[standalone@localhost:9990 /] /subsystem=discovery/static-provider=mod_cluster:write-attribute(name=services,value=[{uri=mod_cluster:http://localhost:8090},{abstract-type=mod_cluster,uri=http://localhost:8090}]
{
    "outcome" => "success",
    "response-headers" => {
        "operation-requires-reload" => true,
        "process-state" => "reload-required"
    }
}

[standalone@localhost:9990 /] reload
Failed to establish connection in 6014ms

00:05:43,104 ERROR [org.jboss.as.controller.management-operation] (ServerService Thread Pool -- 48) WFLYCTL0013: Operation ("add") failed - address: ([
    ("subsystem" => "discovery"),
    ("static-provider" => "mod_cluster")
]): java.lang.IllegalArgumentException: Illegal character in scheme name at index 3: mod_cluster:http://localhost:8090
	at java.net.URI.create(URI.java:852)
	at org.wildfly.extension.discovery.StaticDiscoveryProviderAddHandler.performRuntime(StaticDiscoveryProviderAddHandler.java:60)
	at org.jboss.as.controller.AbstractAddStepHandler$1.execute(AbstractAddStepHandler.java:159)
	at org.jboss.as.controller.AbstractOperationContext.executeStep(AbstractOperationContext.java:999)
	at org.jboss.as.controller.AbstractOperationContext.processStages(AbstractOperationContext.java:743)
	at org.jboss.as.controller.AbstractOperationContext.executeOperation(AbstractOperationContext.java:467)
	at org.jboss.as.controller.ParallelBootOperationStepHandler$ParallelBootTask.run(ParallelBootOperationStepHandler.java:384)
	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:1348)
	at java.lang.Thread.run(Thread.java:748)
	at org.jboss.threads.JBossThread.run(JBossThread.java:485)
Caused by: java.net.URISyntaxException: Illegal character in scheme name at index 3: mod_cluster:http://localhost:8090
	at java.net.URI$Parser.fail(URI.java:2848)
	at java.net.URI$Parser.checkChars(URI.java:3021)
	at java.net.URI$Parser.parse(URI.java:3048)
	at java.net.URI.<init>(URI.java:588)
	at java.net.URI.create(URI.java:850)
	... 12 more

...

00:05:43,164 ERROR [org.jboss.as.controller.management-operation] (Controller Boot Thread) "WFLYCTL0193: Failed executing subsystem discovery boot operations"
00:05:43,164 ERROR [org.jboss.as.controller.management-operation] (Controller Boot Thread) WFLYCTL0013: Operation ("parallel-subsystem-boot") failed - address: ([]) - failure description: "\"WFLYCTL0193: Failed executing subsystem discovery boot operations\""