Port Health Checks wiki info from Sonarr with amends

Health-Checks.md

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+This page contains a list of health checks errors.
+These health checks are periodically performed performed by Radarr and on certain events. The resulting warnings and errors are listed here to give advice on how to resolve them.
+
+### System warnings ###
+
+#### Mono version is less than 3.10, upgrade for improved stability ####
+
+Radarr is written in .Net and requires Mono to run. Versions of 3.10 and above resolved various stability issues we experienced in the past and is considered the minimum supported version.   
+Mono version 4.x and higher are also available and provides a better experience on certain platforms.
+
+#### New update is available ####
+
+Rejoice, the developers have released a new update. This generally means awesome new features and squashed piles of bugs (right?).
+Apparently you don't have Auto-Updating enabled, so you'll have to figure out how to update on your platform.
+Pressing the Install button on the System -> Updates page is probably a good starting point.
+But while you're at it, read the change log to find out what the relevant changes were.
+
+_(This warning will not appear if your current version is less than 14 days old)_
+
+#### Cannot install update because startup folder is not writable by the user ####
+
+This means Radarr will be unable to update itself. You'll have to update Radarr manually or set the permissions on Radarr's Startup directory (the installation directory) to allow Radarr to update itself.
+
+#### Updating will not be possible to prevent deleting AppData on Update ####
+
+Radarr detected that AppData folder for your Operating System is located inside the directory that contains the Radarr binaries. Normally it would be ```C:\ProgramData``` for Windows and, ```~/.config``` for linux.   
+Please look at System -> Info to see the current AppData & Startup directories.
+
+This means Radarr will be unable to update itself without risking data-loss.
+
+If you're on linux, you'll probably have to change the home directory for the user that is running Radarr and copy the current contents of the ```~/.config/Radarr``` directory to preserve your database.
+
+### Download Clients ###
+
+#### No download client is available ####
+
+A properly configured and enabled download client is required for Radarr to be able to download media.
+Since Radarr supports different download clients, you should determine which best matches your requirements.
+If you already have a download client installed, you should configure Radarr to use it and create a category. See Settings -> Download Client.
+
+#### Unable to communicate with download client ####
+
+Radarr was unable to communicate with the configured download client. Please verify if the download client is operational and double check the url. This could also indicate an authentication error.
+
+#### Download clients are unavailable due to failure ####
+
+One or more of your download clients is not responding to requests made by Radarr. Therefore Radarr has decided to temporarily stop querying the download client on it's normal 1 minute cycle, which is normally used to track active downloads and import finished ones.
+However, Radarr will continue to attempt to send downloads to the client, but will in all likeliness fail.
+
+You should inspect System->Logs to see what the reason is for the failures.
+
+If you no longer use this download client, disable it in Radarr to prevent the errors.
+
+#### Enable Completed Download Handling or configure Drone Factory ####
+
+Radarr requires Completed Download Handling or a properly configured Drone Factory to be able to import files that were downloaded by the download client. It is recommended to enable Completed Download Handling.
+
+_(Completed Download Handling is enabled by default for new users.)_
+
+### Drone Factory ###
+
+#### Drone Factory folder does not exist ####
+
+If you configure Radarr to use a Drone Factory the specified folder must exist. Please ensure that it indeed exists, or disable the Drone Factory.
+
+_(You might want to consider using Completed Download Handling since it provides better compatibility for the unpacking and post-processing logic of various download clients.)_
+
+#### Unable to write to Drone Factory folder ####
+
+You configured Radarr to use a Drone Factory, however Radarr was unable to creates a test file, this indicates permission issues.
+Please verify that the user Radarr runs under has the appropriate permissions.
+
+#### Drone Factory is deprecated ####
+
+**Please don't panic.**
+
+The Drone Factory is unreliable in various situations and has been replaced by Completed Download Handling and external API calls over a year ago. This functionality will be removed in a future major version of Radarr and should no longer be used.
+_Please note that the Drone Factory periodic scan functionality will not be removed via an automatic update, but rolled into an future backward-incompatible v3 major release which in most cases will require manual installation._
+
+For occasional manual downloads use Wanted->Manual Import. It'll allow you to select a directory and optionally review the parsing results before actually importing. Useful for the occasional manual download that isn't handled automatically.
+
+If the download client is on a remote machine, consider using remote mounts in combination with Settings->Download Clients->Remote Path Mapping to make Radarr aware of the mount. Alternatives are available.
+
+Please disable the Drone Factory:
+
+- Go to Settings->Download Clients
+- Enable Advanced Settings in the top left
+- Make sure the Drone Factory field is empty
+- Make sure the Drone Factory Interval field is set to 0
+- Save settings
+
+### Completed/Failed Download Handling ###
+
+#### Completed Download Handling is disabled ####
+
+_(This warning is only generated for existing users before when the Completed Download Handling feature was implemented. This feature is disabled by default to ensure the system continued to operate as expected for current configurations.)_
+
+It's recommended to switch to Completed Download Handling since it provides better compatibility for the unpacking and post-processing logic of various download clients.
+With it, Radarr will only import a download once the download client reports it as ready.
+
+If you don't wish to enable Completed Download Handling at all and wants to remove the warning. You can enable and then disable Completed Download Handling. This obviously isn't recommended.
+
+If you wish to enable Completed Download Handling you should verify the following:
+* **Warning**: Completed Download Handling only works properly if the download client and Radarr are on the same machine since it gets the path to be imported directly from the download client.
+* If you added a post-processing script to Sabnzbd/NzbGet to notify Radarr that it should scan the Drone Factory. You _SHOULD_ disable this script to prevent conflicts.
+* Completed Download Handling and the Drone Factory cannot be configured for the same directory. If Completed Download Handling detects a download resides in the Drone Factory it will be ignored. (again to prevent conflicts)  
+   You should reconfigure Radarr to use a different Drone Factory Folder or disable it altogether.  
+   Alternatively you can change the output folder for the Category, as long as that output folder is not a subdirectory of the Drone Factory Folder.
+
+Both Completed Download Handling and the Drone Factory logic generates Import Events in history while importing files. However, only Completed Download Handling associates this Import event with a Download Client history item.
+If Completed Download Handling was enabled recently, your download client may still contain history items that were already imported but do not have a history event with the same unique id.
+Radarr attempts to resolve this issue automatically, occassionally Radarr may be unable to make that association and cause a 'Completed' download to be listed in the History -> Queue table forever.
+The easiest way to resolve this is to clear your Download Client history, or only those individual items. Alternatively you can rename the category.
+
+#### Download Client has history items in Drone Factory conflicting with Completed Download Handling ####
+
+The Download Client put finished downloads inside the Drone Factory even though Completed Download Handling is configured.
+This could potentially cause both Completed Download Handling and the Drone Factory logic to import the same download simultaneously.
+To avoid conflicts Radarr will ignore those downloads during it's Completed Download Handling logic, leaving it to be handled by the Drone Factory.
+This is a suboptimal situation since this effectively disabled Completed Download Handling.
+
+Resolution: Configure the Drone Factory to use a different folder.
+
+_**TODO: Reword**_
+
+### Indexers ###
+
+#### No indexers are enabled ####
+
+Radarr requires indexers to be able to discover new releases.
+Please read the wiki on instructions how to add indexers.
+
+#### Enabled indexers do not support searching ####
+
+None of the indexers you have enabled support searching. This means Radarr will only be able to find new releases via the RSS feeds. But searching for movies (either Automatic Search or Manual Search) will never return any results.
+Obviously, the only way to remedy it is to add another indexer.
+
+#### Indexers are unavailable due to failures ####
+
+Errors occurs while Radarr tried to use one of your indexers. To limit retries, Radarr will not use the indexer for an increasing amount of time (up to 24h).   
+This mechanism is triggered if Radarr was unable to get a response from the indexer (could be dns, connection, authentication or indexer issue), or unable to fetch the nzb/torrent file from the indexer. Please inspect the logs to determine what kind of error causes the problem.   
+
+You can prevent the warning by disabling the affected indexer.
+
+Run the Test on the indexer to force Radarr to recheck the indexer, please note that the Health Check warning will not always disappear immediately.