PrometheusCollector NPE while adding sample supplier

Eduardos-Mini:bin emmartins$ ./standalone.sh 
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  JBoss Bootstrap Environment

  JBOSS_HOME: /Users/emmartins/wildfly/cmtool/test/migrations/wildfly-16.0.0.Final/wildfly-15.0.1.Final/target

  JAVA: /Library/Java/JavaVirtualMachines/jdk1.8.0_181.jdk/Contents/Home/bin/java

  JAVA_OPTS:  -server -Xms64m -Xmx512m -XX:MetaspaceSize=96M -XX:MaxMetaspaceSize=256m -Djava.net.preferIPv4Stack=true -Djboss.modules.system.pkgs=org.jboss.byteman -Djava.awt.headless=true 

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08:47:19,267 INFO  [org.jboss.modules] (main) JBoss Modules version 1.9.0.Final
08:47:19,695 INFO  [org.jboss.msc] (main) JBoss MSC version 1.4.5.Final
08:47:19,706 INFO  [org.jboss.threads] (main) JBoss Threads version 2.3.3.Final
08:47:19,871 INFO  [org.jboss.as] (MSC service thread 1-2) WFLYSRV0049: WildFly Full 16.0.0.Final (WildFly Core 8.0.0.Final) starting
08:47:20,573 INFO  [org.wildfly.security] (ServerService Thread Pool -- 23) ELY00001: WildFly Elytron version 1.8.0.Final
08:47:21,101 INFO  [org.jboss.as.controller.management-deprecated] (Controller Boot Thread) WFLYCTL0028: Attribute 'security-realm' in the resource at address '/core-service=management/management-interface=http-interface' is deprecated, and may be removed in a future version. See the attribute description in the output of the read-resource-description operation to learn more about the deprecation.
08:47:21,128 INFO  [org.jboss.as.controller.management-deprecated] (ServerService Thread Pool -- 35) WFLYCTL0028: Attribute 'security-realm' in the resource at address '/subsystem=undertow/server=default-server/https-listener=https' is deprecated, and may be removed in a future version. See the attribute description in the output of the read-resource-description operation to learn more about the deprecation.
08:47:21,215 INFO  [org.jboss.as.server] (Controller Boot Thread) WFLYSRV0039: Creating http management service using socket-binding (management-http)
08:47:21,235 INFO  [org.xnio] (MSC service thread 1-7) XNIO version 3.6.5.Final
08:47:21,243 INFO  [org.xnio.nio] (MSC service thread 1-7) XNIO NIO Implementation Version 3.6.5.Final
08:47:21,284 INFO  [org.jboss.as.clustering.infinispan] (ServerService Thread Pool -- 49) WFLYCLINF0001: Activating Infinispan subsystem.
08:47:21,289 INFO  [org.jboss.as.naming] (ServerService Thread Pool -- 62) WFLYNAM0001: Activating Naming Subsystem
08:47:21,292 INFO  [org.wildfly.extension.microprofile.opentracing] (ServerService Thread Pool -- 61) WFLYTRACEXT0001: Activating MicroProfile OpenTracing Subsystem
08:47:21,296 WARN  [org.jboss.as.txn] (ServerService Thread Pool -- 70) WFLYTX0013: The node-identifier attribute on the /subsystem=transactions is set to the default value. This is a danger for environments running multiple servers. Please make sure the attribute value is unique.
08:47:21,310 INFO  [org.jboss.as.webservices] (ServerService Thread Pool -- 72) WFLYWS0002: Activating WebServices Extension
08:47:21,311 INFO  [org.jboss.as.jaxrs] (ServerService Thread Pool -- 51) WFLYRS0016: RESTEasy version 3.6.3.Final
08:47:21,314 INFO  [org.wildfly.extension.microprofile.config.smallrye._private] (ServerService Thread Pool -- 58) WFLYCONF0001: Activating WildFly MicroProfile Config Subsystem
08:47:21,315 INFO  [org.jboss.as.security] (ServerService Thread Pool -- 68) WFLYSEC0002: Activating Security Subsystem
08:47:21,333 INFO  [org.wildfly.extension.microprofile.health.smallrye] (ServerService Thread Pool -- 59) WFLYHEALTH0001: Activating Eclipse MicroProfile Health Subsystem
08:47:21,334 INFO  [org.jboss.as.security] (MSC service thread 1-4) WFLYSEC0001: Current PicketBox version=5.0.3.Final
08:47:21,343 INFO  [org.jboss.as.jsf] (ServerService Thread Pool -- 56) WFLYJSF0007: Activated the following JSF Implementations: [main]
08:47:21,342 INFO  [org.wildfly.extension.io] (ServerService Thread Pool -- 50) WFLYIO001: Worker 'default' has auto-configured to 16 core threads with 128 task threads based on your 8 available processors
08:47:21,349 INFO  [org.jboss.as.connector] (MSC service thread 1-6) WFLYJCA0009: Starting JCA Subsystem (WildFly/IronJacamar 1.4.12.Final)
08:47:21,357 INFO  [org.wildfly.extension.microprofile.metrics.smallrye] (ServerService Thread Pool -- 60) WFLYMETRICS0001: Activating Eclipse MicroProfile Metrics Subsystem
08:47:21,364 INFO  [org.jboss.as.mail.extension] (MSC service thread 1-6) WFLYMAIL0002: Unbound mail session [java:jboss/mail/Default]
08:47:21,367 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-8) WFLYUT0003: Undertow 2.0.19.Final starting
08:47:21,419 INFO  [org.jboss.as.connector.subsystems.datasources] (ServerService Thread Pool -- 42) WFLYJCA0004: Deploying JDBC-compliant driver class org.h2.Driver (version 1.4)
08:47:21,429 INFO  [io.smallrye.metrics] (MSC service thread 1-5) Converted [2] config entries and added [4] replacements
08:47:21,442 INFO  [io.smallrye.metrics] (MSC service thread 1-5) Converted [3] config entries and added [14] replacements
08:47:21,443 INFO  [org.jboss.as.connector.deployers.jdbc] (MSC service thread 1-6) WFLYJCA0018: Started Driver service with driver-name = h2
08:47:21,446 INFO  [org.jboss.as.naming] (MSC service thread 1-1) WFLYNAM0003: Starting Naming Service
08:47:21,454 INFO  [org.jboss.as.mail.extension] (MSC service thread 1-8) WFLYMAIL0001: Bound mail session [java:jboss/mail/Default]
08:47:21,482 INFO  [org.jboss.remoting] (MSC service thread 1-6) JBoss Remoting version 5.0.8.Final
08:47:21,672 INFO  [org.jboss.as.connector.subsystems.datasources] (MSC service thread 1-5) WFLYJCA0010: Unbound data source [java:jboss/datasources/ExampleDS]
08:47:21,753 INFO  [org.wildfly.extension.undertow] (ServerService Thread Pool -- 71) WFLYUT0014: Creating file handler for path '/Users/emmartins/wildfly/cmtool/test/migrations/wildfly-16.0.0.Final/wildfly-15.0.1.Final/target/welcome-content' with options [directory-listing: 'false', follow-symlink: 'false', case-sensitive: 'true', safe-symlink-paths: '[]']
08:47:21,758 INFO  [org.jboss.as.ejb3] (MSC service thread 1-8) WFLYEJB0482: Strict pool mdb-strict-max-pool is using a max instance size of 32 (per class), which is derived from the number of CPUs on this host.
08:47:21,759 INFO  [org.jboss.as.ejb3] (MSC service thread 1-3) WFLYEJB0481: Strict pool slsb-strict-max-pool is using a max instance size of 128 (per class), which is derived from thread worker pool sizing.
08:47:21,778 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-8) WFLYUT0012: Started server default-server.
08:47:21,781 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-8) WFLYUT0018: Host default-host starting
08:47:21,885 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-4) WFLYUT0006: Undertow HTTP listener default listening on 127.0.0.1:8080
08:47:21,919 INFO  [org.jboss.as.ejb3] (MSC service thread 1-3) WFLYEJB0493: EJB subsystem suspension complete
08:47:21,998 INFO  [org.jboss.as.connector.subsystems.datasources] (MSC service thread 1-4) WFLYJCA0001: Bound data source [java:jboss/datasources/ExampleDS]
08:47:22,152 INFO  [org.jboss.as.patching] (MSC service thread 1-8) WFLYPAT0050: WildFly Full cumulative patch ID is: base, one-off patches include: none
08:47:22,170 WARN  [org.jboss.as.domain.management.security] (MSC service thread 1-4) WFLYDM0111: Keystore /Users/emmartins/wildfly/cmtool/test/migrations/wildfly-16.0.0.Final/wildfly-15.0.1.Final/target/standalone/configuration/application.keystore not found, it will be auto generated on first use with a self signed certificate for host localhost
08:47:22,173 INFO  [org.jboss.as.server.deployment.scanner] (MSC service thread 1-7) WFLYDS0013: Started FileSystemDeploymentService for directory /Users/emmartins/wildfly/cmtool/test/migrations/wildfly-16.0.0.Final/wildfly-15.0.1.Final/target/standalone/deployments
08:47:22,183 INFO  [org.jboss.as.server.deployment] (MSC service thread 1-6) WFLYSRV0027: Starting deployment of "cmtool-helloworld6.war" (runtime-name: "cmtool-helloworld6.war")
08:47:22,183 INFO  [org.jboss.as.server.deployment] (MSC service thread 1-8) WFLYSRV0027: Starting deployment of "cmtool-helloworld5.war" (runtime-name: "cmtool-helloworld5.war")
08:47:22,332 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-2) WFLYUT0006: Undertow HTTPS listener https listening on 127.0.0.1:8443
08:47:22,408 INFO  [org.jboss.ws.common.management] (MSC service thread 1-2) JBWS022052: Starting JBossWS 5.2.4.Final (Apache CXF 3.2.7) 
08:47:22,932 INFO  [org.jboss.weld.deployer] (MSC service thread 1-5) WFLYWELD0003: Processing weld deployment cmtool-helloworld6.war
08:47:22,932 INFO  [org.jboss.weld.deployer] (MSC service thread 1-3) WFLYWELD0003: Processing weld deployment cmtool-helloworld5.war
08:47:23,058 INFO  [org.hibernate.validator.internal.util.Version] (MSC service thread 1-5) HV000001: Hibernate Validator 6.0.15.Final
08:47:23,477 INFO  [org.jboss.weld.Version] (MSC service thread 1-1) WELD-000900: 3.1.0 (Final)
08:47:23,573 INFO  [org.infinispan.factories.GlobalComponentRegistry] (MSC service thread 1-2) ISPN000128: Infinispan version: Infinispan 'Infinity Minus ONE +2' 9.4.8.Final
08:47:23,948 INFO  [io.smallrye.metrics] (MSC service thread 1-4) MicroProfile: Metrics activated
08:47:23,948 INFO  [io.smallrye.metrics] (MSC service thread 1-3) MicroProfile: Metrics activated
08:47:24,086 INFO  [org.jboss.as.clustering.infinispan] (ServerService Thread Pool -- 74) WFLYCLINF0002: Started client-mappings cache from ejb container
08:47:24,698 INFO  [org.wildfly.extension.undertow] (ServerService Thread Pool -- 74) WFLYUT0021: Registered web context: '/cmtool-helloworld5' for server 'default-server'
08:47:24,698 INFO  [org.wildfly.extension.undertow] (ServerService Thread Pool -- 75) WFLYUT0021: Registered web context: '/cmtool-helloworld6' for server 'default-server'
08:47:24,717 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-7) MSC000001: Failed to start service jboss.deployment.unit."cmtool-helloworld6.war".metrics: org.jboss.msc.service.StartException in service jboss.deployment.unit."cmtool-helloworld6.war".metrics: Failed to start service
	at org.jboss.msc.service.ServiceControllerImpl$StartTask.execute(ServiceControllerImpl.java:1730)
	at org.jboss.msc.service.ServiceControllerImpl$ControllerTask.run(ServiceControllerImpl.java:1558)
	at org.jboss.threads.ContextClassLoaderSavingRunnable.run(ContextClassLoaderSavingRunnable.java:35)
	at org.jboss.threads.EnhancedQueueExecutor.safeRun(EnhancedQueueExecutor.java:1982)
	at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.doRunTask(EnhancedQueueExecutor.java:1486)
	at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1377)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException
	at org.wildfly.extension.microprofile.metrics.PrometheusCollector.addMetricFamilySampleSupplier(PrometheusCollector.java:32)
	at org.wildfly.extension.microprofile.metrics.MetricCollector.collectResourceMetrics0(MetricCollector.java:157)
	at org.wildfly.extension.microprofile.metrics.MetricCollector.collectResourceMetrics0(MetricCollector.java:166)
	at org.wildfly.extension.microprofile.metrics.MetricCollector.collectResourceMetrics0(MetricCollector.java:166)
	at org.wildfly.extension.microprofile.metrics.MetricCollector.collectResourceMetrics(MetricCollector.java:92)
	at org.wildfly.extension.microprofile.metrics.deployment.DeploymentMetricService.start(DeploymentMetricService.java:54)
	at org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1738)
	at org.jboss.msc.service.ServiceControllerImpl$StartTask.execute(ServiceControllerImpl.java:1700)
	... 6 more

08:47:24,953 ERROR [org.jboss.as.controller.management-operation] (Controller Boot Thread) WFLYCTL0013: Operation ("deploy") failed - address: ([("deployment" => "cmtool-helloworld6.war")]) - failure description: {"WFLYCTL0080: Failed services" => {"jboss.deployment.unit.\"cmtool-helloworld6.war\".metrics" => "Failed to start service
    Caused by: java.lang.NullPointerException"}}
08:47:24,966 INFO  [org.jboss.as.server] (ServerService Thread Pool -- 43) WFLYSRV0010: Deployed "cmtool-helloworld5.war" (runtime-name : "cmtool-helloworld5.war")
08:47:24,967 INFO  [org.jboss.as.server] (ServerService Thread Pool -- 43) WFLYSRV0010: Deployed "cmtool-helloworld6.war" (runtime-name : "cmtool-helloworld6.war")
08:47:24,969 INFO  [org.jboss.as.controller] (Controller Boot Thread) WFLYCTL0183: Service status report
WFLYCTL0186:   Services which failed to start:      service jboss.deployment.unit."cmtool-helloworld6.war".metrics: Failed to start service

08:47:25,032 INFO  [org.jboss.as.server] (Controller Boot Thread) WFLYSRV0212: Resuming server
08:47:25,036 INFO  [org.jboss.as] (Controller Boot Thread) WFLYSRV0060: Http management interface listening on http://127.0.0.1:9990/management
08:47:25,037 INFO  [org.jboss.as] (Controller Boot Thread) WFLYSRV0051: Admin console listening on http://127.0.0.1:9990
08:47:25,037 ERROR [org.jboss.as] (Controller Boot Thread) WFLYSRV0026: WildFly Full 16.0.0.Final (WildFly Core 8.0.0.Final) started (with errors) in 6202ms - Started 521 of 711 services (1 services failed or missing dependencies, 334 services are lazy, passive or on-demand)