Scenario:
Create a Sign on service to return list of users in out system. The web App calls this service to fetch list of users one by one and render on UI.
Solution:
Create Server streaming Grpc service for sign on in .Net core 3.0 with GetAllUsers method.
per gRPC documentation
A server-streaming RPC is similar to our simple example, except the server sends back a stream of responses after getting the client’s request message.The client completes once it has all the server’s responses.
- VS 2019 -> New Project -> gRPC Service -> GrpcServer
- Create Service definition [proto file], name signon.proto and define the service as below
syntax = "proto3";
option csharp_namespace = "GrpcServer";
service SignOn {
rpc GetAllUsers (UserRequest) returns (stream User);
}
message UserRequest {
}
message User {
string email = 1;
string name = 2;
}
- Right click on the proto file and make sure below properties are correctly set
gRPC Stub Class
Server only
Protobuf
Class access = Public
- Override GetAllUsers in SignOnService.cs
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| public override async Task GetAllUsers(UserRequest request, IServerStreamWriter<User> responseStream, ServerCallContext context)
{
var response = new SignOnResponse();
response.Sucess = false;
var json = JsonConvert.SerializeObject(request);
var elasticSearch = new ElasticSearchService();
var esResponse = elasticSearch.SearchData(json, "ELK:indexes:userIndex");
var users = new List<User>();
if (!string.IsNullOrWhiteSpace(esResponse))
{
response.Sucess = true;
var rootHits = (JObject)JObject.Parse(esResponse)["hits"];
var hits = (JArray)rootHits["hits"];
for (int i = 0; i < hits.Count; i++)
{
if (hits[i]["_source"]["Email"] != null)
{
users.Add(new User
{
Email = hits[i]["_source"]["Email"] == null ? "" : hits[i]["_source"]["Email"].ToString(),
Name = hits[i]["_source"]["Name"] == null ? "" : hits[i]["_source"]["Name"].ToString(),
});
}
}
}
//return back to client one user at a time
foreach (var user in users)
{
await responseStream.WriteAsync(user);
}
}
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- Create web project - VS 2019 -> New Project -> Web -> MyApp
- Add below nuget packages
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| Google.Protobuff
Grp.Net.Client
Grpc.Tools
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- Add Proto folder to project -> copy file signon.proto from server to here
- Invoke the service from client as below
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| public async Task<IActionResult> Index()
{
var users = new List<string>();
var channel = GrpcChannel.ForAddress(grpServerUrl);
var client = new SignOn.SignOnClient(channel);
using (var call = client.GetAllUsers(new UserRequest()))
{
while (await call.ResponseStream.MoveNext())
{
var user = call.ResponseStream.Current;
users.Add(user.Name);
}
}
ViewBag.success = true;
return View();
}
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