Code to reproduce https://github.com/reactor/reactor-netty/issues/60

Application.java

import io.netty.handler.codec.http.HttpHeaderNames;
import reactor.core.publisher.Hooks;
import reactor.core.publisher.Mono;
import reactor.ipc.netty.NettyContext;
import reactor.ipc.netty.http.server.HttpServer;

import java.io.IOException;
import java.nio.file.FileSystem;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Collections;

import org.springframework.core.io.ClassPathResource;

/**
 * @author Mark Paluch
 */
public class Application {

	private final HttpServer server = HttpServer.create("0.0.0.0", Integer.getInteger("server.port", 8080));
	private final Mono<? extends NettyContext> context;

	Application() throws IOException {
		Hooks.onOperator(h -> h.operatorStacktrace());
		context = server.newRouter(r -> r.get("/**", (res, resp) -> resp.header(HttpHeaderNames.CONTENT_TYPE, "text/html")
				.sendFile(resolveContentPath().resolve("index.html")).then().doOnError(Throwable::printStackTrace)));
	}

	public static void main(String... args) throws Exception {
		Application app = new Application();
		app.startAndAwait();
	}

	public void startAndAwait() {
		context.block().onClose().block();
	}

	private Path resolveContentPath() {

		try {
			ClassPathResource cp = new ClassPathResource("static");
			if (cp.isFile()) {
				return Paths.get(cp.getURI());
			}
			FileSystem fs = FileSystems.newFileSystem(cp.getURI(), Collections.emptyMap());
			Runtime.getRuntime().addShutdownHook(new Thread(() -> {
				try {
					fs.close();
				} catch (IOException io) {
					// ignore
				}
			}));
			return fs.getPath("static");

		} catch (IOException e) {
			e.printStackTrace();
		}

		return null;
	}
}

index.html

bar

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
		 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
		 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>reactor-bugs</groupId>
	<artifactId>reactor-bug-epoll-sendfile-from-jar</artifactId>
	<version>1.0-SNAPSHOT</version>

	<properties>
		<maven.compiler.source>1.8</maven.compiler.source>
		<maven.compiler.target>1.8</maven.compiler.target>
	</properties>

	<dependencies>
		<dependency>
			<groupId>io.projectreactor</groupId>
			<artifactId>reactor-core</artifactId>
			<version>3.0.5.RELEASE</version>
		</dependency>

		<dependency>
			<groupId>io.projectreactor.ipc</groupId>
			<artifactId>reactor-netty</artifactId>
			<version>0.6.2.RELEASE</version>
		</dependency>

		<dependency>
			<groupId>io.netty</groupId>
			<artifactId>netty-transport-native-epoll</artifactId>
			<classifier>linux-x86_64</classifier>
			<version>4.1.8.Final</version>
		</dependency>

		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-core</artifactId>
			<version>5.0.0.BUILD-SNAPSHOT</version>
		</dependency>
	</dependencies>

	<repositories>
		<repository>
			<id>spring-snapshots</id>
			<name>Spring Snapshots</name>
			<url>https://repo.spring.io/libs-snapshot</url>
			<snapshots>
				<enabled>true</enabled>
			</snapshots>
		</repository>
	</repositories>

</project>