[GitHub] [nifi] mattyb149 commented on a change in pull request #4156: NIFI-7273: Add flow metrics REST endpoint with for Prometheus scraping

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mattyb149 commented on a change in pull request #4156: NIFI-7273: Add flow metrics REST endpoint with for Prometheus scraping
URL: https://github.com/apache/nifi/pull/4156#discussion_r403141431
 
 

 ##########
 File path: nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/api/FlowResource.java
 ##########
 @@ -381,6 +388,66 @@ public Response getFlow(
         return generateOkResponse(entity).build();
     }
 
+    /**
+     * Retrieves the metrics of the entire flow.
+     *
+     * @return A flowMetricsEntity.
+     * @throws InterruptedException if interrupted
+     */
+    @GET
+    @Consumes(MediaType.WILDCARD)
+    @Produces(MediaType.WILDCARD)
+    @Path("metrics/{producer}")
+    @ApiOperation(
+            value = "Gets all metrics for the flow from a particular node",
+            response = StreamingOutput.class,
+            authorizations = {
+                    @Authorization(value = "Read - /flow")
+            }
+    )
+    @ApiResponses(
+            value = {
+                    @ApiResponse(code = 400, message = "NiFi was unable to complete the request because it was invalid. The request should not be retried without modification."),
+                    @ApiResponse(code = 401, message = "Client could not be authenticated."),
+                    @ApiResponse(code = 403, message = "Client is not authorized to make this request."),
+                    @ApiResponse(code = 404, message = "The specified resource could not be found."),
+                    @ApiResponse(code = 409, message = "The request was valid but NiFi was not in the appropriate state to process it. Retrying the same request later may be successful.")
+            }
+    )
+    public Response getFlowMetrics(
+            @ApiParam(
+                    value = "The producer for flow file metrics. Each producer may have its own output format.",
+                    required = true
+            )
+            @PathParam("producer") final String producer) throws InterruptedException {
+
+        authorizeFlow();
+
+        if ("prometheus".equalsIgnoreCase(producer)) {
+            // get this process group flow
+            serviceFacade.generateFlowMetrics();
+            // generate a streaming response
+            final StreamingOutput response = output -> {
+                Writer writer = new BufferedWriter(new OutputStreamWriter(output));
+                for (CollectorRegistry collectorRegistry : PrometheusMetricsUtil.ALL_REGISTRIES) {
+                    TextFormat.write004(writer, collectorRegistry.metricFamilySamples());
+                    // flush the response
+                    output.flush();
+                }
+                writer.flush();
+                writer.close();
+            };
+
+            String generatedFilename = "flowMetrics_" + System.currentTimeMillis();
+            return generateOkResponse(response)
+                    .type(MediaType.TEXT_PLAIN_TYPE)
+                    .header("Content-Disposition", String.format("attachment; filename=\"%s\"", generatedFilename))
 
 Review comment:
   Good point, will change

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