singrdk/base/Libraries/Services/ServiceExec.sg

///////////////////////////////////////////////////////////////////////////////
//
//  Microsoft Research Singularity
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//
//  File:   Services\Tests\Calculator\ServiceExec.sg
//
//  Note:   A generic worker-style server implementation
//
using System;
using System.Threading;
using Microsoft.SingSharp;
using Microsoft.Singularity;
using Microsoft.Singularity.Channels;
using Microsoft.Singularity.Directory;
using Microsoft.Singularity.ServiceManager;
using Microsoft.Singularity.Services;

namespace Microsoft.Singularity.Services
{
    // To inherit this class, what you need to do is:
    // 1) To call the base constructor from your sub class.
    // 2) To implement Listen method.
    public abstract class ServiceExec : IRunnable
    {
        protected readonly string!                          path;
        protected TRef<DirectoryServiceContract.Imp:Ready>  directoryRef;
        protected TRef<ThreadTerminationContract.Exp:Start> signalRef;

        /// <summary>
        /// Waits for a client request.  An implementation of this method is
        /// strongly recommended to handle the signal from the parent thread for
        /// terminating the entire process.  Otherwise, the child thread leaks.
        /// </summary>
        protected abstract bool Listen(ServiceProviderContract.Exp:Start! provider,
                                       ThreadTerminationContract.Exp:Start! signal);

        public ServiceExec([Claims]DirectoryServiceContract.Imp:Ready! ep,
                           string! path)
        {
            this.path = path;
            this.directoryRef = new TRef<DirectoryServiceContract.Imp:Ready>(ep);
        }

        public void Signal([Claims]ThreadTerminationContract.Exp:Start! ep)
        {
            this.signalRef = new TRef<ThreadTerminationContract.Exp:Start>(ep);
        }

        public virtual void Run()
        {
            ServiceProviderContract.Exp!            provider;
            ThreadTerminationContract.Exp:Start!    signal;

            if (signalRef == null) {
                throw new Exception("Signal is empty.");
            }

            if (!RegisterName(out provider)) {
                delete provider;
                return;
            }

            signal = signalRef.Acquire();
            while (Listen(provider, signal));
            signalRef.Release(signal);

            DeregisterName(provider);
        }

        protected virtual bool RegisterName(out ServiceProviderContract.Exp! ep)
        {
            bool success = false;
            DirectoryServiceContract.Imp:Ready! ds;
            ServiceProviderContract.Imp!        imp;
            ServiceProviderContract.Exp!        exp;

            ds = directoryRef.Acquire();
            ServiceProviderContract.NewChannel(out imp, out exp);
            ds.SendRegister(Bitter.FromString2(path), imp);
            switch receive {
                case ds.AckRegister():
                    success = true;
                    break;
                case ds.NakRegister(rejected, error):
                    delete rejected;
                    success = false;
                    break;
                case ds.ChannelClosed():
                    success = false;
                    break;
            }
            directoryRef.Release(ds);
            ep = exp;
            return success;
        }

        protected virtual void DeregisterName([Claims]ServiceProviderContract.Exp! ep)
        {
            DirectoryServiceContract.Imp:Ready! ds;
            ds = directoryRef.Acquire();
            ds.SendDeregister(Bitter.FromString2(path));
            switch receive {
                case ds.AckDeregister(imp):
                    delete imp;
                    delete ep;
                    break;
            }
            directoryRef.Release(ds);
        }
    } // class
}