Service Discovery in WCF 4.0 – Part 1 z
When designing a service oriented architecture (SOA) system,
there will be a lot of services with many service contracts, endpoints
and behaviors. Besides the client calling the service, in a large
distributed system a service may invoke other services. In this case,
one service might need to know the endpoints it invokes. This might not
be a problem in a small system. But when you have more than 10 services
this might be a problem. For example in my current product, there are
around 10 services, such as the user authentication service, UI
integration service, location service, license service, device monitor
service, event monitor service, schedule job service, accounting
service, player management service, etc..
Benefit of Discovery Service
Since
almost all my services need to invoke at least one other service. This
would be a difficult task to make sure all services endpoints are
configured correctly in every service. And furthermore, it would be a
nightmare when a service changed its endpoint at runtime.
Hence,
we need a discovery service to remove the dependency (configuration
dependency). A discovery service plays as a service dictionary which
stores the relationship between the contracts and the endpoints for
every service. By using the discovery service, when service X wants to
invoke service Y, it just need to ask the discovery service where is
service Y, then the discovery service will return all proper endpoints
of service Y, then service X can use the endpoint to send the request to
service Y. And when some services changed their endpoint address, all
need to do is to update its records in the discovery service then all
others will know its new endpoint.
In
WCF 4.0 Discovery it supports both managed proxy discovery mode and
ad-hoc discovery mode. In ad-hoc mode there is no standalone discovery
service. When a client wanted to invoke a service, it will broadcast an
message (normally in UDP protocol) to the entire network with the
service match criteria. All services which enabled the discovery
behavior will receive this message and only those matched services will
send their endpoint back to the client.The managed proxy
discovery service works as I described above. In this post I will only
cover the managed proxy mode, where there’s a discovery service. For
more information about the ad-hoc mode please refer to the MSDN.
Service Announcement and Probe
The
main functionality of discovery service should be return the proper
endpoint addresses back to the service who is looking for. In most cases
the consume service (as a client) will send the contract which it
wanted to request to the discovery service. And then the discovery
service will find the endpoint and respond. Sometimes the contract and
endpoint are not enough. It also contains versioning, extensions
attributes. This post I will only cover the case includes contract and
endpoint.
When
a client (or sometimes a service who need to invoke another service)
need to connect to a target service, it will firstly request the
discovery service through the “Probe” method with the criteria.
Basically the criteria contains the contract type name of the target
service.
Then the discovery service will search its endpoint
repository by the criteria. The repository might be a database, a
distributed cache or a flat XML file. If it matches, the discovery
service will grab the endpoint information (it’s called discovery
endpoint metadata in WCF) and send back. And this is called “Probe”.
Finally the client received the discovery endpoint metadata and will use the endpoint to connect to the target service.
Besides
the probe, discovery service should take the responsible to know there
is a new service available when it goes online, as well as stopped when
it goes offline. This feature is named “Announcement”. When a service
started and stopped, it will announce to the discovery service.
So the basic functionality of a discovery service should includes:
1, An endpoint which receive the service online message, and add the service endpoint information in the discovery repository.
2,
An endpoint which receive the service offline message, and remove the
service endpoint information from the discovery repository.
3,
An endpoint which receive the client probe message, and return the
matches service endpoints, and return the discovery endpoint metadata.
WCF 4.0 discovery service just covers all these features in it's infrastructure classes.
Discovery Service in WCF 4.0
WCF
4.0 introduced a new assembly named System.ServiceModel.Discovery which
has all necessary classes and interfaces to build a WS-Discovery
compliant discovery service. It supports ad-hoc and managed proxy modes.
For the case mentioned in this post, what we need to build is a
standalone discovery service, which is the managed proxy discovery
service mode.
To build a managed discovery service in WCF 4.0
just create a new class inherits from the abstract class
System.ServiceModel.Discovery.DiscoveryProxy. This class implemented and
abstracted the procedures of service announcement and probe. And it
exposes 8 abstract methods where we can implement our own endpoint
register, unregister and find logic.
These 8
methods are asynchronized, which means all invokes to the discovery
service are asynchronously, for better service capability and
performance.
1, OnBeginOnlineAnnouncement,
OnEndOnlineAnnouncement: Invoked when a service sent the online
announcement message. We need to add the endpoint information to the
repository in this method.
2, OnBeginOfflineAnnouncement,
OnEndOfflineAnnouncement: Invoked when a service sent the offline
announcement message. We need to remove the endpoint information from
the repository in this method.
3, OnBeginFind, OnEndFind:
Invoked when a client sent the probe message that want to find the
service endpoint information. We need to look for the proper endpoints
by matching the client’s criteria through the repository in this method.
4,
OnBeginResolve, OnEndResolve: Invoked then a client sent the resolve
message. Different from the find method, when using resolve method the
discovery service will return the exactly one service endpoint metadata
to the client. In our example we will NOT implement this method.
Let’s
create our own discovery service, inherit the base
System.ServiceModel.Discovery.DiscoveryProxy. We also need to specify
the service behavior in this class. Since the build-in discovery service
host class only support the singleton mode, we must set its instance
context mode to single.
1: using System;
2: using System.Collections.Generic;
3: using System.Linq;
4: using System.Text;
5: using System.ServiceModel.Discovery;
6: using System.ServiceModel;
7:
8: namespace Phare.Service
9: {
10: [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple)]
11: public class ManagedProxyDiscoveryService : DiscoveryProxy
12: {
13: protected override IAsyncResult OnBeginFind(FindRequestContext findRequestContext, AsyncCallback callback, object state)
14: {
15: throw new NotImplementedException();
16: }
17:
18: protected override IAsyncResult OnBeginOfflineAnnouncement(DiscoveryMessageSequence messageSequence, EndpointDiscoveryMetadata endpointDiscoveryMetadata, AsyncCallback callback, object state)
19: {
20: throw new NotImplementedException();
21: }
22:
23: protected override IAsyncResult OnBeginOnlineAnnouncement(DiscoveryMessageSequence messageSequence, EndpointDiscoveryMetadata endpointDiscoveryMetadata, AsyncCallback callback, object state)
24: {
25: throw new NotImplementedException();
26: }
27:
28: protected override IAsyncResult OnBeginResolve(ResolveCriteria resolveCriteria, AsyncCallback callback, object state)
29: {
30: throw new NotImplementedException();
31: }
32:
33: protected override void OnEndFind(IAsyncResult result)
34: {
35: throw new NotImplementedException();
36: }
37:
38: protected override void OnEndOfflineAnnouncement(IAsyncResult result)
39: {
40: throw new NotImplementedException();
41: }
42:
43: protected override void OnEndOnlineAnnouncement(IAsyncResult result)
44: {
45: throw new NotImplementedException();
46: }
47:
48: protected override EndpointDiscoveryMetadata OnEndResolve(IAsyncResult result)
49: {
50: throw new NotImplementedException();
51: }
52: }
53: }
Then let’s implement the online, offline and find methods one by one. WCF discovery service gives us full flexibility to implement the endpoint add, remove and find logic. For the demo purpose we will use an internal dictionary to store the services’ endpoint metadata.
In the next post we will see how to serialize and store these information in database.
Define a concurrent dictionary inside the service class since our it will be used in the multiple threads scenario.
1: [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple)]
2: public class ManagedProxyDiscoveryService : DiscoveryProxy
3: {
4: private ConcurrentDictionary<EndpointAddress, EndpointDiscoveryMetadata> _services;
5:
6: public ManagedProxyDiscoveryService()
7: {
8: _services = new ConcurrentDictionary<EndpointAddress, EndpointDiscoveryMetadata>();
9: }
10: }
Then we can simply implement the logic of service online and offline.
1: protected override IAsyncResult OnBeginOnlineAnnouncement(DiscoveryMessageSequence messageSequence, EndpointDiscoveryMetadata endpointDiscoveryMetadata, AsyncCallback callback, object state)
2: {
3: _services.AddOrUpdate(endpointDiscoveryMetadata.Address, endpointDiscoveryMetadata, (key, value) => endpointDiscoveryMetadata);
4: return new OnOnlineAnnouncementAsyncResult(callback, state);
5: }
6:
7: protected override void OnEndOnlineAnnouncement(IAsyncResult result)
8: {
9: OnOnlineAnnouncementAsyncResult.End(result);
10: }
11:
12: protected override IAsyncResult OnBeginOfflineAnnouncement(DiscoveryMessageSequence messageSequence, EndpointDiscoveryMetadata endpointDiscoveryMetadata, AsyncCallback callback, object state)
13: {
14: EndpointDiscoveryMetadata endpoint = null;
15: _services.TryRemove(endpointDiscoveryMetadata.Address, out endpoint);
16: return new OnOfflineAnnouncementAsyncResult(callback, state);
17: }
18:
19: protected override void OnEndOfflineAnnouncement(IAsyncResult result)
20: {
21: OnOfflineAnnouncementAsyncResult.End(result);
22: }
Regards the find method, the parameter FindRequestContext.Criteria has a method named IsMatch, which can be use for us to evaluate which service metadata is satisfied with the criteria. So the implementation of find method would be like this.
1: protected override IAsyncResult OnBeginFind(FindRequestContext findRequestContext, AsyncCallback callback, object state)
2: {
3: _services.Where(s => findRequestContext.Criteria.IsMatch(s.Value))
4: .Select(s => s.Value)
5: .All(meta =>
6: {
7: findRequestContext.AddMatchingEndpoint(meta);
8: return true;
9: });
10: return new OnFindAsyncResult(callback, state);
11: }
12:
13: protected override void OnEndFind(IAsyncResult result)
14: {
15: OnFindAsyncResult.End(result);
16: }
As you can see, we checked all endpoints metadata in repository by invoking the IsMatch method. Then add all proper endpoints metadata into the parameter.
Finally since all these methods are asynchronized we need some AsyncResult classes as well. Below are the base class and the inherited classes used in previous methods.
1: using System;
2: using System.Collections.Generic;
3: using System.Linq;
4: using System.Text;
5: using System.Threading;
6:
7: namespace Phare.Service
8: {
9: abstract internal class AsyncResult : IAsyncResult
10: {
11: AsyncCallback callback;
12: bool completedSynchronously;
13: bool endCalled;
14: Exception exception;
15: bool isCompleted;
16: ManualResetEvent manualResetEvent;
17: object state;
18: object thisLock;
19:
20: protected AsyncResult(AsyncCallback callback, object state)
21: {
22: this.callback = callback;
23: this.state = state;
24: this.thisLock = new object();
25: }
26:
27: public object AsyncState
28: {
29: get
30: {
31: return state;
32: }
33: }
34:
35: public WaitHandle AsyncWaitHandle
36: {
37: get
38: {
39: if (manualResetEvent != null)
40: {
41: return manualResetEvent;
42: }
43: lock (ThisLock)
44: {
45: if (manualResetEvent == null)
46: {
47: manualResetEvent = new ManualResetEvent(isCompleted);
48: }
49: }
50: return manualResetEvent;
51: }
52: }
53:
54: public bool CompletedSynchronously
55: {
56: get
57: {
58: return completedSynchronously;
59: }
60: }
61:
62: public bool IsCompleted
63: {
64: get
65: {
66: return isCompleted;
67: }
68: }
69:
70: object ThisLock
71: {
72: get
73: {
74: return this.thisLock;
75: }
76: }
77:
78: protected static TAsyncResult End<TAsyncResult>(IAsyncResult result)
79: where TAsyncResult : AsyncResult
80: {
81: if (result == null)
82: {
83: throw new ArgumentNullException("result");
84: }
85:
86: TAsyncResult asyncResult = result as TAsyncResult;
87:
88: if (asyncResult == null)
89: {
90: throw new ArgumentException("Invalid async result.", "result");
91: }
92:
93: if (asyncResult.endCalled)
94: {
95: throw new InvalidOperationException("Async object already ended.");
96: }
97:
98: asyncResult.endCalled = true;
99:
100: if (!asyncResult.isCompleted)
101: {
102: asyncResult.AsyncWaitHandle.WaitOne();
103: }
104:
105: if (asyncResult.manualResetEvent != null)
106: {
107: asyncResult.manualResetEvent.Close();
108: }
109:
110: if (asyncResult.exception != null)
111: {
112: throw asyncResult.exception;
113: }
114:
115: return asyncResult;
116: }
117:
118: protected void Complete(bool completedSynchronously)
119: {
120: if (isCompleted)
121: {
122: throw new InvalidOperationException("This async result is already completed.");
123: }
124:
125: this.completedSynchronously = completedSynchronously;
126:
127: if (completedSynchronously)
128: {
129: this.isCompleted = true;
130: }
131: else
132: {
133: lock (ThisLock)
134: {
135: this.isCompleted = true;
136: if (this.manualResetEvent != null)
137: {
138: this.manualResetEvent.Set();
139: }
140: }
141: }
142:
143: if (callback != null)
144: {
145: callback(this);
146: }
147: }
148:
149: protected void Complete(bool completedSynchronously, Exception exception)
150: {
151: this.exception = exception;
152: Complete(completedSynchronously);
153: }
154: }
155: }
1: using System;
2: using System.Collections.Generic;
3: using System.Linq;
4: using System.Text;
5: using System.ServiceModel.Discovery;
6: using Phare.Service;
7:
8: namespace Phare.Service
9: {
10: internal sealed class OnOnlineAnnouncementAsyncResult : AsyncResult
11: {
12: public OnOnlineAnnouncementAsyncResult(AsyncCallback callback, object state)
13: : base(callback, state)
14: {
15: this.Complete(true);
16: }
17:
18: public static void End(IAsyncResult result)
19: {
20: AsyncResult.End<OnOnlineAnnouncementAsyncResult>(result
21: }
22:
23: }
24:
25: sealed class OnOfflineAnnouncementAsyncResult : AsyncResult
26: {
27: public OnOfflineAnnouncementAsyncResult(AsyncCallback callback, object state)
28: : base(callback, state)
29: {
30: this.Complete(true);
31: }
32:
33: public static void End(IAsyncResult result)
34: {
35: AsyncResult.End<OnOfflineAnnouncementAsyncResult>(result
36: }
37: }
38:
39: sealed class OnFindAsyncResult : AsyncResult
40: {
41: public OnFindAsyncResult(AsyncCallback callback, object state)
42: : base(callback, state)
43: {
44: this.Complete(true);
45: }
46:
47: public static void End(IAsyncResult result)
48: {
49: AsyncResult.End<OnFindAsyncResult>(result
50: }
51: }
52:
53: sealed class OnResolveAsyncResult : AsyncResult
54: {
55: EndpointDiscoveryMetadata matchingEndpoint;
56:
57: public OnResolveAsyncResult(EndpointDiscoveryMetadata matchingEndpoint, AsyncCallback callback, object state)
58: : base(callback, state)
59: {
60: this.matchingEndpoint = matchingEndpoint;
61: this.Complete(true);
62: }
63:
64: public static EndpointDiscoveryMetadata End(IAsyncResult result)
65: {
66: OnResolveAsyncResult thisPtr = AsyncResult.End<OnResolveAsyncResult>(result
67: return thisPtr.matchingEndpoint;
68: }
69: }
70: }
Now we have finished the discovery service. The next step is to host it. The discovery service is a standard WCF service. So we can use ServiceHost on a console application, windows service, or in IIS as usual. The following code is how to host the discovery service we had just created in a console application.
1: static void Main(string[] args)
2: {
3: using (var host = new ServiceHost(new ManagedProxyDiscoveryService()))
4: {
5: host.Opened += (sender, e) =>
6: {
7: host.Description.Endpoints.All((ep) =>
8: {
9: Console.WriteLine(ep.ListenUri);
10: return true;
11: });
12: };
13:
14: try
15: {
16: // retrieve the announcement, probe endpoint and binding from configuration
17: var announcementEndpointAddress = new EndpointAddress(ConfigurationManager.AppSettings["announcementEndpointAddress"]);
18: var probeEndpointAddress = new EndpointAddress(ConfigurationManager.AppSettings["probeEndpointAddress"]);
19: var binding = Activator.CreateInstance(Type.GetType(ConfigurationManager.AppSettings["bindingType"], true, true)) as Binding;
20: var announcementEndpoint = new AnnouncementEndpoint(binding, announcementEndpointAddress);
21: var probeEndpoint = new DiscoveryEndpoint(binding, probeEndpointAddress);
22: probeEndpoint.IsSystemEndpoint = false;
23: // append the service endpoint for announcement and probe
24: host.AddServiceEndpoint(announcementEndpoint);
25: host.AddServiceEndpoint(probeEndpoint);
26:
27: host.Open();
28:
29: Console.WriteLine("Press any key to exit.");
30: Console.ReadKey();
31: }
32: catch (Exception ex)
33: {
34: Console.WriteLine(ex.ToString());
35: }
36: }
37:
38: Console.WriteLine("Done.");
39: Console.ReadKey();
40: }
What we need to notice is that, the discovery service needs two endpoints for announcement and probe. In this example I just retrieve them from the configuration file. I also specified the binding of these two endpoints in configuration file as well.
1: <?xml version="1.0"?>
2: <configuration>
3: <startup>
4: <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
5: </startup>
6: <appSettings>
7: <add key="announcementEndpointAddress" value="net.tcp://localhost:10010/announcement"/>
8: <add key="probeEndpointAddress" value="net.tcp://localhost:10011/probe"/>
9: <add key="bindingType" value="System.ServiceModel.NetTcpBinding, System.ServiceModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/>
10: </appSettings>
11: </configuration>
And this is the console screen when I ran my discovery service. As you can see there are two endpoints listening for announcement message and probe message.
Discoverable Service and Client
Next, let’s create a WCF service that is discoverable, which means it can be found by the discovery service. To do so, we need to let the service send the online announcement message to the discovery service, as well as offline message before it shutdown.
Just create a simple service which can make the incoming string to upper. The service contract and implementation would be like this.
1: [ServiceContract]
2: public interface IStringService
3: {
4: [OperationContract]
5: string ToUpper(string content);
6: }
1: public class StringService : IStringService
2: {
3: public string ToUpper(string content)
4: {
5: return content.ToUpper();
6: }
7: }
Then host this service in the console application. In order to make the discovery service easy to be tested the service address will be changed each time it’s started.
1: static void Main(string[] args)
2: {
3: var baseAddress = new Uri(string.Format("net.tcp://localhost:11001/stringservice/{0}/", Guid.NewGuid().ToString()));
4:
5: using (var host = new ServiceHost(typeof(StringService), baseAddress))
6: {
7: host.Opened += (sender, e) =>
8: {
9: Console.WriteLine("Service opened at {0}", host.Description.Endpoints.First().ListenUri);
10: };
11:
12: host.AddServiceEndpoint(typeof(IStringService), new NetTcpBinding(), string.Empty);
13:
14: host.Open();
15:
16: Console.WriteLine("Press any key to exit.");
17: Console.ReadKey();
18: }
19: }
Currently this service is NOT discoverable. We need to add a special service behavior so that it could send the online and offline message to the discovery service announcement endpoint when the host is opened and closed. WCF 4.0 introduced a service behavior named ServiceDiscoveryBehavior. When we specified the announcement endpoint address and appended it to the service behaviors this service will be discoverable.
1: var announcementAddress = new EndpointAddress(ConfigurationManager.AppSettings["announcementEndpointAddress"]);
2: var announcementBinding = Activator.CreateInstance(Type.GetType(ConfigurationManager.AppSettings["bindingType"], true, true)) as Binding;
3: var announcementEndpoint = new AnnouncementEndpoint(announcementBinding, announcementAddress);
4: var discoveryBehavior = new ServiceDiscoveryBehavior();
5: discoveryBehavior.AnnouncementEndpoints.Add(announcementEndpoint);
6: host.Description.Behaviors.Add(discoveryBehavior);
The ServiceDiscoveryBehavior utilizes the service extension and channel dispatcher to implement the online and offline announcement logic. In short, it injected the channel open and close procedure and send the online and offline message to the announcement endpoint.
On client side, when we have the discovery service, a client can invoke a service without knowing its endpoint. WCF discovery assembly provides a class named DiscoveryClient, which can be used to find the proper service endpoint by passing the criteria.
In the code below I initialized the DiscoveryClient, specified the discovery service probe endpoint address. Then I created the find criteria by specifying the service contract I wanted to use and invoke the Find method. This will send the probe message to the discovery service and it will find the endpoints back to me.
The discovery service will return all endpoints that matches the find criteria, which means in the result of the find method there might be more than one endpoints. In this example I just returned the first matched one back. In the next post I will show how to extend our discovery service to make it work like a service load balancer.
1: static EndpointAddress FindServiceEndpoint()
2: {
3: var probeEndpointAddress = new EndpointAddress(ConfigurationManager.AppSettings["probeEndpointAddress"]);
4: var probeBinding = Activator.CreateInstance(Type.GetType(ConfigurationManager.AppSettings["bindingType"], true, true)) as Binding;
5: var discoveryEndpoint = new DiscoveryEndpoint(probeBinding, probeEndpointAddress);
6:
7: EndpointAddress address = null;
8: FindResponse result = null;
9: using (var discoveryClient = new DiscoveryClient(discoveryEndpoint))
10: {
11: result = discoveryClient.Find(new FindCriteria(typeof(IStringService)));
12: }
13:
14: if (result != null && result.Endpoints.Any())
15: {
16: var endpointMetadata = result.Endpoints.First();
17: address = endpointMetadata.Address;
18: }
19: return address;
20: }
Once we probed the discovery service we will receive the endpoint. So in the client code we can created the channel factory from the endpoint and binding, and invoke to the service.
When creating the client side channel factory we need to make sure that the client side binding should be the same as the service side. WCF discovery service can be used to find the endpoint for a service contract, but the binding is NOT included. This is because the binding was not in the WS-Discovery specification.
In the next post I will demonstrate how to add the binding information into the discovery service. At that moment the client don’t need to create the binding by itself. Instead it will use the binding received from the discovery service.
1: static void Main(string[] args)
2: {
3: Console.WriteLine("Say something...");
4: var content = Console.ReadLine();
5: while (!string.IsNullOrWhiteSpace(content))
6: {
7: Console.WriteLine("Finding the service endpoint...");
8: var address = FindServiceEndpoint();
9: if (address == null)
10: {
11: Console.WriteLine("There is no endpoint matches the criteria.");
12: }
13: else
14: {
15: Console.WriteLine("Found the endpoint {0}", address.Uri);
16:
17: var factory = new ChannelFactory<IStringService>(new NetTcpBinding(), address);
18: factory.Opened += (sender, e) =>
19: {
20: Console.WriteLine("Connecting to {0}.", factory.Endpoint.ListenUri);
21: };
22: var proxy = factory.CreateChannel();
23: using (proxy as IDisposable)
24: {
25: Console.WriteLine("ToUpper: {0} => {1}", content, proxy.ToUpper(content));
26: }
27: }
28:
29: Console.WriteLine("Say something...");
30: content = Console.ReadLine();
31: }
32: }
Similarly, the discovery service probe endpoint and binding were defined in the configuration file.
1: <?xml version="1.0"?>
2: <configuration>
3: <startup>
4: <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
5: </startup>
6: <appSettings>
7: <add key="announcementEndpointAddress" value="net.tcp://localhost:10010/announcement"/>
8: <add key="probeEndpointAddress" value="net.tcp://localhost:10011/probe"/>
9: <add key="bindingType" value="System.ServiceModel.NetTcpBinding, System.ServiceModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/>
10: </appSettings>
11: </configuration>
OK, now let’s have a test. Firstly start the discovery service, and then start our discoverable service. When it started it will announced to the discovery service and registered its endpoint into the repository, which is the local dictionary. And then start the client and type something. As you can see the client asked the discovery service for the endpoint and then establish the connection to the discoverable service.
And more interesting, do NOT close the client console but terminate the discoverable service but press the enter key. This will make the service send the offline message to the discovery service. Then start the discoverable service again. Since we made it use a different address each time it started, currently it should be hosted on another address. If we enter something in the client we could see that it asked the discovery service and retrieve the new endpoint, and connect the the service.
Summary
In this post I discussed the benefit of using the discovery service and the procedures of service announcement and probe. I also demonstrated how to leverage the WCF Discovery feature in WCF 4.0 to build a simple managed discovery service.
For test purpose, in this example I used the in memory dictionary as the discovery endpoint metadata repository. And when finding I also just return the first matched endpoint back. I also hard coded the bindings between the discoverable service and the client.
In next post I will show you how to solve the problem mentioned above, as well as some additional feature for production usage.
You can download the code here.
Hope this helps,
Shaun
Service Discovery in WCF 4.0 – Part 1 z的更多相关文章
- Service Discovery in WCF 4.0 – Part 2 z
Service Discovery in WCF 4.0 – Part 2 In the previous post I discussed about the basic usage of WCF ...
- Service Discovery with Apache Curator
Curator的介绍 Curator就是Zookeeper的一个客户端工具(不知道Zookeeper的同学可以到http://www.ibm.com/developerworks/cn/opensou ...
- [译]Ocelot - Service Discovery
原文 你可以指定一个service discovery provider,ocelot将使用它来找下游的host和port. Consul 下面的配置要放在GlobalConfiguration中.如 ...
- Service Discovery And Health Checks In ASP.NET Core With Consul
在这篇文章中,我们将快速了解一下服务发现是什么,使用Consul在ASP.NET Core MVC框架中,并结合DnsClient.NET实现基于Dns的客户端服务发现 这篇文章的所有源代码都可以在G ...
- 中小研发团队架构实践之生产环境诊断工具WinDbg 三分钟学会.NET微服务之Polly 使用.Net Core+IView+Vue集成上传图片功能 Fiddler原理~知多少? ABP框架（asp.net core 2.X+Vue）模板项目学习之路（一） C#程序中设置全局代理(Global Proxy) WCF 4.0 使用说明 如何在IIS上发布，并能正常访问
中小研发团队架构实践之生产环境诊断工具WinDbg 生产环境偶尔会出现一些异常问题,WinDbg或GDB是解决此类问题的利器.调试工具WinDbg如同医生的听诊器,是系统生病时做问题诊断的逆向分析工具 ...
- WCF 4.0 如何编程修改wcf配置，不使用web.config静态配置
How to programmatically modify WCF without web.config setting WCF 4.0 如何编程修改wcf配置,不使用web.config静态配置 ...
- 【转帖】Service Discovery: 6 questions to 4 experts
https://highops.com/insights/service-discovery-6-questions-to-4-experts/ What’s Service Discovery? I ...
- WCF 4.0 进阶系列 -- 随笔汇总
WCF4.0 进阶系列–前言 WCF4.0 进阶系列--第一章 WCF简介 WCF4.0进阶系列--第二章 寄宿WCF服务 WCF4.0进阶系列--第三章 构建健壮的程序和服务 WCF4.0进阶系列- ...
- WCF 4.0 使用说明
WCF 4.0开发说明,工具VS2013 ,IIS,使用http协议 打开VS2013,新建项目Visual C#>Web>Asp.NET Web应用程序,添加相关引用: System.S ...
随机推荐
- Node.js 文件夹目录结构创建
第一次接触NodeJS的文件系统就被它的异步的响应给搞晕了,后来发现NodeJS判断文件夹是否存在和创建文件夹是还有同步方法的,但是还是想尝试使用异步的方法去实现. 使用的方法:fs.exists(p ...
- Android多渠道打包工具
http://www.cnblogs.com/huangtianhui/archive/2012/07/14/2591382.html 鉴于Android市场众多,基于各种利益考虑,以及未来app能够 ...
- html中使用滚动条
1. 在html页面中使用滚动条,效果如下: 代码如下: <div style="height:auto !important;max-height:200px;overflow:sc ...
- 栈C++实现
栈的核心是LIFO(Last In First Out),即后进先出 出栈和入栈只会对栈顶进行操作,栈底永远为0.如果是入栈,要将入栈元素赋值给栈数组,再将栈顶上移一位:出栈时要先将栈顶下移一位,再将 ...
- step1: python & scrapy安装
#首先安装python,这里安装python所需依赖包yum install zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-dev ...
- 常用工具说明--搭建基于rietveld的CodeReview平台(未测试)
为什么要codereview . 整个团队的编码风格是统一的. . 有高手能对自己的代码指点一二,从而提高编码水平. . 减少低级错误的出现 . 约束自己写高质量的代码,因为是要给人看的. 我们对co ...
- VMware workstation 非正常关机导致开机失败，解决方法
问题:VMware workstation 非正常关机导致开机失败!如下图:
- hibernate 返回自定义对象
关键代码老是忘记 setResultTransformer(Transformers.aliasToBean(LabourResult.class)) 代码用例: public List<Lab ...
- 比较2个文件内容不同行的shell脚本
第一种:grep命令法 命令如下:grep -vxFf file1 file2 > a.txt 其中file2是大文件,file1是小文件 第一种:comm命令法 命令如下:comm file ...
- DIY了一下自己blog的UI
当年才学前端时就想改自己blog的UI,然鹅当时没看见那个“申请JS权限”,一直以为blog不能随意DIY样式,只改了少许CSS.现在重新看看设置管理选项,简单修改了一下样式(注意:修改样式之前发邮件 ...