unit test polly retry c#

See these example links: 1; 2; 3; 4. To make sure all calls to the APIs will have a high success rate I had to implement retry mechanisms for different scenarios. This is useful if you have many concurrent requests because it spreads out retry attempts. using Polly; using System; using System.Diagnostics; using System.Net.Cache; using System.Net.Http; public class RetryClient { private HttpClient httpClient = new HttpClient (new WebRequestHandler () { CachePolicy = new HttpRequestCachePolicy (HttpRequestCacheLevel.NoCacheNoStore) }); public HttpResponseMessage PostAsyncWithRetry ( String url, Right-click on a test for other options, including running it in debug mode with breakpoints enabled. And, even better, a mechanism to do some retries before throwing an exception. We use it so often to make web requests. Is there a generic term for these trajectories? I actually just found what I was looking for in Polly itself! I updated my existing integration test method to below, but the retry policy is not activated. According to my understanding in your provided sample you are making asserting only against the result. How does having the Polly policy in play affect your existing unit tests? To add a new test project to an existing solution. as GitHub blocks most GitHub Wikis from search engines. Please view the original page on GitHub.com and not this indexable Does anyone know who is caching the response, and how do I disable it? First you create a retry policy, and then you use it to execute the error prone code: This retry policy means when an exception of type TransientException is caught, it will delay 1 second and then retry. How can Config be setup for Integration test within WithWebHostBuilder() in TestRetry() method if it is the correct method, and for unit test in HttpClientFactory_Polly_Policy_Test class. preview if you intend to, Click / TAP HERE TO View Page on GitHub.com , https://github.com/App-vNext/Polly/wiki/Unit-testing-with-Polly. This can be done with a simple DummyMethod that keeps track of its invocations and has a sorted and predefined collection of response http status codes. The following sections show the basic steps to get you started with C++ unit testing. (As at Polly v6.0, the Polly codebase has around 1700 tests per target framework.). @reisenberger I think it's good to let consumers of the Polly API be able to provide a time-provider. Which was the first Sci-Fi story to predict obnoxious "robo calls"? I posted the same question on StackOverflow a few weeks ago without any answer. I will answer the question at three different levels, and you can choose what suits best. This only tests that a mock is being called, not that the retry policy is working. Instead it inherits HttpMessageInvoker class. About GitHub Wiki SEE, a search engine enabler for GitHub Wikis Disclaimer: this article and sample code have nothing to do with the work I did for the eCommerce website. Next, in your unit test .cpp file, add an #include directive for any header files that declare the types and functions you want to test. Polly is a .NET resilience and transient-fault-handling library that allows developers to express policies such as Retry, Circuit Breaker, Timeout, Bulkhead Isolation, and Fallback in a fluent and thread-safe manner. This brings us to unit testing. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. as a singleton or in the constructor of the service, this having the same scope as the service itself). You may want to test how your code reacts to results or faults returned by an execution through Polly. Thanks. Visual Studio includes these C++ test frameworks with no extra downloads required: You can use the installed frameworks, or write your own test adapter for whatever framework you want to use within Visual Studio. URL: https://github.com/App-vNext/Polly/wiki/Unit-testing-with-Polly. An application can combine these two patterns. If you want to know more of how to easily retry and make your application more resilient to poor and unstable network connection check articleIncrease service resilience using Polly and retry pattern in ASP.NET Core. At the end, Ill show a full example of retrying HttpClient requests with Polly. The signatures use the TEST_CLASS and TEST_METHOD macros, which make the methods discoverable from the Test Explorer window. Initialize CodeLens for a C++ unit test project in any of the following ways: Edit and build your test project or . A good example of a library which allows the user to modify the flow of time is the ReactiveExtensions project. Ubuntu won't accept my choice of password. Finally, I want to verify that my code will work if no Polly policy is in use. When you add new source files to your project, update the test project dependencies to include the corresponding object files. Perhaps you have code modules for which you already had unit tests, including success and failure cases. When theres no errors, it succeeds and does no retries 2. Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. Implement the retry delay calculation that makes the most sense in your situation. It will retry up to 3 times. Alternatively, you could write your own very short StubDelegatingHandler. It allows you to inject exceptions, return BadRequests and etc. Choose Add > Reference. This means every outbound call that the named-client "test" makes would return HttpStatusCode.InternalServerError; it's a minimal example of what HttpClientInterception does, but HttpClientInterception does more, does it with much more configurability, and with a nice fluent syntax. If somebody changes the configuration, the test provides regression value by failing. With HTTP requests, its not a question of if youll run into transient errors, but when. For more information on unit testing, see Unit test basics. For Google Test documentation, see Google Test primer. The indexable preview below may have Example if GET /person/1 responded in 404 it COULD mean 1 doesnt exist but the resource is still there. He also rips off an arm to use as a sword, Adding EV Charger (100A) in secondary panel (100A) fed off main (200A). Not sure why, but it looks like the responses queue is only being Dequeue once, this leads me to believe the response is being cache. In Test Explorer, choose Run All, or select the specific tests you want to run. Create the retry policy. I am using polly to handle retry (see below code). What are the advantages of running a power tool on 240 V vs 120 V? So, lets say hi to the circuit breaker. Install nuget Microsoft.Extensions.Http.Polly. P.S. To show the results, I executed the following code several times to produce different output: Sometimes the server will return errors on every request attempt, and itll error out after 3 retry attempts: Other times itll retry a few times and then succeed: Note: I called WeatherClient.GetWeather() in a console app to produce these results. When the configured delay time has been passed it will reset the circuit and start all over. To test that the retry policy is invoked, you could make the test setup configure a fake/mock ILog implementation, and (for example) assert that the expected call .Error ("Delaying for {delay}ms, .") in your onRetry delegate is made on the fake logger. How my code behaves when the policy throws an exception, such as TimeoutRejectionException, BulkheadRejectedException or BrokenCircuitException. But, to allow you to concentrate on delivering your business value rather than reinventing Polly's test wheel, keep in mind that the Polly codebase tests its own operation extensively. For failed tests, the message displays details that help to diagnose the cause. Please view the original page on GitHub.com and not this indexable Find them at Test adapter for Boost.Test and Test adapter for Google Test. Use CodeLens. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. privacy statement. From the Polly repository: Polly is a .NET resilience and transient-fault-handling library that allows developers to express policies such as Retry, Circuit Breaker, Timeout, Bulkhead Isolation, and Fallback in a fluent and thread-safe manner. Therefore it makes sense to be prepared and implement retry logic. There are still a lot of classes that we use daily in our code which we do not realize we cannot easily test until we get to writing unit tests for our existing code. Connect and share knowledge within a single location that is structured and easy to search. In your test code, inject an equivalent policy that doesn't do any waiting, eg Retry (3) // etc Extract static SystemClock to interface Whenever youre dealing with code that can run into transient errors, its a good idea to implement retries. If it fails with a different exception or status code, it propagates the exception to the caller. invoking the "test" configuration from HttpClientFactory (as I believe it should, from what you have described as the code intention). How can one simulate all the scenarios at a time to verify the behavior of all policies? You can also explore and run the Polly-samples to see policies working individually, and in combination. Sign in Also, tell me if you happen to know alternative libraries, I would very much like that! The microsoft example also sets .SetHandlerLifetime (TimeSpan.FromMinutes (5)). To do this, I pass in a NoOp policy. If we got to HttpClient class definition you will see that it does not implement any interface we can mock. Can be useful as a specification for, and regression check on, the faults you intend to handle. Polly allows http retries with exponential backoff so if the resource you are trying to reach throws a transient error (an error that should resolve itself) like 500 (Server Error) or 408 (Request Timeout) then the request will auto-magically be re-tried x times with an increased back-off (the period between re-tries) before giving up. Well occasionally send you account related emails. Which ability is most related to insanity: Wisdom, Charisma, Constitution, or Intelligence? In your test you recreate an alternative HttpClient + retry integration. Note: You may have noticed this is checking HttpRequestException.StatusCode. While this is not a complete solution it can already handle some issues. Don't include object files that have a main function or another standard entry point such as wmain, WinMain, or DllMain. to your account. Repeat for any more headers. Boost.Test is included as a default component of the Desktop development with C++ workload. Here are the scenarios I test for - How my code behaves when the policy throws an exception, such as TimeoutRejectionException, BulkheadRejectedException or BrokenCircuitException. Lets extend it a bit. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. You signed in with another tab or window. In this case, the policy is configured to try six times with an exponential retry, starting at two seconds. The only difference is I made it randomly return the 429 error status code. retryAttempt => TimeSpan.FromSeconds(Math.Pow(retrySleepDuration, retryAttempt)), InlineData(1, HttpStatusCode.RequestTimeout), InlineData(0, HttpStatusCode.InternalServerError), GetRetryPolicy_Retries_Transient_And_NotFound_Http_Errors. I updated my existing integration test method to below, but the retry policy is not activated. Polly is an awesome open source project part of the .Net Foundation. You may be tempted to create additional infastructure and unit test an injected HttpClient with mocked out http responses but its simpler to just unit test the extension method. The unit test itself does not look so sophisticated as it would be as if you would wrap HttpClient class to implementation of an interface, but this way you get to keep using IHttpClientFactorywhich is more beneficial for your application than adapting it to much to have simpler unit tests. Has the Melford Hall manuscript poem "Whoso terms love a fire" been attributed to any poetDonne, Roe, or other? If you havent already, install the Polly nuget package by executing this command (this is using View > Other Windows > Package Manager Console): After that, to use Polly, add the following using statement: The onRetry parameter allows you to pass in a lambda that will be executed between retries. This is a simple implementation of a retry method. Create test projects in the same solution as the code you want to test. and configure it after the Polly policy on the HttpClient ('inside' the Polly policy , it terms of the nested DelegatingHandlers). PolicyResult and PolicyResult have public factory methods, allowing you to mock .ExecuteAndCapture() overloads to return the PolicyResult of your choice. How a simple API call can get way too complex This will be a different type of exception and it will also need a different solution to solve the problem. For more information, see Install third-party unit test frameworks. Thanks for contributing an answer to Stack Overflow! Connect and share knowledge within a single location that is structured and easy to search. Thanks for your suggestions. #161: Simple Retry Policy with Polly Asp.Net Monsters 3.95K subscribers Subscribe 49 Share 2.3K views 2 years ago The ASP.NET Monsters Weekly Exceptions in production are a matter of course for. Question 2: Well occasionally send you account related emails. tar command with and without --absolute-names option. Not the answer you're looking for? This will be my full AuthenticationService: Now I can test the behavior with Moq to mock the API: Let us dive a bit deeper into policies and Polly and combine different policies (and even add two more). After all the tests run, the window shows the tests that passed and the ones that failed. For Boost.Test, see Boost Test library: The unit test framework. Readme Issues Note Important Announcement: Architectural changes in v8 I Honestly love this approach, thanks for the article, this was really helpful, i was able to get a simple retry working using this. If you want to know more about mocking System.IO classes you can checkoutMocking System.IO filesystem in unit tests in ASP.NET Core article. If you check the constructor of HttpClient you will see that it inherits and abstract class IHttpMessageHandler which can be mocked since it is an abstract class. One of those classes is System.Net.HttpClient class. In your tests, inject NoOpPolicy rather than the policies you use in production, and Polly is stubbed out of those tests. The Assert class contains many other methods to compare expected results with actual results. Then you would know the retry had been invoked. Simply set the InjectionRate to 1 to guarantee a fault in your unit test. TL;DR Mock your policies to return or throw particular outcomes, to test how your code responds. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Thank you for asking and answering the question. This is a great way how to easily implement retrials when using .NET Core dependency injection, but in case of using Autofac with .NET Framework 4.x you do not have many out of the box solutions. [TestMethod()] public void TestProcessor_WhenError_Retries() { //arrange var mockProcessor = new Mock(); mockProcessor.SetupSequence(p => p.Process()) .Throws() //1st attempt .Throws() //retry 1 .Throws() //retry 2 .Pass(); //retry 3 succeeds (note: it's a void method, hence Pass() instead of Returns()). Updated Integration Test method With Polly it is possible to create complex and advanced scenarios for error handling with just a few lines of code. Using the Executor Class Once we have defined the Executorclass and its methods, it is time to execute the FirstSimulationMethodand the SecondSimulationMethodmethods. It has helped me a lot today, github.com/App-vNext/Polly/blob/master/src/Polly.SharedSpecs/, How a top-ranked engineering school reimagined CS curriculum (Ep. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, C# Kafka: How to Create a NetworkException Error, Unit testing internal methods in VS2017 .NET Standard library, Using Polly to retry on different Urls after failing retries. Although there are abundant resources about Polly on the web I wanted to write a post with a lot of sample code to provide a quick and practical example of how easy it is to use Polly to create advanced exception handling with APIs. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? Theres only one instance of Random, and there could be multiple threads making requests concurrently. It will break when the configured number of exceptions have been thrown. To test that the retry policy is invoked, you could make the test setup configure a fake/mock ILog implementation, and (for example) assert that the expected call .Error("Delaying for {delay}ms, ") in your onRetry delegate is made on the fake logger. Retry & Circuit Breaker Patterns in C# with Polly Retry and circuit-breaker patterns are the 2 most common approaches when coding for resiliency. You can download the Google Test adapter and Boost.Test Adapter extensions on the Visual Studio Marketplace. If there are going to be many concurrent requests, then it makes sense to use the exponential backoff with jitter strategy. These interfaces describe the .Execute/Async() overloads available on policies. Adding Polly retry policy to a mocked HttpClient? The RetryAsync () helper method will execute the API call a fixed number of times if it fails with a TooManyRequests status code. Refactor to inject the Policy into the method/class using it (whether by constructor/property/method-parameter injection - doesn't matter). Run CTest tests from the CMake main menu. Writing unit-tests to verify that Polly works can be a very valuable way to explore and understand what Polly does. Imagine the order api is really broken. Sign in However, I still have problem getting the named HttpClient, and other questions. In this article, Ill go into more details about how to use Polly to do retries. preview if you intend to use this content. I want an advanced scenario that looks like this: I will not implement authentication in this flow but I guess you can already imagine: a) the flow will be much more complicated, b) it will still be quite easy to implement with Polly using the example from above. Should_Return_999_When_TimeoutRejectedException_Thrown, // if there is a TimeoutRejectedException in this CallSomeSlowBadCode it will return 999, Using the HttpClientInterception to Test Methods That Use a HttpClient, Polly with .NET 6, Part 8 - Policy Registry with Minimal APIs, and HttpClientFactory, Polly with .NET 6, Part 7 - Policy Wraps with Minimal APIs, and HttpClientFactory, Polly with .NET 6, Part 6 - Policy Wraps with Minimal APIs, Polly with .NET 6, Part 5 - Using a Cancellation Token. How do you unit test LoggerMessage.Define() in .NET Core 3.1 with Moq? If the test code doesn't export the functions that you want to test, add the output .obj or .lib files to the dependencies of the test project. It is documented here: Microsoft.VisualStudio.TestTools.CppUnitTestFramework API reference. That's exactly the way we handle it within Polly's own specs, to allow tests to run instantly where time-delays are involved: specs either substitute SystemClock.UtcNow or SystemClock.Sleep , depending on whether the policy-under-test is waiting passively for time to pass elsewhere (as in CircuitBreaker moving to half-open) or actively controlling the delay (as in WaitAndRetry). Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Hi, There is a nice way to test these type of scenario using Http interceptions - using JustEat nuget, checkthis out ->. The WeatherClient contains this single HttpClient instance. This is what the flow will look like in code: And the unit test to test the full flow (check the repository on Github to see the mock setups): So now we have a retry and a fallback. To add a new test project to an existing solution. you directly to GitHub. A test adapter integrates unit tests with the Test Explorer window. - Peter Csala Jul 24, 2022 at 16:07 (It's slightly questionable whether SystemClock should really be public that inherited from before AppvNext stewardship of Polly SystemClock is really an internal concern but it does have this benefit for user testing.). There are multiple endpoints, all authenticated with OAuth. It will open the circuit for a certain amount of time which means it will not even try to execute the call but immediately throw an exception. This class is passed into the client so it can be used as the sleepDurationProvider Polly parameter. Want to learn more about Polly? It has nothing to do with caching. Retry setting is set via a config file in JSON (e.g. How do I test what my code does without Polly 'interfering'? Hi, Thanks. With both previous methods, we can use this retry logic in C# for both, Actionand Funcdelegates. Do all the tests need adjusting? Mocking HttpClient in unit tests with Moq and Xunit when using IHttpClientFactory, Mocking System.IO filesystem in unit tests in ASP.NET Core, Increase service resilience using Polly and retry pattern in ASP.NET Core. .NET Core has done a great job by introducing interface for most of classes which makes them easy to write unit tests around them. For this kind of scenarios there is a very cool library: Polly which I have been using for some years now (together with Refit) and I am just deeply in love with both libraries. Can I use an 11 watt LED bulb in a lamp rated for 8.6 watts maximum? For insight into how to do this, pull down the codebase and check out how Polly's own unit tests manipulate the clock. What my code should do if there was no policy in place. Have a question about this project? Several third-party adapters are available on the Visual Studio Marketplace. For examples taking this concept further with PolicyRegistry or a policy factory, see our Unit testing with examples page. Let's check it: Executor.Execute(FirstSimulationMethod, 3); You signed in with another tab or window. C# Polly WaitAndRetry policy for function retry, Unit test Polly - Check whether the retry policy is triggered on timeout / error. For more information, see How to: Use Google Test in Visual Studio. For example, lets say youre implementing an algorithm to calculate predictions and its prone to transient errors. TEST_CLASS and TEST_METHOD are part of the Microsoft Native Test Framework. I want to unit test a polly retry logic. It is possible simply to new up a ServiceCollection; configure a named client using HttpClientFactory; get the named client back from the IServiceProvider; and test if that client uses the policy. For more information, see To link the tests to the object or library files. How my code behaves when a policy becomes active and changes the outcome of a call, such as when an unreliable request works because Polly performs a retry. Thanks again for the prompt reply and the great answer. That is, it only sends request one time, not three times. Imagine this: I want a retry on the authentication api but only when I receive a RequestTimeout (Http status code 408).
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