Hi, do you remember my previous post about Foreach in WCF? Today I would like to show you only code samples of the same problem but with REST technology because I searched the Internet, and there is no example of server and client site setup property in .NET 4.0. In my opinion, you can often find implementation with the HttpClient class that wastes time. I will present you with a project stored in tree assemblies ForeachREST.Contracts, ForeachREST.Server and ForeachREST.Client. If you have trouble with that code examples, let me know in the comments. It is a quite an advanced topic, and I do not want to write a saga about every mechanism. I try only to focus on the correct usage of parts on .NET 4.0 Framework by clear example.
ForeachREST.Contracts
using System;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.ServiceModel.Web;
namespace ForeachREST.Contracts
{
[ServiceContract(SessionMode = SessionMode.NotAllowed)]
public interface IForeachREST<TKey, TValue>
{
[OperationContract]
[WebGet(ResponseFormat = WebMessageFormat.Xml)]
TValue[] GetNext(TKey key);
}
[DataContract]
[Serializable]
public class Entity
{
[DataMember]
public string Value { get; set; }
}
}
ForeachREST.Server.Service
using System;
using System.Collections.Generic;
using System.Collections.Concurrent;
using System.ServiceModel;
using System.Threading;
using ForeachREST.Contracts;
namespace ForeachREST.Server.Service
{
[ServiceBehavior(
InstanceContextMode = InstanceContextMode.Single,
ConcurrencyMode = ConcurrencyMode.Multiple
)]
public class ForeachREST<TKey, TValue> : IForeachREST<TKey, TValue>
where TValue : class, new()
{
private readonly Func<IEnumerable<TValue>> Enumerator;
private readonly int BufferSize;
private readonly int MaxTimeout;
public ForeachREST(Func<IEnumerable<TValue>> enumerator,
int bufferSize,
int maxTimeout) {
if (enumerator == null)
throw new InvalidOperationException(
"Enumerator cannot be null.");
if (bufferSize <= 0)
throw new InvalidOperationException(
"BufferSize cannot be less or equal than 0.");
if (maxTimeout <= 0)
throw new InvalidOperationException(
"MaxTimeout cannot be less or equal than 0.");
Enumerator = enumerator;
BufferSize = bufferSize;
MaxTimeout = maxTimeout;
}
private readonly ConcurrentDictionary<TKey, ConcurrentQueue<TValue>>
enumerators = new ConcurrentDictionary<TKey, ConcurrentQueue<TValue>>();
public TValue[] GetNext(TKey key) {
var count = BufferSize;
var data = new TValue[count];
ConcurrentQueue<TValue> queue = null;
if (!enumerators.ContainsKey(key)) {
queue = new ConcurrentQueue<TValue>();
enumerators.TryAdd(key, queue);
new Thread(
() => FetchDataFromDataStore(key, queue)
) { IsBackground = true }.Start();
} else {
queue = enumerators[key];
}
SpinWait.SpinUntil(() => !queue.IsEmpty);
TValue value;
var fetched = 0;
RETRY:
if (queue.TryDequeue(out value)) {
if (value == null) {
enumerators.TryRemove(key, out queue);
for(var pos = fetched; pos < count; ++pos)
data[pos] = value;
return data;
}
data[fetched++] = value;
if (fetched < count) {
SpinWait.SpinUntil(() => !queue.IsEmpty);
goto RETRY;
}
} else {
SpinWait.SpinUntil(() => !queue.IsEmpty);
goto RETRY;
}
return data;
}
private void FetchDataFromDataStore(
TKey key,
ConcurrentQueue<TValue> queue) {
foreach (var next in Enumerator()) {
if (SpinWait.SpinUntil(
() => queue.Count < BufferSize, MaxTimeout)) {
queue.Enqueue(next);
} else {
enumerators.TryRemove(key, out queue);
break;
}
}
}
}
}
ForeachREST.Server
using System;
using System.Collections.Generic;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.ServiceModel.Description;
using ForeachREST.Contracts;
namespace ForeachREST.Server
{
class Server
{
static void Main(string[] args) {
ServiceHost serviceHost = null;
try {
string addressStr = "http://localhost:27272/ForeachREST";
var binding = new WebHttpBinding(WebHttpSecurityMode.None);
var addressUri = new Uri(addressStr);
var service = new Service.ForeachREST<Guid, Entity>(
// Enumerator Injection.
GetEnumeratorFromDataStore,
// 1000 entities is max buffer size for one enumeration.
1000,
// 10 seconds is max timeout for getting next value from server.
10000
);
serviceHost = new ServiceHost(service, addressUri);
var endpoint = serviceHost.AddServiceEndpoint(
typeof(IForeachREST<Guid, Entity>),
binding,
addressUri);
endpoint.Behaviors.Add(new WebHttpBehavior());
serviceHost.Open();
Console.WriteLine(
"ForeachREST service is running, press any key to stop.");
Console.ReadKey();
} catch (Exception ex) {
Console.WriteLine(ex.ToString());
} finally {
serviceHost.Close();
}
}
#region Enumerator for Injection
// Last yield return shall be null;
private static IEnumerable<Entity> GetEnumeratorFromDataStore() {
for (int i = 0; i < 1000000; ++i) {
yield return new Entity { Value = i.ToString() };
}
yield return null;
}
#endregion
}
}
ForeachREST.Client
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.ServiceModel;
using System.ServiceModel.Description;
using System.Text;
using ForeachREST.Contracts;
namespace ForeachREST.Client
{
class Client
{
static void Main(string[] args) {
var count = 0;
var meter = Stopwatch.StartNew();
foreach (var element in ForeachRESTConsumer.GetEnumerator()) {
var value = element.Value;
++count;
//Console.WriteLine(value);
}
meter.Stop();
Console.WriteLine("{0} elements was feched in {1} ms.",
count, meter.ElapsedMilliseconds);
Console.ReadKey();
}
}
public static class ForeachRESTConsumer
{
static IForeachREST<Guid, Entity> client;
static ForeachRESTConsumer() {
var binding = new WebHttpBinding(WebHttpSecurityMode.None);
var address = new EndpointAddress("http://localhost:27272/ForeachREST");
var channelFactory = new ChannelFactory<IForeachREST<Guid, Entity>>(binding, address);
channelFactory.Endpoint.Behaviors.Add(new WebHttpBehavior());
client = channelFactory.CreateChannel(address);
}
public static IEnumerable<Entity> GetEnumerator() {
var key = Guid.NewGuid();
Entity[] nexts = null;
while ((nexts = client.GetNext(key)) != null) {
for (int i = 0; i < nexts.Length; ++i) {
var value = nexts[i];
if (value == null)
yield break;
yield return value;
}
}
}
}
}
Again, if you need more information let me know in comments.
P ;).