ONCRPC4J

This is a part of dCache.ORG's NFSv4.1 work.

Technically, this is not a fork of Remote Tea RPC library, but formally it is as we was inspired by Remote Tea RPC and took lot of ideas from it including xdr language parser. The goal to be able to use stubs generated by Remote Tea (no need to rewrite existing RPC servers) with minimal changes.

The library supports IPv6, RPCSEC_GSS and compliant with rfc1831 and rfc2203.

There are several options how to use ONCRPC4J in your application

Embedding service into an application

package me.mypackage;

import org.dcache.oncrpc4j.rpc.OncRpcException;
import org.dcache.oncrpc4j.rpc.RpcDispatchable;
import org.dcache.oncrpc4j.rpc.RpcCall;
import org.dcache.oncrpc4j.xdr.XdrVoid;

public class Svcd {

    private static final int DEFAULT_PORT = 1717;
    private static final int PROG_NUMBER = 111017;
    private static final int PROG_VERS = 1;

    public static void main(String[] args) throws Exception {

        int port = DEFAULT_PORT;

        RpcDispatchable dummy = new RpcDispatchable() {

            @Override
            public void dispatchOncRpcCall(RpcCall call)
                          throws OncRpcException, IOException {
                call.reply(XdrVoid.XDR_VOID);
            }
        };

        OncRpcSvc service = new OncRpcSvcBuilder()
                .withTCP()
                .withAutoPublish()
                .withPort(port)
                .withSameThreadIoStrategy()
                .withRpcService(new OncRpcProgram(PROG_NUMBER, PROG_VERS), dummy)
                .build();
        service.start();
    }
}

or as a spring bean

package me.mypackage;

import org.dcache.oncrpc4j.rpc.OncRpcException;
import org.dcache.oncrpc4j.rpc.RpcDispatchable;
import org.dcache.oncrpc4j.rpc.RpcCall;
import org.dcache.oncrpc4j.xdr.XdrVoid;
import java.io.IOException;

public class Svcd implements RpcDispatchable {

    @Override
    public void dispatchOncRpcCall(RpcCall call)
                throws OncRpcException, IOException {
        call.reply(XdrVoid.XDR_VOID);
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

    <bean id="my-rpc-svc" class="me.mypackage.Svcd">
        <description>My RPC service</description>
    </bean>

     <bean id="my-rpc" class="org.dcache.oncrpc4j.rpc.OncRpcProgram">
        <description>My RPC program number</description>
        <constructor-arg index="0" value="1110001" />
        <constructor-arg index="1" value="1" />
    </bean>

    <bean id="rpcsvc-builder" class="org.dcache.oncrpc4j.rpc.OncRpcSvcFactoryBean">
        <description>Onc RPC service builder</description>
        <property name="port" value="1717"/>
        <property name="useTCP" value="true"/>
        <property name="rpcServices">
            <map>
                <entry key-ref="my-rpc" value-ref="my-rpc-svc"/>
            </map>
        </property>

    </bean>

    <bean id="oncrpcsvc" class="org.dcache.oncrpc4j.rpc.OncRpcSvc" init-method="start" destroy-method="stop">
        <description>My RPC service</description>
        <constructor-arg ref="rpcsvc-builder"/>
    </bean>
</beans>

Notice, that included SpringRunner will try to instantiate and run bean with id oncrpcsvc.

java -cp $CLASSPATH org.dcache.oncrpc4j.spring.SpringRunner svc.xml

Migration from ONCRPC4J-2.x

With version 3.0.0 a new package schema is introduced. As the change is not backward compatible with older version some minimal code changes are required.

Removed methods

org.dcache.utils.Bytes#{fromHexString|toHexString} methods are removed in favour of com.google.common.io.BaseEncoding.

Renamed packages

org.dcache.utils => org.dcache.oncrpc4j.util org.dcache.utils.net => org.dcache.oncrpc4j.rpc.net org.dcache.xdr split into org.dcache.oncrpc4j.rpc, org.dcache.oncrpc4j.xdr and org.dcache.oncrpc4j.grizzly

Renamed classes

org.dcache.utils.Opaque => into org.dcache.oncrpc4j.XdrOpaque org.dcache.xdr.XdrTransport => into org.dcache.oncrpc4j.rpc.RpcTransport org.dcache.xdr.GrizzlyXdrTransport => into org.dcache.oncrpc4j.grizzly.GrizzlyRpcTransport

Removed classes

org.dcache.xdr.XdrBuffer is removed. Use org.dcache.oncrpc4j.xdr.Xdr.

Behavior change

The Xdr#xdrEncodeByteBuffer changed to not flip provided byte buffer. As a result, the Xdr#xdrEncodeByteBuffer will encode data in the buffer from buffers current position up to the limit:

ButeByffer buffer = ...;
Xdr xdr = ...;

buffer.put(...);
buffer.flip();
xdr.xdrEncodeByteBuffer(buffer);

Using RPCGEN to generate client and server stubs

Assume a service which calculates a the length of a string. It provides a single remote call strlen which takes a string as an argument ans returns it's length. Let describe that procedure according XDR language specification:

/* strlen.x */
program STRLEN {
    version STRLENVERS {
        int strlen(string) = 1;
    } = 1;
} = 117;

Here we define STRLEN program number to be 117 and version number 1. Now we can generate stub files for client and server:

java -jar oncrpc4j-rpcgen.jar -c StrlenClient strlen.x

Simply extend this class and implement abstract methods:

//StrlenSvcImpl.java
import org.dcache.oncrpc4j.rpc.*;
import org.dcache.oncrpc4j.xdr.*;

public class StrlenSvcImpl extends strlenServerStub {

   public int strlen_1(RpcCall call$, String arg) {
       return arg.length();
   }
}

Now it's ready to be complied and deployed as standalone or Spring application:

// StrlenServerApp.java
// standalone application example
import org.dcache.oncrpc4j.rpc.*;
import org.dcache.oncrpc4j.xdr.*;

public class StrlenServerApp {

    static final int DEFAULT_PORT = 1717;

    public static void main(String[] args) throws Exception {

        OncRpcSvc service = new OncRpcSvcBuilder()
                .withTCP()
                .withAutoPublish()
                .withPort(DEFAULT_PORT)
                .withSameThreadIoStrategy()
                .withRpcService(new OncRpcProgram(strlen.STRLEN, strlen.STRLENVERS), new StrlenSvcImpl())
                .build();
        service.start();
        System.in.read();
    }
}

In addition, a client will be generated as well which can be used as:

// StrlenClientApp.java
import java.net.InetAddress;
import org.dcache.oncrpc4j.rpc.*;
import org.dcache.oncrpc4j.xdr.*;

public class StrlenClientApp {

    static final int DEFAULT_PORT = 1717;

    public static void main(String[] args) throws Exception {
        InetAddress address = InetAddress.getByName(args[0]);

        StrlenClient client = new StrlenClient(address, DEFAULT_PORT,
                strlen.STRLEN,
                strlen.STRLENVERS,
                IpProtocolType.TCP);
        System.out.println("Length of " + args[1] + " = " + client.strlen_1(args[1]));
        client.shutdown();
    }
}

Your RPC client and server are ready!

Use ONCRPC4J in your project

As maven dependency

<dependency>
    <groupId>org.dcache</groupId>
    <artifactId>oncrpc4j-core</artifactId>
    <version>3.0.2</version>
</dependency>

<repositories>
    <repository>
        <id>dcache-snapshots</id>
        <name>dCache.ORG maven repository</name>
        <url>https://download.dcache.org/nexus/content/repositories/releases</url>
        <layout>default</layout>
    </repository>
</repositories>

Accessing client subject inside RPC service

In some situation, OncRpcSvc can internally call other services which require client subject to be set in the context of the current thread. We use standard Java's Subject.doAs() mechanism to inject user subject into processing thread. As a result, the user subject can be extracted from AccessControlContext.

// SomeService.java
import javax.security.auth.Subject;
import java.security.AccessController;

public class SomeService {
    public void doSomeTask() {
        Subject subject = Subject.getSubject(AccessController.getContext());
        // start using subject
    }
}

// SubjectAvareSvcImpl.java
public class SubjectAvareSvcImpl implements RpcDispatchable {
    @Override
    public void dispatchOncRpcCall(RpcCall call)
                throws OncRpcException, IOException {
        externalService.doSomeTask();
        call.reply(XdrVoid.XDR_VOID);
    }
}

To avoid unnecessary overhead, subject propagation is not enabled by default:

OncRpcSvc service = new OncRpcSvcBuilder()
        .withTCP()
        .withAutoPublish()
        .withSameThreadIoStrategy()
        .withRpcService(... , new SubjectAvareSvcImpl())
        .withSubjectPropagation()
        .build();

Enabling JMX based monitoring

oncrpc4j uses Grizzly NIO framework which comes with it's own JMX monitoring capabilities. To enable it just add grizzly-framework-monitoring jar with it's dependencies into the application's classpath. See Grizzly framework dependencies for the instructions.

Usage with JDK 9 module system

With the provided stable automatic module name org.dcache.oncrpc4j, oncrpc4j can be used in modular java9 application:

module com.foo.bar {
    requires org.dcache.oncrpc4j;
}

RPC-over-TLS

oncrpc4j supports rpc-over-tls IETF activity. The goal of the project is to protect in-transit Remote Procedure Call messages with TLS. To enable RPC-over-TLS:

SSLContext sslServerContext = ...;

svc = new OncRpcSvcBuilder()
    .withTCP()
    ....
    .withSSLContext(sslServerContext)
    .withStartTLS()
    .withServiceName("svc")
    .build();
svc.start();

or, if special SSLParameters configuration is required, like cipher types, then:

SSLContext sslServerContext = ...;
SSLParameters parameters = ...;

svc = new OncRpcSvcBuilder()
    .withTCP()
    ....
    .withSSLContext(sslServerContext)
    .withSSLParameters(parameters)
    .withStartTLS()
    .withServiceName("svc")
    .build();
svc.start();

How to contribute

oncrpc4j uses the linux kernel model of using git not only a source repository, but also as a way to track contributions and copyrights.

Each submitted patch must have a "Signed-off-by" line. Patches without this line will not be accepted.

The sign-off is a simple line at the end of the explanation for the patch, which certifies that you wrote it or otherwise have the right to pass it on as an open-source patch. The rules are pretty simple: if you can certify the below:

Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
    have the right to submit it under the open source license
    indicated in the file; or

(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
    license and I have the right under that license to submit that
    work with modifications, whether created in whole or in part
    by me, under the same open source license (unless I am
    permitted to submit under a different license), as indicated
    in the file; or

(c) The contribution was provided directly to me by some other
    person who certified (a), (b) or (c) and I have not modified
    it.

(d) I understand and agree that this project and the contribution
    are public and that a record of the contribution (including all
    personal information I submit with it, including my sign-off) is
    maintained indefinitely and may be redistributed consistent with
    this project or the open source license(s) involved.

then you just add a line saying ( git commit -s )

Signed-off-by: Random J Developer <random@developer.example.org>

using your real name (sorry, no pseudonyms or anonymous contributions.)