You can also see structured logging in use in the http4k by

Question

You can also see structured logging in use in the http4k by example repo upside down face <https github com http4k http4k by example blob 68a56c96cdacaf4567bba74ec910f41b2e44a1af src main kotlin verysecuresystems SecuritySystem kt L37|https github com http4k http4k by example blob 68a56c96cdacaf4567bba74ec910f41b2e44a1af src main kotlin verysecuresystems SecuritySystem kt L37>

Elizabeth Thomas · Answer

I just came across the structured logging yesterday Is there a way to test that structured logging is happening when EventFilters are used in combination with the Http filters

Elizabeth Thomas · Answer

I have my filter defined like this ```data class IncomingHttpRequest val message String = val status Int = 0 val duration Long = 0L Event object ReportHttpTransactionFilter operator fun invoke events Events = EventFilters AddTimestamp then AutoMarshallingEvents Jackson event Event = null Filter = Filter next gt request gt next request apply ResponseFilters ReportHttpTransaction httpTransaction gt events event IncomingHttpRequest httpTransaction request toMessage httpTransaction response status code httpTransaction duration toMillis ``` And my test class like this which fails ```class ReportHttpTransactionFilterSpec Spek val request = Request Method GET bob val response = Response OK val recording = RecordingEvents test report http transaction filter emits events with timestamp val events = EventFilters AddTimestamp then AutoMarshallingEvents Jackson then recording val event = IncomingHttpRequest some message 200 10 val handler = ReportHttpTransactionFilter events event then response expectThat handler request isEqualTo response expectThat recording toList isEqualTo listOf lt Event gt MetadataEvent event mapOf timestamp to Clock systemUTC instant ```

Elizabeth Thomas · Answer

The recording comes back as emptylist

Elizabeth Thomas · Answer

Am I missing something here

dave · Answer

It looks strange why are you passing in the event which then falls back ```events event IncomingHttpRequest httpTransaction request toMessage httpTransaction response status code httpTransaction duration toMillis ```

Razvan · Answer

I think is yout ReportHttpTransactionFilter that is strange We did it this way ```val events = EventFilters AddTimestamp then AutoMarshallingEvents AppJackson fun LogIncomingRequests = ResponseFilters ReportHttpTransaction events LogHttpTransaction fromTransaction it val app = LogIncomingRequests then response ```

Elizabeth Thomas · Answer

< Razvan> do you mean to say I will have to use LogHttpTransaction in my filter code instead of events event

Elizabeth Thomas · Answer

< dave> if an event is passed it will be events event call as in the test code but if event is not passed it will use the httpTransaction to create IncomingHttpRequest and use it with events

Razvan · Answer

LogHttpTransaction is just a custom object like IncomingHttpRequest juste a data class with informations you can replace that with ```fun LogIncomingRequests = ResponseFilters ReportHttpTransaction events IncomingHttpRequest itrequest toMessage it response status code it duration toMillis ``` if it helps to undersand

dave · Answer

< Elizabeth Thomas> Yes and that s exactly what you want to test upside down face

Elizabeth Thomas · Answer

Okay let me try that

Elizabeth Thomas · Answer

< Razvan> My `events` is configured as `val events = EventFilters AddTimestamp then AutoMarshallingEvents Jackson then recording ` in my test class And after running through the filter when I check the `recording` object I see it being empty

Elizabeth Thomas · Answer

< dave> ^^

Elizabeth Thomas · Answer

I am missing to see how to validate that events with timestamp were generated

dave · Answer

< Elizabeth Thomas> something like this

dave · Answer

but really you should be testing that your events stack is doing the right thing assuming that you always want metadata then isolate that part and test it separately to the filter

dave · Answer

then you can just test your filter by testing that the correct events IncomingHttpRequest were generated regardless of the metadata

Elizabeth Thomas · Answer

Thanks < dave> will use this approach

dave · Answer

thumbsup

Elizabeth Thomas · Answer

< dave> your approach worked Thanks But I am failing to understand why my filter defined like this won t work ```object ReportHttpTransactionFilter object Log operator fun invoke rawEvents Events clock Clock = Clock systemUTC Filter = Filter next gt request gt val events = AddTimestamp clock then rawEvents next request apply ResponseFilters ReportHttpTransaction clock = clock httpTransaction gt events IncomingHttpRequest httpTransaction request method httpTransaction request uri path httpTransaction response status code httpTransaction duration toMillis ```

dave · Answer

because you re defining a filter within a filter and that s not how filters work slightly smiling face

dave · Answer

```ResponseFilters ReportHttpTransaction clock = clock httpTransaction gt events IncomingHttpRequest httpTransaction request method httpTransaction request uri path httpTransaction response status code httpTransaction duration toMillis ``` is a filter

dave · Answer

you need to do `filter then filter then handler `

Elizabeth Thomas · Answer

Ah okay I thought filter within a filter is possible slightly smiling face

Elizabeth Thomas · Answer

When you get a chance could you share if there is any documentation that outlines this

dave · Answer

filters <https www http4k org rationale >

Elizabeth Thomas · Answer

I was following this from ReportHttpTransaction ```object ReportHttpTransaction operator fun invoke clock Clock = Clock systemUTC transactionLabeler HttpTransactionLabeler = it recordFn HttpTransaction gt Unit Filter = Filter next gt clock instant let start gt next it apply recordFn transactionLabeler HttpTransaction it this between start clock instant ```

dave · Answer

yes but the `apply ` there is actually doing something and not creting another filter

Elizabeth Thomas · Answer

Ah gotcha Makes sense Thanks for explaining it to me

Elizabeth Thomas · Answer

Also the `LogHttpTransaction fromTransaction` which < Razvan> pointed out is it in http4k core or some other module I couldnt get the package for it Again its probably me doing something wrong

Razvan · Answer

No is just a personal data class with fields I want to log that has a lot of fields and I don t want to bother pas then in the constructor