JSON-Binding breaks prometheus metrics format

[tomas-langer]

When I enable JsonBindingSupport for the webserver routing and MetricsSupport:

Routing.builder()
 .register(JsonBindingSupport.create())
 .register(MetricsSupport.create())
 .build()

The clear-text Prometheus format is broken:

curl http://localhost:8080/metrics/vendor
"# TYPE vendor:requests_count counter\n# HELP vendor:requests_count Each request (regardless of HTTP method) will increase this counter\nvendor:requests_count 2\n# TYPE vendor:requests_meter_total counter\n# HELP vendor:requests_meter_total Each request will mark the meter to see overall throughput\nvendor:requests_meter_total 2\n# TYPE vendor:requests_meter_rate_per_second gauge\nvendor:requests_meter_rate_per_second 0.3750436866122316\n# TYPE vendor:requests_meter_one_min_rate_per_second gauge\nvendor:requests_meter_one_min_rate_per_second 0.2\n# TYPE vendor:requests_meter_five_min_rate_per_second gauge\nvendor:requests_meter_five_min_rate_per_second 0.2\n# TYPE vendor:requests_meter_fifteen_min_rate_per_second gauge\nvendor:requests_meter_fifteen_min_rate_per_second 0.2\n"%

Expected output:

curl http://localhost:8080/metrics/vendor
# TYPE vendor:requests_count counter
# HELP vendor:requests_count Each request (regardless of HTTP method) will increase this counter
vendor:requests_count 1
# TYPE vendor:requests_meter_total counter
# HELP vendor:requests_meter_total Each request will mark the meter to see overall throughput
vendor:requests_meter_total 1
# TYPE vendor:requests_meter_rate_per_second gauge
vendor:requests_meter_rate_per_second 0.21839295518592852
# TYPE vendor:requests_meter_one_min_rate_per_second gauge
vendor:requests_meter_one_min_rate_per_second 0.0
# TYPE vendor:requests_meter_five_min_rate_per_second gauge
vendor:requests_meter_five_min_rate_per_second 0.0
# TYPE vendor:requests_meter_fifteen_min_rate_per_second gauge
vendor:requests_meter_fifteen_min_rate_per_second 0.0

Environment Details

• Helidon Version: 1.0.3, 1.0.4-SNAPSHOT
• Helidon SE
• JDK version: 1.8
• OS: MacOS

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[tomas-langer]

The string is wrapped in quotes and end of line characters are removed.
In this case the string should not be touched by JsonBindingSupport

[ljnelson]

Hi, @tomas-langer; should this be special-cased? As you can see from the code there's nothing special going on. You added JsonBindingSupport, so it simply uses the writer created:

https://github.com/oracle/helidon/blob/8454a8d7fe07ae2ce91769b3a61a6c8e3027baa0/media/jsonb/common/src/main/java/io/helidon/media/jsonb/common/JsonBinding.java#L85

Should there be some way for JsonBindingSupport to know that it is not supposed to do this, even though it was registered? Or did you have something else in mind?

[barchetta]

Maybe a quick fix would be to change JsonBindingSupport so it does not register the writer if payload instanceof String?

But we do have a general problem here. Metrics (and Health and others) can't know or care about what media support the user has registered. And the media support the user has registered should not impact these built-in services (since they likely hand craft their responses).

So we either need a way to suppress the media support per response, or do something like having specific entity/writers for these built in services so the selection of the appropriate writer is unambiguous. Or maybe a RawPayload entity that wraps a string and indicates media specific content writers should keep their hands off.

[tomas-langer]

My first solution would be to ignore String. The RawPayload suggested by Joe seems like a good approach as well.
Maybe a workaround for the RawPayload would be to use Publisher<DataChunk> in these services , as I guess that gets around the writers as well?

[barchetta]

The bookstore functional test did not catch this since it only checks metrics with the JSON-P support configured. I'll update the test to run with JSON-B and Jackson as well.

[barchetta]

JacksonSupport has the same problem.

[barchetta]

See PR #669