[GitHub] [bookkeeper] addisonj opened a new issue #2161: When httpServerEnabled=true, Prometheus reports doesn't sent content-type

[GitBox <gi...@apache.org>]

addisonj opened a new issue #2161: When httpServerEnabled=true, Prometheus reports doesn't sent content-type
URL: https://github.com/apache/bookkeeper/issues/2161
 
 
   **BUG REPORT**
   
   ***Describe the bug***
   
   When running with `httpServerEnabled` set to true, `/metrics` endpoint stops sending a `content-type` header (this uses the `MetricsService`, see code here https://github.com/apache/bookkeeper/blob/28dee8464764b0edceeb31ce24424f0947b5789b/bookkeeper-server/src/main/java/org/apache/bookkeeper/server/http/service/MetricsService.java).
   With the `httpServerEnabled=false` the `PrometheusServlet` is used, and it does set a content-type header (https://github.com/apache/bookkeeper/blob/28dee8464764b0edceeb31ce24424f0947b5789b/bookkeeper-stats-providers/prometheus-metrics-provider/src/main/java/org/apache/bookkeeper/stats/prometheus/PrometheusServlet.java#L44)
   
    The content-type header is expected by some prometheus tools to differentiate between plaintext and protobuf formatted metrics and no content-type is considered an error.
   
   ***To Reproduce***
   
   Steps to reproduce the behavior:
   1. Set `httpServerEnabled=false` and enable prometheus reporter
   2. run `curl localhost:8000/metrics` and notice that a content-type header is set
   3. Set `httpServerEnabled=true` and enable prometheus reporter
   4. run `curl localhost:8000/metrics -v` notice that there is no content-type header set
   
   ***Expected behavior***
   
   I expect a content-type header
   
   It seems like the statsProvider interface should have a method for allowing to set headers on the response. Default to a given content type might cause problems with other providers.
   

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