ASP NET Core Health Checks

thank you so I think I'm life yes you hopefully cool so let's start yeah I will talk about the asp.net core health checks today but first I will quickly introduce myself so my name is Sharon Gooch I'm from southern Germany I'm a Microsoft MVP for several years five years I think I'm blogging writing a lot leading it on a user group since years and speaking at several community events and meetups and I also started a stream on Twitch not regularly but from time to time and I'm a software engineer at the U in Basel so I'm working Switzerland living in in southern Germany hopefully the sound is good last turn last year the first 10 minutes were awful it's it's going well this time so I have a quick agenda oh I need to quickly close not close minimize Skype window as well I see two versions of the agenda currently so yeah I will quickly quickly introduce asp.net core health checks and then I will show a basic implementation of the health checks and there are also a lot of checks in the community so we'll have a quick look there and how to visualize the health of subsystems of an application and if it's some time left I will show you quickly on an enhanced scenario so I built something with docker containers to show how this could look like so all the sources I will show today are will be available on github so the repo already exists but I will push it afterwards so what's next exactly about the health checks what are the health checks so that health checks are kind of a framework inside of the ASP and framework to check the health of application subsystems maybe databases or services which are not inside the application or you can also check your your system you can check memory you can check your space of your hard drive whatever you want to check you can also handle the health of your subsystems we get a feedback and the checks give you the state of your subsystems and you can handle them we can show the states in your weekly application and you can provide an endpoint to show the information about the health of your current application and of the subsystems of the current application so the namespace is Microsoft add extensions that diagnostic start health checks you'll find all the stuff here and yeah a little bit of history so I'm was pretty much involved into health checks so the development started at 2016 I think I'm not sure when exactly but during the MVP summit in 2016 LAN Condren asked via Twitter if there's anyone who want to attend the asp.net hackathon and help him through write checks for the asp.net health checks the first version I think it was a draft at that time so Damien said yes I said yes and we met Glenn Conner in an Andhra nurse at the asp.net hackathon and started hacking some checks then it moved through some repositories until it makes it into the product so it is in the product still in speed on that code 2.2 I think what can you do with health checks you know maybe mention it it is monitoring the health of parts of your application or yours or subsystems of application imagine it databases some Web API is G RPC service is any other services or the environment of application you can check memory performance drive space and so on and you can provide the health state of your application including the health of the subsystems you want to check so you get an endpoint that that tells you about the health of the whole system the entire system I think yeah that's almost about the theory why should you use the health checks yeah you can handle unhealthy states in the application you can maybe provide information to the users that some of the subsystems or databases aren't available currently you can keep you a partially running in case of an unhealthy state of an subsystem maybe there's yeah a specific database not running and you can keep your application partially running without this database for example or you can tell the users about the unhealthy state and so on I can switch to alternative subsystems in case of an unhealthy state of this specific system subsystem maybe you have a different one and what I didn't mention here in the slide is you can provide a an end point I think it's the exactly same endpoint to the what is called Essure a load balancer thing as I can connect your Asia environment to this end point and the load billets I can is able to to switch the applications or they the switch between the instances of your application okay let's share some code and this section I will demo you a simple implementation of health checks so this is the kind of agenda of this section just created a spill don't care a SP donate core MVC application using the.net CLI I already did this then we will configure some basic simple health checks without any logic in it we will implement a custom health check and we will use the health health check service to to curl the checks and to to visualize the states of the subsystems this is the basic configuration of the startup of your SP donut corportation you can add the health checks services and the configure service method and you need to provide the the endpoint I mentioned this is the endpoint which provides the state of your application including the subsystems so we say abuse health checks is the mom exactly I will switch to the console hopefully the font size is okay we can increase it a little bit and I'll open yes code and go to the startup and this is common asp.net MVC application already added the health checks here I'll check your services and I added the endpoint this is a little different than in the slides because in asp.net core 3.0 we have the new endpoint routing and the middleware which provides routes are now registered here with map something map controller route or map health checks this is the endpoint I mentioned so this is the basic configuration just to add health checks or just to have the possibility to bad health checks so now I want to add a few health checks so this is a way to add the liquid based Orlando based health check pretty simple this doesn't add us nothing here it just outputs unhealthy state so we can say add check yeah I'm sum over I to you you can do it the delegate way or we can add an health check instance we don't see this later we can do it the generic way to add an health health check type here Oh as well with thee with a funk we get a health check result so we return the result that's that so that's one I can also return an unhealthy States or some options some things to return we can return healthy unhealthy or something but in between degrade it so we leave this and I have another quick sample which is more useful I think it is a check to ping a subsystem okay this one starts a ping oops wrong keys here I did you know that you can press windows start to add emojis here yeah what works okay we create a new ping I said send the ping to localhost because it's currently it's hard to find a service on Azure or somewhere which responds to a ping I think all the edges services don't respond so I can't ping dead confident nets are also kind of ping my own block and so on so I need to find find a host to ping so if it's not a success state then I will return unhealthy if this needs more than 100 milliseconds I think yes then it's degraded it's pretty slow then and if it's all fine I will return and healthy state so in case of errors I will also return an unhealthy state I think that's with the delegate a checks but we can also create more your more complex checks using classes so it's this one you can create an eye health check so I need to find the interface it's not implemented correctly so I need to get this one the cancellation token and now it's implemented so it's almost similar to their to the lambda expressions here so I in this so we will return a health check result and get a context and we get a cancellation token so this is more complex way we can check the state of something so this is just an example I set it to true so it's healthy and if it's if the subsystem is healthy or we return our healthy state and otherwise unhealthy state so here this line you can put your checks whatever you want to check I will show you a more useful sample later okay so we need to add this you say add check I'll use that generic way it's so I don't need to add a name next ups let's get be null I think and here we need to add some tax a different keyboard layout here so now it's working so I'm switching between German and US American layout okay so this should work but I this should work if I call the endpoint let's try it I press ofin the five also the language is switching between German and English I'll place only if something bad with the with a stream font size audio and so on okay if this should work buzzer OH open up in the wrong window so yeah yes so it's running if I press f5 um I see something's going on here and the end and wash think it's unhealthy yep it's unhealthy the complete application is unhealthy because of this here if I switch this to the healthy state I've said it okay I'm to restart it it will be healthy so this is the endpoint okay you can't extend the endpoint a little bit so I need to find the snippet for this yep there's some options we need to set and configure and we can have this lines here say predicated true say response writer s d-u-i response writer to find the using so this isn't there okay let's check the namespace check options response my turn okay let's remove this I was sure in the next day more than okay that's about the one endpoint but what about visualizing so to visualize the the health of the epic of your application now I can use their health check service and you can call all the checks on demand and display reserve and the results in your view so to do this I'll go to the home controller and inject the health check service so like this this is already in the DI container so I can use it wherever we want and I'm going to add a new view so I also need to add the views here so just copy the privacy and call it health and put some code in it so okay so we use the diagnostic self checks here our model is the health report and then we write out the the status of the models of the model is the health report we return this from the control action we can display the duration of all the checks and we can iterate through the checks and display the state of all the checks we have okay let's change this back to unhealthy turn a better message and restarted so paid there so we haven't created a link for the health I will do it so I think I did something wrong at the end point end point and if you do have the same URL so I will rename this end point no I'm wrong I did it wrong so I shouldn't have changed the the end point here it should be under home health exactly so that's it so the state is unhealthy yeah needed five milliseconds seconds or milliseconds than that so the foo is healthy the bar is not healthy healthy and we have the ping here you should have set the name and we have the simple health check so the ping is healthy don't we have a name here tag [Music] should be pink they don't see it yet I don't know why anyway so it's working we have the the health state of our sub substance here and we can also add an indicator to the page to see if the entire application is healthy or not so to do this open the layout see is HTML pennants injection here so you can do a dependency injection in your view I inject the health check service and I use it in our code block let's put it here so we await that check health async armed with this we get the health health state so I think this is a health state response our health result so as you can see it here this is a health report okay that we have the same in the layout and we can check the states here so as SATA background come current in case the state is unhealthy degraded or I don't set it in case it's all healthy so and I'm able to set it here and let's see what happens I need to repeal it I think yep so let's close this one now the head is red and unhealthy and if you changed this and let's say this is decorate it to rebuild it again it should be orange them or whatever set here orange yes so under and healthy state doesn't have a background color so it's it's white okay do we have any questions until yet if not that will continue with the slides out there and let's have a quick look into what the community did so what was expected after I had another look into the health checks health checks um a post playing around with the health checks for a year or so uh didn't had a look until this time this period and after had another look expected some health checks created by Microsoft but there are almost no health checks the reason is that it's pretty simple to implement some and the other reason is that the community already created a lot of health checks so if you see this slide yeah if you entered interested go to this repository that's better it's a burial I'll pronounce it right he created the asp.net core diagnostic health checks package or packages on the right side let me see a list of nougat packages available so you can check the system cat Network sequel server MongoDB and so on ready event store secret light a lot of other stuff also um Amazon Web Services can't be checked and fire a signal or and so on Kuban eighties and I think the list will increase a lot so this project is port from beat pulse and it also provides UI features so well show you in there more enhanced steam off so please have a look also you some of these packages to check sequel server or or Seco light and so on um also try to check circulate I think this doesn't work currently I need to check it again maybe I did something wrong and if not I will a pricing issue you also it wasn't possible to connect to and secure light database you know inside the docker container that's didn't work okay so about the health check your ISO also ends of this project they created a pretty nice health check UI so you can add it with with this service registration and with these middlewares here and this also provides another endpoint which is specific for this UI and it also provides health checks UI endpoint with them with a nice HTML UI so let's have a look what I did for this demonstration I created something like dummy weather statistics application downloaded a lot of weather data from Washington State I have implemented four different with the station spree mutton Cedar Lake and Monroe and a health monitoring app and what's missing currently so where the data visualization app but this is not important here and it's all running on docker I'll close this one here and go to the console this one oops openly is coached there so these are six applications this one doesn't count it's not implemented yet at at a common library to share classes also shared the the dbcontext this is this is the health monitoring app and we have the four different weather stations here I'll go through the f qor to connect to the secret light database so this is all wired together with docker compose this is the visualization of the health health visualization export some ports it depends on the day and therefore stations and also need to link the docker containers together it was talking it working stuff here and I created four different docker files per container one to run so so let's quickly look here this is the configure services of the of the check visualization app so I created the dummy foo health check just to check whether it's working or not and edit a database context check I think this is the only health check provided by Microsoft the only finished health check then added a check for URI so this is called your group it's in the URI package you can set your I want to check give a name like with the other ones you need to tack this or it make sense to tag this let me to filter it later on so I created for ping checks and for data checks there's this one for checks only check whether the services are available or not and the other one are really loading data and check whether there's a result or not so I also added the health checks UI and also set it to the to the after the apps here so this is the health checks this is what I wanted to show in the previous demo you need to define a different response writer and with this you can enhance your own endpoint to add some more information I will show it quickly and I need to add the hell check CIA middleware so I don't want to start it here with Mia's code I used the console one and run docker come powers up it's all compiled and it only needs to start so all the services are available so we see the name docker container here tennis here this one is the monitoring app and the other ones are the stations so it's called 5,000 that's not HTTP and it's running this one is just a single Web API application and this is our endpoint we extend it so now we get a JSON result we get this state here it's not a longer a simple text and we get a lot of more informations so the duration we get all the entries these are all the checks we have they have the checks I also provide it's an endpoint this is almost the same but needed for the for the UI so and this is the after checks UI provided by these guys by the community so and here we see all they all the services that are running so these are running in the docker container this is in the alternate docker container but in the end the visualization yep and this is our dummy justice to check so what happens if we kill one of these ok a little bit so here are the containers running so looks a little bit bad I will resize it all the way around so like this ok I want to kill one of them let's say the weather station in canvas well don't have container killer okay some it was the idea it's just darker kill it's it's not docker container kill really try to lift up your containers there you go yeah no it's killed thank you almost almost done let's just this last demo okay you can see now there that station in Kent was offline its offline and you see the checks are unhealthy no okay so that's pretty much it um I say thank you and hopefully you enjoyed it I thought I really liked seeing the level of community interaction here with the health checks you're right they're so simple to write and already so many of these that really help with those other integrations and services that we want to know the health of mm-hmm yeah absolutely there's a lot of implementation see a lot of documentation and from the community yep the user interface right we saw the same thing with the folks who do swagger stuff to have health checks you want yes it's something every user administrator is going to need yeah absolutely yeah I didn't know that I'm I definitely need to make sure I had that to my applications going forward thanks to thanks for hosting thanks for having me for champagne