Metrics call causes java.util.ConcurrentModificationException ------------------------------------------------------------- Key: WFLY-12690 URL: https://issues.redhat.com/browse/WFLY-12690 Project: WildFly Issue Type: Bug Components: MP Metrics Affects Versions: 18.0.0.Final Environment: I ran the tests in our integration test environment. This includes a prometheus, scraping the metrics with an intervall of 5s. Reporter: Ralf Battenfeld Assignee: Jeff Mesnil Priority: Major Fix For: 19.0.0.Beta3 Hi I ran our integrations tests together with prometheus calls. In Wildfly 18, I get this errors constantly: {code:java} 2019-10-18 14:22:57,284 ERROR [io.undertow.request] (management I/O-2) UT005071: Undertow request failed HttpServerExchange{ GET /metrics}: java.util.ConcurrentModificationException at java.util.HashMap$HashIterator.nextNode(HashMap.java:1445) at java.util.HashMap$EntryIterator.next(HashMap.java:1479) at java.util.HashMap$EntryIterator.next(HashMap.java:1477) at java.util.HashMap.putMapEntries(HashMap.java:512) at java.util.HashMap.<init>(HashMap.java:490) at io.smallrye.metrics.MetricsRegistryImpl.getMetadata(MetricsRegistryImpl.java:560) at io.smallrye.metrics.exporters.OpenMetricsExporter.exposeEntries(OpenMetricsExporter.java:157) at io.smallrye.metrics.exporters.OpenMetricsExporter.getEntriesForScope(OpenMetricsExporter.java:150) at io.smallrye.metrics.exporters.OpenMetricsExporter.exportAllScopes(OpenMetricsExporter.java:101) at io.smallrye.metrics.MetricsRequestHandler.handleRequest(MetricsRequestHandler.java:116) at io.smallrye.metrics.MetricsRequestHandler.handleRequest(MetricsRequestHandler.java:73) at org.wildfly.extension.microprofile.metrics.MetricsContextService$1.handleRequest(MetricsContextService.java:81) at org.jboss.as.domain.http.server.security.RealmReadinessHandler.handleRequest(RealmReadinessHandler.java:51) at org.jboss.as.domain.http.server.security.ServerErrorReadinessHandler.handleRequest(ServerErrorReadinessHandler.java:35) at io.undertow.server.handlers.PathHandler.handleRequest(PathHandler.java:91) at io.undertow.server.handlers.ChannelUpgradeHandler.handleRequest(ChannelUpgradeHandler.java:211) at io.undertow.server.handlers.cache.CacheHandler.handleRequest(CacheHandler.java:92) at io.undertow.server.handlers.error.SimpleErrorPageHandler.handleRequest(SimpleErrorPageHandler.java:78) at io.undertow.server.handlers.CanonicalPathHandler.handleRequest(CanonicalPathHandler.java:49) at org.jboss.as.domain.http.server.ManagementHttpRequestHandler.handleRequest(ManagementHttpRequestHandler.java:57) at org.jboss.as.domain.http.server.cors.CorsHttpHandler.handleRequest(CorsHttpHandler.java:75) at org.jboss.as.domain.http.server.ManagementHttpServer$UpgradeFixHandler.handleRequest(ManagementHttpServer.java:666) at io.undertow.server.Connectors.executeRootHandler(Connectors.java:376) at io.undertow.server.protocol.http.HttpReadListener.handleEventWithNoRunningRequest(HttpReadListener.java:255) at io.undertow.server.protocol.http.HttpReadListener.handleEvent(HttpReadListener.java:136) at io.undertow.server.protocol.http.HttpReadListener.handleEvent(HttpReadListener.java:59) at org.xnio.ChannelListeners.invokeChannelListener(ChannelListeners.java:92) at org.xnio.conduits.ReadReadyHandler$ChannelListenerHandler.readReady(ReadReadyHandler.java:66) at org.xnio.nio.NioSocketConduit.handleReady(NioSocketConduit.java:89) at org.xnio.nio.WorkerThread.run(WorkerThread.java:591) {code}