$ crc version
crc version: 1.11.0+883ca49
OpenShift version: 4.4.5 (embedded in binary)

$ oc set env statefulset my-broker-ss AMQ_ENABLE_METRICS_PLUGIN=true

$ oc logs my-broker-ss-0 | grep metrics
Enable artemis metrics plugin
Adding artemis metrics plugin

$ METRICS_URL="http://$(oc get route my-broker-wconsj-0-svc-rte -o=jsonpath='\{.status.ingress[0].host}{"\n"}')/metrics"

$ curl -v curl -v $METRICS_URL
HTTP/1.1 302 Found
location: http://my-broker-wconsj-0-svc-rte-broker.apps-crc.testing/metrics/

$ curl -v curl -v $METRICS_URL
HTTP/1.1 200 OK
# no metrics in the body

$ oc logs my-broker-ss-0 | grep metrics
2020-07-16 12:06:48,679 WARN [org.eclipse.jetty.server.HttpChannel] /metrics/: java.lang.NullPointerException
 at org.apache.activemq.artemis.core.server.metrics.plugins.ArtemisPrometheusMetricsPluginServlet.doGet(ArtemisPrometheusMetricsPluginServlet.java:49)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:687) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.servlet.ServletHolder$NotAsyncServlet.service(ServletHolder.java:1386) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:755) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1617) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.apache.activemq.artemis.component.JolokiaFilter.doFilter(JolokiaFilter.java:50) [artemis-web-2.13.0.redhat-00006.jar:2.13.0.redhat-00006]
 at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1604) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:545) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:590) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:127) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:235) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1607) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:233) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1297) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:188) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:485) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1577) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:186) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1212) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.handler.HandlerList.handle(HandlerList.java:59) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:127) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.Server.handle(Server.java:500) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.HttpChannel.lambda$handle$1(HttpChannel.java:383) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.HttpChannel.dispatch(HttpChannel.java:547) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:375) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:270) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:311) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:103) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:117) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.runTask(EatWhatYouKill.java:336) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:313) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.tryProduce(EatWhatYouKill.java:171) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:129) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:388) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:806) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]
 at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:938) [jetty-all-9.4.26.v20200117-redhat-00001-uber.jar:9.4.26.v20200117-redhat-00001]