Let's Talk HTTP in .NET Core

This presentation covers refactoring some code to use HTTP best practices and new features in ASP.NET Core 2.1 such as IHttpClientFactory.

Transcript

1. @stevejgordon www.stevejgordon.co.uk Let's Talk HTTP in .NET Core with IHttpClientFactory and Polly Steve Gordon @stevejgordon | stevejgordon.co.uk https://www.meetup.com/dotnetsoutheast
2. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { using (var client = new HttpClient()) { client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my-user-agent"); var url = "https://api.github.com/orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await _httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } } }
3. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { using (var client = new HttpClient()) { client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my-user-agent"); var url = "https://api.github.com/orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await _httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } } }
4. @stevejgordon www.stevejgordon.co.uk What’s the solution?
5. @stevejgordon www.stevejgordon.co.uk public class Startup { public Startup(IConfiguration configuration) { Configuration = configuration; } public IConfiguration Configuration { get; } public void ConfigureServices(IServiceCollection services) { services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { app.UseMvc(); } }
6. @stevejgordon www.stevejgordon.co.uk public class Startup { public Startup(IConfiguration configuration) { Configuration = configuration; } public IConfiguration Configuration { get; } public void ConfigureServices(IServiceCollection services) { services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { app.UseMvc(); } }
7. @stevejgordon www.stevejgordon.co.uk public class Startup { public Startup(IConfiguration configuration) { Configuration = configuration; } public IConfiguration Configuration { get; } public void ConfigureServices(IServiceCollection services) { services.AddSingleton<HttpClient>(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { app.UseMvc(); } }
8. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { using (var client = new HttpClient()) { client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my-user-agent"); var url = "https://api.github.com/orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await client.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } } }
9. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly HttpClient _httpClient; public GitHubController(HttpClient httpClient) => _httpClient = httpClient; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { using (var client = new HttpClient()) { client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my-user-agent"); var url = "https://api.github.com/orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await client.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } } }
10. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly HttpClient _httpClient; public GitHubController(HttpClient httpClient) => _httpClient = httpClient; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { using (var client = new HttpClient()) { client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my-user-agent"); var url = "https://api.github.com/orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await client.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } } }
11. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly HttpClient _httpClient; public GitHubController(HttpClient httpClient) => _httpClient = httpClient; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my-user-agent"); var url = "https://api.github.com/orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await client.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
12. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly HttpClient _httpClient; public GitHubController(HttpClient httpClient) => _httpClient = httpClient; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "https://api.github.com/orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); request.Headers.Add("Accept", "application/vnd.github.v3+json"); request.Headers.Add("User-Agent", "my-user-agent"); var response = await client.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
13. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly HttpClient _httpClient; public GitHubController(HttpClient httpClient) => _httpClient = httpClient; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "https://api.github.com/orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); request.Headers.Add("Accept", "application/vnd.github.v3+json"); request.Headers.Add("User-Agent", "my-user-agent"); var response = await client.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
14. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly HttpClient _httpClient; public GitHubController(HttpClient httpClient) => _httpClient = httpClient; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "https://api.github.com/orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); request.Headers.Add("Accept", "application/vnd.github.v3+json"); request.Headers.Add("User-Agent", "my-user-agent"); var response = await _httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
15. @stevejgordon www.stevejgordon.co.uk But…
16. @stevejgordon www.stevejgordon.co.uk IHttpClientFactory • Manages the lifetime of HttpMessageHandlers • Provides a central location for naming and configuring logical HttpClients • Codifies the concept of outgoing middleware via delegating handlers • Integrates with Polly for transient-fault handling • Improved diagnostics and logging
17. @stevejgordon www.stevejgordon.co.uk Converting Our Code
18. @stevejgordon www.stevejgordon.co.uk public class Startup { public Startup(IConfiguration configuration) { Configuration = configuration; } public IConfiguration Configuration { get; } public void ConfigureServices(IServiceCollection services) { services.AddSingleton<HttpClient>(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { app.UseMvc(); } }
19. @stevejgordon www.stevejgordon.co.uk public class Startup { public Startup(IConfiguration configuration) { Configuration = configuration; } public IConfiguration Configuration { get; } public void ConfigureServices(IServiceCollection services) { services.AddSingleton<HttpClient>(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { app.UseMvc(); } }
20. @stevejgordon www.stevejgordon.co.uk public class Startup { public Startup(IConfiguration configuration) { Configuration = configuration; } public IConfiguration Configuration { get; } public void ConfigureServices(IServiceCollection services) { services.AddHttpClient(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { app.UseMvc(); } }
21. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly HttpClient _httpClient; public GitHubController(HttpClient httpClient) => _httpClient = httpClient; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "https://api.github.com/orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); request.Headers.Add("Accept", "application/vnd.github.v3+json"); request.Headers.Add("User-Agent", "my-user-agent"); var response = await _httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
22. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly HttpClient _httpClient; public GitHubController(HttpClient httpClient) => _httpClient = httpClient; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "https://api.github.com/orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); request.Headers.Add("Accept", "application/vnd.github.v3+json"); request.Headers.Add("User-Agent", "my-user-agent"); var response = await _httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
23. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly IHttpClientFactory _factory; public GitHubController(IHttpClientFactory factory) => _factory = factory; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "https://api.github.com/orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); request.Headers.Add("Accept", "application/vnd.github.v3+json"); request.Headers.Add("User-Agent", "my-user-agent"); var response = await _httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
24. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly IHttpClientFactory _factory; public GitHubController(IHttpClientFactory factory) => _factory = factory; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "https://api.github.com/orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); request.Headers.Add("Accept", "application/vnd.github.v3+json"); request.Headers.Add("User-Agent", "my-user-agent"); var response = await _httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
25. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly IHttpClientFactory _factory; public GitHubController(IHttpClientFactory factory) => _factory = factory; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "https://api.github.com/orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); request.Headers.Add("Accept", "application/vnd.github.v3+json"); request.Headers.Add("User-Agent", "my-user-agent"); var httpClient = _factory.CreateClient(); var response = await httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
26. @stevejgordon www.stevejgordon.co.uk Named Clients
27. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddHttpClient(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
28. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddHttpClient("github", client => { client.BaseAddress = new Uri("https://api.github.com/"); client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my-user-agent"); }); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
29. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddHttpClient("github", client => { client.BaseAddress = new Uri("https://api.github.com/"); client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my-user-agent"); }); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
30. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddHttpClient("github", client => { client.BaseAddress = new Uri("https://api.github.com/"); client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my-user-agent"); }); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
31. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly IHttpClientFactory _factory; public GitHubController(IHttpClientFactory factory) => _factory = factory; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "https://api.github.com/orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); request.Headers.Add("Accept", "application/vnd.github.v3+json"); request.Headers.Add("User-Agent", "my-user-agent"); var httpClient = _factory.CreateClient(); var response = await httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
32. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly IHttpClientFactory _factory; public GitHubController(IHttpClientFactory factory) => _factory = factory; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); request.Headers.Add("Accept", "application/vnd.github.v3+json"); request.Headers.Add("User-Agent", "my-user-agent"); var httpClient = _factory.CreateClient(); var response = await httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
33. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly IHttpClientFactory _factory; public GitHubController(IHttpClientFactory factory) => _factory = factory; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); request.Headers.Add("Accept", "application/vnd.github.v3+json"); request.Headers.Add("User-Agent", "my-user-agent"); var httpClient = _factory.CreateClient(); var response = await httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
34. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly IHttpClientFactory _factory; public GitHubController(IHttpClientFactory factory) => _factory = factory; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var httpClient = _factory.CreateClient(); var response = await httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
35. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly IHttpClientFactory _factory; public GitHubController(IHttpClientFactory factory) => _factory = factory; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var httpClient = _factory.CreateClient(); var response = await httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
36. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly IHttpClientFactory _factory; public GitHubController(IHttpClientFactory factory) => _factory = factory; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var httpClient = _factory.CreateClient("github"); var response = await httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
37. @stevejgordon www.stevejgordon.co.uk Typed Clients
38. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; public GitHubClient(HttpClient client) { client.BaseAddress = new Uri("https://api.github.com/"); client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my_user_agent"); _httpClient = client; } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await _httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data); } }
39. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; public GitHubClient(HttpClient client) { client.BaseAddress = new Uri("https://api.github.com/"); client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my_user_agent"); _httpClient = client; } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await _httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data); } }
40. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; public GitHubClient(HttpClient client) { client.BaseAddress = new Uri("https://api.github.com/"); client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my_user_agent"); _httpClient = client; } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await _httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data); } }
41. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; public GitHubClient(HttpClient client) { client.BaseAddress = new Uri("https://api.github.com/"); client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my_user_agent"); _httpClient = client; } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await _httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data); } }
42. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddHttpClient("github", client => { client.BaseAddress = new Uri("https://api.github.com/"); client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my-user-agent"); }); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
43. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddHttpClient<IGitHubClient, GitHubClient>(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
44. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly IHttpClientFactory _factory; public GitHubController(IHttpClientFactory factory) => _factory = factory; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var httpClient = _factory.CreateClient("github"); var response = await httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
45. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly IGitHubClient _gitHubClient; public GitHubController(IGitHubClient gitHubClient) => _gitHubClient = gitHubClient; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var httpClient = _factory.CreateClient("github"); var response = await httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
46. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly IGitHubClient _gitHubClient; public GitHubController(IGitHubClient gitHubClient) => _gitHubClient = gitHubClient; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var httpClient = _factory.CreateClient("github"); var response = await httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return Ok(JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data)); } }
47. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly IGitHubClient _gitHubClient; public GitHubController(IGitHubClient gitHubClient) => _gitHubClient = gitHubClient; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var data = await _gitHubClient.GetAspNetReposAsync(); return Ok(data); } }
48. @stevejgordon www.stevejgordon.co.uk Outgoing "middleware" https://api.github.com Our Application HttpClient H t t p R e q u e s t M e s s a g e H t t p R e s p o n s e M e s s a g e
49. @stevejgordon www.stevejgordon.co.uk Outgoing "middleware" Outer Handler Middle Handler Inner Handler HttpClientHandler SocketsHttpHandler https://api.github.com Our Application HttpClient H t t p R e q u e s t M e s s a g e H t t p R e s p o n s e M e s s a g e
50. @stevejgordon www.stevejgordon.co.uk Delegating Handlers
51. @stevejgordon www.stevejgordon.co.uk public class StatusCodeMetricHandler : DelegatingHandler { private readonly IMonitoringService _monitoringService; public StatusCodeMetricHandler(IMonitoringService monitoringService) => _monitoringService = monitoringService; protected override async Task<HttpResponseMessage> SendAsync( HttpRequestMessage request, CancellationToken ct) { // note: we could do things with the request before passing it along var response = await base.SendAsync(request, ct); _monitoringService.RecordStatusCodeMetric((int)response.StatusCode); return response; } }
52. @stevejgordon www.stevejgordon.co.uk public class StatusCodeMetricHandler : DelegatingHandler { private readonly IMonitoringService _monitoringService; public StatusCodeMetricHandler(IMonitoringService monitoringService) => _monitoringService = monitoringService; protected override async Task<HttpResponseMessage> SendAsync( HttpRequestMessage request, CancellationToken ct) { // note: we could do things with the request before passing it along var response = await base.SendAsync(request, ct); _monitoringService.RecordStatusCodeMetric((int)response.StatusCode); return response; } }
53. @stevejgordon www.stevejgordon.co.uk public class StatusCodeMetricHandler : DelegatingHandler { private readonly IMonitoringService _monitoringService; public StatusCodeMetricHandler(IMonitoringService monitoringService) => _monitoringService = monitoringService; protected override async Task<HttpResponseMessage> SendAsync( HttpRequestMessage request, CancellationToken ct) { // note: we could do things with the request before passing it along var response = await base.SendAsync(request, ct); _monitoringService.RecordStatusCodeMetric((int)response.StatusCode); return response; } }
54. @stevejgordon www.stevejgordon.co.uk public class StatusCodeMetricHandler : DelegatingHandler { private readonly IMonitoringService _monitoringService; public StatusCodeMetricHandler(IMonitoringService monitoringService) => _monitoringService = monitoringService; protected override async Task<HttpResponseMessage> SendAsync( HttpRequestMessage request, CancellationToken ct) { // note: we could do things with the request before passing it along var response = await base.SendAsync(request, ct); _monitoringService.RecordStatusCodeMetric((int)response.StatusCode); return response; } }
55. @stevejgordon www.stevejgordon.co.uk public class StatusCodeMetricHandler : DelegatingHandler { private readonly IMonitoringService _monitoringService; public StatusCodeMetricHandler(IMonitoringService monitoringService) => _monitoringService = monitoringService; protected override async Task<HttpResponseMessage> SendAsync( HttpRequestMessage request, CancellationToken ct) { // note: we could do things with the request before passing it along var response = await base.SendAsync(request, ct); _monitoringService.RecordStatusCodeMetric((int)response.StatusCode); return response; } }
56. @stevejgordon www.stevejgordon.co.uk public class StatusCodeMetricHandler : DelegatingHandler { private readonly IMonitoringService _monitoringService; public StatusCodeMetricHandler(IMonitoringService monitoringService) => _monitoringService = monitoringService; protected override async Task<HttpResponseMessage> SendAsync( HttpRequestMessage request, CancellationToken ct) { // note: we could do things with the request before passing it along var response = await base.SendAsync(request, ct); _monitoringService.RecordStatusCodeMetric((int)response.StatusCode); return response; } }
57. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddHttpClient<IGitHubClient, GitHubClient>(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
58. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddTransient<IMonitoringService, MonitoringService>(); services.AddTransient<StatusCodeMetricHandler>(); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddHttpMessageHandler<StatusCodeMetricHandler>(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
59. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddTransient<IMonitoringService, MonitoringService>(); services.AddTransient<StatusCodeMetricHandler>(); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddHttpMessageHandler<StatusCodeMetricHandler>(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
60. @stevejgordon www.stevejgordon.co.uk Polly • Polly is a .NET resilience and transient-fault-handling library • Integrates easily with IHttpClientFactory • Retry • Circuit-breaker • Timeout • Bulkhead isolation • Cache • Fallback • PolicyWrap
61. @stevejgordon www.stevejgordon.co.uk Our Application H t t p R e q u e s t M e s s a g e 5 0 3 U n a v a i l a b l e
62. @stevejgordon www.stevejgordon.co.uk Our Application H t t p R e q u e s t M e s s a g e 5 0 3 U n a v a i l a b l e H t t p R e q u e s t M e s s a g e 5 0 3 U n a v a i l a b l e H t t p R e q u e s t M e s s a g e 2 0 0 O K
63. @stevejgordon www.stevejgordon.co.uk Handling Transient Errors with Polly
64. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddTransient<IMonitoringService, MonitoringService>(); services.AddTransient<StatusCodeMetricHandler>(); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddHttpMessageHandler<StatusCodeMetricHandler>(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
65. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddTransient<IMonitoringService, MonitoringService>(); services.AddTransient<StatusCodeMetricHandler>(); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddTransientHttpErrorPolicy(builder => builder.WaitAndRetryAsync(3, retryCount => TimeSpan.FromSeconds(Math.Pow(2, retryCount)))) .AddHttpMessageHandler<StatusCodeMetricHandler>(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
66. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddTransient<IMonitoringService, MonitoringService>(); services.AddTransient<StatusCodeMetricHandler>(); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddTransientHttpErrorPolicy(builder => builder.WaitAndRetryAsync(3, retryCount => TimeSpan.FromSeconds(Math.Pow(2, retryCount)))) .AddHttpMessageHandler<StatusCodeMetricHandler>(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
67. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddTransient<IMonitoringService, MonitoringService>(); services.AddTransient<StatusCodeMetricHandler>(); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddTransientHttpErrorPolicy(builder => builder.WaitAndRetryAsync(3, retryCount => TimeSpan.FromSeconds(Math.Pow(2, retryCount)))) .AddHttpMessageHandler<StatusCodeMetricHandler>(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
68. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddTransient<IMonitoringService, MonitoringService>(); services.AddTransient<StatusCodeMetricHandler>(); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddTransientHttpErrorPolicy(builder => builder.WaitAndRetryAsync(3, retryCount => TimeSpan.FromSeconds(Math.Pow(2, retryCount)))) .AddHttpMessageHandler<StatusCodeMetricHandler>(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
69. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddTransient<IMonitoringService, MonitoringService>(); services.AddTransient<StatusCodeMetricHandler>(); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddTransientHttpErrorPolicy(builder => builder.WaitAndRetryAsync(3, retryCount => TimeSpan.FromSeconds(Math.Pow(2, retryCount)))) .AddHttpMessageHandler<StatusCodeMetricHandler>(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
70. @stevejgordon www.stevejgordon.co.uk Dynamically Applying Policies
71. @stevejgordon www.stevejgordon.co.uk var noOpPolicy = Policy.NoOpAsync().AsAsyncPolicy<HttpResponseMessage>(); var retryPolicy = HttpPolicyExtensions .HandleTransientHttpError() // HttpRequestException, 5XX and 408 .WaitAndRetryAsync(3, retryCount => TimeSpan.FromSeconds(Math.Pow(2, retryCount))); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddPolicyHandler(message => { return message.Method == HttpMethod.Get ? retryPolicy : noOpPolicy; });
72. @stevejgordon www.stevejgordon.co.uk var noOpPolicy = Policy.NoOpAsync().AsAsyncPolicy<HttpResponseMessage>(); var retryPolicy = HttpPolicyExtensions .HandleTransientHttpError() // HttpRequestException, 5XX and 408 .WaitAndRetryAsync(3, retryCount => TimeSpan.FromSeconds(Math.Pow(2, retryCount))); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddPolicyHandler(message => { return message.Method == HttpMethod.Get ? retryPolicy : noOpPolicy; });
73. @stevejgordon www.stevejgordon.co.uk var noOpPolicy = Policy.NoOpAsync().AsAsyncPolicy<HttpResponseMessage>(); var retryPolicy = HttpPolicyExtensions .HandleTransientHttpError() // HttpRequestException, 5XX and 408 .WaitAndRetryAsync(3, retryCount => TimeSpan.FromSeconds(Math.Pow(2, retryCount))); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddPolicyHandler(message => { return message.Method == HttpMethod.Get ? retryPolicy : noOpPolicy; });
74. @stevejgordon www.stevejgordon.co.uk Using the Policy Registry
75. @stevejgordon www.stevejgordon.co.uk var timeout = Policy.TimeoutAsync(10); var longTimeout = Policy.TimeoutAsync(45); var registry = services.AddPolicyRegistry(); registry.Add("regular", timeout); registry.Add("long", longTimeout); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddPolicyHandlerFromRegistry("regular");
76. @stevejgordon www.stevejgordon.co.uk var timeout = Policy.TimeoutAsync(10); var longTimeout = Policy.TimeoutAsync(45); var registry = services.AddPolicyRegistry(); registry.Add("regular", timeout); registry.Add("long", longTimeout); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddPolicyHandlerFromRegistry("regular");
77. @stevejgordon www.stevejgordon.co.uk var timeout = Policy.TimeoutAsync(10); var longTimeout = Policy.TimeoutAsync(45); var registry = services.AddPolicyRegistry(); registry.Add("regular", timeout); registry.Add("long", longTimeout); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddPolicyHandlerFromRegistry("regular");
78. @stevejgordon www.stevejgordon.co.uk var timeout = Policy.TimeoutAsync(10); var longTimeout = Policy.TimeoutAsync(45); var registry = services.AddPolicyRegistry(); registry.Add("regular", timeout); registry.Add("long", longTimeout); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddPolicyHandlerFromRegistry("regular");
79. @stevejgordon www.stevejgordon.co.uk var timeout = Policy.TimeoutAsync(10); var longTimeout = Policy.TimeoutAsync(45); var registry = services.AddPolicyRegistry(); registry.Add("regular", timeout); registry.Add("long", longTimeout); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddPolicyHandlerFromRegistry("regular");
80. @stevejgordon www.stevejgordon.co.uk Configuring the Primary Handler
81. @stevejgordon www.stevejgordon.co.uk services.AddHttpClient<IGitHubClient, GitHubClient>() .ConfigurePrimaryHttpMessageHandler(() => { var handler = new HttpClientHandler { ClientCertificateOptions = ClientCertificateOption.Manual, SslProtocols = SslProtocols.Tls12, AllowAutoRedirect = false }; handler.ClientCertificates.Add(new X509Certificate2("mycert.crt")); return handler; });
82. @stevejgordon www.stevejgordon.co.uk Other HTTP-based Tips
83. @stevejgordon www.stevejgordon.co.uk Taking care when handling response content
84. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; public GitHubClient(HttpClient client) { client.BaseAddress = new Uri("https://api.github.com/"); client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my_user_agent"); _httpClient = client; } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await _httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data); } }
85. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; public GitHubClient(HttpClient client) { client.BaseAddress = new Uri("https://api.github.com/"); client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my_user_agent"); _httpClient = client; } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await _httpClient.SendAsync(request); var data = await response.Content.ReadAsStringAsync(); return JsonConvert.DeserializeObject<IEnumerable<GitHubRepo>>(data); } }
86. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; public GitHubClient(HttpClient client) { client.BaseAddress = new Uri("https://api.github.com/"); client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my_user_agent"); _httpClient = client; } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await _httpClient.SendAsync(request); return await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>(); } }
87. @stevejgordon www.stevejgordon.co.uk Handling Errors
88. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; public GitHubClient(HttpClient client) { // hidden for brevity ... } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await _httpClient.SendAsync(request); return await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>(); } }
89. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; public GitHubClient(HttpClient client) { // hidden for brevity ... } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await _httpClient.SendAsync(request); response.EnsureSuccessStatusCode(); return await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>(); } }
90. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; public GitHubClient(HttpClient client) { // hidden for brevity ... } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await _httpClient.SendAsync(request); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>() : Array.Empty<GitHubRepo>(); } }
91. @stevejgordon www.stevejgordon.co.uk Handling Cancellation
92. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; public GitHubClient(HttpClient client) { // hidden for brevity ... } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync() { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await _httpClient.SendAsync(request); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>() : Array.Empty<GitHubRepo>(); } }
93. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; public GitHubClient(HttpClient client) { // hidden for brevity ... } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync(CancellationToken ct = default) { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); var response = await _httpClient.SendAsync(request); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>() : Array.Empty<GitHubRepo>(); } }
94. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; public GitHubClient(HttpClient client) { // hidden for brevity ... } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync(CancellationToken ct = default) { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); ct.ThrowIfCancellationRequested(); var response = await _httpClient.SendAsync(request); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>() : Array.Empty<GitHubRepo>(); } }
95. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; public GitHubClient(HttpClient client) { // hidden for brevity ... } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync(CancellationToken ct = default) { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); ct.ThrowIfCancellationRequested(); var response = await _httpClient.SendAsync(request, ct); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>() : Array.Empty<GitHubRepo>(); } }
96. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; public GitHubClient(HttpClient client) { // hidden for brevity ... } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync(CancellationToken ct = default) { var url = "orgs/aspnet/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); ct.ThrowIfCancellationRequested(); var response = await _httpClient.SendAsync(request, ct); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>(ct) : Array.Empty<GitHubRepo>(); } }
97. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly IGitHubClient _gitHubClient; public GitHubController(IGitHubClient gitHubClient) => _gitHubClient = gitHubClient; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos() { var data = await _gitHubClient.GetAspNetReposAsync(); return Ok(data); } }
98. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly IGitHubClient _gitHubClient; public GitHubController(IGitHubClient gitHubClient) => _gitHubClient = gitHubClient; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos(CancellationToken ct) { var data = await _gitHubClient.GetAspNetReposAsync(ct); return Ok(data); } }
99. @stevejgordon www.stevejgordon.co.uk public class GitHubController : ControllerBase { private readonly IGitHubClient _gitHubClient; public GitHubController(IGitHubClient gitHubClient) => _gitHubClient = gitHubClient; [HttpGet] public async Task<ActionResult<IEnumerable<GitHubRepo>>> GetAspNetRepos(CancellationToken ct) { var data = await _gitHubClient.GetAspNetReposAsync(ct); return Ok(data); } }
100. @stevejgordon www.stevejgordon.co.uk Caching
101. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddTransient<IMonitoringService, MonitoringService>(); services.AddTransient<StatusCodeMetricHandler>(); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddTransientHttpErrorPolicy(builder => builder.WaitAndRetryAsync(3, retryCount => TimeSpan.FromSeconds(Math.Pow(2, retryCount)))) .AddHttpMessageHandler<StatusCodeMetricHandler>(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
102. @stevejgordon www.stevejgordon.co.uk public class Startup { ... public void ConfigureServices(IServiceCollection services) { services.AddMemoryCache(); services.AddTransient<IMonitoringService, MonitoringService>(); services.AddTransient<StatusCodeMetricHandler>(); services.AddHttpClient<IGitHubClient, GitHubClient>() .AddTransientHttpErrorPolicy(builder => builder.WaitAndRetryAsync(3, retryCount => TimeSpan.FromSeconds(Math.Pow(2, retryCount)))) .AddHttpMessageHandler<StatusCodeMetricHandler>(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { … } }
103. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; public GitHubClient(HttpClient client) { client.BaseAddress = new Uri("https://api.github.com/"); client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my_user_agent"); _httpClient = client; } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync(CancellationToken ct = default) { // ... contents of this method hidden for brevity ... } }
104. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { private readonly HttpClient _httpClient; private readonly IMemoryCache _memoryCache; public GitHubClient(HttpClient client, IMemoryCache memoryCache) { client.BaseAddress = new Uri("https://api.github.com/"); client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); client.DefaultRequestHeaders.Add("User-Agent", "my_user_agent"); _httpClient = client; _memoryCache = memoryCache; } public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync(CancellationToken ct = default) { // ... contents of this method hidden for brevity ... } }
105. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { // ctor - hidden for brevity ... public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync(CancellationToken ct = default) { return await _memoryCache.GetOrCreateAsync("aspnet-repo-data", entry => { entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(5); return GetFromGitHub(); }); async Task<IEnumerable<GitHubRepo>> GetFromGitHub() { var request = new HttpRequestMessage(HttpMethod.Get, "orgs/aspnet/repos"); ct.ThrowIfCancellationRequested(); var response = await _httpClient.SendAsync(request, ct); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>(ct) : Array.Empty<GitHubRepo>(); } } }
106. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { // ctor - hidden for brevity ... public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync(CancellationToken ct = default) { return await _memoryCache.GetOrCreateAsync("aspnet-repo-data", entry => { entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(5); return GetFromGitHub(); }); async Task<IEnumerable<GitHubRepo>> GetFromGitHub() { var request = new HttpRequestMessage(HttpMethod.Get, "orgs/aspnet/repos"); ct.ThrowIfCancellationRequested(); var response = await _httpClient.SendAsync(request, ct); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>(ct) : Array.Empty<GitHubRepo>(); } } }
107. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { // ctor - hidden for brevity ... public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync(CancellationToken ct = default) { return await _memoryCache.GetOrCreateAsync("aspnet-repo-data", entry => { entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(5); return GetFromGitHub(); }); async Task<IEnumerable<GitHubRepo>> GetFromGitHub() { var request = new HttpRequestMessage(HttpMethod.Get, "orgs/aspnet/repos"); ct.ThrowIfCancellationRequested(); var response = await _httpClient.SendAsync(request, ct); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>(ct) : Array.Empty<GitHubRepo>(); } } }
108. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { // ctor - hidden for brevity ... public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync(CancellationToken ct = default) { return await _memoryCache.GetOrCreateAsync("aspnet-repo-data", entry => { entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(5); return GetFromGitHub(); }); async Task<IEnumerable<GitHubRepo>> GetFromGitHub() { var request = new HttpRequestMessage(HttpMethod.Get, "orgs/aspnet/repos"); ct.ThrowIfCancellationRequested(); var response = await _httpClient.SendAsync(request, ct); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>(ct) : Array.Empty<GitHubRepo>(); } } }
109. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { // ctor - hidden for brevity ... public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync(CancellationToken ct = default) { return await _memoryCache.GetOrCreateAsync("aspnet-repo-data", entry => { entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(5); return GetFromGitHub(); }); async Task<IEnumerable<GitHubRepo>> GetFromGitHub() { var request = new HttpRequestMessage(HttpMethod.Get, "orgs/aspnet/repos"); ct.ThrowIfCancellationRequested(); var response = await _httpClient.SendAsync(request, ct); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>(ct) : Array.Empty<GitHubRepo>(); } } }
110. @stevejgordon www.stevejgordon.co.uk Bonus Tip 1 – Extension Methods Credit to: @randompunter and @leastprivilege
111. @stevejgordon www.stevejgordon.co.uk public static class HttpClientExtensions { public static async Task<IEnumerable<GitHubRepo>> GetReposAsync( this HttpClient client, string org, CancellationToken ct = default) { if (string.IsNullOrEmpty(org)) throw new ArgumentException(nameof(org)); var url = $"orgs/{org}/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); ct.ThrowIfCancellationRequested(); var response = await client.SendAsync(request, ct); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>(ct) : Array.Empty<GitHubRepo>(); } }
112. @stevejgordon www.stevejgordon.co.uk public static class HttpClientExtensions { public static async Task<IEnumerable<GitHubRepo>> GetReposAsync( this HttpClient client, string org, CancellationToken ct = default) { if (string.IsNullOrEmpty(org)) throw new ArgumentException(nameof(org)); var url = $"orgs/{org}/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); ct.ThrowIfCancellationRequested(); var response = await client.SendAsync(request, ct); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>(ct) : Array.Empty<GitHubRepo>(); } }
113. @stevejgordon www.stevejgordon.co.uk public static class HttpClientExtensions { public static async Task<IEnumerable<GitHubRepo>> GetReposAsync( this HttpClient client, string org, CancellationToken ct = default) { if (string.IsNullOrEmpty(org)) throw new ArgumentException(nameof(org)); var url = $"orgs/{org}/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); ct.ThrowIfCancellationRequested(); var response = await client.SendAsync(request, ct); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>(ct) : Array.Empty<GitHubRepo>(); } }
114. @stevejgordon www.stevejgordon.co.uk public static class HttpClientExtensions { public static async Task<IEnumerable<GitHubRepo>> GetReposAsync( this HttpClient client, string org, CancellationToken ct = default) { if (string.IsNullOrEmpty(org)) throw new ArgumentException(nameof(org)); var url = $"orgs/{org}/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); ct.ThrowIfCancellationRequested(); var response = await client.SendAsync(request, ct); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>(ct) : Array.Empty<GitHubRepo>(); } }
115. @stevejgordon www.stevejgordon.co.uk public static class HttpClientExtensions { public static async Task<IEnumerable<GitHubRepo>> GetReposAsync( this HttpClient client, string org, CancellationToken ct = default) { if (string.IsNullOrEmpty(org)) throw new ArgumentException(nameof(org)); var url = $"orgs/{org}/repos"; var request = new HttpRequestMessage(HttpMethod.Get, url); ct.ThrowIfCancellationRequested(); var response = await client.SendAsync(request, ct); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>(ct) : Array.Empty<GitHubRepo>(); } }
116. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { // ctor - hidden for brevity ... public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync(CancellationToken ct = default) { return await _memoryCache.GetOrCreateAsync("aspnet-repo-data", entry => { entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(5); return GetFromGitHub(); }); async Task<IEnumerable<GitHubRepo>> GetFromGitHub() { var request = new HttpRequestMessage(HttpMethod.Get, "orgs/aspnet/repos"); ct.ThrowIfCancellationRequested(); var response = await _httpClient.SendAsync(request, ct); return response.IsSuccessStatusCode ? await response.Content.ReadAsAsync<IEnumerable<GitHubRepo>>(ct) : Array.Empty<GitHubRepo>(); } } }
117. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { // ctor - hidden for brevity ... public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync(CancellationToken ct = default) { return await _memoryCache.GetOrCreateAsync("aspnet-repo-data", entry => { entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(5); return GetFromGitHub(); }); async Task<IEnumerable<GitHubRepo>> GetFromGitHub() { return await _httpClient.GetReposAsync("aspnet", ct); } } }
118. @stevejgordon www.stevejgordon.co.uk public class GitHubClient : IGitHubClient { // ctor - hidden for brevity ... public async Task<IEnumerable<GitHubRepo>> GetAspNetReposAsync(CancellationToken ct = default) { return await _memoryCache.GetOrCreateAsync("aspnet-repo-data", entry => { entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(5); return GetFromGitHub(); }); async Task<IEnumerable<GitHubRepo>> GetFromGitHub() { return await _httpClient.GetReposAsync("aspnet", ct); } } }
119. @stevejgordon www.stevejgordon.co.uk Bonus Tip 2 - Correlation IDs https://github.com/stevejgordon/CorrelationId https://www.nuget.org/packages/CorrelationId
120. @stevejgordon www.stevejgordon.co.uk SocketsHttpHandler • Sockets are the basis of both outgoing and incoming networking communication • SocketsHttpHandler is a brand-new managed HttpMessageHandler and is the default implementation for HttpClient • Consistent behaviour across platforms and platform/dependency versions. Built on top of System.Net.Sockets • Elimination of platform dependencies on libcurl (for Linux) and WinHTTP (for Windows) – simplifies both development, deployment and servicing • Enabled by default in .NET Core 2.1 (Does not support HTTP/2)
121. @stevejgordon www.stevejgordon.co.uk In Summary • Use IHttpClientFactory in .NET Core 2.1 • Use Polly for transient-fault handling • Beware content.ReadAsStringAsync and client.GetStringAsync • Expect and handle errors • Pass cancellation tokens • Cache wisely • Pass correlation IDs • Go enjoy talking HTTP! ☺
122. @stevejgordon www.stevejgordon.co.uk Thanks for listening! @stevejgordon www.stevejgordon.co.uk youtube.stevejgordon.co.uk https://www.meetup.com/dotnetsoutheast
123. @stevejgordon www.stevejgordon.co.uk Resources 1. http://bit.ly/httpslides 2. https://www.stevejgordon.co.uk 3. https://aspnetmonsters.com/2016/08/2016-08-27-httpclientwrong/ 4. https://docs.microsoft.com/en-us/aspnet/core/fundamentals/http- requests?view=aspnetcore-2.1 5. https://github.com/App-vNext/Polly 6. https://leastprivilege.com/2018/06/18/making-the-identitymodel-client- libraries-httpclientfactory-friendly/