let's say you're writing an application that calls out to a web API and that web API crashes find out how you can make your application Not Crash by writing some code with Copilot all right so this is the web application that we're going to make not crash it has a bunch of pizza menus on it and what this does we have one web application calling out to a web API that returns well pizzas and when I go over here and I keep on clicking refresh it refreshes pizza's just fine but what I wanted to do now is go through and introduce an error into my web API that Returns the menu of pizzas so right here as you can see I have just a minimal web API that has returning pizzas and so what I'm going to do here is introduce using some co-pilot to help me out an air so I'm going to type in a comment and I'm just going to say generate a random number between one and two because I can never remember how to use the random number generator all right and it doesn't remember for me between one and two let's see if it does it now all right so how about we just do VAR random equals new random and see if it does it here all right so now we have it then if random number is one I'm going to want to return a 503 error so all I'm doing now is setting up my web API so it returns an error every time that it's a random number generator is number one and if it comes back be number two we're gonna return good so just setting things up any copilot help me out writing that by me prompting it just a little bit all right so I'm going to restart my web application and we're going to go over to the Swagger tooling and see it air out hopefully roughly every other time that we call it coming back up Swagger that's my cart here's my pizzas I'm gonna try it out real quick execute go down here and I did I got a 503 execute 503 and now I got the 200 to come back so it's airing out roughly every now and then so we're implementing some transient errors coming back from our web API and so what I really don't want to have happen then is my web application you can see right here has crash it tried calling out to my web API got that 503 and crashed but if I refresh it eventually it'll come back up like right here because it actually got the good response back so what I want to have happen and this is the key what we're all here today to see is to make sure our web app stays up by implementing some kind of retry policy to try that web app web API again keep on going to that transient error resolves itself oh hey back to the code and so what I want to do then is right here this get menu method is the one that is responsible for calling out to the pizza service to return to menu and so the first thing I'm going to ask is I'm going to actually open up GitHub copilot chat and I'm just going to want to say what's ah good.net Library for doing retries of http error and see what it comes up for me and it says when it's done typing everything poly so I'm going to go through and bring in poly for my packages to my web project browse through the little poly you bet and as it brings it all back in I'm going to jump back over to copilot chat for just a second and it actually is going to show me something pretty neat in that it shows me how to implement knows what I want to try or wait and retry async it's already guessing by where my code is and what it what what it thinks I want to do but I'm going to save here and then I'm going to highlight the code I'm going to right click on it and I'm going to say hey ask Copilot how can I retry this code when an HTTP error occurs copilot thinks about it and then gives me a way to do it so I don't like the way that it just gave me to do it I want to actually use poly to do it so one of these things about when you're using copilot or copilot chat is that you want to Trust but verify the code that it brings back and so what it has here let me open it up just a little bit more is that if it fails three times you know go back you know while retries less than three I want to use poly I want poly to do all the work for me I don't want to have to think about it myself so let's actually do that for us let's try it one more time right click ask Copilot have Ollie create a poly policy to retry when HTTP exception occurs how about that and let's see what a copilot comes up with this time make this a little bit larger so we can see what's going on and then I'll scroll up because I want to get the menu and here we go what I'm going to do is I'm just going to copy this in topic comment on what I had and then put the new one in make sure I actually copy it from the copilot chat happy paste is very hard for me let's see if I can get it now roll C TRL V and here we go and so what it's saying you know what we're gonna try a wait and retry a sync policy first time's gonna be three seconds next time is five one second three five seconds five seconds and then retry and it's saying you know what all the pizzas that might be null here so initially I'm just going to say new list Pizza so again trust but verify so let's start it up and see if what copilot gave us works there were Bill Bears what did I do wrong new expression after the type let's see line 35. have to do my parentheses all right let's go again start everything spins up so let's try our Swagger tooling out try it out let's see we should just be getting 200 values back code 200 we should not see a 503 coming back at all but we or we should still see the 503 coming back from here because we're calling directly to the web API web API is still an error what we shouldn't have happen is our web app should be catching those and continuing on assuming that we don't get three errors in a row looks good so far let's refresh good good still looks like we fixed it all right there we go so you've seen now actually a couple good points here you saw that how we use copilot and GitHub copilot chat to introduce well we how we use it to find a random number and then introduce a random error into our code to return a 503 status code and then how we use copilot chat put in the poly nuget Library so we can have a retry policy inside of our web code to retry whenever our web API blew up but the cool thing that you saw is that sometimes co-pilot and copilot chat aren't 100 correct so you have to trust but verify and we saw that oh what a return the first time wasn't what we thought it would do or was so we went through tried it again and it did give us something that worked better so press but verify sometimes everything's great sometimes you're just on the start of it so anyways at the end of the day we got it working and so there we have it making sure our application can call a web API not fail even when web API on us blows up
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