Symptoms
You are trying to configure a client application to connect to a virtual topic. The client fails to connect and the logs include an unhandled exception similar to the following example:
ERROR NULL io.vertx.core.impl.ContextImpl - [:] Unhandled exception
java.lang.NullPointerException: Cannot invoke "java.lang.String.getBytes(java.nio.charset.Charset)" because "this.key" is null
The exception message appears every few minutes in the Event Gateway logs and does not disappear even after a restart of the gateway.
Causes
The client identity is misconfigured. Multiple clients connect by using the same application and group ID, but use different client IDs, or do not set a client ID at all.
Resolving the problem
Set both client ID and group ID, and ensure every client that shares the application uses the same pair of values. For example,
myClientApplication1: <GROUP_ID>=BOB, <CLIENT_ID>=ABC
myClientApplication2: <GROUP_ID>=BOB, <CLIENT_ID>=ABC
Restart the clients after you update the configuration.