Ignore accept header in requests to metrics service

CHANGELOG.md

@@ -8,6 +8,8 @@
 
 ### Bug Fixes
 
+* The metrics HTTP server no longer rejects requests containing `Accept` header that doesn't precisely match the prometheus text format [\#1345](https://github.com/hyperledger/besu/pull/1345)
+
 #### Previously identified known issues
 
 - [Logs queries missing results against chain head](KNOWN_ISSUES.md#Logs-queries-missing-results-against-chain-head)

metrics/core/src/main/java/org/hyperledger/besu/metrics/prometheus/MetricsHttpService.java

@@ -91,11 +91,7 @@ public CompletableFuture<?> start() {
  router.route("/").method(HttpMethod.GET).handler(this::handleEmptyRequest);
 
  // Endpoint for Prometheus metrics monitoring.
- router
- .route("/metrics")
- .method(HttpMethod.GET)
- .produces(TextFormat.CONTENT_TYPE_004)
- .handler(this::metricsRequest);
+ router.route("/metrics").method(HttpMethod.GET).handler(this::metricsRequest);
 
  final CompletableFuture<?> resultFuture = new CompletableFuture<>();
  httpServer

metrics/core/src/test/java/org/hyperledger/besu/metrics/prometheus/MetricsHttpServiceTest.java

@@ -174,6 +174,22 @@ public void metricsAreAbsentWhenFiltered() throws Exception {
  }
  }
 
+ @Test
+ // There is only one available representation so content negotiation should not be used
+ public void acceptHeaderIgnored() throws Exception {
+ final Request metricsRequest =
+ new Request.Builder().addHeader("Accept", "text/xml").url(baseUrl + "/metrics").build();
+ try (final Response resp = client.newCall(metricsRequest).execute()) {
+ assertThat(resp.code()).isEqualTo(200);
+ // Check general format of result, it maps to java.util.Properties
+ final Properties props = new Properties();
+ props.load(resp.body().byteStream());
+
+ // We should have JVM metrics already loaded, verify a simple key.
+ assertThat(props).containsKey("jvm_threads_deadlocked");
+ }
+ }
+
  private Request buildGetRequest(final String path) {
  return new Request.Builder().get().url(baseUrl + path).build();
  }