12.1.0 - ResourceHandler is unable to serve content from PathResource that doesn't support mapped file buffers.

[joakime]

Jetty version(s)
12.1.0.alpha1

Jetty Environment
core

Java version/vendor (use: java -version)

openjdk 17.0.11 2024-04-16
OpenJDK Runtime Environment Temurin-17.0.11+9 (build 17.0.11+9)
OpenJDK 64-Bit Server VM Temurin-17.0.11+9 (build 17.0.11+9, mixed mode, sharing)

OS type/version
Linux / Ubuntu

Description
If you have a Resource Base that is a PathResource that points to a FS that doesn't support file mapping, like zipfs, then you are unable to serve files from ResourceHandler.

This works in 12.0.16 just fine.

2025-01-09 13:43:22.809:WARN :oejs.Response:qtp2008106788-169: writeError: status=500, message=java.lang.UnsupportedOperationException, response=ErrorResponse@1e15b2b8{500,GET@2e2db70a http://192.168.1.221:40715/jars/webjars/bootstrap/5.3.3/js/bootstrap.bundle.js HTTP/1.1}
java.lang.UnsupportedOperationException
	at jdk.zipfs/jdk.nio.zipfs.ZipFileSystem$1.map(ZipFileSystem.java:1102)
	at org.eclipse.jetty.util.BufferUtil.toMappedBuffer(BufferUtil.java:1178)
	at org.eclipse.jetty.util.BufferUtil.toMappedBuffer(BufferUtil.java:1171)
	at org.eclipse.jetty.http.content.FileMappingHttpContentFactory$SingleBufferFileMappedHttpContent.<init>(FileMappingHttpContentFactory.java:103)
	at org.eclipse.jetty.http.content.FileMappingHttpContentFactory.getContent(FileMappingHttpContentFactory.java:78)
	at org.eclipse.jetty.http.content.VirtualHttpContentFactory.getContent(VirtualHttpContentFactory.java:60)
	at org.eclipse.jetty.http.content.PreCompressedHttpContentFactory.getContent(PreCompressedHttpContentFactory.java:48)
	at org.eclipse.jetty.http.content.CachingHttpContentFactory.getContent(CachingHttpContentFactory.java:229)
	at org.eclipse.jetty.server.ResourceService.getContent(ResourceService.java:88)
	at org.eclipse.jetty.server.handler.ResourceHandler.handle(ResourceHandler.java:174)
	at org.eclipse.jetty.server.Handler$Wrapper.handle(Handler.java:740)
	at examples.PathMappingServer$PathNameWrapper.handle(PathMappingServer.java:177)
	at org.eclipse.jetty.server.handler.PathMappingsHandler.handle(PathMappingsHandler.java:116)
	at org.eclipse.jetty.server.Server.handle(Server.java:182)
	at org.eclipse.jetty.server.internal.HttpChannelState$HandlerInvoker.run(HttpChannelState.java:672)
	at org.eclipse.jetty.server.internal.HttpConnection.onFillable(HttpConnection.java:411)
	at org.eclipse.jetty.server.internal.HttpConnection$FillableCallback.succeeded(HttpConnection.java:1688)
	at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:99)
	at org.eclipse.jetty.io.SelectableChannelEndPoint$1.run(SelectableChannelEndPoint.java:53)
	at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:979)
	at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.doRunJob(QueuedThreadPool.java:1209)
	at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:1164)
	at java.base/java.lang.Thread.run(Thread.java:840)

I think the toMappedBuffer should catch UnsupportedOperationException and fallback to non-mapped option.

[joakime]

The issue isn't zipfs specific, it's just the easiest way to trigger this UnsupportedOperationException.

See https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/nio/channels/FileChannel.html#map(java.nio.channels.FileChannel.MapMode,long,long)

We should also consider if a file is too small for memory mapping, per the recommendations in the javadoc linked above.

"For most operating systems, mapping a file into memory is more expensive than reading or writing a few tens of kilobytes of data via the usual read and write methods. From the standpoint of performance it is generally only worth mapping relatively large files into memory."