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**HOW TO REFRESH ONLINE FOLDERS ON DEMAND FROM THE CLIENT**

__THE NEED FOR REFRESH ON DEMAND__

By default, Serviio will automatically refresh the content "Online sources" ("feeds"), with each restart and on a periodic basis according to the "Feed expiry interval (hours)" set in the console.  This is adequate for "Online Sources" that are relatively static, but there are some Online sources" ("feeds") that are dynamic, with their "feed items" constantly changing, so the "feed" must be refreshed in order for Serviio to obtain and display the latest set of "feed items".  Sports Event sites such as HaHaSport and News sites such as Video.AP are two examples of this.

There are two ways to initiate those more frequent refreshes.

One approach is to create a WebResource groovy for the feed and set the expiry date to initiate refreshes of that feed on periodic basis consistent with the known dynamics of the source for example just before the start of the next scheduled sports event or every few minutes for a news feed. 

The Online Source ("feed") HAHASPORT.COM and its WebResource groovy is an example. This site maintains and provides a list of scheduled events by sport, and provides links to embedded player streams of events as they go live ("feed items"). To maintain currency of a Serviio menu, the list of scheduled events must be reviewed by the groovy at least hourly since new events ("feed items") can be added or removed at any time; live events ("feed items") must be detected minutes prior to their scheduled start, and if not yet started, again at their scheduled start and a few minutes thereafter; and then live events ("feed items") must be removed a few minutes after their scheduled end time. 

The problem with this approach is the continual use of resources by the groovy to refresh and maintain the current set of feed items even though they may never be used. Secondly, this constant stream of refreshes particularly when multiple sport feeds are enabled, is beyond the capacity of most systems and feed refreshes are constantly backlogged due to insufficient time to access the changing feed items.

The better approach is to be able to "Force Refresh" a feed just prior to its use. However the problem with this approach is that if a significant number of new feed items have been created since the previous refresh, it may take Serviio many minutes to refresh and make the feed available again, since each new item can take 30 seconds or more to add. Another problem is that while the Serviio Server Console and various Remote Device Console implementations offer the ability to "Force Refresh" Online Sources On Demand, no capability is offered to initiate a "Force Refresh" on demand from the menus on a Client device. so users must access the server or obtain a device which has 3rd party remote console support.

The ultimate solution therefore is to implement these dynamic feeds with a Web Resource that refreshes on a periodic basis in order to minimize the number of new feed items that will need to be added by a "Force Refresh", and to provide a "Force Refresh" capability from the menus on the client device, that may be used just prior to using the dynamic feed. 

The facility to initiate periodic refreshes in a Web Resource plugin groovy, more frequently than the console default refresh value, is documented in the "Serviio Online Resource plugin implementation Guide" under "Date expiresOn".  Date is based on the current time {long curTimea = System.currentTimeMillis()} plus the milliseconds to the desired expiry time. Note that expiry will be on the earliest of that Date and the console default, and the refresh will actually be performed by Serviio 5 minutes ahead of that time. 

The hahasports.groovy implements this option via a refresh=nnn parameter that removes the automatic refresh based on event times and only refreshes the feed every nnn minutes. Other dynamic feeds should implement a similar capability. A "Force Refresh" from the server or a remote console, or from a client device menu may then be used to refresh the feeds prior to opening them. 

The facility to initiate "Force Refresh" from an online menu on a client device consists of a WebResource Refresh.groovy that generates a menu of "Force Refresh" feed items for all enabled WebResource feeds in the Serviio online library. Clicking on a listed feed item initiates a "Force Refresh" of that feed by intercepting the call to play the video associated with that menu item. The feed is then removed from the list of Online menu feeds while it refreshes and it becomes available again by opening the Online menu once the refresh is complete. The implementation is documented below.

__ON DEMAND METHODOLOGY__

The ability to implement "Force Refresh" feed items in the Refresh.groovy is based on 6 prerequisite one time implementations:

1) The installation of CURL.EXE which provides the abilty to access the Serviio repository data and initiate forced refreshes per the latest "Serviio REST interface specification.pdf".  The curl.exe may be obtained from http://curl.haxx.se/dlwiz/?type=bin and use the wizard to select the correct package for your operating system and install it in the appropriate system library. I used the generic Win64-ssl package and copied curl.exe into C:\windows\sysWOW64. W32 users should get the generic Win32 package and copy curl.exe into C:\windows\system32

2) The availability of a live Stream URL which can be used as the trigger to initiate calls to curl.exe to initiate individual library refresh requests. The live Stream URL for the International Space Station (ISS) feed %%"rtsp://a1709.l1856953708.c18569.g.lm.akamaistream.net:554/D/1709/18569/vnnn/reflector:53708"%% is currently used by RefreshWebResources.groovy as the live stream associated with each "Force Refresh" feed item, where the "v Value" nnn is the online library id to be refreshed.

3) The availability of a "Force Refresh" icon to be used by RefreshWebResources.groovy for each "Force Refresh" "feed item" associated with the ISS live stream. The icon %%https://sites.google.com/site/serviiorss/refresh.jpg%% is currently used which displays "CLICK TO REFRESH FOLDER" and the "feed item" title is used to display any additional information.

4) The addition of the line -Dffmpeg.location="C:\Program Files\Serviio\lib\ffmpeg.bat" to the file C:\Program Files\Serviio\bin\ServiioService.exe.vmoptions to cause all Serviio ffmpeg calls to be sent to ffmpeg.bat  This needs to be repeated after each Serviio new install, which will restore that file.
After the addition it will contain:
<code>-Xmx512m
-Dffmpeg.location="C:\Program Files\Serviio\lib\ffmpeg.bat"
</code>
5) The installation of the attached ffmpeg.bat as C:\Program Files\Serviio\lib\ffmpeg.bat which will detect the ffmpeg calls containing the ISS URL, extract the "vValue" nnn and issue the curl command to refresh the Serviio online library nnn, before calling ffmpeg to process the original ffmpeg call. Note the ffmpeg.bat also logs each ffmpeg call in C:\Program Files\Serviio\log\ffmpeg.log which I have found useful for debugging. The bat may be edited to comment out that line as noted in the bat.

6) The addition of WebResource to the Library Online Sources section of the console using the dummy url http://www.refresh.com

With these changes, a Refresh menu will be created with items showing the library id and name of each active Web Resource online source together with a "Click to Refresh Folder" icon. Clicking on an item, initiates playback of the ISS stream while the feed refreshes. Note that a refresh can require up to 30 seconds to cache a new item, but with hourly automatic updates many of the new events should already be cached. After waiting an appropriate period, playback may be stopped, the Refresh and Online Folders exited, and the Online Folder reopened. If the refresh is complete the Refreshed folder should appear. If not repeat the closing and reopening of the Online Folder until it does.

__The FFMPEG.BAT - Updated for Serviio 1.0__
Download {{:ffmpeg.bat.zip}}

**How to setup Refresh on demand from client for Linux and Synology NAS:** [[refresh_on_demand_linux|refresh_on_demand_linux]]
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