When creating my own deployment-scanner, I have to provide path attribute where given value is checked whether it is a real directory on current filesystem. Although when I change value of this attribute in existing deployment-scanner instance, such check is not performed and I can provide non-existent directory. This leads to server crash after calling reload operation:

1. start EAP7 server and connect to CLI
2. create your own deployment-scanner instance pointing to existing directory

   [standalone@localhost:9990 /] /subsystem=deployment-scanner/scanner=mysc:add(path=/home/jstourac/Downloads/jboss-eap-7.0/standalone/deployments)
   {"outcome" => "success"}
   

3. change path of deployment-scanner to some nonexisting directory

   [standalone@localhost:9990 /] /subsystem=deployment-scanner/scanner=mysc:write-attribute(name=path,value=/nonexistent)
   {
       "outcome" => "success",
       "response-headers" => {
           "operation-requires-reload" => true,
           "process-state" => "reload-required"
       }
   }
   

4. perform reload operation
5. server fails with following output in console.log

   15:29:08,039 INFO  [org.jboss.as.server.deployment.scanner] (MSC service thread 1-5) WFLYDS0013: Started FileSystemDeploymentService for directory /home/jstourac/Downloads/jboss-eap-7.0/standalone/deployments
   15:29:29,068 INFO  [org.jboss.as.connector.subsystems.datasources] (MSC service thread 1-3) WFLYJCA0010: Unbound data source [java:jboss/datasources/ExampleDS]
   15:29:29,070 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-8) WFLYUT0019: Host default-host stopping
   15:29:29,071 INFO  [org.jboss.as.connector.deployers.jdbc] (MSC service thread 1-5) WFLYJCA0019: Stopped Driver service with driver-name = h2
   15:29:29,073 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-4) WFLYUT0008: Undertow HTTP listener default suspending
   15:29:29,075 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-4) WFLYUT0007: Undertow HTTP listener default stopped, was bound to 127.0.0.1:8080
   15:29:29,076 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-2) WFLYUT0004: Undertow 1.3.21.Final-redhat-1 stopping
   15:29:29,081 INFO  [org.jboss.as.mail.extension] (MSC service thread 1-2) WFLYMAIL0002: Unbound mail session [java:jboss/mail/Default]
   15:29:29,082 INFO  [org.jboss.as] (MSC service thread 1-8) WFLYSRV0050: JBoss EAP 7.0.0.GA (WildFly Core 2.1.2.Final-redhat-1) stopped in 16ms
   15:29:29,083 INFO  [org.jboss.as] (MSC service thread 1-8) WFLYSRV0049: JBoss EAP 7.0.0.GA (WildFly Core 2.1.2.Final-redhat-1) starting
   15:29:29,135 ERROR [org.jboss.as.controller.management-operation] (ServerService Thread Pool -- 13) WFLYCTL0013: Operation ("add") failed - address: ([
       ("subsystem" => "deployment-scanner"),
       ("scanner" => "mysc")
   ]): java.lang.IllegalArgumentException: WFLYDS0023: /nonexistent does not exist
   	at org.jboss.as.server.deployment.scanner.FileSystemDeploymentService.<init>(FileSystemDeploymentService.java:273)
   	at org.jboss.as.server.deployment.scanner.DeploymentScannerAdd.execute(DeploymentScannerAdd.java:124)
   	at org.jboss.as.controller.AbstractOperationContext.executeStep(AbstractOperationContext.java:890)
   	at org.jboss.as.controller.AbstractOperationContext.processStages(AbstractOperationContext.java:659)
   	at org.jboss.as.controller.AbstractOperationContext.executeOperation(AbstractOperationContext.java:370)
   	at org.jboss.as.controller.ParallelBootOperationStepHandler$ParallelBootTask.run(ParallelBootOperationStepHandler.java:359)
   	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
   	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
   	at java.lang.Thread.run(Thread.java:745)
   	at org.jboss.threads.JBossThread.run(JBossThread.java:320)
   
   15:29:29,139 ERROR [org.jboss.as.controller.management-operation] (Controller Boot Thread) "WFLYCTL0193: Failed executing subsystem deployment-scanner boot operations"
   15:29:29,140 ERROR [org.jboss.as.controller.management-operation] (Controller Boot Thread) WFLYCTL0013: Operation ("parallel-subsystem-boot") failed - address: ([]) - failure description: "\"WFLYCTL0193: Failed executing subsystem deployment-scanner boot operations\""
   15:29:29,141 FATAL [org.jboss.as.server] (Controller Boot Thread) WFLYSRV0056: Server boot has failed in an unrecoverable manner; exiting. See previous messages for details.
   15:29:29,144 INFO  [org.jboss.as.server] (Thread-2) WFLYSRV0220: Server shutdown has been requested.
   15:29:29,159 INFO  [org.jboss.as] (MSC service thread 1-8) WFLYSRV0050: JBoss EAP 7.0.0.GA (WildFly Core 2.1.2.Final-redhat-1) stopped in 4ms
   

6. one has to manually modify EAP_HOME/standalone/configuration/standalone.xml removing problematic deployment-scanner part to be able to start server again

It would be great if there is same check to path atribute performed when changing it in existing instance of deployment-scanner as what is performed during the adding a new instance of deployment-scanner.