Not sure how to check whether the retry policy is triggered three times when ever client throws timeout Advertisement C# - How to use Polly to do retries | MAKOLYTE How my code behaves when the policy throws an exception, such as TimeoutRejectionException, BulkheadRejectedException or BrokenCircuitException. 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. If there are going to be many concurrent requests, then it makes sense to use the exponential backoff with jitter strategy. In this case, the policy is configured to try six times with an exponential retry, starting at two seconds. Also, the shown code might not always show the best way to implementat things, it is just an example to explain some use cases of Polly. While this is not a complete solution it can already handle some issues. Thanks for your suggestions. Choose Debug to step through the function where the failure occurred. After the final attempt, it stopped retrying and let the exception bubble up. Lets try and implement the same scenario in a more clean and maintainable way by using Polly! The simplest way to check how many times code was executed is by using a mock. Several third-party adapters are available on the Visual Studio Marketplace. Run CTest tests from the CMake main menu. This will add quite a few extra scenarios where things can go wrong, the most commonly be timeouts and expiration of tokens. I don't want to wait more than one minute in my tests. If we got to HttpClient class definition you will see that it does not implement any interface we can mock. I like the way you explain things, tell why, and offer alternatives. I am using Refit because it is quick and easy to use with REST APIs but Polly can be used with any kind of C# code. But how can we verify all these scenarios work? Using Polly for retrial policies with Autofac - WebLog Retry & Circuit Breaker Patterns in C# with Polly - Medium For instance, you may want to test how your code reacts if, despite resilience strategies, the execution eventually fails. In your tests, inject NoOpPolicy rather than the policies you use in production, and Polly is stubbed out of those tests. TL;DR Mock your policies to return or throw particular outcomes, to test how your code responds. HTTP Retry with Polly | Carl Paton | There are no silly questions Note: You may have noticed this is checking HttpRequestException.StatusCode. Thanks for that @rog1039 . Did the drapes in old theatres actually say "ASBESTOS" on them? In your production code, inject the real policy you want to use. A test adapter integrates unit tests with the Test Explorer window. Right-click on the failing test for a pop-up menu. What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond? For example, lets say youre implementing an algorithm to calculate predictions and its prone to transient errors. Find them at Test adapter for Boost.Test and Test adapter for Google Test. privacy statement. I want to find out how Polly retry polly configured via Startup.ConfigureServices() can be tested. Some time ago I wrote an article which explains how to Increase service resilience using Polly and retry pattern in ASP.NET Core. c# - Polly retry unit test - Stack Overflow 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. One of those classes is System.Net.HttpClient class. I also wasnt sure on the value of using async when its just a log, so I switched it out. (in response to "I cannot retrieve the HttpClient that has been configured with the Polly polly"), (to respond to the question title: "Test Polly retry polly configured via Startup.ConfigureServices() with ASP.NET Core API"). TL:DR; Bear in mind the Polly codebase already tests this for you extensively. The Circuit Breaker pattern prevents an application from performing an operation that's likely to fail. 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. The test uses WebApplicationFactory to exercise your normal app startup in configuring the HttpClient/policy to be tested; but then pull the "test" HttpClient configuration out for a tighter unit test. Notice the last line. For . Boost.Test requires that you manually create a test project. After adding some logging to the service and creating the unit test I got this log result: The unit test is a bit funny. 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 ->. What are the advantages of running a power tool on 240 V vs 120 V? Want to learn more about Polly? This can be simple, like hardcoding a delay time: You can use the attempt count in the calculation, like this: The most complex calculation is the exponential backoff with jitter strategy (Note: This is implemented in the HttpClient example section below). He also rips off an arm to use as a sword, Adding EV Charger (100A) in secondary panel (100A) fed off main (200A). Theres only one instance of Random, and there could be multiple threads making requests concurrently. It will retry up to 3 times. When developing an application with Polly you will also probably want to write some unit tests. Let's see how our unit test for the controller method from above would look like. For more information, see How to: Use CTest in Visual Studio. That is, it only sends request one time, not three times. It will retry for a number of time when receiving any exception. Most people just throw code at you and dont explain anything. NoOpPolicy does nothing but execute the governed delegate as if Polly was not involved. Generating points along line with specifying the origin of point generation in QGIS, Adding EV Charger (100A) in secondary panel (100A) fed off main (200A). This is a simple implementation of a retry method. Perhaps you have code modules for which you already had unit tests, including success and failure cases. The microsoft example also sets .SetHandlerLifetime(TimeSpan.FromMinutes(5)). But the next problem arises: the API is going to be protected with OAuth so we have to get an access token from another endpoint and provide a bearer token to be able to retrieve products. This was helpful when manually testing my worker as its a console application. c# - Testing Polly retry policy with moq - Stack Overflow Example if GET /person/1 responded in 404 it COULD mean 1 doesnt exist but the resource is still there. Generic Doubly-Linked-Lists C implementation. The WeatherClient contains this single HttpClient instance. I have another question on setting system clock. The "Retry pattern" enables an application to retry an operation in the expectation that the operation will eventually succeed. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. How do I test what my code does without Polly 'interfering'? This retry policy means when an exception of type TransientException is caught, it will delay 1 second and then retry. I guess I should be able to create an exact test but for demonstration purposes this will serve its purpose. Edit and build your test project or solution. appsettings.json). Build Resilient HTTP Clients in C# on .NET 6 With Polly @reisenberger I agree with @jiimaho in that there should be a supported way to manipulate the passage of time. 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. For Google Test documentation, see Google Test primer. Ill show the client and service (stubbed to return the error response) code below and the results of running it. There are multiple endpoints, all authenticated with OAuth. 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. Visual Studio 2017 and later (Professional and Enterprise editions) CodeLens lets you quickly see the status of a unit test without leaving the code editor. Polly is able to wrap different policies to handle different scenarios: While this is not the way I would structure my code in a real app, I believe this is understandable and maintainable code. A common need is to test the logic of your system-under-test as if Polly were not part of the mix. It will retry up to 3 times. In the Add Reference dialog, choose the project(s) you want to test. That is, it only sends request one time, not three times. To make sure all calls to the APIs will have a high success rate I had to implement retry mechanisms for different scenarios. Already on GitHub? Test Polly retry polly configured via Startup.ConfigureServices() with ASP.NET Core API. To add a new test project to an existing solution. 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. If you write your own integration tests around policies in your project, note the possibility to manipulate Polly's abstracted SystemClock. For insight into how to do this, pull down the codebase and check out how Polly's own unit tests manipulate the clock. Example: Thanks for contributing an answer to Stack Overflow! For more information, see Run unit tests with Test Explorer. You can do retries with and without delays. This can be facilitated by using dependency injection to pass policies into code. Disclaimer: this article and sample code have nothing to do with the work I did for the eCommerce website. In the DI container set the handler to be applied to the injected http client, this will be avalible to the constructor of FooService. The test can be read as a specification of the resilience behaviour for that piece of code. Test Polly retry polly configured via Startup - Github So for the test to succeed, your app must be configured such that invoking the http://localhost:1234/api/v1/car/ endpoint eventually chains on internally to something (via HttpClientService?) Does a password policy with a restriction of repeated characters increase security? Retry setting is set via a config file in JSON (e.g. To do this, I pass in a NoOp policy. Implementing the Circuit Breaker pattern | Microsoft Learn In addition, Ill show the exponential backoff with jitter calculator class. Since it is an interface it is easy to mock it for the class constructors, but when it comes to actual unit tests we need to mock HttpClient class instance. The test simply proves that HttpClientFactory does configure the HttpClient to use the policy. To do this, it can be helpful to mock your Polly policy to return particular results or throw particular outcomes on execution. Lets try and create a unit test to test the behavior of the circuit breaker. Alternatively, you could write your own very short StubDelegatingHandler. See these example links: 1; 2; 3; 4. According to my understanding in your provided sample you are making asserting only against the result. I closed the my issue as it's not relevant anymore. Some features such as Live Unit Testing, Coded UI Tests and IntelliTest aren't supported for C++. Testing Your Code When Using Polly | no dogma blog Which language's style guidelines should be used when writing code that is supposed to be called from another language? You can also explore and run the Polly-samples to see policies working individually, and in combination. The 3rd parameter of onRetry is an int which represents retryAttempt, this can be added to logs. For example: it causes the policy to throw SocketException with a probability of 5% if enabled, For example: it causes the policy to return a bad request HttpResponseMessage with a probability of 5% if enabled. The .cpp file in your test project has a stub class and method defined for you. If it fails with a different exception or status code, it propagates the exception to the caller. Does anyone know who is caching the response, and how do I disable it? Boolean algebra of the lattice of subspaces of a vector space? Published with Wowchemy the free, open source website builder that empowers creators. GitHub blocks most GitHub Wikis from search engines. For more information, see How to: Use Boost.Test in Visual Studio. When you retry without a delay, it means youll be changing something that should fix the problem so that the retries succeed. Making statements based on opinion; back them up with references or personal experience. The ability to manipulate Pollys abstracted, ambient-context SystemClock is intended to provide exactly this: you can manipulate time so that tests which would otherwise incur a time delay, dont. I'm trying to write a unit test for polly, but it looks like the return is cached. Choose Add > Reference. It should be easy to expand this sample to test more sophisticated policies, for example to test .SetWaitAndRetryPolicy1(). public void PassingTest () {. By clicking Sign up for GitHub, you agree to our terms of service and 1. TL:DR; Polly's NoOpPolicy allows you to stub out Polly, to test your code as if Polly were not in the mix. Running this outputs the following: 03:22:26.56244 Attempt 1 03:22:27.58430 Attempt 2 03:22:28.58729 Attempt 3 03:22:29.59790 Attempt 4 Unhandled exception. Question 2: 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). If that code expectation is not all wired up properly inside the app, it could be a cause of test failure. Heres a simple example of using Polly to do retries with a delay. Unit testing retry policies with timeout intervals #156 - Github That could be with a full DI container, or just simple constructor injection or property injection, per preference. .NET Core: Use HttpClientFactory and Polly to build rock solid services Queston 1: Am I missing something? The RetryAsync () helper method will execute the API call a fixed number of times if it fails with a TooManyRequests status code. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Retry and fallback policies in C# with Polly - Jacobs Blog Too me, this is one of the most important (and fun) parts. 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. @reisenberger I think it's good to let consumers of the Polly API be able to provide a time-provider. It is documented here: Microsoft.VisualStudio.TestTools.CppUnitTestFramework API reference. Right-click on a test for other options, including running it in debug mode with breakpoints enabled. Maybe the API is spinning up, rebooting or there might be a network issue: But what if the API throws an exception because my access token is expired? How to verify that method was NOT called in Moq? Was Aristarchus the first to propose heliocentrism? Can my creature spell be countered if I cast a split second spell after it? I offer this variant in case you just want the shortest possible test of the functionality declared in a method like .SetWaitAndRetryPolicy1(). github.com/justeat/httpclient-interception, How a top-ranked engineering school reimagined CS curriculum (Ep. Embedded hyperlinks in a thesis or research paper. If you want to use the InjectionRate less than 1 you can use xunit and moq chaining via SetupSequence and Moq.Language.ISetupSequentialResult. I hope you did learn something here. Other errors may require you to do something to fix the problem so that the retry attempt will work. In Test Explorer, choose Run All, or select the specific tests you want to run. They show an example of how to write test code. Create the retry policy. rev2023.5.1.43404. 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. Where a test would usually incur a delay (for example, waiting the time for a circuit-breaker to transition from open to half-open state), manipulating the abstracted clock can avoid real-time delays. So, lets add some simple retry (this is kind of pseudo-code, just for demonstration purpose): Although it is not the most beautiful code, it might actually work for you. Then you would know the retry had been invoked. The following sections show the basic steps to get you started with C++ unit testing. Visual Studio 2017 and later (Professional and Enterprise), Visual Studio 2017 and later (all editions). No problem, glad it could help. All Rights Reserved. Why is it shorter than a normal address? Per my original post, if you just want a tight unit-test on the HttpClient "test" configured via HttpClientFactory, you can also do this with the "shortest-possible approach", without needing to involve WebApplicationFactory. in order to trigger Polly's fault and resilience policies such as WaitAndRetry. For this test the following should be true per invocation, services.AddHttpClient(), .OrResult(msg => msg.StatusCode == System.Net.HttpStatusCode.NotFound). We do not want to loose any order because this will directly result in money loss. 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. Adding Polly retry policy to a mocked HttpClient? Polly is a .NET resilience and transient-fault-handling library that allows developers to express policies such as Retry, Circuit Breaker, Timeout, Bulkhead Isolation, Rate-limiting and Fallback in a fluent and thread-safe manner. Right-click on the test project node in Solution Explorer for a pop-up menu. So, how does it test the integration between the HttpClient and the retry policy? Choose the icon for more information, or to run or debug the unit test: More info about Internet Explorer and Microsoft Edge, To link the tests to the object or library files, Microsoft.VisualStudio.TestTools.CppUnitTestFramework API reference, Boost Test library: The unit test framework. Has the Melford Hall manuscript poem "Whoso terms love a fire" been attributed to any poetDonne, Roe, or other? (As at Polly v6.0, the Polly codebase has around 1700 tests per target framework.). This integration can be tested via an integration or component test. The signatures use the TEST_CLASS and TEST_METHOD macros, which make the methods discoverable from the Test Explorer window. (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.). Please view the original page on GitHub.com and not this indexable You can write and run your C++ unit tests by using the Test Explorer window. Implement HTTP call retries with exponential backoff with Polly .NET Core has done a great job by introducing interface for most of classes which makes them easy to write unit tests around them. Thanks. Polly is an awesome open source project part of the .Net Foundation. 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). Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Add a jitter strategy to the retry policy Create test projects in the same solution as the code you want to test. Imagine the order api is really broken. Post an issue on the issues board. I will answer the question at three different levels, and you can choose what suits best. When all retry attempts fail, it fails. You can configure these methods on a mock policy, to return or throw faults you want to simulate. 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. How a simple API call can get way too complex CTest support is included with the C++ CMake tools component, which is part of the Desktop development with C++ workload. Please view the original page on GitHub.com and not this indexable What's the function to find a city nearest to a given latitude? When developing an application with Polly you will also probably want to write some unit tests. Now all client instances with name "sitemap" we use in our code will already have predefined base URL and retry policy configured by Polly. Connect and share knowledge within a single location that is structured and easy to search. The app-under-test in their sample app is also using typed-clients from IHttpClientFactory; and is also using WebApplicationFactory to orchestrate the tests; so is a close fit for the test approach you have already started on. There are many overloads that you can choose to implement. I want to unit test a polly retry logic. Why did US v. Assange skip the court of appeal? I should add another retry around the retrieval of the access token, handle more cases in the switch statement, in short, this simple API is becoming an unmaintainable mess. I have a few classes to demonstrate these scenarios, BusinessLogic.cs and OtherBusinessLogic.cs are the classes under test. We can include 404 (Not Found) but that depends on the use case, in some APIs 404 means the data you were looking for is not avalible. The basic configuration is similar for both the Microsoft and Google Test frameworks. CodeLens lets you quickly see the status of a unit test without leaving the code editor. As I stated in this answer you can't unit test such code, since the retry policy is attached to the HttpClient via the DI. I Honestly love this approach, thanks for the article, this was really helpful, i was able to get a simple retry working using this. Currently I don't see a way to unit test a retry policy if you use the time-based retry policy. Before we jump to an actual problem of writing a test for IHttpClientFactory and HttpClient which instance is create by IHttpClientFactory, let's see how the actual setup looks like in Startup.cs class file. This means when the retry conditions are met, it retries the request. A boy can regenerate, so demons eat him for years. In this simple example, I will demonstrate how to . as GitHub blocks most GitHub Wikis from search engines. preview if you intend to use this content. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? The microsoft example also sets .SetHandlerLifetime (TimeSpan.FromMinutes (5)). Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? When I first tried the circuit breaker I made a trivial mistake: I initialized the breaker on every call, resulting in a recount at every call so the circuit would never break. Install nuget Microsoft.Extensions.Http.Polly. Going further and checking HttpMessageInvoker, you can see that it is not an abstract class nor it implements any interface other than IDisposable which is not much helpful for us in this case since we need to mock behaviors id GetStringAsync method which does not come from IDisposable.