This looks like a potential bug in the SSE negotiation logic. URLs of the form "in.<client-id>.erraiBus" are used for SSE connections (where a single SSE connection is meant to be used to deliver all messages from the server bus to a particular client bus).
But SSE is not supported by the StandardAsyncServlet. It should be the case that when the bus connection is negotiated, the client is informed that SSE is not enabled and falls back to long-polling, but evidently something has gone wrong where the client attempts an SSE connection and continually attempts to reopen it.
I encourage you open a JIRA issue with more details (including browser logs of the entire bus connection in a failing case). In the mean time, here are some workarounds you can try:
- Use the DefaultBlockingServlet (which supports SSE)
- Explicitly disable SSE support in your ErraiService.properties with the property: "errai.bus.enable_sse_support=false"