Add ResourceHandler.setUseFileMapping(boolean) option

[cowwoc]

Jetty Version
12.0.3

Jetty Environment
Windows 10

Java Version
JDK 21

Question
In the past, one had to set useFileMappedBuffer=false to avoid holding file locks on Windows, but this configuration option seems to be gone. I am using the Handler API to serve static files. I don't use the servlet API at all.

When I'm developing JS code, I run Jetty for the backend and esbuild-watch for the frontend. Every time the file changes, esbuild-watch tries to re-build it; unfortunately it seems that Jetty is holding a lock and I'm not sure how to get around this.

[joakime]

@cowwoc how are you declaring your Base Resource? (code examples please)
Also, how are you accessing your static files? (hopefully via a Resource Base and not a ClassLoader).

[joakime]

On Jetty 9 / Jetty 10 / Jetty 11 the useFileMappedBuffer option disabled the ContentFactory from using java file mapped ByteBuffers.

On Jetty 12, the useFileMappedBuffer configuration still exists, but only for ee10 / ee9 / ee8 DefaultServlet (which you said you are not using).

If you used ResourceService on Jetty 9 / Jetty 10 / Jetty 11, you were responsible for passing in the useFileMappedBuffer option when you created the ResourceService.

On Jetty 12, the ResourceService has a tree of ContentFactory implementations, using the FileMappingHttpContentFactory (or not) at the top level determines the behavior.

[cowwoc]

@joakime

On Jetty 12, the ResourceService has a tree of ContentFactory implementations, using the FileMappingHttpContentFactory (or not) at the top level determines the behavior.

That makes sense, but how do I get ResourceService not to use FileMappingHttpContentFactory? I don't see any obvious way.

When reading the following code, keep in mind that the file being locked is inside the target/classes directory. Here is the relevant code snippet that creates the resource handlers:

ResourceHandler staticFiles = new ResourceHandler();
staticFiles.setDirAllowed(true);

if (scope.getRunMode() == RunMode.RELEASE)
	staticFiles.setEtags(true);

ResourceFactory resourceFactory = ResourceFactory.of(server);
List<Resource> resources = new ArrayList<>(3);

Path serverClassesPath = getPathOfDefaultPackage();
// Paths must be normalized; otherwise, Jetty will reject them for security reasons (symlinks can be
// redirected)
Path browserDirectory = serverClassesPath.resolve("../../../../client/browser/").normalize();

// Source code may be updated during development
Path srcPath = browserDirectory.resolve("src").normalize();
if (Files.exists(srcPath))
	resources.add(resourceFactory.newResource(srcPath));
Path browserClassesPath = browserDirectory.resolve("target/classes");
if (Files.exists(browserClassesPath))
	resources.add(resourceFactory.newResource(browserClassesPath));
Path browserJar = browserDirectory.resolve("target/client.browser-" + scope.getVersion() + ".jar");
if (Files.exists(browserJar))
	resources.add(resourceFactory.newJarFileResource(browserJar.toUri()));
staticFiles.setBaseResource(ResourceFactory.combine(resources));

log.debug("Loading files from: {}", staticFiles.getBaseResource());
return staticFiles;

Does anything jump out at you? I am seeing FileMappingHttpContentFactory.getMappedByteBuffer():118 getting invoked by the following stack trace:

getMappedByteBuffer:118, FileMappingHttpContentFactory$FileMappedHttpContent (org.eclipse.jetty.http.content)
getBytesOccupied:109, FileMappingHttpContentFactory$FileMappedHttpContent (org.eclipse.jetty.http.content)
getBytesOccupied:206, HttpContent$Wrapper (org.eclipse.jetty.http.content)
isCacheable:220, CachingHttpContentFactory (org.eclipse.jetty.http.content)
isCacheable:99, ValidatingCachingHttpContentFactory (org.eclipse.jetty.http.content)
getContent:242, CachingHttpContentFactory (org.eclipse.jetty.http.content)
getContent:87, ResourceService (org.eclipse.jetty.server)
handle:162, ResourceHandler (org.eclipse.jetty.server.handler)
handle:159, RewriteHandler$LastRuleHandler (org.eclipse.jetty.rewrite.handler)
handle:108, Rule$Handler (org.eclipse.jetty.rewrite.handler)
handle:89, HeaderPatternRule$1 (org.eclipse.jetty.rewrite.handler)
handle:108, Rule$Handler (org.eclipse.jetty.rewrite.handler)
handle:89, HeaderPatternRule$1 (org.eclipse.jetty.rewrite.handler)
handle:108, Rule$Handler (org.eclipse.jetty.rewrite.handler)
handle:143, RewriteHandler (org.eclipse.jetty.rewrite.handler)
handle:785, Handler$Sequence (org.eclipse.jetty.server)
handle:594, GzipHandler (org.eclipse.jetty.server.handler.gzip)
handle:809, ContextHandler (org.eclipse.jetty.server.handler)
handle:179, Server (org.eclipse.jetty.server)
run:649, HttpChannelState$HandlerInvoker (org.eclipse.jetty.server.internal)
onFillable:471, HttpConnection (org.eclipse.jetty.server.internal)
succeeded:322, AbstractConnection$ReadCallback (org.eclipse.jetty.io)
fillable:100, FillInterest (org.eclipse.jetty.io)
run:53, SelectableChannelEndPoint$1 (org.eclipse.jetty.io)
run:314, ThreadPerTaskExecutor$TaskRunner (java.util.concurrent)
[application code follows]

Thanks

[cowwoc]

I should clarify that I am using Jetty 12.0.3

[cowwoc]

Thanks to you pointing me in the right direction, I discovered the following workaround:

ResourceHandler staticFiles = new ResourceHandler()
{
	@Override
	protected HttpContent.Factory newHttpContentFactory()
	{
		HttpContent.Factory contentFactory = new ResourceHttpContentFactory(
			ResourceFactory.of(getBaseResource()), getMimeTypes());
		contentFactory = new VirtualHttpContentFactory(contentFactory, getStyleSheet(), "text/css");
		contentFactory = new PreCompressedHttpContentFactory(contentFactory, getPrecompressedFormats());
		contentFactory = new ValidatingCachingHttpContentFactory(contentFactory,
			Duration.ofSeconds(1).toMillis(), getByteBufferPool());
		return contentFactory;
	}
};

Meaning, I just took ResourceHandler.newHttpContentFactory() and removed the contentFactory = new FileMappingHttpContentFactory(contentFactory); line.

I hope that's safe... That said, does it make sense to add a configuration option to do this without having to subclassing ResourceHandler?

[joakime]

Meaning, I just took ResourceHandler.newHttpContentFactory() and removed the contentFactory = new FileMappingHttpContentFactory(contentFactory); line.

I hope that's safe... That said, does it make sense to add a configuration option to do this without having to subclassing ResourceHandler?

Yup, that's safe.
And it was what I was going to recommend as well.

[joakime]

The other option is to use the ResourceService directly (not via the ResourceHandler) so you can control the content factories yourself. (like how the DefaultServlets do)

I'm going to rename this as an issue to add useFileMapping option to the ResourceHandler as well.

[cowwoc]

Thank you!

[joakime]

PR #11071 merged