Low level servlet request exception if connection is broken while loading a Vite resource

[Artur-]

Description of the bug

1. Create a new app npx @vaadin/cli init load
2. Start it cd load && mvn
3. Open in the browser and check the url vaadin-router is loaded from, e.g. http://localhost:8080/VAADIN/@fs/some-folder/load/node_modules/@vaadin/router/dist/vaadin-router.js?v=c742f5f9
4. Put a breakpoint in StaticFileServer.serveStaticResource
5. Run curl http://localhost:8080/VAADIN/@fs/some-folder/load/node_modules/@vaadin/router/dist/vaadin-router.js?v=c742f5f9
6. Once the breakpoint is hit, press ctrl-c for the curl command
7. Let the server continue

Then you see something like

2023-11-06T16:06:13.695+02:00 ERROR 81361 --- [io-8080-exec-10] c.vaadin.flow.server.StaticFileServer    : Unable to load /VAADIN/@fs/some-folder/load/node_modules/@vaadin/router/dist/vaadin-router.js from the frontend dev server: java.io.IOException: Broken pipe
2023-11-06T16:06:13.699+02:00 ERROR 81361 --- [io-8080-exec-10] o.a.c.c.C.[.[.[/].[springServlet]        : Servlet.service() for servlet [springServlet] threw exception

java.lang.IllegalStateException: Cannot create a session after the response has been committed
        at org.apache.catalina.connector.Request.doGetSession(Request.java:2907) ~[tomcat-embed-core-10.1.15.jar:10.1.15]
        at org.apache.catalina.connector.Request.getSession(Request.java:2381) ~[tomcat-embed-core-10.1.15.jar:10.1.15]
        at org.apache.catalina.connector.RequestFacade.getSession(RequestFacade.java:639) ~[tomcat-embed-core-10.1.15.jar:10.1.15]
        at jakarta.servlet.http.HttpServletRequestWrapper.getSession(HttpServletRequestWrapper.java:221) ~[tomcat-embed-core-10.1.15.jar:6.0]

seems like sometimes the error is instead

java.lang.IllegalStateException: Cannot call sendError() after the response has been committed
	at org.apache.catalina.connector.ResponseFacade.checkCommitted(ResponseFacade.java:485) ~[tomcat-embed-core-10.1.15.jar:10.1.15]
	at org.apache.catalina.connector.ResponseFacade.sendError(ResponseFacade.java:329) ~[tomcat-embed-core-10.1.15.jar:10.1.15]
	at jakarta.servlet.http.HttpServletResponseWrapper.sendError(HttpServletResponseWrapper.java:89) ~[tomcat-embed-core-10.1.15.jar:6.0]
	at com.vaadin.flow.server.VaadinService.handleRequest(VaadinService.java:1528) ~[flow-server-24.2.2.jar:24.2.2]
	at com.vaadin.flow.server.VaadinServlet.service(VaadinServlet.java:398) ~[flow-server-24.2.2.jar:24.2.2]
	at com.vaadin.flow.spring.SpringServlet.service(SpringServlet.java:106) ~[vaadin-spring-24.2.2.jar:na]

Expected behavior

There is nothing in the log. The request for a static file was aborted. Nothing special about that.

Minimal reproducible example

As above

Versions

• Vaadin / Flow version: 24.2.2
• Java version: 21
• OS version: macOs

[Artur-]

This happens every now and then in my projects, does nobody else see it? The reproduction instructions here seem wrong though because I cannot reproduce it (anymore) with those and the "Unable to load... from the frontend dev server" sounds like it's a problem with the servlet <-> Vite connection and not user <-> servlet

[knoobie]

I'm also seeing this quite often

[Artur-]

I think the reason is this code

  try {
            if (devModeHandler != null
                    && !"/index.html".equals(filenameWithPath)
                    && devModeHandler.serveDevModeRequest(request, response)) {
                // We don't know what the dev server can serve, but if it served
                // something we are happy. There is always an index.html in the
                // dev server but we never want to serve that one directly.
                return true;
            }
        } catch (IOException e) {
            getLogger().error("Unable to load " + filenameWithPath
                    + " from the frontend dev server: " + e.getMessage());
        }

where Flow is catching an IOException coming from writing the vite server response to the disconnected client but not aborting handling the request

[Artur-]

So probably the real error is somewhere before those exceptions in the log as the exceptions only tell that we cannot continue to serve index.html to a request that was already closed