.condition: > > > > and(has-header(my-header), > > > > >>> > > not(topic-matches(my-prefix-.*)))". There would be > additional > > > > >>> complexity > > > > >>> > > here with the need to escape parentheses and commas that > are > > > > >>> intended to be > > > > >>> > > treated literally (as part of a header name, for example) > > instead > > > > of > > > > >>> as > > > > >>> > > part of the syntax for the condition itself, but a little > > > > additional > > > > >>> > > complexity for edge cases like that may be warranted if > it > > heavily > > > > >>> reduces > > > > >>> > > complexity for the common cases. The rationale for the > proposed > > > > >>> > > parentheses-based syntax here instead of what's > mentioned in > > the > > > > KIP > > > > >>> > > (something like "and: <condition1>, <condition2>") is to > help > > with > > > > >>> > > readability; we probably wouldn't need that with the > approach > > of > > > > >>> naming > > > > >>> > > conditions via separate properties, but things may get a > little > > > > >>> nasty with > > > > >>> > > literal conditions included there, especially with the > > possibility > > > > of > > > > >>> > > nesting. Finally, the shift in syntax here should make it > > easier to > > > > >>> handle > > > > >>> > > cases like the header value matching brought up by > Sönke; it > > might > > > > >>> look > > > > >>> > > something like "header-matches(header-name, > > header-value-pattern)". > > > > >>> > > > > > > >>> > > Cheers, > > > > >>> > > > > > > >>> > > Chris > > > > >>> > > > > > > >>> > > On Wed, Apr 1, 2020 at 9:00 AM Tom Bentley < > > tbent...@redhat.com> > > > > >>> wrote: > > > > >>> > > > > > > >>> > > > Hi Sönke, > > > > >>> > > > > > > > >>> > > > Thanks for taking a look. > > > > >>> > > > > > > > >>> > > > Let me answer in reverse order, since I think it might > make > > more > > > > >>> sense > > > > >>> > > that > > > > >>> > > > way... > > > > >>> > > > > > > > >>> > > > Also, while writing that, I noticed that you have a > version > > with > > > > >>> and > > > > >>> > > > > without "name" for your transformation in the KIP: > > > > >>> > > > > > > > > >>> > > > > transforms.conditionalExtract.condition.hasMyHeader: > > > > >>> > > has-header:my-header > > > > >>> > > > > and > > > > >>> > > > > transforms.conditionalExtract.condition: > > has-header:my-header > > > > >>> > > > > > > > > >>> > > > > > > > >>> > > > The example > > > > >>> > > > transforms.conditionalExtract.condition: > > has-header:my-header > > > > >>> > > > is a "has-header" condition (the prefix of the config > value), > > > > >>> which will > > > > >>> > > > match records with a "my-header" header (given in the > > suffix). > > > > >>> > > > > > > > >>> > > > The other example given is: > > > > >>> > > > transforms.conditionalExtract.condition: > not:hasMyHeader > > > > >>> > > > > transforms.conditionalExtract.condition.hasMyHeader: > > > > >>> > > > has-header:my-header > > > > >>> > > > The root of the condition is a "not" condition (the > prefix > > of the > > > > >>> value > > > > >>> > > for > > > > >>> > > > the transforms.conditionalExtract.condition key) of > another > > named > > > > >>> > > condition > > > > >>> > > > called "hasMyHeader" (the suffix). Any name could be > used > > for the > > > > >>> other > > > > >>> > > > condition. That other condition is configured at > > > > >>> > > > > "transforms.conditionalExtract.condition.<conditionName>". > > That > > > > >>> condition > > > > >>> > > > is a "has-header" condition (the prefix), which will > match > > > > records > > > > >>> with a > > > > >>> > > > "my-header" header (given in the suffix). So the > > "has-header:" > > > > >>> condition > > > > >>> > > > type would always require a suffix, as would the "not:" > > condition > > > > >>> type. > > > > >>> > > > Hypothetically you could have a "true" condition type > (which > > > > would > > > > >>> not > > > > >>> > > > require a suffix), and the hypothetical binary > conditions > > "and:" > > > > >>> and > > > > >>> > > "or:" > > > > >>> > > > would require a pair of other condition names. > > > > >>> > > > > > > > >>> > > > So what's proposed is a scheme for encoding conditions > where > > the > > > > >>> > > condition > > > > >>> > > > type is the prefix of the value of some "....condition" > > config > > > > >>> key, and > > > > >>> > > the > > > > >>> > > > optional suffix provides parameters for the condition. > This > > makes > > > > >>> those > > > > >>> > > > parameters a bit inflexible, but is relatively > succinct. > > > > >>> > > > > > > > >>> > > > This leads on to your first point. You're right that > use > > cases > > > > >>> might > > > > >>> > > appear > > > > >>> > > > which need other conditions, and we should make it > flexible > > > > enough > > > > >>> to be > > > > >>> > > > able to cope with future use cases. On the other hand, > I was > > > > >>> concerned > > > > >>> > > that > > > > >>> > > > we end up with something which is quite complicated to > > configure. > > > > >>> (There > > > > >>> > > > comes a point where it might makes more sense for the > user to > > > > >>> write their > > > > >>> > > > own SMT). > > > > >>> > > > > > > > >>> > > > Just of the top of my head it might look like: > > > > >>> > > > > > > > > >>> > > > > transforms.conditionalExtract.condition.hasMyHeader: > > > > >>> type:has-header > > > > >>> > > > > transforms.conditionalExtract.condition.hasMyHeader: > > > > >>> > > > header-name:my-header > > > > >>> > > > > transforms.conditionalExtract.condition.hasMyHeader: > > > > >>> > > field-value:my-value > > > > >>> > > > > > > > > >>> > > > > > > > >>> > > > That won't work because the format is basically a > > > > >>> Properties/Map<String, > > > > >>> > > > String> and what you've suggested has duplicate keys. > > > > >>> > > > > > > > >>> > > > One thing I did briefly consider what the ability to > treat > > > > >>> conditions as > > > > >>> > > > Configurable objects in their own right (opening up the > > > > >>> possibility of > > > > >>> > > > people supplying their own Conditions, just like they > can > > supply > > > > >>> their > > > > >>> > > own > > > > >>> > > > SMTs). That might be configured something like this: > > > > >>> > > > > > > > >>> > > > transforms.conditionalExtract.condition: not > > > > >>> > > > transforms.conditionalExtract.condition.not.type: > Not > > > > >>> > > > > transforms.conditionalExtract.condition.not.negated: foo > > > > >>> > > > transforms.conditionalExtract.condition.foo.type: > > > > >>> HasHeaderWithValue > > > > >>> > > > transforms.conditionalExtract.condition.foo.header: > > my-header > > > > >>> > > > transforms.conditionalExtract.condition.foo.value: > > my-value > > > > >>> > > > > > > > >>> > > > I didn't propose that I couldn't see the use cases to > justify > > > > this > > > > >>> kind > > > > >>> > > of > > > > >>> > > > complexity, especially as the common case would surely > be > > > > matching > > > > >>> > > against > > > > >>> > > > topic name (to be honest I wasn't completely convinced > by the > > > > need > > > > >>> for > > > > >>> > > > "has-header"). In the current version of the KIP > that's just > > > > >>> > > > > > > > >>> > > > transforms.conditionalExtract.condition: > topic-matches: > > > > >>> my-prefix-.* > > > > >>> > > > > > > > >>> > > > but using the more flexible scheme that would require > > something > > > > >>> more like > > > > >>> > > > this: > > > > >>> > > > > > > > >>> > > > transforms.conditionalExtract.condition: bar > > > > >>> > > > transforms.conditionalExtract.condition.bar.type: > > TopicMatch > > > > >>> > > > > transforms.conditionalExtract.condition.bar.pattern: > > > > >>> my-prefix-.* > > > > >>> > > > > > > > >>> > > > If people know of use cases which would justify more > > > > >>> sophistication, I'm > > > > >>> > > > happy to reconsider. > > > > >>> > > > > > > > >>> > > > Thanks again for taking a look! > > > > >>> > > > > > > > >>> > > > Tom > > > > >>> > > > > > > > >>> > > > On Wed, Apr 1, 2020 at 2:05 PM Sönke Liebau > > > > >>> > > > <soenke.lie...@opencore.com.invalid> wrote: > > > > >>> > > > > > > > >>> > > > > Hi Tom, > > > > >>> > > > > > > > > >>> > > > > sounds useful to me, thanks for the KIP! > > > > >>> > > > > The only thought that I had while reading was that > this > > will > > > > >>> probably > > > > >>> > > > raise > > > > >>> > > > > questions about more involved conditions fairly > quickly. > > For > > > > >>> example > > > > >>> > > the > > > > >>> > > > > "has-header" will cause an appetite for conditions > like > > > > >>> > > > > "this-header-has-that-value". > > > > >>> > > > > This would necessitate two parameters to be passed > into the > > > > >>> condition, > > > > >>> > > > > which I think is not currently included in the KIP. > I am > > not > > > > >>> saying add > > > > >>> > > > > this now, but might it make sense to discuss a > concept of > > how > > > > >>> that > > > > >>> > > might > > > > >>> > > > > look now, to avoid potential changes later on. > > > > >>> > > > > > > > > >>> > > > > Just of the top of my head it might look like: > > > > >>> > > > > > > > > >>> > > > > transforms.conditionalExtract.condition.hasMyHeader: > > > > >>> type:has-header > > > > >>> > > > > transforms.conditionalExtract.condition.hasMyHeader: > > > > >>> > > > header-name:my-header > > > > >>> > > > > transforms.conditionalExtract.condition.hasMyHeader: > > > > >>> > > field-value:my-value > > > > >>> > > > > > > > > >>> > > > > > > > > >>> > > > > Also, while writing that, I noticed that you have a > version > > > > with > > > > >>> and > > > > >>> > > > > without "name" for your transformation in the KIP: > > > > >>> > > > > > > > > >>> > > > > transforms.conditionalExtract.condition.hasMyHeader: > > > > >>> > > has-header:my-header > > > > >>> > > > > and > > > > >>> > > > > transforms.conditionalExtract.condition: > > has-header:my-header > > > > >>> > > > > > > > > >>> > > > > > > > > >>> > > > > Is this intentional and the name is optional? > > > > >>> > > > > > > > > >>> > > > > > > > > >>> > > > > Best regards, > > > > >>> > > > > > > > > >>> > > > > Sönke > > > > >>> > > > > > > > > >>> > > > > > > > > >>> > > > > > > > > >>> > > > > On Wed, 1 Apr 2020 at 11:12, Tom Bentley < > > tbent...@redhat.com> > > > > >>> wrote: > > > > >>> > > > > > > > > > >>> > > > > > Does anyone have any comments, feedback or > thoughts about > > > > this? > > > > >>> > > > > > > > > > >>> > > > > > Thanks, > > > > >>> > > > > > > > > > >>> > > > > > Tom > > > > >>> > > > > > > > > > >>> > > > > > On Tue, Mar 24, 2020 at 11:56 AM Tom Bentley < > > > > >>> tbent...@redhat.com> > > > > >>> > > > > wrote: > > > > >>> > > > > > > > > > >>> > > > > > > Hi, > > > > >>> > > > > > > > > > > >>> > > > > > > I've opened KIP-585 which is intended to provide > a > > > > mechanism > > > > >>> to > > > > >>> > > > > > > conditionally apply SMTs in Kafka Connect. I'd be > > grateful > > > > >>> for any > > > > >>> > > > > > > feedback: > > > > >>> > > > > > > > > > > >>> > > > > > > > > >>> > > > > > > > > >>> > > > > > > > >>> > > > > > > >>> > > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-585%3A+Conditional+SMT > > > > >>> > > > > > > > > > > >>> > > > > > > Many thanks, > > > > >>> > > > > > > > > > > >>> > > > > > > Tom > > > > >>> > > > > > > > > > > >>> > > > > > > > > >>> > > > > > > > >>> > > > > > > >>> > > > > >>> > > > > > > > > > > >
